Scipedia: Documents published in 2023

COMPARATIVE ANALYSIS OF THE INTERNATIONAL VOCATIONAL EDUCATION AND TRAINING SYSTEMS IN THE CONTEXT OF GLOBAL TURBULENT ECONOMIC SITUATION

Elisaveta Grebennikova — Wed, 11 Oct 2023 13:37:02 +0200

The main aim of international comparative studies is to identify trends in the functioning and development of vocational education and training systems, to describe institutional units that ensure successful development of VET system and to identify bottlenecks and problem areas that need to be addressed. Basing on the data obtained, methodological recommendations for the implementation of best practices are usually compiled. When conducting this study, we were limited in information resources, since the topic of VET systems in developing countries of Asia are out of focus for most scientific institutions and researchers. Basing on the existing methodological approaches of international organizations, an analytical framework was developed. Its application made possible, despite scarce information resources, to conduct research of the functioning of VET systems in India, China in the context of global turbulent economic situation. The results obtained testify the great heterogeneity of VET systems. In India even today the most important task remains teaching basic literacy to the majority of population, creating acceptable conditions for students in educational institutions, expanding the availability of vocational education. At the same time, China faces the challenge of transforming the economy into innovative one, and the world's largest VET system must be adapted to the needs of this economy. The implementation of unified and standard solutions derived from the 'reference' systems of vocational education of European countries is unlikely to give a stable positive effect in developing countries. The main conclusion that can be drawn from the results of the analysis conducted is that VET systems are a product of the politics, economy and culture of their countries. Their institutional structure is unique in each case and the mechanisms that allow it to fulfill tasks and to develop require a close and rigorous study. In case of some structural changes to implement, preliminary experimental work is a necessity. The purpose of the preprint is to present the results of a carried comparative analysis of the functioning and development process of vocational education and training systems in developing countries basing on developed analytical framework that makes possible to identify and to compare fundamental institutions, to identify the main trends despite scarce information resources. The study is based on the methodology of system analysis, the method of comparative analysis, the method of systematization and generalization of scientific literature and educational practice, the method of descriptive statistics were used. As a result, the outcome of a comparative analysis of the systems of vocational education and training of "friendly" countries India, China a were presented. The main development trends were highlighted, statistical indicators and the institutional structure of VET were analyzed. The novelty of the is the synthetic methodology for conducting comparative analysis, based on the methodological approaches of the OECD, UNEVOC and the World Bank. The results of the study can be applied while developing the VET policy and implementing institutions that increase the flexibility and adaptability of the VET system to the external impacts.

TRENDS IN THE EVOLUTION OF AUTHORITIES OF SUBJECTS OF THE RUSSIAN FEDERATION WITHIN JOINT JURISDICTION WITH THE RUSSIAN FEDERATION

Elisaveta Grebennikova — Wed, 11 Oct 2023 13:21:02 +0200

The relevance of identifying the main trends in the system of powers legally assigned to the subjects of the Russian Federation is due to the lack of relevant work for more than twenty years of its existence. The purpose of the study is to establish the main trends in the evolution of the content and functional areas of the powers of the subjects of the Russian Federation within the joint jurisdiction of the Russian Federation and the subjects of the Russian Federation in accordance with the federal legislation. The object of the study is the mechanism of distribution of powers in the budgetary system of the Russian Federation. The hypothesis of the study was that during the long period of the formation of the mechanism of the distribution of powers, the goal of their clear differentiation was not achieved, independence of the state authorities remained low, and a new federal law regulating this area did not make cardinal changes. According to the results obtained, federal legislation allows for the actual expansion of the closed list of powers of the subjects of the Russian Federation on within the joint jurisdiction. Taking into account the possibility of delegating federal state powers and the absence of a closed list of powers of the Russian Federation, this causes the absence of a clear distribution of authority between the Russian Federation and the subjects of the Russian Federation. The tendency to expand the areas assigned to the subjects along with a constant amount of budget revenues actualize the risks of imbalance and financial instability. The novelty of the research consists in establishing the main trends in the evolution of the content and functional areas of the powers of the subjects of the Russian Federation within the joint jurisdiction of the Russian Federation and the subjects of the Russian Federation. For the first time, the nature of the change in the composition of powers due to the adoption of the new federal law No. 414-FZ instead of federal law No. 184-FZ are analyzed. Research methodology: structural and substantive analysis of federal legislation, grouping and systematization, comparative analysis.

Economic resilience: theory and empiricism

Elisaveta Grebennikova — Wed, 11 Oct 2023 09:41:02 +0200

Sanctions pressure, disruption of production chains leads to crisis phenomena in the Russian economy in the context of most regions. For both federal and regional authorities, it is necessary not only to understand the main characteristics of the socio-economic development of the regions, but also to consider the sensitivity of regional resilience (shock resilience). The resilience of regions in terms of the rate of decline and recovery of GRP, investment activity, and budget revenues is calculated based on a large number of factors. The causes and factors of crisis phenomena in the economy, as well as the resilience, can be considered in the prism of theory and empiricism and become the basis for understanding public policy and making anti-crisis decisions. The aim of the study is to fully cover the phenomena of shock resilience of the economy using the analysis of theoretical views and empirical approaches. Research methods and methodology: historical-economic, comparative and system analysis, scientific-logical method, cartographic methods, index method. Scientific novelty consists in conducting a thorough and in-depth analysis of theories and concepts that describe the causes and factors of crisis phenomena in the economy with a final presentation of a comprehensive review of them, in which the emphasis is on revealing the historical context of their occurrence and describing crisis theories and models of modern economic reality. In addition, approaches to the definition of the phenomenon of shock resilience are classified, structural aspects and methods for calculating resilience are systematically described, and the author's systematization of works on the study of socioeconomic resilience is presented. Results: The analysis of economic cycles and models of economic crises revealed a regular cyclicity in the development of the views of economists on the nature of economic cycles, causes and overcoming possible consequences. Modern crisis processes happen largely because they are associated with two types of contradictions or imbalances - there are political and financial-economic ones, while the deep causes are universal world processes associated with changes in technological patterns. A grounded theory approach as the qualitative sociological method is becoming more and more in demand in modern studies related to the crisis in the economy; the results of its application to the disease pandemic, for example, showing that the corona crisis is a complex phenomenon that is directly or indirectly affected by the health crisis, government policies and human behavior. Among the most common methods of empirical research of economic resilience, the construction of complex indices and regression analysis of research resilience indicators stand out. The evolution of scientists' views on the causes and factors of crises, a review of the main approaches to the analysis of the phenomena of shock resilience, as well as an analysis of empirical studies of its results at the level of the economy of countries and regions are the main results of this study that expand the possibilities for understanding public policy and making the right anti-crisis decisions.

Current approaches to the study of local entrepreneurial ecosystems

Elisaveta Grebennikova — Wed, 11 Oct 2023 09:28:02 +0200

Relevance of the research: In economics, a variety of approaches are used to study local entrepreneurial ecosystems from statistical methods to network analysis, which allow to quantify the scale of a phenomenon or the magnitude of the potential effect. In the case when it is necessary to determine the key causes and factors of the process under study, the methodological tools of the scientist can be expanded through the methods of sociological survey of entrepreneurship. The results of the presented work will allow not only to expand the methodological apparatus of researchers of local SME ecosystems, but also to develop proposals for improving the effectiveness of state support measures for entrepreneurship in the regions of Russia. The aim of the study is to reveal the possibilities of using different methods to study entrepreneurship at the local level, as well as to analyze and generalize Russian and foreign experience in studying entrepreneurship. Research methods and methodology: comparative analysis, system analysis, qualitative analysis, historical and economic analysis. Scientific novelty is the author's classification of possible sociological approaches to the study of SMEs within local entrepreneurial ecosystems, as well as systematization of Russian and international empirical studies of entrepreneurship at the local level and identification of factors that stimulate business development. Results: Sociological methods, namely in-depth interviews, allow us to explore key causal relationships and offer new research hypotheses that can be further evaluated using statistical analysis methods. Achieving sustainable socio-economic development of the region will be facilitated by the implementation of targeted programs to support SMEs, taking into account regional institutional conditions and the specifics of the development of local entrepreneurial ecosystems. The key factors for the development of SMEs are the high volatility of markets, which motivates the development of new ideas for business, the availability of physical and commercial infrastructure. High risks for SMEs are associated with insufficient functional coordination of power structures, the lack of dialogue between business and government, the quality of government support measures implemented and business financing mechanisms. For start-up young entrepreneurs (under 30), the main barriers are the lack of start-up capital and the necessary business competencies, the lack of a business idea, and high taxes.

Mechanical property and sealing performance analysis of the diaphragm compressor cylinder head for the hydrogen refueling station under the mutation impact load

Mingxin Li — Sat, 07 Oct 2023 05:08:03 +0200

Under the combined action of structure-process -load, the stiffness and stress distribution at the sealing interface of the ultra-high pressure diaphragm compressor cylinder head exhibit significant nonlinear and uncertain characteristics, resulting in damage to the sealing interface, diaphragm and sealing ring. This paper first establishes a finite element numerical model considering assembly process parameters based on sudden impact load conditions, and analyzes the dynamic characteristics under different assembly process parameters. It is found that some modal frequencies transition with bolt loosening. Then, the mechanical characteristics of the assembly interface of the compressor sealing system under sudden impact load were studied. The maximum equivalent stress at the assembly interface was 298.9 MPa, and the maximum deformation at the top of the air chamber was 0.167mm. Finally, the nonlinear effects of sealing ring compression rate, sealing ring diameter, and sealing groove structure on contact stress and sealing performance were obtained. The results show that as the compression ratio increases by 20% and 25%, the contact pressure at the sealing interface increases by 42.0% and 77.5%, respectively; When the compression rate is 25%, the width of the sealing groove increases by 0.5mm, and the maximum contact pressure decreases by 8.1%. The research on the dynamic characteristics and sealing performance of diaphragm compressors provides technical support for the structural optimization design of diaphragm compressors cylinder head.

Research on Personalized Tourism Recommendation Algorithm

Dongshu Cheng — Fri, 06 Oct 2023 20:56:04 +0200

Project recommendation plays an important role in tourism management. It can not only promote the overall development of tourism, but also improve the satisfaction of tourists. However, in the process of tourism recommendation, there are some problems, such as insufficient personalized recommendation, low satisfaction with recommendation, inaccurate recommendation and so on. Therefore, this paper proposes a personalized tourism recommendation algorithm based on remote network control technology, which classifies the tourism needs of different groups and summarizes the data. On this basis, the tourism resources database is constructed, and the tourism resources are numbered. Combined with map list, real-time location of tourists, weather conditions, traffic conditions and other information, it provides tourists with more accurate and practical tourism recommendation services. Finally, through remote network control technology, the matching of tourism resources and demand can be realized, and the accurate transmission of personalized recommendation data can be ensured, and the recommendation algorithm can be promoted. The research results show that under the remote network control technology, personalized recommendation algorithm can improve the matching rate of all tourism resources, realize the rational development of tourism resources, and meet various needs of tourists.

THE FORMATION OF A METHODOLOGY FOR ANALYZING THE STATE OF PERSONNEL WORK AND THE PERSONNEL OF THE STATE CIVIL SERVICE USING THE SERVICES OF FEDERAL STATE INFORMATION SYSTEMS AND OTHER PLATFORM SOLUTIONS

Elisaveta Grebennikova — Fri, 06 Oct 2023 09:59:03 +0200

The relevance of the research is due to the need to form a system of personnel audit in the civil service through the application of a unified methodology using the capabilities of the national information system for managing the personnel of the state civil service. The purpose of the research is to develop a methodology for a comprehensive analysis of the personnel, its processes (personnel dynamics) and the conditions of personnel work in the state civil service in the federal executive authorities and authorities of the constituent entities of the Russian Federation using the services of state information systems and other platform solutions.The objectives of the study are: to determine the conceptual foundations of the personnel audit of the state civil service; the development of a system of indicators characterizing the effectiveness of personnel management processes; the study of the possibility of the integration system and accumulation of information, analytical and statistical data, depending on the areas of personnel audit; the determination of the need for the development of specialized diagnostic tools to reach the goals of personnel audit; the development of a methodology for conducting a personnel audit, including: technologies for analyzing personnel processes (HR analytics); personnel statistics; algorithms for integrating data on the level of maturity of personnel and management technologies; the results of standardized socio-psychological surveys and public opinion surveys, as well as the possibility of taking into account the results of personal and professional diagnostics; preparation of a "road" map for the implementation of a methodology for analyzing the state of personnel work and the staffing of the state civil service in federal executive authorities and authorities of the constituent entities of the Russian Federation using state information systems services and other platform solutions; description of the methodology for organizing and conducting an audit of the state of the civil service in the federal executive authorities and authorities of the constituent entities of the Russian Federation; preparation of the regulative document’s draft fixing the methodology. The research methods and methodology: the comparative analysis, the method of expert assessments, the appraisal work, the analysis of statistical data, the group discussion method, the results of sociopsychological surveys and personal and professional diagnostics. While summarizing and analyzing empirical materials, methods of statistical data processing were used. The main practical results of the study: the preparation of a "road" map for the implementation of a methodology for analyzing the state of personnel work and personnel of the state civil service in federal executive authorities and authorities of the constituent entities of the Russian Federation using the services of state information systems and other platform solutions; the preparation of a methodology for organizing and conducting an audit of the state of the civil service in federal executive authorities and authorities of the constituent entities of the Russian Federation: the general procedure for organizing and conducting an audit, criteria for evaluating the effectiveness of each element of the work, the general estimated indicators of the personnel services work, the procedure for eliminating shortcomings; the preparation of the regulative document’s draft fixing the methodology; the development of a methodology for conducting a personnel audit, including: technologies for analyzing personnel processes (HR analytics); personnel statistics (data on the personnel, staff turnover, absenteeism, reasons for dismissals, etc.). The main conclusions: the results of the research can be useful for scientific and methodological support for improving the mechanisms for implementing personnel policy and personnel technologies in the state civil service; a comprehensive increase in the effectiveness of personnel policy in the state civil service, including increasing the involvement of employees in the processes of personal professional and career development, reducing the possibility of unreasonable personnel decisions and corruption risks; reducing the imbalance in the processes of managing human resources in the system of the state civil service. The research prospects may be related to: refinement of the results and conclusions obtained through testing in one of the federal government bodies, as well as the development of algorithms for using the services of the Federal State Information Systems and other platform solutions that allow systematizing the data obtained and using the results of data analysis in operational activities.

FOOD INSECURE HOUSEHOLD GROUPS: DEFINITION AND CHARACTERISTICS

Elisaveta Grebennikova — Fri, 06 Oct 2023 09:45:02 +0200

The relevance of the topic - assessing the level of economic access to food - remains poorly developed in Russia. This study aims to fill this gap within the framework of the main ideas of the Food Security Doctrine of the Russian Federation. The purpose of this work is to develop approaches for assessing the level of food security among household members and highlight the main characteristics of households with different levels of food insecurity. The statistical basis for this study is the microdata from budget surveys conducted by Rosstat. The main content and results of this study are as follows: The concept of "food insecurity of the household" and its members is introduced. An overview of approaches used in different countries to identify individuals experiencing food insecurity is provided. The focus of the assessment shifts from evaluating the level of economic affordability of food based on decile groups and available resources to assessing the level of economic affordability of food for each household member. This analysis highlights the main characteristics of households or their members with varying levels of food insecurity.

SHARE OF SCHOOL GRADUATES ENTERING HIGHER EDUCATION IS DECLINING

Elisaveta Grebennikova — Fri, 06 Oct 2023 09:30:03 +0200

Social and economic changes resulted in a transformation of youth’ values: the attitude towards higher education, granting both social status and, consequently, privileges in employment, became a history. However, the changes taking place in Russia, external to the vocational education system, may have a serious impact on the behavior of young people in the near future, especially young men, who will be more targeted to enroll in full-time higher education programs.

Consequences of economic inequality of countries dependent on oil exports

Elisaveta Grebennikova — Fri, 06 Oct 2023 09:20:02 +0200

The final part of the presented study, which consisted of four parts, is devoted to assessing the consequences of the economic inequality of countries, including those dependent on the export of hydrocarbon energy. Note that the estimates presented in this paper also cover the period of various types of sanctions, which also have certain consequences for income inequality. Based on the presented thesis, the purpose of this part of the study is to assess the consequences of economic inequality in the group of countries under study based on the use of econometric models, as well as to conduct a dynamic assessment of indicators of income inequality between countries.

Modern trends and problems of income inequality in an open economy

Elisaveta Grebennikova — Thu, 05 Oct 2023 13:59:02 +0200

This section of the present study analyzes current trends and problems of income inequality. It should be noted that the studies structurally analyzed in the work were divided taking into account the theoretical, country, as well as the general part concerning the most modern aspects of international trade related to the sanctions confrontation and the coronavirus pandemic.

Relationship between inequality and economic growth in countries highly dependent on oil exports

Elisaveta Grebennikova — Thu, 05 Oct 2023 13:52:03 +0200

This section of the work is devoted to the analysis of the relationship between inequality and economic growth in countries with a high dependence on oil exports. In this section, as in the first part of the study, approaches to modeling the relationship of various types of inequality, mainly related to income inequality in countries with a high dependence on oil exports, are considered, but not from the point of view of the quality of the institutional development of the countries under study, but in the context of dependence of the formation of the revenue part of the country's budget on the export of hydrocarbon energy. Thus, the purpose of this study was to determine the place and role of oil revenues in modeling the relationship between income inequality and economic growth in oil exporting countries and to quantify their significance in reducing inequality in the country and increasing economic growth rates.

Institutional foundations and peculiarities of the classification of income inequality in countries with a raw material oriented economy

Elisaveta Grebennikova — Thu, 05 Oct 2023 11:34:02 +0200

In the presented work, various aspects and methods for conducting a quantitative assessment of the relationship between income inequality and the level of institutionalization of the country's economy are considered. As the main quantitative method for assessing income inequality, this study uses the regression analysis technique, as well as vector autoregressive models.

Macroeconomic Forecasting with the Use of News Data

Elisaveta Grebennikova — Thu, 05 Oct 2023 11:14:02 +0200

During the last decade a lot of academic papers consider the possibility of predicting the economic fluctuations and macroeconomic variables volatility with the use of news data. The reason for this is the development of new machine learning techniques and enhancement of the existed methods. The scientific problem of our study is the investigation of whether predictive power of the forecast of macroeconomic variables can be improved with the use of news data in the context of Russia. We apply NLU algorithms and techniques for topic modeling. Especially, we implement LDA (Latent Dirichlet Allocation) since this approach has shown its effectiveness in the published papers related to the mentioned framework. Then the frequency news and sentiment news indexes are constructed with the use of modeled topics. The end point of our research is the forecast analysis of the set of macroeconomics variables [CPI (π), Business Confidence Index (BCI), Consumer Confidence Index (CCI), Export (EX), Import (IM), Net Export (NX)] supplemented by inclusion of frequency and sentiment news indexes in order to evaluated the improvement in predictive power. We have shown that the inclusion of frequency news indexes and sentiment news indexes, based on the LDA approach in the forecast models can improve the quality of the predictions and increase the predictive power for some variables.

Modern Approaches to Modeling the Function of Household Consumption on Microeconomic Data

Elisaveta Grebennikova — Thu, 05 Oct 2023 10:34:03 +0200

As part of the presented literature review, foreign and Russian experience in using microeconomic data to model the household consumption function using various types of models for the US, EU and Russia, based on the respective types of panel data: PSID, ECHP and RLMS, respectively, is considered. The construction of such models is necessary for the state in connection with the need to achieve a rational level of differentiation of incomes and consumption of the population. Thus, the purpose of the presented work is to analyze the approaches used to assess the level of income of the population based on the use of panel microeconomic data for the US, EU and Russia.

Toward a competence model of data literacy for middle and secondary school

Elisaveta Grebennikova — Thu, 05 Oct 2023 09:42:11 +0200

The study examines the practices of teaching data literacy for adolescents. The intersections of data literacy with statistical literacy, quantitative thinking, computational skills, and Data Science are explored. A competence model for data literacy is introduced with key competency clusters – technical, scientific, and social – aligned with the components of a scientific practice and data mining research cycle. The conclusions underscore the importance of students engaging in the exploration and modeling of socio-humanitarian data as part of their learning process. This content, firstly, aligns most closely with the sociocognitive specificity of the age, secondly, it lays the foundations for students’ interdisciplinary understanding of contemporary phenomena, which is in demand across a wide range of professions. Future directions encompass refining the data literacy model, creating methodological resources for developing data literacy within education systems, and providing pedagogical guidance and materials for educators adopting data literacy techniques.

DYNAMICS OF THE POPULATION'S ATTITUDE TO THE NON-CRIMINAL SHADOW ECONOMY

Elisaveta Grebennikova — Wed, 04 Oct 2023 16:50:05 +0200

The scientific report presents a study conducted by the Research Center for Socio-Political Monitoring of the Institute of Social Sciences of the RANEPA. The relevance of research. Involvement of a significant part of the employed population in shadow processes. The demand for the shadow market of goods and services among the population. The need to obtain regular operational scientific information about the processes taking place in the shadow labor market in the new socio-economic reality, as well as the effect of the measures already taken aimed at limiting the shadow labor market. The purpose of the study is to analyze and evaluate of the dynamics of the prevalence of shadow forms of relationships in the modern labor market. The subject of the study is the main trends in the shadow labor market in modern conditions. The main research method is an all-Russian sociological survey of the employed Russian population and a comparison of the results obtained with the results of previous surveys. Based on the results of the study, an analysis and assessment of the attitude of the employed population to non-criminal shadow economic activity, from the point of view of the involvement of the population in the shadow labor market and the consumption of products produced on it. The study allows us to draw the following conclusions. Over the past year, there has been a decrease in the involvement of workers in various forms of shadow relations in the labor market. The decrease in the participation of respondents is recorded for various forms of their employment in the shadow labor market, including main and additional work. A significant part of the respondents still believe that informal (shadow) economic activity brings both benefits and harm to society in equal measure. This rather loyal attitude of employed citizens to informal employment and tax evasion supports the shadow labor market and creates prerequisites for their personal participation in shadow processes. The results of the study demonstrate a certain effect of the activities of state authorities to limit the participation of workers in the shadow labor market. Among those engaged in private practice, the attractiveness of using the new tax regime (NPD) is noted. At the same time, the fear of changing the conditions of the experiment act as constraining factors for its use among potential users. The results of the study demonstrate that awareness of the illegality of non-payment of taxes and the need to bear responsibility in this case is gradually increasing among citizens. Scientific novelty lies in obtaining up-to-date sociological information about the main trends in the field of noncriminal shadow economic activity, including the dynamics of population involvement in the shadow labor market. The recommendations based on the results of the study are related to the need to adjust management decisions in the field of stimulating official employment and limiting the participation of the population in the shadow labor market.

Trends and imbalances in the development of additional professional education for workers and specialists

Elisaveta Grebennikova — Wed, 04 Oct 2023 16:36:04 +0200

The relevance of the study is determined by the current Russian agenda in the field of personnel advanced training and retraining in connection with the change in technological priorities and the policy of 'import substitution'. The objects of observation were the programs of advanced training and professional retraining of workers, employees and mid-level specialists being implemented in the regions of Russia and the organizations providing these programs. The purpose of the study is to identify the state and trends in the development of the system of personnel with applied qualifications advanced training and professional retraining in the context of transformations in the qualification demand in regional labor markets. The research tools included indicators that characterize various aspects of the implementation process and results of additional professional programs for personnel with applied qualifications. To describe the structure of data and their distributions, dynamic and structural analysis, mapping and other tools of descriptive statistics were used. Main results. Inter-regional differences and intra-regional disproportions in the field of additional professional education and training of workers and mid-level specialists in Russia are revealed. Significant disproportions in the employment structures of the regions in the context of workers categories and contingents of advanced training and retraining programs for personnel with applied qualifications have been established. A rating of subjects of the Russian Federation to the Structural Imbalance Index, which fixes the level of mismatch between the coverage of additional professional programs for workers and mid-level specialists and their place in the region labor market was formed. Scientific novelty. For the first time, a comprehensive study of the evolution of additional vocational education and training of workers, employees and mid-level specialists was carried out, in which inter-regional and intra-regional comparisons were made, revealing trends and disproportions in its development, taking into account the regional economic context. Recommendations. The data obtained make it possible to assess the extent to which the potential of personnel with applied qualifications is maintained, increased and updated in the Russian regions, taking into account their place in the structure of employment of a constituent entity of the Russian Federation. The results of the study can be used by federal and regional executive authorities in order to eliminate imbalances in the quality of labor markets staffing.

INDONESIA’S CLIMATE POLICY

Elisaveta Grebennikova — Wed, 04 Oct 2023 15:16:02 +0200

This paper studies Indonesia’s climate policy and its transformation in the context of the geopolitical and economic crisis. Indonesia is one of the world's fastest growing economies and a major emitter. Its actions to combat climate change will facilitate achievement of Paris goals globally. In addition, the country is playing an increasing role in developing the tools of global economic governance, including in the field of climate. The purpose of the study is to distinguish the main priorities and directions of Indonesia's climate policy and their transformation. Based on the results of the study, the authors conclude that Indonesia is demonstrating its commitment to the goals of decarbonization, showing its readiness to introduce even the strictest instruments, including carbon pricing. International partners need to support Indonesia's aspirations and efforts as they advance the achievement of the Paris goals. The principle of common and differentiated responsibilities enshrined in the UNFCCC processes takes into account the national context, therefore, given the centrality of coal to the economic development model and the traditionally high share of emissions from land and forest use, Indonesia's strategy and policy can be considered ambitious.

International practices of supporting small and medium-sized enterprises’ (SMEs’) in times of coronavirus pandemic crisis

Elisaveta Grebennikova — Tue, 03 Oct 2023 15:53:04 +0200

The small and medium-sized businesses (SMEs) are the most vulnerable in times of crisis due to their scarce resources: financial, human, information etc., that is why the issues of providing support to entrepreneurs are relevant during crisis. The analysis of SMEs’ support international practices during recent economic crisis caused by COVID-19 infection might be used to form new approaches to supporting entrepreneurship in times of crises in Russia. The scientific novelty of the study lies in the analysis of foreign practices of supporting SMEs during the recent COVID-19 crisis. The purpose of this article is to summarize international experience in supporting SMEs in times of crisis. For this, the following objectives were set: the analysis of institutional, fiscal, monetary and regional measures of supporting entrepreneurs during the pandemic, as well as the analysis of the empirical works that access their effectiveness. General scientific methods are applied - generalizations, comparisons, synthesis, inductive approach. The authors come to the following conclusions: In response to the economic crisis caused by coronavirus, many countries have taken comprehensive measures to support small and medium-sized businesses; the most common are fiscal support measures, which include grants for entrepreneurs, direct investment, finance guarantees, temporary reimbursement of expenses and temporary tax holidays for entrepreneurs. According to the first empirical evidence, the most significant positive effect is caused by measures aimed at reducing the tax burden on entrepreneurs and compensating for their operating expenses.

RESEARCH OF LEGAL AND REGULATORY ENVIRONMENT FOR THE RETARGETING OF INDUSTRIAL PRODUCTION TO DIVERSE EQUIPMENT AND TECHNOLOGIES (INCLUDING IMPORT SUBSTITUTION)

Elisaveta Grebennikova — Tue, 03 Oct 2023 15:21:03 +0200

The aim of a study on the legal and regulatory framework for the retargeting of industrial production to diverse equipment and technologies is to identifying the stages and directions for the development of sectors of the economy that are strategically important for the country (end-to-end technologies, critical industries, etc.). The idea is to analyze the logic of the state regulation, tracking measures in terms of implementation of anti-sanction policy, fixing opportunities and conditions for import substitution and import independence. The data obtained are the first stage of the study on retargeting of industrial production to diverse equipment and technologies, including import substitution. The main conclusion that can be drawn from the results of the analysis is that monitoring state regulation allows us to see the logic of the retargeting of industrial production to diverse equipment and technologies, to see emerging of a system of measures to counter the sanctions policy, and also to identify the conditions for import substitution. The purpose of the preprint is to present the results of the study on the legal framework for the retargeting of industrial production to diverse equipment and technologies (including import substitution), which makes it possible to see the stages and sequence of application of state regulation mechanisms. The research is based on the methodology of system analysis, the method of systematization and generalization of the regulatory legal framework is used. During the study, regulatory legal documents were studied in chronological order, considering them as a set of tools (mechanisms) for the retargeting of industrial production to diverse equipment and technologies (including import substitution). The results of the study can be applied while developing public policy that can enhances the flexibility and adaptability of the system of vocational education and training system in the context of the retargeting of industrial production, technology and software, taking into account industry specifics (end-to-end technologies, critical industries, etc.) and the anti-sanction measures.

Challenges of Digital Platforms Regulation

Elisaveta Grebennikova — Tue, 03 Oct 2023 15:11:03 +0200

The working paper studies the problems of digital platforms regulation related to consumer protection, countering anti-competitive practices, designing preventive (ex-ante) regulations, interdepartmental and international cooperation. The study is highly relevant since digital platforms act as private regulators of their ecosystems. They set rules for users, shape the business environment, control the implementation of rules and the behavior of ecosystem participants. Thus, digital platforms control the behavior of citizens and businesses, while they (until recently) have not been controlled by the state and society. The working paper aims to analyze the main challenges that states face when shaping the new and extending the existing regulatory practices to digital platforms’ activities. Based on the results of the study, the authors assess the main regulatory challenges related to consumer protection, countering the monopoly behavior of developing platforms, developing ex-ante measures, establishing cooperation between various government bodies and international cooperation. The authors conclude with recommendations for improving digital platforms regulation, taking into account the identified challenges.

ESSENTIAL CHARACTERISTICS OF PEDAGOGICAL SUPPORT CHILDREN IN DIFFICULT LIFE SITUATIONS IN RUSSIA AND ABROAD

Elisaveta Grebennikova — Tue, 03 Oct 2023 14:55:03 +0200

The relevance of the study we determine the need to study pedagogical support as a factor that can have a significant impact on the formation of conditions for the development and positive socialization of children in difficult situations. Addressing this issue is associated with the solution of problems of the state level in terms of prevention of destructive phenomena in children and adolescents. The subject of the study is the specifics of the conditions of pedagogical support for children in difficult life situations in Russian and foreign practice. The purpose of the study: analysis of scientific approaches and developments that provide theoretical and methodological justification and effectiveness of practical activities to provide pedagogical support for children in difficult life situations as a condition for preventing victimization of the child population and the development of destructive phenomena in the child and adolescent environment. The basis of the study were the results of content analysis of Russian dissertations for the period 1996-2019 years and foreign scientific articles in the framework of the stated problems. Research methods: content analysis of dissertation studies and scientific publications, systematization, analysis and synthesis of the information obtained. Scientific novelty of the study is to assess the current state and development of the problems of pedagogical support for children in difficult situations in contemporary Russian scientific research. As a result, we found that Russian scholars in their dissertations widely presented the areas of study of pedagogical support. The study examined 340 Russian dissertations for degrees in pedagogy and psychology. Among the angles of scientific development of the problems of pedagogical support are the varied aspects of support for children with difficulties in the educational process (56%), issues of support for students (27%), and families (17%). However, Russian researchers have reflected the specifics of pedagogical support for children in difficult situations in a small number of works (14%), usually focused on children with disabilities. Among the deficient aspects of studying pedagogical support are such areas as research on comparative basis (2%), development of methodological and technological support of pedagogical support (14%), addressing the problem of teachers' readiness to provide pedagogical support to children in the educational process (13%). Russian scholars in their dissertation studies have not sufficiently disclosed the potential of the participatory approach in solving the problems of pedagogical support (14%). Based on the results obtained, the main conclusion is that the study of the essential characteristics of the phenomenon of pedagogical support for children of socially vulnerable categories is important for the development of pedagogical science. Currently, science and practice are in demand to develop promising scientific directions for the methodology of designing conditions of support for various groups of children in difficult life situations, not focusing only on children with disabilities. There is a particular need to develop scientific research on this issue in the direction of supporting children from low-income families, from migrant families, from families with socially destructive educational content. Recommendations: at a time of global geopolitical transformation, in order to create conditions for the development and positive socialization of children in difficult situations, it is necessary to disseminate among practicing teachers the results of scientific developments in the field of pedagogical support for children of socially vulnerable categories. The model of resistant schools, which has proven effective in working with children from families with low socio-economic and cultural status, should now be widely implemented in the Russian education system. In the conditions of Russian reality, the application of an empathic and participatory approach and facilitation. Implementation of these recommendations is possible if teachers and heads of educational organizations are better prepared to master modern evidence-based approaches and evidence-based practices in solving the problems of pedagogical support for children of socially vulnerable categories.

LABIOPLASTIA DE LABIOS MENORES CON LÁSER DIODO EN ADOLESCENTE, A PROPÓSITO DE UN CASO

Luis Traviezo — Tue, 03 Oct 2023 14:39:03 +0200

Labia hypertrophy is a completely normal condition, six out of ten patients have labia minora hypertrophy, but not all are surgical, it is related to hormonal factors, trauma, and hereditary factors, however, a large percentage is of unknown cause. In the present case, the labia minora labiaplasty with diode laser applied to an adolescent is briefly described.

LÁSER DIODO COMO INSTRUMENTO DE CORTE VERSUS BISTURÍ EN PRESENCIA DE PÓLIPO FIBROEPITELIAL VULVAR: REPORTE DE DOS CASOS

Luis Traviezo — Tue, 03 Oct 2023 14:36:03 +0200

Benign tumors of epithelial connective tissue located in the vulvar region have a very low incidence; the most frequent of these is fibroepithelial polyp, also known as acrochordon. The vulvar fibroepithelial polyp is extremely rare before menarche and after menopause, predominantly in obese and diabetic women. Descontrol hormone may facilitate its development as well as the high level of estrogen and progestogen during pregnancy. There are no reports regarding their relationship with human papillomavirus infections. They are histologically composed of fibrovascular stroma rich in collagen and fibrous tissue which sometimes has a mild chronic inflammatory reaction in the stroma. It is covered with keratinizing epithelium that can be thick with acanthosis, papillomatosis and hyperkeratosis. With the objective of reporting the benefits of diode laser in the treatment of benign tumors of epithelial tissue in the vulvar area and at the same time; To document the presence of this pathology and its ambulatory surgical approach comparing the aesthetic results of the excision with scalpel and laser diode, two cases are presented to which of acrochordon cutting off were performed, comparing surgical time, scarring, blood loss and better aesthetic gynecological outcome. Patients were followed up for 8 months without complications or recurrences. A better adhesion to the diode laser therapy was obtained, demonstrated in a fast recovery, null blood loss, effective healing and very favorable immediate cosmetic gynecological results.

LABIOPLASTIA OFICINAL CON LÁSER DIODO 30 WATTS, 980NM: INDICACIONES Y RESULTADOS

Luis Traviezo — Tue, 03 Oct 2023 14:32:02 +0200

Objective: To evaluate the indications for labiaplasty with 30 watt, 980nm diode laser performed in the office in the period 2016-2017 and the results obtained in terms of postoperative pain scale, sexual satisfaction scale and associated complications. Methods: A retrospective, descriptive and analytical study of the results obtained from labiaplasties performed in the office by surgeons was carried out, with a sample of 23 patients, in the period between 2016 -2017 in Caracas, Venezuela. The Trim technique with a 30-Watt Laser Diode was used in a continuous mode with a 980 Nm fiber. The patients were classified according to reason for consultation, degree of hypertrophy according to González's classification and pain scale, index of sexual satisfaction and associated complications. Results: The age range prevailed in patients between 29 and 39 years, the reason why all the patients underwent surgery was primarily discomfort referred to as 'discomfort', one patient also referred functional disorders, specifically dyspareuria. 65.2% of the cases presented generalized hypertrophy, followed by central asymmetric in 34.7%. On the analogue scale of postoperative pain, only 8.6% reported pain II to III; there were no intraoperative complications and postoperative complications were absent in 82.6% of them, 8.6% presented labial dehiscence, 4.3% pruritus and 4.3% granuloma, all complications had secondary resolution and the post-procedure sexual satisfaction index 10 / 10 pts. 100%. Conclusion: after surgery the patients achieved symmetrical lips, with a good aesthetic appearance.

BENEFICIOS DEL TENSADO VAGINAL CON LASER CO2 PARA EL BIENESTAR SEXUAL FEMENINO. EXPERIENCIA EN CONSULTA PRIVADA

Luis Traviezo — Tue, 03 Oct 2023 14:26:02 +0200

Female sexual dysfunction is a disorder that occurs when there is a change in a woman's usual sexual response. The reasons for consultation are more frequent, are the problems related to the sexual part, we have, in 80%, problems, errors, pathologies of pelvic floor dysfunction, such as obesity, childbirth, age, Physical activity, sedentary lifestyle, menopause, etc. Methodology: a descriptive, prospective, observational, and experimental study was conducted in 15 patients aged between 35 and 45 years, who attended the consultation from September 2018 to February 2019, presenting signs and symptoms compatible with sexual dysfunction. A vaginal test with Japanese co2 laser of 15w was performed, with a handpiece designed for vaginal tension with a power of 4ww and amplitude of 0.30, they were assessed with controls at 21 days and 6 months, applying 3 sessions of vaginal tenses. Results: of 67% of sexual dysfunction in patients, carrying out the PISQ-12 survey of sexual dysfunction and physical examination with manual manometry with a Kegel perinometer. The predominant symptomatology was

LASER DIODO 980 NM ASOCIADO A FIBRINA RICA EN PLAQUETAS, EN PACIENTES CON FISURA VULVAR RECIDIVANTE. BARQUISIMETO, ESTADO LARA

Luis Traviezo — Tue, 03 Oct 2023 14:22:02 +0200

Las disfunciones sexuales son consideradas como un problema de salud pública que afecta la calidad de vida de la mujer en cualquier etapa de su vida adulta, y entre las asociadas al dolor destaca la dispareunia asociada al vaginismo, en la que figura como manifestación clínica la fisura vulvar recidivante, la cual es infradiagnosticada en la consulta ginecológica, y el manejo y/o tratamiento es tardío. De acuerdo al grado, la resolución puede llegar a ser quirúrgica, en este sentido, con la finalidad de evidenciar la eficacia del Láser Diodo 980nm, asociado a fibrina rica en plaquetas en el manejo de la fisura vulvar recidivante, se desarrolló un estudio cuasiexperimental, en una muestra de 45 pacientes entre 23 a 76 años, que acudieron a una consulta privada. El motivo principal de consulta estuvo asociado a sequedad vaginal o atrofia, seguido de infecciones urinarias y dispareunia. Se realizó diagnóstico clínico e histológico, y se practicó la perineoplastia con láser Diodo 980 nm asociado a fibrina rica en plaquetas (PRF) con la finalidad de corregir la fisura vulvar recidivante. Tras un periodo de seguimiento de 4 meses se constató la curación de la patología, con toma activa de la función sexual, reflejado a través del IFSF (índex de función y satisfacción sexual femenina). Se concluye que, la perineoplastia con Láser asociada a PRF, constituye una técnica mínimamente invasiva, ambulatoria, con menos recidiva y excelente resultado funcional, regenerativo y estético. Se espera que este estudio sea de utilidad para el Ginecólogo en el manejo no convencional en la consulta ginecológica, esta técnica mínimamente invasiva y que mostró ser efectiva en el tratamiento de fisura vulvar recidivante

LIPOLÁSER DEL MONTE DE VENUS CON LÁSER DIODO 980-nm

Luis Traviezo — Tue, 03 Oct 2023 14:15:03 +0200

Objective: Evaluate the safety of the technique: Laser-assisted liposuction Diode 980-nm, presenting the rate of complications obtained in our interventions. Methods: A retrospective, descriptive and analytical study was carried out that included ten (10) patients selected with inclusion criteria between the months of January and September 2018, using a 980-nm Diode Laser (SixLáserDuo®) equipment whose energy used was 12 to 15 watts through a 600 μm fiber. Results: The average age of the patients was 29.6 years (range: 18 to 42 years), the complication was the hematoma 10% (1/10 patients) due to omission of medication and ecchymosis by 3% (3/10 patients). Pain control time of 1 to 2 days. Conclusions: The Lipoláser of mons pubis with the Laser Diode 980-nm, is a less traumatic proven technique, without major complications and with a low rate of minor complications reducing the recovery period of patients.

LABIOPLASTIA CON LÁSER CO2: BENEFICIOS Y COMPLICACIONES

Luis Traviezo — Tue, 03 Oct 2023 13:16:02 +0200

La labioplastia es un procedimiento quirúrgico que se emplea para mejorar el aspecto funcional, estético y psicosocial de la vulva, cada día aumenta su demanda debido a los múltiples beneficios que conlleva. Han sido descritas diversas técnicas, con el objetivo de obtener mejores resultados, así como disminuir las complicaciones intra y postoperatorias. Objetivo: evaluar los beneficios del uso del Láser CO2 en las labioplastias. Método: se realizó un estudio observacional, longitudinal y retrospectivo en 50 pacientes quienes acudieron a consulta privada, en el periodo comprendido entre los años 2014-2016, con diagnóstico de hipertrofia de labios menores grado II - III según la clasificación de Motakef. Se les realizó labioplastia en consultorio con Láser CO2 y seguimiento a dos años, donde fue evaluada la evolución de las mismas y la presencia o no de complicaciones. Resultados: la edad promedio de solicitud de la intervención fue de 30 años, donde el 80% de las pacientes tenía entre 20 y 39 años. En el 86% de los casos el grado de hipertrofia de labios fue Grado III y el motivo de consulta más frecuente el Disconfort, con un 44 % de prevalencia. El 4% presentó complicaciones a causa del procedimiento. Conclusiones: La labioplastia con Láser CO2 es un procedimiento seguro, realizado por manos expertas con amplios conocimientos de la tecnología Láser, con una baja tasa de complicaciones y una alta tasa de satisfacción.

ADIESTRAMIENTO EN EL USO DEL LÁSER, PARA EL TRATAMIENTO DE PATOLOGÍAS DEL TRACTO GENITAL INFERIOR, ASOCIADAS AL VIRUS DEL PAPILOMA HUMANO (VPH)

Luis Traviezo — Tue, 03 Oct 2023 13:10:03 +0200

El Virus del Papiloma Humano (VPH), causa cáncer del cuello del útero, la mayor parte de las infecciones por VPH son asintomáticos y categorizados, de alto o bajo riesgo. En la actualidad una de las técnicas, “mínimamente invasivo” en las patologías del tracto genital inferior, es el uso de láser CO2 de 15 ww y Diodo de 30 ww. El conocimiento y práctica de la Medicina Fotónica, no está incluida en el pensum del Programa de Postgrado de Obstetricia y Ginecología, UCLA, por lo que, se elaboró un plan de adiestramiento y se adquirió las técnicas y protocolos, para el uso adecuado de los equipos láser CO2 de 15 ww y Diodo de 30 ww, como herramienta en la consulta ginecológica, y método terapéutico, en pacientes con patologías del tracto genital inferior, asociadas a VPH. Se identificaron y evaluaron 20 pacientes con patologías del tracto genital inferior, asociadas a VPH, al 60% (12) de las pacientes diagnosticadas de condilomatosis vulvoperineal, se trató con la técnica láser CO2 de 15 ww, y se fotovaporizaron las lesiones menores de 0,5 cm y las lesiones mayores de 0,5 cm, se realizó exceresis; el 30% (06) de pacientes con diagnóstico citohistológico de neoplasia intraepitelial cervical de bajo grado, se realizó la técnica de láser Diodo de 30 ww, fotovaporizando las lesiones en cuello uterino y al 10% (02) de las pacientes diagnosticadas con neoplasia intraepitelial cervical de alto grado, se le realizó la técnica tipo cono, de láser Diodo de 30 ww. Los resultados del plan de entrenamientos obtenidos, indican un conocimiento teórico apropiado, con una concordancia alta, alcanzando un puntaje de 28/30 en relación al criterio del tutor, clasificado como Aprobado; en la evaluación práctica, se obtuvo una concordancia alta, en relación al criterio del tutor, con un puntaje de 37/40 clasificado como Aprobado.

EFECTIVIDAD DE LA APLICACIÓN DE PLASMA RICO EN PLAQUETAS EN LABIOPLASTIA REALIZADA CON LÁSER DIODO

Luis Traviezo — Tue, 03 Oct 2023 12:53:02 +0200

In recent years, the usefulness of PRP (Platelet Rich Plasma) for soft tissue healing has been published. In the gynecological area, it is used to stimulate vaginal and clitoral rejuvenation to recover its function globally, contributing to improving the patient's self-esteem, as well as improving the sexual experience. In the case of labiaplasty, it is indicated in labia minora hypertrophy. Another non-invasive gynecological aesthetic method is the use of Diode laser because it does not require incisions, it is ambulatory and has a fast recovery. At present there are few studies and literature on the matter. Hence, a clinical study was carried out with 28 patients to determine the effectiveness of the application of PRP in labiaplasty performed with Diodo laser, with patients between 20 and 46 years old, who attended consultations due to discomfort, pain in relationships and low self-esteem. 54% presented grade 3 hypertrophy of the labia minora and the remaining 46% grade 2 hypertrophy. After the application of the treatment, 86% did not present complications, only 14% manifested dehiscence. The recovery period was 5 weeks in 50% of the patients. Obtaining a degree of satisfaction in all patients between 9 to 10. PRP has been gaining relevance among gynecological aesthetic treatments, however, due to its recent use there are still few studies that deepen and corroborate its effectiveness. It is necessary to carry out studies in which the clinical evolution, healing and repair of vaginal tissues are evaluated.

Tuning the incompatibility between recycled plastic aggregates and cement matrix with polymer-nano silica hybrids

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:52:36 +0200

Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental benefits. However, the soft plastics and rigid cement matrix can naturally induce the great aggregate-matrix incompatibility, which results in the degradation of engineering properties of cement-based materials containing recycled plastic aggregates (RPAs). To overcome this shortage, this work reports a strategy of tuning the cement matrix with polymer-nano silica (P-nS) hybrids. Ethylene vinyl acetate (EVA) and recycled polypropylene (PP) were selected as the coating polymer and RPA, respectively. Density, strength, water sorptivity and carbonation resistance were measured to assess the physical and mechanical properties of the mortars with recycled PP particles. Microstructure was analyzed using scanning electron microscopy (SEM) with backscattered electron (BSE) and energy-dispersive X-ray spectroscopy (EDS). Results showed that the addition of P-nS hybrids into cement decreases density, mitigates strength reduction, obstructs water sorption, but have positive and negative effects on carbonation resistance of the cement mortars with RPA. The P-nS hybrids build the organic–organic links between the cement matrix and RPA, and coordinate their deformations. The findings of this work proof the proposed strategy of tuning the compatibility between soft aggregates and rigid matrix with the engineered microstructure towards enhancing the recyclability of waste plastics in construction materials.

Recycling of Polypropylene Fibre Reinforced Concrete: Use of Recycled Aggregate and Recovered Fibre in New Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:51:36 +0200

The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete (PPFRC) in new concrete production. The mechanical properties were compared between a parent concrete, polypropylene fibre reinforced recycled aggregate concrete (PPRAC), and recovered polypropylene fibre concrete (Re-PPRFC). All concretes were designed to have the same compressive strength and slump. The parent concrete was produced with 9 kg/m3 of polypropylene fibre. After recycling, the RA and RF were collected and new concretes with RA and RF, PPRAC and PPRFC, respectively, were produced with the same fibre content as the parent concretes. The strain-stress relationship in compression and residual tensile strength were tested. The results obtained for PPFRC, PPRAC and rePPRFC were compared. The results show that the RA and RF obtained by PPFRC recycling can benefit new concrete production.

Numerical Simulation on the Influences of Wind Pressure on Jet Characteristics of Shotcrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:50:37 +0200

A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding with a wall based on computational fluid dynamics theory, in which concrete was regarded as a Bingham fluid. The influences of wind pressures、 pumping speeds、 air incident angles and rheological parameters on five characteristic parameters including spouting velocity, jet velocity, jet trajectory, collision velocity and distribution of shotcrete on the wall were analyzed in depth. Results showed that concrete was gradually mixed well with air in the nozzle with an increasing average velocity, and the increase of velocity was most pronounced in the contraction section of nozzle. With the increases of wind pressures and pumping speeds, the spouting velocity and spouting mass of concrete both increased. Higher wind pressure and pumping speed led to larger jet velocity and more concentrated distribution, resulting in significantly longer jet distance, higher collision velocity and larger distribution area. The collision velocity and volume fraction of concrete on the wall were distributed symmetrically along Y axis, shifting towards the direction of gravity. With the increases of air incident angles, the spouting velocity and spouting mass of concrete both decreased, the shifting to gravity is weakened and the volume fraction decreased first and then increased. When plastic viscosity decreased, the spouting velocity and spouting mass of concrete both increased, accompanying with a higher jet velocity, a longer spraying distance and a larger distribution area.

Effect of Pre-calcination of Lead-zinc Tailings on the Activation of Blast Furnace Slag

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:49:36 +0200

Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs were pre-calcined at different temperatures and then explored whether it is capable of being the activator of slag. The effects of pre-calcination on the phase composition of LZTs were elucidated by XRD. The compressive strength of LZTs-activated slag pastes was investigated, and the mineral composition and microstructure of the pastes were detected by XRD and SEM. The results imply that with the elevating of heating temperature from 500 ℃ to 1000 ℃, the dolomite in LZTs decompose into CaO and MgO, and the oxidation of pyrite resulted in the formation of Fe2O3 and gaseous SO3, then SO3 reacted with a part of formed CaO to produce CaSO4. The resulting CaSO4 and CaO can become the sulfate activator and alkaline activator of slag, respectively. The LZTs-activated slag pastes prepared with the LZTs preheated at 800 ℃ exhibit the highest strength at 90 d, which yield 24 MPa. The hydration products of LZTs-activated slag were ettringite and calcium silicate hydrates (C-S-H gel). Large amounts of dense C-S-H gel bond together, connecting most of the ettringite networks into a whole, thus forming a dense structure and effectively improving the strength of LZTs-activated slag. The outcome of this study provides a potential disposing or reusing approach of the large amounts of LZTs.

Probability Durability Assessment of Existing Concrete Structures in Carbonation Environment

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:48:36 +0200

In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. This paper presents a methodology for assessing the probability durability of existing structures, taking into account the nondestructive testing results and the target reliability index. The initial step involves introducing a correction coefficient into the carbonation and corrosion development theory model. This coefficient is necessary to account for the correction associated with the corrosion monitoring of steel. The values of this coefficient should be determined based on the actual testing results, specifically considering the presence of reinforcing steel corrosion. Next, a probability expression is proposed using the measured results of probability characteristics and the target reliability index. This approach takes inspiration from the design-value method and the existing theory of structure reliability. It also takes into account the specific variables of concrete protective cover thickness and the compressive strength as the fundamental random variables. The residual working life can be calculated as the outcome of a durability assessment through quantitative analysis. This calculation can serve as a valuable reference for the maintenance program.

Overview on Testing Method of Internal Damage to Special-shaped Stone Components in Palace Museum

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:47:37 +0200

Irregular historic stone components are very important parts of the ancient architecture in the Palace Museum. They have been subjected to deteriorations from surface to interior under the combined effects of many factors such as wetting and drying, salt dissolution and recrystallization, selfload, external load, and environment action. The internal damages in these stone components are difficult to detect but are crucial for the assessment of the intact of these components. In order to detect the internal damage of stone components, especially the special-shaped stone components, which cannot be tested by comment methods. Taking evaluation on preservation status of stone components in a qualitative and quantitative way， with application of ultrasonic computerized tomography and regular inspection, a convenient, safe, economical, efficient, and readable method for detecting the internal damage of irregular stone components can be established in order to detect any safety hazards as early as possible and provide data support for assessment and conservation, achieving a better preventive conservation.

Evaluating the Future Moisture Performance of the Stucco-Clad Wall Assembly in Selected Canadian Cities

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:46:37 +0200

Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed to such climate could experience a higher moisture load than in the past, which could have a negative impact on its performance in the long run. The stucco-clad wall assembly, which has been widely employed in the construction of low-rise residential buildings throughout Canada may not be adequately designed to be resilient to the future climate. Thus, in the study described in this paper, the future moisture performance of the stucco-clad wall assembly located in two Canadian cities with different levels of moisture load, i.e., Vancouver and Calgary, subjected to projected future climate is investigated. The analysis includes two phases: conducting watertightness for a full-scale stucco wall specimen to determine the relationship between the climate data and the moisture load in the wall assembly and implementing hygrothermal simulations using the relationship obtained from the watertightness test for the performance assessment. Mould growth index at the exterior surface of the oriented strand board of stucco-clad wall assembly for the historical and projected future time periods is compared and discussed.

UN PASO FIRME EN LOS ESTUDIOS DE LA GINECOLOGÍA REGENERATIVA

Luis Traviezo — Tue, 03 Oct 2023 12:46:03 +0200

El área de la ginecología regenerativa data de más de tres décadas en el mundo, y en nuestro país, Venezuela, tiene sus inicios desde el 2007, a través, del Dr. Jorge E. Gaviria, quien inicia con los primeros avances en esta ciencia, continuando ese legado hasta la actualidad, donde se ha mantenido una formación continua en, talleres, diplomados y training, sistematizados, donde los que trabajamos en el área, queremos la mejor formación para el discípulo.

Hoy decidimos reforzar con un espacio abierto para la publicación, las experiencias que hemos desarrollado, no solo en Venezuela, sino en toda Latinoamérica, específicamente en este maravilloso campo de las ciencias médicas.

El área de la ginecología regenerativa, enfoca de manera integral el manejo de nuestras pacientes, para el mejoramiento de su función sexual y por ende de su calidad de vida.

Nuestra revista, representa el vehículo expedito de difusión, en el avance científico, en esta área emergente, constituyendo el medio de expresión de las distintas especialidades entre los grupos de investigación que desarrollan esta disciplina.

Igualmente, constituirá un elemento inestimable para la formación continua de los profesionales que practican o desean incursionar en esta área, tanto por la actualización, como por las pautas que puedan ser recomendadas a través de los diversos trabajos de investigación.

Es para nosotros, un logro indescriptible a través de la logística y organización de nuestro comité editorial, en especial del Dr. Traviezo, por haber abierto las puertas a un área emergente, que solo va en pro de la mejora de su calidad de vida y del esmero en la construcción de su femineidad.

Esta revista tendrá como eje central la ginecología regenerativa, pero no será excluyente de todos los profesionales de áreas y temas afines, que tengan el propósito de acompañarnos.

La Revista Latinoamericana de Ginecología Regenerativa, tiene ya proyectada su inclusión en los distintos y mejores índices y plataformas electrónicas internacionales, para garantizarle a autores y usuarios en general, la mayor y mejor visibilidad de los artículos, las 24 horas del día, los 365 días del año, con el respaldo DOI de cada artículo y garantizando el acceso gratuito y oportuno a todos, para contribuir, desde nuestra humilde tribuna, al acceso libre a la información, en esta importante área de las ciencias de la salud.

La revista recibirá manuscritos durante todo el año y tendrá una regularidad semestral (dos números al año, junio y diciembre) e igualmente podrá contar con suplementos especiales, por volumen, los cuales dependerán de la misma dinámica que exista entre la revista y sus colaboradores.

No me queda más que, en nombre de todo el comité editorial, darles la bienvenida a nuestra revista, la cual está abierta a todas sus contribuciones y sugerencias, para que juntos, naveguemos en este bello río de conocimientos científicos, que nos unen en la ginecología regenerativa, sin olvidar que, la investigación continua, es el camino para el aprendizaje a lo largo de la vida y la perfección en el acto médico.

Analysis of Thermal Bridges in Concrete and Cross-Laminated Timber (CLT) Constructions: A Numerical Study

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:45:35 +0200

The thermal efficiency of a building envelope relies on various factors, including insulation resistance, continuity, the thermal conductivity of structural materials, and the presence of thermal bridges. This study focuses on studying the thermal performance of thermal bridge details in two construction types: concrete and Concrete and Cross-Laminated Timber (CLT). For the study, two common building envelope details with significant thermal bridges are considered, balcony and intermediate wall-to-floor connections. Utilizing the finite element program COMSOL Multiphysics, hourly transient simulations were conducted over a one-year period to assess the heat loss/gain associated with thermal bridges, considering daily, seasonal, and annual heat flow for two diverse climatic conditions (hot weather Houston-Climate Zone 2 and cold weather Toronto-Climate Zone 6). The findings demonstrate that thermal bridges constructed from CLT outperformed those made of concrete. In Toronto, the annual heat flow for the concrete balcony was 146% higher compared to CLT, while in Houston, it was 67% higher. However, this trend was significantly reduced for the wall-to-floor detail, with a concrete detail showing a 13% increase in heat flow for Toronto and a 7% decrease in annual heat flow for Houston. Furthermore, the dynamic analysis revealed notable heat flow magnitude changes in the balcony detail, highlighting the importance of thermal conductivity, while the wall-to-floor detail exhibited dampening fluctuations in heat flow, emphasizing the material's heat capacity importance in this context.

Use of Machine Learning in Processes Optimization for Drinking Water Treatment Plant Butoniga (Istria, Croatia)

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:44:38 +0200

Drinking water treatment plant Butoniga is located in central Istria (Croatia) downstream of the Butoniga reservoir. The Butoniga reservoir is an artificial lake created in 1987 with two main objectives: 1) protection from adverse water impacts, and 2) drinking water supply. The operation of the drinking water treatment plant is mainly related to the tourist season, and the 5.000.000 m3 of produced and distributed drinking water annually, 3.000.000 m3 is produced and distributed during June 15 to September 15, when the raw water quality in the Butoniga reservoir is the worst. Regarding this, main problem with Butoniga reservoir and thus drinking water treatment plant appear in summer months when water temperature is the most critical parameter and raw water for the treatment process must be captured from the lowest layer of the reservoir which have increased concentrations of Mn, Fe, NH4 and lower pH values and thus influence on the treatment processes. To deal with this problem, model predicting Mn, seven days in advance is build using machine learning approaches. Build model have high accuracy compared to the measured data, with a good prediction of the peak values. As such, obtained model can help in optimization of the treatment processes which are depending on the quality of raw water, and overall, in sustainability and management of the drinking water treatment plant Butoniga.

Proposal of Soundness Index for Existing RC Apartment Building for Proper Management Through Visual Monitoring

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:43:40 +0200

A numerical index for housing complexes of reinforced concrete maintained properly was proposed. First, based on the literature review, deterioration grade and a method for evaluating soundness for RC housing complexes, which determined by visual inspection, was proposed. And then, accelerated deterioration experiments of small RC wall and investigation of existing buildings were conducted. From the study, a correlation between the deterioration grade determined visually and rebar corrosion grade was confirmed. By using building health H(t), that is proposed as index of soundness for existing RC housing complexes, RC housing complexes whose age were 46 to 69 years were evaluated. From the study, it was confirmed how much deterioration the evaluation value indicates.

Effect of Moderately Elevated Temperatures on Performance of Portland Cement Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:42:37 +0200

High temperature is one of the critical factors leading to the change in concrete performance since it affects the physical structure and chemical components of concrete. However, some concrete structures are continuously subjected to moderately elevated temperatures (typically less than 200 ℃) when operating, such as chimneys for the metallurgical industry and structures in nuclear power plants. The deterioration process of these structures could be caused and accelerated by a high-temperature environment. Thus, the safety and performance of these concrete structures at elevated temperatures during service life are crucial. This paper aims to investigate the change in concrete performance exposed to sustained moderately high temperatures. The concrete cured for 56 days was subjected to temperatures ranging from 65℃ to 200 ℃ for 28 days. The mechanical properties of concrete at different heating temperatures were tested, including compressive strength, splitting tensile strength and modulus of elasticity. Meanwhile, concrete’s durability after heating was evaluated using the concrete electrical resistivity test. The concrete elevated-temperature performance was compared to identical concretes at room temperatures, and the evolution of each property was analyzed. Based on experimental results, the long-term performance of concrete in a moderately elevated temperature environment is predicted.

Heavy Metals Immobilization Property and Mechanisms of LDHs-modified Cementitious Materials

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:41:36 +0200

Layered double hydroxide (LDH) has a positive effect on the adsorption and immobilization of heavy metals. The compressive strength and the heavy metal ions Pb2+ immobilization of CaAl-LDH modified cement paste were studied in this paper. Through research, it was found that compared with the cement paste sample with a Pb2+ content of 1% after curing for 7d and 28d, the addition of CaAlLDH to the cement paste sample increased the compressive strength by 6.1% and 1.6%, respectively, demonstrating the enhancing effect of CaAl-LDH on the strength of cement paste. Compared with the sample containing only Pb2+, the addition of CaAl-LDH to the cement increased the immobilization rate by 0.3% after 12 hours of leaching time and showed varying degrees of improvement at different leaching times. The immobilization mechanism of heavy metals in LDH blended cement paste was revealed by microstructure characterization. It was founded that Pb2+ can replace Ca2+ in AFt, AFm, and LDH, and can co-precipitate with OH-.

Chemo-physical Analysis on Corrosion Initiation of Offshore Structures under Chloride Attack

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:40:36 +0200

Chloride ingress has been recognized as a main factor inducing the corrosion of offshore reinforced concrete structures. It is acknowledged that the chemical attack can lead to concrete property deterioration, which inevitably affects the reinforcement corrosion. Herein, the influence of the concrete aging on the chloride-induced corrosion initiation is systematically evaluated by a novel numerical framework. In this framework, the chemo-physical analysis is conducted based on coupled NernstPlanck model and Gibbs energy minimization model. The proposed method is first validated against reported experimental results. It is found that the chloride ingress is always accompanied by leaching of hydrates near the exposure surface, leading to the porosity enlargement. Moreover, due to chemical binding of chloride to monosulfoaluminate, ettringite continuously precipitates under the function of released sulfate ions. Through a series of numerical analyses, it is revealed that the newly formed hydrates impose competitive effects on chloride transportation due to the simultaneous pore-clogging and expansion-induced microcracks. Chloride-induced corrosion occurs earlier in the situation that the effect of microcracks overcomes that of pore clogging, otherwise, the corrosion is delayed.

Carbonation-induced Early Corrosion Propagation Based Service Life Assessment Model (CECP-SAM)

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:39:35 +0200

Supplementary cementitious materials (SCMs) are widely used for sustainable concrete. However, this is challenged due to the deteriorated resistance towards carbonation-induced corrosion. This paper introduces the establishment of a novel carbonation-induced early corrosion propagation based service life assessment model (CECP-SAM). This model is characterized by considering the early corrosion propagation (incipient cracking) and the use of supplementary cementitious materials. Based on experimental and numerical methods, the effects of binders, water/binder (W/B) ratio, exposure condition, cover thickness, rebar diameter, semi-carbonation zone, cathode-anode ratio on service life are investigated by CECP-SAM. The model is justified by using the results from a field investigation in Hong Kong. Performance-based service life equations are also given based on CECP-SAM.

Service Life Prediction of Concrete Against Freezing and Thawing Based on Water Absorption Results

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:38:38 +0200

Freezing and thawing resistance performance of concrete is a critical issue when evaluating the durability performance of concrete. This paper aims to predict the freezing and thawing resistance performance of concrete based water absorption indexes, meanwhile, five groups of experiments on porosity, short-term water absorption, long-term water absorption, MIP and pore structure scanning were respectively carried out for concrete. According to the experimental results, the important indexes such as porosity, water absorption, gas content and bubble spacing coefficient were obtained, which provided the basis for the prediction of durability and service life. The concept of equilibrium time ratio is introduced to simplify the calculation process. Based on the critical saturation theory, the service life of concrete against freezing and thawing is predicted by combining the environmental parameters and the indexes measured in experiments. The calculated results verified that the freeze-thaw durability life of air-entrained concrete is significantly increased compared with that of concrete without air-entrained concrete. In addition, a wide range of the service life was predicted for the 5 mixes, and the results could provide a guidance for selecting a proper mix design of concrete subjected to freezing and thawing.

Microstructure of Cement Paste with Expansive Additives under Free and Restrained Conditions

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:37:37 +0200

Expansive additives (EAs) have been widely used to reduce the risk of cracking due to shrinkage. Such additives cause early age expansion of concrete due to the formation of Portlandite and Ettringite in the pores of the cement paste, which affects the cement paste's microstructure. The presence of external restraints in the form of reinforcement and support affects the expansion and, ultimately the microstructure of cement paste. In the current study, the microstructure of cement paste with expansive additives is studied using mercury intrusion porosimetry (MIP). A free lime-based EA, with 10 and 15% (by weight) cement replacement ratios, is studied in the current study. The porosity and pore size distribution of the cement paste with EA were studied under free and restrained conditions. Results show that the under the stress-free condition, the porosity of the paste increased, while under the restrained condition, the porosity remained much similar to the reference case of OPC. Further, the pore size distribution of the cement paste with EA under free and restrained conditions is explained, and the effect of EA and restraint on the microstructure is discussed.

Study on Release Performance of Concrete Release Agent

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:36:38 +0200

In this paper, the effects of types of concrete release agent, the amount of brushing per unitarea and the 1d's strength of concrete on the release performance were studied. The adhesion and filmforming ability of O/W emulsion release agent was improved by adding high polymer. The results showthat the 1d's strength of concrete has no effect on the release performance of the release agent. The mostimportant factors affecting the release performance are brushing amount per unit area and the type ofrelease agent. O/W emulsion release agent with polyacrylamide and polyethylene glycol all stick mold. The more they are added, the heavier the stickiness is. While, the release performance with polyethyleneglycol is very close to blank sample.

Properties of Mineral Powders Modified Foamed Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:35:35 +0200

In order to improve the stability of lightweight foamed concrete, the particle-stabilized foam (PSF) has been proposed because of its high stability. However, most PSFs added particles to foams, and few researchers have investigated whether the stabilization effect exists when particles are added to the paste. In this study, a new type of foamed concrete was prepared by adding different kinds of mineral powders to cement and using ionic surfactants to prepare foam. The influence of different mineral powders on the mechanical properties and durability of foamed concrete was investigated. Results showed that mineral powders decreased the drainage and disproportionation of foam, which stabilizes the foam. The excellent stability is attributed to the interaction between the mineral powders and ionic surfactants, which allows the mineral powders to adhere to the foam surface and form a dense granular film layer. Moreover, due to the interaction between mineral powders and ionic surfactants, hardened foamed concrete has a robust pore structure, which improves its properties.

Influence of Alkali-resistant Glass Fibers Distribution on Properties of Cementitious Composites

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:34:38 +0200

The waste hierarchy establishes a prioritized framework for effective waste management, where higher levels such as prevention, re-use, and recovery are associated with the conservation of primary resources and the retrieval of secondary resources. This approach aligns with the objectives of the construction industry, which aims to promote the efficient utilization of resources by treating raw materials in an environmentally responsible manner. In this context, utilizing waste fibers to reinforce cementitious composites becomes more logical than producing new fibers with similar properties. These waste fibers typically originate from the production of high-performance technical textiles used for structural repair and rehabilitation. By reusing these waste materials, the construction industry contributes a circular economy in its own sector and fosters cross-sectoral industrial symbiosis. Although the potential benefits and positive environmental impact of utilizing such materials are recognized, their influence on the properties of composites requires further investigation. This study examines the impact of production waste glass fibers on the properties of the mortar in both the fresh and hardened states. The study focusses on properties such as compressive strength and toughness. To gain a better understanding of the fibers’ contribution to the matrix properties, an investigation was conducted using µCT. The study focuses on investigating the effects of waste fibers with lengths of 5 and 10 mm and different dosages (0.2, 0.6 vol.%) on the properties of high-strength mortar, comparing them with factory fibers.

Study on Natural Passivation Behavior of Corrosion-resistant Steel Rebars in the Mortar

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:33:35 +0200

The passivation behavior of HRB400 carbon steel rebar, 304 austenitic stainless steel rebar and 2304 austenitic-ferritic duplex stainless steel rebar during curing stage of mortar was studied by electrochemical testing techniques such as open-circuit potential, electrochemical impedance spectroscopy and linear polarization curve, and the corrosion resistance of the passivation film of the three rebars was compared to provide a reference for the practical engineering application of corrosion-resistant steel rebars. The study shows that all three types of steel rebars can be passivated during the 28 days curing stage of mortar, and 2304 duplex stainless steel rebars have the best passivation film corrosion resistance, followed by 304 stainless steel rebars, and HRB400 steel rebar was the worst.

Property and Environment Evaluation of Cement Replaced with Treated Reclaimed Concrete Slurry Waste

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:32:38 +0200

The development of the cement industry consumes piles of natural resources and generating huge amount of waste and causing serious pollution, which can be partially solved by replacing with other cementitious materials, in particularly, solid waste. Reclaimed concrete slurry waste (RCSW), a corrosive and hazardous the residues from the reclaimed system for retrieving the aggregates from the returned concrete or cleaning the concrete mixer and trucks in the ready-mixed concrete plant, could that cannot be used to manufacture reclaimed concrete. However, the pre-hydration limits the hydraulic property of RCSW, which requires the proper treatment. This paper investigated the effect of three different treatment methods in improving the performance of RCSW and its feasibility of replacing cement under different substitution ratio in manufacturing reclaimed concrete. The treatment included sieving, shearing and ball-milling, and the substitution ratio was set as 15%, 30% and 45%, respectively. In addition to compressive strength and hydration properties, the environment impact of the cement paste replaced with RCSW were investigated as well. The results showed that compared within three methods, the shearing and ball-milling generated the treated RCSW with smaller particle size and high roundness. For the RCSW substituted cement paste, the substitution with 15% of treated RCSW provided the highest strength, meanwhile, while at a higher substitution ratio significantly reduced the compressive strength. The 15% of ball milling treated RCSW produced more products during the hydration process, resulting in a denser structure. According to the economic and environmental calculations, RCSW substitution reduced CO2 emissions, in which, the ball-milling method showed a lower carbon footprint.

Oxygen Diffusion Property of Fatigue Damaged Concrete under Drying-wetting Cycle

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:31:37 +0200

Oxygen diffusion has an important influence on the corrosion process of reinforced concrete structures. In the marine environment, concrete is subject to both fatigue loads and periodic drying-wetting conditions. In this study, the oxygen diffusion performance of damaged concrete due to fatigue is studied under drying-wetting cycle condition, which is of great significance to the development of concrete durability theory. The pore structures of concrete specimens with different damage degrees after drying-wetting cycle were measured by nuclear magnetic resonance (NMR). The effects of drying-wetting cycle and damage degree on pore structure were studied, and the oxygen diffusivity of damaged concrete before and after drying-wetting cycle was compared and analyzed. The results show that the pore size distribution curves of concrete specimens move to the smaller pores and the peaks decrease after 28 days of drying-wetting cycle. The proportion of gel pores (< 10 nm) increases and the proportion of medium and large capillary pores (10 - 1000 nm) decreases. After the drying-wetting cycle, the porosity of the damaged concrete specimens all decreased to certain degrees. It shows that the microstructure of the specimen is improved and the internal structure of concrete becomes more complex in the early stage of drying-wetting accelerated erosion. After the drying-wetting cycle, the oxygen diffusivity of all concrete specimens decreased, and the oxygen diffusivity of undamaged concrete decreased the most, about 10 times, but with the increase of damage degree, the reduction effect generally decreased.

Optimal Amorphous Oxide Ratios and Multifactor Models for Binary Geopolymers from Metakaolin Blended with Substantial Sugarcane Bagasse Ash

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:30:35 +0200

As a potential precursor, the utilization of sugarcane bagasse ash imparts enormous technical and environmental benefits to human society. However, its rich crystal content challenges the mix design of sugarcane bagasse ash-involved geopolymers. The present study is aimed to contribute toward the substantial utilization of sugarcane bagasse ash in geopolymers and develop a guideline for designing binary geopolymers from metakaolin and sugarcane bagasse ash. The experimental results show that when suitably designed, the compressive strength of metakaolin-sugarcane bagasse ash geopolymers satisfied the structural use in building engineering, and the sugarcane bagasse ash proportion could substantially reach up to 50%. Moreover, through a combination of mechanical, economic and environmental assessments, the optimal mixing proportions fall into the following ranges: SiO2/Al2O3=4.63~5.60, Na2O/Al2O3=1.5~2.0 and H2O/Na2O=8~10. Further, multi-factor models are proposed to regulate the mix design of binary geopolymers, with a R2 value beyond 0.9 .

Negative Emission Potentials Using Biogenic Building Materials - A Case Study from Denmark

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:29:40 +0200

Significant reductions in carbon footprint can be achieved by increasing the use of biogenic materials in construction. In biogenic materials, carbon is embedded as long as the materials are not biologically degraded, and they consequently act as carbon reservoirs that keep CO2 out of the atmosphere. The reservoirs of carbon are maintained if the biogenic materials during maintenance and renovation are replaced by similar ones. Buildings containing more wood, straw, and other biogenic materials and less concrete, steel, and mineral wool are therefore part of the way forward for a sustainable restructuring of the construction industry. Until now, the main focus has been on reducing energy consumption of buildings, while less focus has been on energy consumption and the climate impact from the production of materials and the construction process itself. This paper examines the potential carbon reservoir in the building stock in Denmark for the next 100 years. In detail the paper describes potential building components made from biogenic resources, outlines the necessary amounts and qualities of biogenic materials, and summarizes the available biogenic resources. The article is based on the conditions for construction in Denmark and the opportunities Denmark has as an industrialized agricultural country with a long coastline, which can be utilized in the production of biogenic resources for manufacturing of building materials.

Molecular Dynamics Study between Amine Solution and Calcium Hydroxide

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:28:37 +0200

Carbon dioxide can be captured by amines and carried into calcium hydroxide to generate calcium carbonate. In this study, molecular dynamics simulations were performed to study the interaction energy and structure between amine solution and calcium hydroxide crystal slab at the molecular level. MDEA was chosen as a representative amine. According to the one-dimensional concentration function, it was found that at a low ratio of MDEA, it was preferentially distributed close to the calcium hydroxide. And as the content in the solution increased, MDEA was gradually distributed equally throughout the aqueous solution. Compared to water, the interaction energy between MDEA and calcium hydroxide is greatly reduced and gradually decreases with increasing amine content. This means that the interaction between the two is reduced, and the reaction is more difficult to occur. In addition, the system of carbon dioxide dissolved in a solution of amine and water was simulated. The distribution of carbonate and bicarbonate was found to be relatively uniform at MDEA ratios of 5% and became irregular above 20%.

Laboratory and Pilot Investigation on Properties of precast Engineered Cementitious Composites (ECC) Subjected to Carbonation Curing

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:28:05 +0200

The concrete industry is facing an increasing challenge for sustainability. Besides the large embodied carbon, the intensive operational carbon associated with repetitive repair becomes the main hurdle for lifecycle emission reduction. In this study, the feasibility of sequestering CO2 into durable engineered cementitious composite (ECC) through early-age carbonation curing was investigated. The goal is to demonstrate a simultaneous reduction of the material’s embodied carbon (by CO2 sequestration) and lifecycle emissions (by ECC’s superior durability). The material was processed at both lab and pilot scales and was demonstrated on precast pedestrian pavement slabs. Results show that ECC was highly reactive to CO2 at lab scale, with 26.5% CO2 uptake by cement mass after 24-hour carbonation. However, the early-age carbonation was subjected to a significant size effect and attained a 4.3% CO2 uptake for pilot-scale specimens with a low specific surface area. Despite this reduction in carbonation efficiency, the calcite precipitation through carbonation curing was found to densify the fiber/matrix interface and improve the composite ultimate tensile and flexural strength by up to 28.8%. Carbonation curing also enhanced ECC’s crack width control, thus mitigating sulfate attack and lowering surface salt scaling on freeze-thaw exposure. It is suggested that producing ECC through carbonation curing is technically viable, and the carbon-sequestered ECC is recommended for small-scale precast components for enhanced durability and sustainability.

Impact of the Thaumasite Sulfate Attack on the Pore Structure and Gas Permeability of Cement Mortar

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:27:47 +0200

In this study, the impact of the thaumasite sulfate attack (TSA) on cement mortar was investigated by comparing it to the ettringite sulfate attack (ESA). Mortar specimens with three binders, corresponding to the blank, ESA, and TSA, were exposed to sulfate solution. The evolutions of thaumasite and ettringite formation, pore structure, and gas permeability on the mortar specimens were characterized through XRD, 1H NMR, and CemBureau device. The experimental results show that: (1) both ettringite and thaumasite were formed in TSA; (2) ESA reduces the capillary pore space, whereas TSA decreases both the capillary pore and interlayer pores; and (3) ESA decreases the gas permeability while TSA significantly increases it.

Fracture Process of In-situ Polymerization Modified Cementitious Materials

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:27:33 +0200

By regulating cement hydration reaction and organic monomer polymerization, the strength and deformability of in-situ polymerization modified cement-based materials are greatly improved. However, the fracture processes of this type of organic-inorganic composites have not been systematically investigated. In this work, sodium acrylate (SA) monomer in-situ polymerization modified cementitious composites (iPSA) were fabricated. Three-point bending (TPB) test was conducted with digital image correlation (DIC) technique for characterizing the fracture process zone (FPZ). Microscopic test was conducted to unravel the crosslinked organic-inorganic composite structures in the iPSA matrix. Results showed that an obvious strain concentration region occurred and grew at the notch tip of the iPSA beams with load. The gradually expanding width of FPZ was normally distributed. Microscopic test suggested that the physical interlinks between the cement hydrates and sodium polyacrylate may resist again the FPZ development of iPSA. The findings of this work would deepen the understandings of fracture process of polymer modified cementitious composites with broad engineering applications.

Evaluation of Carbonation Degree of Hardened Cement Paste with Different Water-Cement Ratio in Wet-Dry Cycle

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:27:20 +0200

One of the global environmental problems, CO2 emissions from cement production intensifies in these decades. To solve this problem, countermeasures for CO2 emissions using waste concrete, which has ability to absorb CO2 due to contain calcium-silicate-hydrate (C-S-H) and portlandite (Ca(OH)2), are in the spotlight recently. However, considering the limited time before recycling as roadbed materials, it is important to increase CO2 absorption efficiency so that as much CO2 as possible reacts with waste concrete. In this study, hardened cement paste powders (HCPWs) with the water-to-cement ratios of 0.4, 0.5 and 0.6 were evaluated for the degree of carbonation under various humidity conditions. HCPWs were pulverized to a particle size of 0.6 to 1.18mm and put in desiccators keeping constant humidity condition of RH60 and RH80. In addition, desiccators were prepared with RH60-80 cycle (wet-dry cycle) of 30 minutes, 1 hour, 2 hours and 4 hours to determine the degree of carbonation promotion according to periodic humidity changes. The degree of carbonation of HCPWs were measured by thermogravimetric analysis (TGA). The result shows that the degree of carbonation was improved as the water-cement ratio increased, because the higher the water-to-cement ratio, the more open pores were contained. In addition, vaterite and aragonite caused by the decomposition of C-S-H were the most produced under RH60-80 cycle conditions. This is considered to be because the reaction area with CO2 was increased by weakening the C-S-H by repeating drying and wetting.

Evaluate the Ability to Determine the Carbonation Depth of Concrete by Hyperspectral Imaging

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:18:20 +0200

In recent years, using concrete to absorb CO2 in the atmosphere has attracted attention as one of the global warming countermeasures. In general, destructive methods have been used to evaluate the amount of CO2 absorption in concrete buildings and civil engineering structures. However, it needs to sample a portion of the concrete, and it is impractical to conduct continuous disruptive sampling of the structures in use. Therefore, it is necessary to develop non-destructive tests to evaluate the amount of CO2 absorption in concrete. In this study, Multi-spectral imaging, which are the methods of non-destructive tests, were used to visualize the presence of calcium carbonate with depth-axis from surface of the concrete specimen which have been the preliminary drilled holes. In addition, moistened cotton swabs were used to extract the pore solution by pressing the inner wall of the hole and to test it for determination of the distribution of pH with depth. The results indicate that Multi-spectral imaging can evaluate different carbonation depths of concrete samples. Moreover, PH of each point examined in the specimens can evaluate as the depth distribution of calcium carbonate. Results were compared and discussed with each other depending on each methodological characteristic.

Effects of Multi-scale Siliceous additives on Hydration and Microstructure of Hardened Cement Pastes

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:17:57 +0200

Siliceous materials are commonly used in concrete with physical filling and higher pozzolanic reactivity, such as silica fume (SF) and nano-silica (NS). Investigations were conducted into the effects of SF, hydrophobic silica fume (HSF), and synthesized NS on the mechanical properties and microscopic characteristics of hardened cement pastes (HCPs). The surface of silica fume was hydrophobically modified using isooctyltriethoxysilane. Fourier infrared spectrometer (FTIR), X-ray diffractometer (XRD), and energy spectrometer (EDS) were used to evaluate the hydration, while mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were used to analyze the pore structure and microscopic morphology of HCPs. The results demonstrated that HSF has better dispersion in cement pore solution. The addition of HSF exhibits the higher pozzolanic reactivity, weakens CH diffraction peaks, generates higher levels Q3 C-S-H gels, and significantly lowers the Ca/Si ratio of C-S-H gels. Due to the hydrophobicity, HSF increases the volume of micro-pores in range of 10-100 nm, resulting in a decrease in strength. Compounding HSF and NS further weakens the CH diffraction peak, decreases the Ca/Si ratio of C-S-H gels, and reduces the micro-pore volume to refines the pore structure.

Effect of Sulfate Attack on Compressive Strength of Foamed Cement Paste under Static Cyclic Loading

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:17:45 +0200

Foamed cement paste has been increasingly used as backfill material in roadways and railway embankments due to its advantages of adjustable density and strength. The embankments constructed by foamed cement paste in coastal regions is subjected to both traffic loading and chemical erosion in service life. This paper conducted a series of durability tests to investigate the reduction of static and dynamic strength of foamed cement paste after the specimens were immersed in sodium sulfate solutions.The specimens were prepared with densities of 800 and 900 kg/m3. The influence factors of specimen density, concentration and cation type of sulfate solution on the strength degradation of the specimens were discussed. The results showed that the corrosion resistant coefficient of the specimens was reduced with the increase of immersion time and concentration of sodium sulfate solution. The degradation of the compressive strength under cyclic loading is more serious than that under static loading. The high density specimens perform better durability than low-density specimens, as the specimens with 900 kg/m3 under 28 and 56 days of sulfate attack had smaller reduction in both dynamic and static strengths than the specimens with 800 kg/m3.

Effect of Endogenous Chloride Ion on Corrosion of Rebar in Sea-sand Ultra-high Performance Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:17:24 +0200

Ultra-high performance concrete (UHPC) is an innovative cement-based composite material characterized by extremely high durability and mechanical properties, which provides a potential possibility of using non-desalted sea-sand as aggregate. However, the long-term steel corrosion behavior in UHPC prepared by simulated sea-sand under different immersion environments remains unclear. In this study, the pore structure of sea-sand UHPC matrix was measured using nitrogen adsorption/desorption method. The corrosion behavior of rebar in sea-sand UHPC with different endogenous chloride ion contents soaking in pure water and NaCl solution was characterized by electrochemical workstation. The experimental results show that the initial UHPC pore structure is refined by incorporation ofsea-sand, and is similar to that of ordinary UHPC at the later hydration. Regardless of the endogenous chloride ion content and immersion environment, the corrosion rate evaluated by corrosion current density (icorr) and polarization resistance (Rp) of reinforcement in UHPC is extremely low. The measurement of EIS shows that UHPC group has higher matrix resistance (Rc) and charge transfer resistance (Rct), while lower electric double layer capacitance (CPEdl) of reinforcement, which indicates that the steel in UHPC made of sea-sand is still in a state ofpassivation. However, the steel bar in comparison specimen OPC soaking in NaCl solution is in the corrosion stage. Furthermore, sea-sand UHPC possesses of excellent ability of anti- pitting corrosion ofreinforcement after 180 days ofimmersion in NaCl solution.

Carbonation of Concrete Cured Under Different Conditions

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:17:08 +0200

Concrete is cured under different conditions to preserve the moist state of the concrete matrix for continuous hydration as it is done on most construction sites. In this study, the effect of different curing techniques on the carbonation depth of concrete mix is presented. Concrete matrix of mix ratio 1 :2 :4 with a water-cement ratio of 0.5 was prepared and cast into cubes of sizes 150 mm. After 24 hours, the concrete cubes were removed from moulds and cured using different techniques for 3, 7, 28, 56, and 91 days. Thereafter, the compressive strength of the concrete cubes and carbonation depths were determined for each curing day. The curing techniques investigated were immersion in water (IM), sprinkling (SP), polyethylene membrane (PM), damp sand (DS), indoor (OI), outdoor (OT), and saturated wet covering (SWC). The results indicated that carbonation depth differed with each of the concrete cured in different techniques. It was observed that concrete exposed outside was worst affected by carbonation followed by those cured indoor, while those cured with polythene showed the least carbonation depth. It was concluded that the polythene membrane curing technique was the best curing technique to limit the effect of carbonation of concrete.

Biomimetic Organic-Inorganic Hybrid Magnesium Oxychloride Cement as Green Adhesive for Biomimetic Organic-Inorganic Hybrid Magnesium Oxychloride Cement as Green Adhesive for Wood Industry

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:16:55 +0200

Benefiting from the negative carbon footprint of wood, wood composites have been considered as eco-friendly alternative building materials. However, adhesives for bonding wood components are mainly formaldehyde-based resins, which are highly combustible and continuously release volatile hazardous substances during service. Therefore, the development of magnesium oxychloride cement (MOC) as wood adhesive is highly compliant with environmental regulations and green material requirements. Unfortunately, the extensive application of MOC adhesive is hindered by poor water resistance and weak interfacial interaction with wood. Herein, an oyster-inspired organic-inorganic hybrid strategy was proposed to develop MOC with high adhesion strength and excellent water resistance. Specifically, the renewable chitosan (CS) and tartaric acid (TA) were selected as organic reinforcing constituents to construct a dense double chelating network in MOC, which induced the structural regulation at the bonding interface, thus enhancing the cohesion strength and interfacial properties. Thanks to the biomimetic organic-inorganic hybrid structure, the dry and wet shear strength of the MOC-CS-TA reached 3.08 MPa and 1.77 MPa, making increases of 27.27% and 53.91% compared to the control sample, respectively. Meanwhile, the MOC-CS-TA adhesive presented excellent flame-retardant properties compared with urea-formaldehyde resin adhesives and soy protein adhesives. The design path presented here provides workable guidance for the preparation of eco-friendly cementitious materials and green wood composites in further applications.

Application of Nanomaterials for Enhancing the Performance of Recycled Aggregate Concrete-A Short Review

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:16:40 +0200

Incorporation of recycled concrete aggregates (RA) produced from construction and demolition wastes in concrete contributes to the sustainability from two perspectives: reducing environmental pollution and reserving natural resources by reducing the consumption of natural aggregates (NA). However, comparing to NA, RA has lower mechanical properties and higher water absorptivity due to the old mortar attached on RA surface, resulting in weakened interfacial transition zones (ITZs) in the concrete and the consequent reduced durability of concrete when RA was used to replace NA for producing recycled aggregates concrete (RAC). Therefore, extensive research work had been devoted to the enhancement of RAC performance and nanomaterials have demonstrated great potential in this regard. This paper reviews recent progress on the application of various nanomaterials for improving the microstructure as well as nano/mechanical properties of ITZs in RAC, and special attentions were given to the dispersion strategies for nanomaterials which determines the amount of nanomaterials required to achieve reliable improvement in RAC performance and thus the cost of using nanomaterials in RAC.

Modification of Recycled Cement with Different Additives

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:16:22 +0200

The unmodified recycled cement (RC) paste has unfavorable properties (like fast setting, high water demand and low strength) restricting application. This paper intends to rectify these shortcomings and improve RC with different additives. A comprehensive experimental program combining flowability, setting time, isothermal calorimetry and mechanical tests of modified recycled cement (M-RC) paste with different proportions were conducted. The results indicate that adding TEA and pectin could significantly improve the early flowability of RC and delay its setting, but it will have adverse effects on the mechanical properties of RC paste. Adding 0.5% TEA or 0.075% pectin can increase the fluidity by 240% and 293%. For the 0.5% TEA and 0.075% pectin groups, the 3-day compressive strengths were reduced by 44.3% and 49.5%, respectively.

Influence of Waste Fibers on the Total Porosity of Cementitious Composites

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:15:38 +0200

The amount of water is essential to explain the shrinkage process. It is determined by the water-cement ratio, but also by the moisture content. Water in hydrated cement paste occurs in various forms: chemically bound, interlayer, adsorbed, free water and water vapor. During cement hydration, the balance between various forms of water changes. For example, the amount of physically bound water diminishes, and the moisture content changes at similar environmental conditions. Moisture changes occur first in the larger pores and then in the smaller pores. The air pores are larger than the hydration pores (capillary pores, gel pores) and have a greater effect on strength and permeability properties, while the cement hydration pores have a greater effect on shrinkage. At early ages, when composite properties are not fully developed, higher shrinkage influences the development and propagation of cracks. These (micro)cracks represent weak points and affect durability. To reduce shrinkage and bridge the cracks, fibers are added to the cementitious composite. Depending on the type and geometry, the fibers can reduce shrinkage and bridge the cracks. To reduce the environmental impact of fiber production, the use of waste fibers in cementitious composites is proposed. The main objective of this study was to investigate the influence of alkali-resistant glass fibers from production waste on the development of the microstructure of cementitious composites, i.e., the influence on the total porosity. The pore content was determined on fresh cementitious composites after mixing, while the total porosity of the material was measured after 28 days using a mercury intrusion porosimeter. Results were complemented by X-ray computed microtomography (micro-CT). The influence of production waste fibers is presented as a function of length and fiber content. In addition to the reference mixture, results were also compared with mixtures containing factory-produced fibers.

Effect of Current Modes on Electrochemical Chloride Extraction Treatments for Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:15:15 +0200

The current mode plays an important role in the Electrochemical Chloride Extraction (ECE) treatment for concrete. In this study, the experiments were conducted to investigate how the ECE process would be affected by different current modes (continuous and intermittent current modes). The results showed that there were remaining amounts of chloride ions that were hard to be removed by both current modes. Additionally, the porosity under the two current modes showed the same upward trend compared to the initial value, and the chloride diffusion coefficient increased by 1 - 2 times. Also, the chloride-contaminated concrete subjected to the continuous current mode had a higher cumulative chloride extraction content than that subjected to the intermittent mode. The intermittent current mode could not increase the effectiveness of extracting chloride when the current density was not greater than 3 A/m2 and the on-off ratio was not less than 3.2.

Comparison of Non-calcined and Calcined Red Muds from Different Sources as Potential Supplementary Cementitious Material

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:15:01 +0200

Red mud (RM) is a hazardous by-product of alumina refining processes. Due to its high alkalinity, large specific surface area, and complex and variable composition, RM is hard to treat or utilize on a large scale. To date, more than 4 billion tons of RM have been stockpiled globally and is still growing by more than 120 million tons annually. Many investigations have focused on the largescale utilization of RM as a construction material, either in its virgin form or after heat treatment. However, the huge differences among the chemical/mineralogical compositions of RMs due to differences among bauxite ores from different sources and/or different refining processes, it is difficult to prescribe a unique process for activating RM cementitious/pozzolanic properties. The present study aims to identify the key chemical and process-dependent factors that influence the cementitious/pozzolanic properties of RM. Two types of RM from different sources are investigated to determine the effects of the chemical/mineralogical composition, the alumina refining process, and calcination on the mineralogical phases and compressive strength of mortar cubes made with ordinary Portland cement (OPC)- RM blended cement. Mortar made with 15 wt.% OPC replaced by one type of virgin RM produced by the Bayer’s process was found to have better strength than a control mortar made with 15% OPC replaced by sand, which indicates that this RM had cementitious/pozzolanic property without requiring heat treatment. On the other hand, the RM produced by the bauxite calcination method needed heat treatment to improve its pozzolanicity, but, despite the improvement, mortar made with its optimally treated form had lower 91-day compressive strength than the companion control mortar made with extra sand as RM replacement. The compressive strength of mortars made with calcined RM was not only affected by the phase changes of the virgin RM properties brought about by calcination but also by changes to its physical.

Rebar-matrix Interface in Extrusion Molded Cementitious Filaments

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:14:48 +0200

Extrusion molding enables automatic construction through the pattern of material addition. The unique molding would result in several features that are different from those in conventional framework molding, such as weak interlayer bonding and a laminar structure with high anisotropy. To strengthen the interlayer bonding, reinforcement is often implanted to penetrate through the extrusion molded filaments (EMF). However, different from the pre-implantation of reinforcement before concrete casting, the post-implantation of reinforcement in EMF may trigger the problems concerning the interface bonding between reinforcement and material matrix. In this work, saddle stitches, a type of Ushape rebar or fiber, are taken as an example to demonstrate the effect of the post-implantation of reinforcement on the interfacial structure between the rebar and EMF matrix. X-ray computed tomography (XCT) is employed to non-destructively probe the post-implanted saddle stitches as well as the surrounded EMF materials. Regions of interest (ROI) are set on the rebar-matrix interfaces to elaborately analyze the material or defect distributions around the saddle stitches. Results demonstrate that insufficient material filling is observed at the outboard of the U-shape rebar, while material pressing is shown at the inboard. Large defects unevenly form in the rebar-matrix interface. Mechanisms of the observations may be ascribed to the low flowability of EMF materials that can hardly migrate to the rebar-matrix interfacial gaps spontaneously. The findings would deepen the understandings in rebar-matrix interfacial structure of EMF with post-implantation of reinforcement.

Effectiveness of Paraffin-based Curing Compound for Mitigation of the Plastic Shrinkage and Related Cracking of the 3D-printed Concrete Elements

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:14:35 +0200

3D-printed concrete elements are highly vulnerable to early-age shrinkage and cracking compared to conventionally cast concrete elements. Material compositions of printable concretes and complete renunciation of shuttering are responsible for accelerated capillary pressure build-up, leading to volumetric constructions of the 3D-printed layers at a very early age after extrusion and enhanced shrinkage at a later age. Shrinkage-induced cracks can severely impair the durability and appearance of 3D-printed concrete structures. The study at hand analyses the efficacy of the paraffin-based curing agent for reducing the shrinkage and cracking of 3D-printed elements and structures. Development of the temperature and capillary pressure, as well as shrinkage strains, were reported for the cured and uncured specimens. The study results show that applying paraffin-based curing agents can considerably reduce shrinkage-indued deformations of the 3D-printed elements produced even under extreme environmental conditions.

Effect of Delayed Addition of TEA on the Performance of Cement with Different Sulfate Carriers

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:14:16 +0200

Concrete 3D printing is one promising technique used for future construction. However, a bottleneck limiting this technology's rapid development and practical application is the conflicting requirements for concrete properties before and after printing. Hence, the application of the accelerator and a deep understating of its working mechanism is becoming more and more important. As one commonly used accelerator, triethanolamine (TEA) has the advantage of low dosage and high efficiency to reach a fast setting. However, it is still unclear how the delayed addition of TEA affects the performance of cementitious materials. Besides, it is found that the different types and combinations of sulfate carriers can significantly affect the performance of TEA on cement hydration. However, the combined effect of different sulfate carriers and different addition times of TEA on the hydration process of cement paste is also unclear. The effect of different TEA addition times on the hydration and setting performance of cement pastes containing different types and combinations of sulfate carriers were thoroughly investigated in this study. It is found that, depending on the types of sulfate carriers inside, the different addition times of TEA can significantly affect the hydration and setting performance of cement paste. Specifically, to artificial cement (ArC) prepared with hemihydrate (HH), the different TEA addition times do not affect the setting performance of cement paste. To ArC with the two sulfate carriers of anhydrite (AH) and HH, a flash setting was observed when the TEA was added simultaneously. However, a delayed addition of TEA for just 5 min can make the setting performance back to normal. To ArC with only AH, a longer addition time of 15 min is needed to eliminate the flash setting behavior. This phenomenon could be originated from the competed interaction of sulfate ions released from sulfate carriers and TEA with the aluminate phase contained in the clinker.

Adapting Construction and Demolition Waste to Circular Building Materials and Evaluation of Life Cycle Environmental Impacts

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:13:58 +0200

Upcycling of construction and demolition wastes (CDWs) into value-added building materials that can be used for rapid construction and housing in developing countries and disasterprone areas is important and offers a fast, cost-effective, and eco-friendly solution. The objective of this study is to investigate the feasibility of using different-size recycled concrete aggregates (RCAs) in geopolymers made entirely from CDW-based masonry components including hollow brick (HB), red clay brick (RCB), and roof tile (RT) as precursors. To improve the strength development, thermal curing was applied to the developed geopolymer mortars. Compressive strength test was used for mechanical characterization. To assess the environmental impact of geopolymer mortars, a cradle-to-gate life cycle assessment (LCA) was carried out. Findings revealed that RT-based geopolymer mortars were with the highest compressive strength level reaching 66.2 MPa based on different mixture and curing parameters. Compressive strength increased with the reduction in the maximum RCA size. According to LCA analysis, CDW-based geopolymer mortars resulted in similar strength but significant reduction in CO2 emissions (up to 60%) and are with comparable energy consumption to the Portland cement-based mortars.

A Conceptual Model for Assessing Circularity Potential of Building Materials at the Product Manufacturing Stage

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:10:37 +0200

The construction industry presently accounts for 30% of natural resource extraction and 25% of solid waste generation. The prevailing economy is “Linear” which is summarised as take-makedispose. On the contrary, the “circular economy” model is a systematic model to restore, regenerate and expand the lifecycle of materials. Most of the existing circularity assessment methods are focused on the end-of-life wastage of building materials while neglecting resource consumption and wastage at the product manufacturing stage. Further, these methods only consider direct material flows for assessing the circularity potential of building materials and overlook the indirect material flows associated with product manufacturing. There is a need to develop metrics to assess the circularity performance of building materials more holistically. Therefore, this study proposes a conceptual model to assess the circularity potential of building materials by analysing both direct and indirect material flow processes of the product manufacturing stage including raw material extraction, transportation, and manufacturing. The method used to design the conceptual model includes a comprehensive literature review in two stages. First, the existing circular assessment methods are reviewed to identify the methods used for assessing the circularity potential of building materials. Secondly, the circularity options are explored to develop the circularity metrics. According to the findings of this study, in the absence of a comprehensive method to assess the circularity potential of building materials, the life cycle assessment and material flow analysis are the most prominent circularity assessment methods used. Furthermore, circularity options such as industrial waste (by-products), biodegradability, biofuels, renewable energy, reusability, recoverability, recyclability and product life span are identified as the circularity metrics for building materials at the product manufacturing stage.

State-of-Art of Construction 4.0: An Academia Vs Industry Comparative Study

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:10:23 +0200

The manufacturing industry is experiencing the 4th Industrial Revolution, also known as Industry 4.0. It encapsulates cyber-physical systems (i.e., combining sensing, computation, control and networking into physical objects and infrastructure) integrated towards digitalization and automation of the manufacturing sector. The construction industry has also benefited from these technologies, which go by Construction 4.0. Despite the construction industry often being blamed for its reluctance to implement emerging technologies and non-traditional management methods, recent research attempted to integrate Industry 4.0 emerging technologies to keep up with the manufacturing sector. This shows that academia and industry need each other’s hand-in-hand support in order to implement these technological advances. This study investigates the status of Construction 4.0 technologies adoption in academia and industry in the United States of America (USA) and measures the level of collaboration. Relevant data is collected via web-based questionnaire surveys that are distributed to academia and industry professionals within the USA to inquire about the status of construction 4.0 technologies and their adoption rate. The collected data are analyzed and important findings are reported in this paper. The results show that around 61% of the professionals from academia and 33% from industry are fully or somehow familiar with the term – ‘Construction 4.0’. There has been significant adoption of BIM, laser scanners, and drones in each sector. The rest of the technologies show potential in upcoming years, and academia and industry have methods in place of updating the workforce on new technologies. However, a lack of collaboration has been observed as 50% of the respondents reported no ongoing or past research projects between academia and industry in this domain. It is hoped that the findings of this research will help both academia and industry to join forces to modernize the construction industry.

Reality Capture (RC) Technology for Drywall Installation: A Scan-toPrefab Approach

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:10:08 +0200

Drywall, also known as gypsum board, sheetrock, or plasterboard, is a widely used building sheathing material in the US and Canada to create interior walls and ceilings. Typically, the design and construction documents of a project exclude detailed information about the layout of drywall sheets on interior surfaces. Such information is left to the drywall installation crews to determine solely based on their experience. This inconsistent approach often results in substantial rework and waste of material in the field. The construction industry has seen a significant increase in the adoption of Reality Capture (RC) technology in recent years, with the goal of improving the quality and productivity of various construction activities. This research aims to investigate the implementation of RC technology, explicitly Terrestrial Laser Scanning (TLS) and Structure from Motion (SfM, also referred to as photogrammetry), in drywall installation. The research team has developed a framework that utilizes RC tools to capture the as-built information of the framing members of interior walls and penetrations of the MEP systems and uses these RC data to develop prefabricating shop drawings in a Building Information Modeling (BIM) platform for drywall cutting and installation. This framework has been tested and studied on active construction project sites. The preliminary findings indicate that this framework has the potential to lead to a more precise and efficient drywall installation process. This paper also proposes a process model for the execution of the proposed framework for improving drywall installation.

Lateral Behavior of Modular Steel Buildings with Diaphragm Connections

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:09:54 +0200

Modular steel buildings are increasingly popular due to their high level of industrialization. Corner-supported modular steel buildings are typically connected by inter-module connections at the corners of each module without continuous diaphragm slab. Therefore, rigid diaphragm assumption could not be adopted when designing modular steel buildings as in-plane deformation of the slab level is significant. To address this issue, the present study introduces diaphragm connections along the edges of modules at the floor slab levels. Then the lateral behavior of modular steel buildings with and without diaphragm connections is evaluated, as well as when a rigid diaphragm is assumed in the structures. The effect of diaphragm connection on lateral behavior of modular steel building under different parameters is discussed, including modular aspect ratio, number of modules in one storey, bracing system, and number of storeys. It is concluded that using diaphragm connections could improve the lateral behavior of modular steel buildings and simplify the design process.

Investigation of the Initial Quality of Robotic Tile Installation Based on Coupled Eulerian-Lagrangian Approach

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:09:37 +0200

In this study, the initial quality of robotic tile installation under various construction parameters and material properties of adhesive were investigated based on the fluid–structure coupling construction models for the first time. First, the models of adhesive application and tile leveling were developed based on the coupled Eulerian–Lagrangian approach. Then, on the basis of these models, various patterns of adhesive application, types of tile leveling loads, numbers of adhesive strips and yield stresses of adhesive were simulated and their influence laws on the initial quality of robotic tile installation were analyzed. Finally, the influence mechanisms of these parameters on the installation quality were revealed in terms of the spacing between adhesive strips, tile rebounding, contact areas and defect distribution. Results showed that the adhesive with horizontal application possessed smaller plastic deformation, kept stable shape of strips and distributed at equal spacing, compared with the one with vertical application. In contrast to a single compression load, its couplings with vibration loads were beneficial to the reduction of tile rebounding. Among the coupling loads, the coupling of shear vibration with compression considerably increased the tile–adhesive contact area until no interfacial defect appeared. The increase of the number of adhesive strips exerts few effects on the installation quality, including slight increases of contact areas as well as diminished interfacial defects. In the case of relatively low and high yield stresses of adhesive, the shear vibration effects were respectively large and small which decrease the installation quality.

Intelligent Construction via Digital Twin Approach

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:08:35 +0200

The paper presents the results of an ongoing research activity dealing with Digital Twin (DT) approaches for Intelligent Construction, optimizing Operation and Maintenance of buildings and urban areas. DT is an essential technological node of Industry 5.0, which leads to the growth of a Collaborative Industry based on the cooperation between machines and human beings to give added value to processes that meet the needs of users. DT realizes the synchronization between two realities: physical objects in real space, virtual objects in virtual space, remaining connected through the mutual exchange of data throughout the entire life cycle of the object. The construction sector is also adopting the new DT perspective to enforce innovative, responsible, and sustainable governance of the life cycle of buildings improving their durability and reducing environmental impacts. Due to IoT, AI, and virtualization, DT approaches permit prediction of future performance in-use, prevent anomalies, downtime, and inefficiencies, to experiment improvements or changes without having to test them on the construction itself or on special mock-ups. The research assumes the aforesaid considerations and states as its principal operational and experimental assets as-built virtual models in OpenBIM connected with Geographic Information Systems and an IoT infrastructure. They realize intelligent constructions integrated with an analytical data communication network for control and performance simulations. Through the study cases analyzed, the paper also introduces arguments for a critical literature review on current statements and future challenges of the DT approach for Intelligent Construction.

Influence of Temperature Increase on the Degradation Evolution of Rendered Façades

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:07:37 +0200

Climate change could alter the natural degradation pattern of buildings and their components. Façade claddings are directly exposed to the action of environmental agents, thus being particularly vulnerable to climate change impacts. Determining the expected degradation of the façades’ external layer, according to climate parameters’ projections, could be useful in the context of maintenance planning and adaptation to climate change. The present study intends to deepen the knowledge about the influence of temperature on the degradation evolution of rendered façades, considering the analysis of possible correlations between variables, based on observed and recorded climate data. It covers the degradation evolution of a sample of 26 rendered façades located in Lisbon, Portugal, based on the mean triennial degradation rate (∆Sw,mt) for periods of three years between 1990 and 2020. The severity of degradation index (Sw) of each façade, assessed through visual inspections in two moments in time, is used to model the individual degradation of the respective case study, necessary to calculate the sample’s ∆Sw,mt of to each triennium. The correlation between the dependent variable ∆Sw,mt and the independent variable ‘maximum temperature’ is significant, with a Pearson correlation coefficient of approximately -0.89. The negative trend shows that the degradation of the sample tends to decelerate with the increase of maximum temperature. Therefore, the temperature warming projected for the end of the century could contribute to lessen the rate of rendered façades’ degradation in the future, in Portugal or in analogous areas of the Mediterranean. The present study is part of a methodology that is being developed to quantify the impact of changes in climate parameters on the future degradation of rendered façades. Further research is necessary regarding the degradation projections, based on the climate change signal for maximum temperatures.

Impact of High-resolution Regional Climate Conditions on the Moisture Performance of Wood-frame Building Envelopes

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:06:39 +0200

Climate data is one of the most important inputs for hygrothermal simulations and significantly influences the simulation results that are used for moisture performance assessment of building envelopes. Conventionally, climate data from representative weather stations are used for hygrothermal simulations to assess the moisture performance of the buildings. Recently, the Construction Research Centre of the National Research Council Canada generated historical and future climate data for 564 locations across Canada. In this paper, the climate data of four urban locations within Vancouver (a humid and warm coastal city in Canada) were selected for hygrothermal simulations. These include an open area at the airport, a city center, an area surrounded by plants, and an area surrounded by a water body. The 31-year-long simulations were performed for a typical woodframe wall assembly complying with moisture protection designs as provided in the National Building Code Canada (NBCC 2020) but rain penetration was assumed considering the deficiency of exterior cladding. The differences in its hygrothermal response across the four locations were analyzed. It was found that some climate parameters are significantly different among the selected locations, although the values for moisture indices given in the NBCC 2020 for these locations are all similar. The results show that high values of WDR are the dominant factor that drives the moisture performance but there is no indication that the design of the assembly could be different among the tested locations.

Hygrothermal Performance of External Wall Systems Under Current Climatic Conditions and Future Climate Projections of Turkey

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:06:18 +0200

External wall failures caused by rainwater ingress are very common in Turkey. External wall systems that fail to meet the expected watertightness performance may cause premature deterioration of building components, create health hazards for users, and lead to a financial burden for building owners and in respect to the premature deterioration of public buildings, this also has repercussions on the national economy. In addition to the current climatic conditions, thermal and moisture loads that effect the buildings are expected to increase in the future due to climate change. In regards to climate change mitigation strategies, as have been emphasized for the building sector in Turkey, the national government is promoting the use of thermal insulation. However, given that the thermal performance of the most commonly used thermal insulation materials in Turkey are affected by moisture, it is important to evaluate the hygrothermal performance of external wall systems to help ensure the effectiveness and longevity of any proposed measures to mitigate the effects of climate change on building performance. In this paper, the state of the art is presented in respect to investigations of the hygrothermal performance of external wall systems. The research is analyzed based on climatic conditions to which the wall is exposed, the type of external wall assembly investigated, and the method of investigation described in the studies reviewed. The results indicate that the hygrothermal performance of external walls has been extensively investigated; however, there is relatively little research focusing on the hygrothermal performance of external walls subjected to the current climatic conditions of Turkey. In those studies that focused on evaluating the hygrothermal performance of external wall systems under future climate projections, these have been conducted for the cold climate regions of Canada, USA, Norway, and Finland. The hygrothermal performance of external walls under future climate projections for any region of Turkey has not yet been explored.

Evaluation of Defects Incidence and Severity on Building Façade: A Case Study

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:06:02 +0200

20th century buildings are referred to as modern heritage and suggested to be conserved them because they reflect the particular characteristics of the period. To conserve and sustain modern buildings against agents of degradation, such as the inherent quality characteristics, environmental agents, and operational conditions, an important consideration is the observation, from inspection, and documentation of building defects as may reflect the current condition state of the building. In the scope of the study, façade defects of one of the modern period buildings located in the Fatih district of Istanbul/Turkey – the Istanbul Esnaf Hospital was inspected and analyzed. This building was constructed between 1955-1963 with T-shaped plan which consists of eight façades, for which defects, located on six of the building’s façades, were evaluated. The aim of the study is the evaluation of defects in relation to: the orientation of the façade; the location defects on the façade; the façade material, that consisted of a rendered and painted façade, incorporating a mosaic of ceramics, and; the perceived causes of defects. The study consists of three stages (i) data collection, (ii) analysis of defects, and (iii) comparative evaluation of defects. In the first stage, environmental, architectural, and material data are presented. After which, defects on the building façade were detected through a field inspection and were systematically classified. In the final stage, the findings from comparative evaluations of defects and their relation to the orientation of the façade, location on the façade, material, and causes are given. The analysis shows that the incidence of defects is primarily related to design decisions, i.e., the architectural features of the building. Dirt/stain and cracking are two of the most observed defects. Stain/dirt defects are mostly observed under windowsills and recessed areas due to architectural features typical of this modern period. Whereas it was observed that cracks were generally locate around openings and balconies. Material loss and detachment were generally related to impact from vehicles and were concentrated on two of the façades having high usage. On the other hand, biological growth, and efflorescence were principally caused by outdoor environmental conditions.

A Comparison of Nature-based Solutions and Related Policies for UrbanEnvironment in China and Canada

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:05:43 +0200

Nature-based solutions (NBS) are considered and implemented in many places around the world as a means to mitigate the impact of climate change on the urban environment. NBS can provide useful approaches to mitigate the urban heat island effect, reduce energy consumption of buildings, sequestrate carbon from the atmosphere, as well as improve comfort to pedestrians in the urban environment. However, the implementation of NBS usually requires extra resources, i.e., valuable land within the urban fabric, additional funds for the design and construction of buildings that incorporate NBS, and additional operational costs for maintaining relevant systems, which may conflict with individual building owner’s interests, but nonetheless, be beneficial for the public at large. Under these circumstances, relevant policies should be established to set minimum performance requirements and incentives be introduced to encourage the implementation of relevant practices. China and Canada have set a target of achieving carbon neutral, by 2060 and 2050, respectively. Implementing such policies is critical for realizing the contributions of NBS in the building sector and helping achieve carbon neutrality in urban areas. For the study described in this paper, polices related to the implementation of NBS as issued by selected cities in China and Canada are reviewed. Scopes and limitations of policies from these two countries are summarized and compared. Suggestions and requirements provided in the policies are discussed in conjunction with the findings and conclusions from scientific articles related to the NBS.

How Environmental Circumstances Influence Water Repellent Treatment Efficiency – A Case Study of Bentheim Sandstone

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:05:27 +0200

Water repellents are widely applied directly to the outer surfaces of existing buildings to increase the hydrophobicity and durability of historic facades. Nevertheless, there is little control over the initial moisture content inside masonry and boundary conditions in practice. The fluctuating temperature and moisture content of a wall are inevitable when applying the treatment under natural climatic conditions, therefore the efficiency under realistic application approaches may not be as optimal as in the lab. This research aims to understand how application circumstances affect the hydrophobic efficiency of a siloxane-based water-repellent solvent on sandstone. Samples with different moisture content were treated and cured under different temperature to simulate various field climate conditions in practical applications. The experiments indicate that application temperature and relative humidity have little effect on water-repellent efficiency. The water-repellent product is also effective on saturated walls.

Holism vs. Sustainability in Construction

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:05:15 +0200

Introduction, motivation: almost 40 years of observation, work and cooperation with investors, designers, contractors, manufacturers, distributors, authorities directly in the construction, rescue of monuments, problem solving, design, implementation, maintenance of facilities is a field of research. I have been there to see how and why construction facilities are implemented, used and protected. The title holism is a good method for analyzing problems but also a tool for predicting the necessary characteristics of what we want to create. Holism is a way of thinking about a problem. Where it is applied it gives good results, especially in the long term. It allows one to see the consequences of the flow of time more easily than reductionism. The study of the causes of a problem is broader which allows us to better diagnose and solve it. It makes you always analyze the effects on the whole object and its environment. It places each problem in the context of nearer, farther, sometimes very far and the passage of time. An important element is the analysis of human behavior during the creation and life of the object. Most of the ways to research and determine the condition of objects are obviously known and used. The problem is to determine them (almost) all and the details. Understanding Aristotle's "The more you know, the more you realize you don't know." is crucial here. The point is to explore and come to a conclusion without "closing the door" to more sometimes diametrically opposed knowledge as you go along. Holism in construction can be formulated, describing principles so as to facilitate broader analysis. Such an approach is desirable, which will give the opportunity to benefit from the results to people with different levels of competence, that is, the majority. The purpose of the paper is to try to systematize the approach and show, with examples, why it is worth using. Method: shown in the table are the elements of the research method used in the appraiser's practice. Some areas and elements should be analyzed for the recognition and determination of conditions, impacts and behaviors of construction objects are described. It was determined how to situate the problem in the broadest possible context, with particular attention to typical human behavior. As it turns out, this context is underestimated here. Due to the small volume of the text, examples were limited to the analysis of two relevant elements: lime mortar brick masonry and monolithic reinforced concrete. Objects from the appraiser's practice were selected. For masonry, a school building from the early 20th century and a farmhouse from the mid-19th century. For reinforced concrete, the school swimming pool erected in 1968 and the building of the printing house from 1972, both in emergency condition. Results: The time caesura is important for the results of the conducted research. The indicated errors in the selection of repair methods and materials are due to simplistic methods of analyzing problems. Overlooking the longevity of existence under different conditions and the most important influence of human behavior at each stage of the establishment, use and existence of building structures prove to be crucial.

Corrosion Initiation Period for Stainless Steel Reinforcement in Concrete Structures

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:04:52 +0200

The designed service life of reinforced concrete structure is often shortened when disposed in aggressive environments. In certain situations, stainless steel reinforcement may be an appropriate replacement to attain a higher level of durability. This paper presents the findings of an experimental study conducted to determine the critical chloride threshold for two types of stainless steel reinforcement (UNS S40977 and UNS S32001). For each steel grade, a prediction model for the corrosion initiation period was obtained, applying the electrochemical test data in a Monte Carlo analysis. Results show that if the initiation period is taken as the corresponding for a 7% corrosion probability, that will occur at 6.5 years of age for carbon steel and over 150 years for UNS S32001 stainless steel.

Assessing Different Insulation Strategies for Historic Wooden Facades Based on Modeled Mold Growth Risk

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 12:04:34 +0200

Wood makes up a considerable proportion of applied construction materials in Chinese historic building envelopes. With increasing awareness of preserving historic heritage by promoting their further use and occupation, it becomes necessary to improve the current poor indoor thermal environment in abundantly existing historic buildings in southern China. One common approach for improvement is to install insulation materials on historic building envelopes, which can additionally improve their sustainability by reducing buildings’ energy demand for heating and cooling. However, this measure of deep retrofits requires cautious design regarding the hygrothermal performance of insulated wooden facades, since an improper construction way would lead to mold growth in wooden materials, causing problems of durability and indoor hygiene. Therefore, this study investigates the mold growth risk of different insulation systems for historic wooden facades in the Chinese HotSummer-Cold-Winter zone based on a parameter study. The considered parameters are internal and external insulation systems, vapor-open (mineral wool) and vapor-tight (XPS) insulation materials, a U-value of 0.8 W/(m²K) as well as a lower U-value of 0.24 W/(m²K) for the insulated walls, different capabilities and positions of an additional vapor control layer, as well as different cooling/dehumidification conditions in the warm period of a year. The hygrothermal performance of insulated wooden facades is simulated with WUFI®Plus software, while the mold growth risk is assessed with mold index values of the Viitanen mold model. The results of this paper will provide a quantitative evaluation of different insulation strategies for historic buildings in southern China regarding the mold growth risk in wooden materials, which is of essential importance for the durability of construction materials. This study can also give instructions for deeply retrofitting wooden historic buildings in China.

A Dose-response Approach for Predicting Frost Damage with Hygrothermal Simulations

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:59:00 +0200

Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the materials, which may not always be an option due to heritage values, it is highly important to quantify the risk of frost damage in advance. Hygrothermal simulations have proven to be a valuable tool to assess the risk of deterioration of building facades. The performance criterion method generally applied today quantifies the number of critical freeze-thaw cycles (FTCcrit) as described by Mensinga et al (2010). This method is based on frost resistance tests that adopt high moisture contents and extremely low frost temperatures. However, building facades often experience milder frost temperatures and lower moisture contents rather than these extreme conditions. A journal article published by Feng et al. (2019) investigated the relationship of frost damage with temperature and moisture content, which enables a dose-response approach that goes beyond the existing threshold level criteria. The experimental study tested freezing temperatures from -2°C to -20°C and moisture saturation degrees from 0.1 to 1.0. This paper studies freeze-thaw risk using this advanced approach, and investigates whether the dose-response approach can lead to a clarification at what number of FTCcrit actual deterioration occurs and how this can be predicted by the use of hygrothermal simulations. Thereby, an attempt is made to derive a more representative performance criterion for frost damage.

Why the Quality of Concrete Construction for Infrastructure Contracts Must Not be Undermined by Inappropriate Design Code Assumptions

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:58:46 +0200

The concept of a draft international project specification (DIPS) has long been under consideration in relevant fib Task Groups, - even before the framework Standard, ISO 22966 (Execution of concrete structures) was published (2009). However, the quality requirements of ISO 22966 were developed from the product quality inspection principles of the Eurocodes and ISO 9001:2000; and the author has explained why these principles cannot be applied directly to contract works. Furthermore, these principles do not demand the necessary level of high-performance concreting and supervision to produce defect-free structures and the 100 plus year service life which Owners expect. The original ISO 9001:1987 was a simple, contractually effective model quality system specification which “aimed primarily at preventing nonconformity,” (the fundamental purpose of quality assurance). Its most powerful element was ‘process control’ (including ‘special processes’), and it demanded that all processes which could adversely affect quality must be addressed by effective documented preventive procedures in the Contractor’s Project Quality Plan (PQP). The Contractor had to document exactly how he would perform each (special) concreting process and then demonstrate that his proposed procedures worked. Since 2000, this powerful combination of mandatory quality planning requirements has been removed from most specifications for concrete works; but this is precisely what needs to be restored if Owners’ and Designers’ durability expectations are to be consistently achieved. The author now proposes an amended draft version of the International Project Specification, - hoping that it will soon be used on a trial basis on selected construction contracts for reinforced and prestressed concrete bridgeworks in China, Australia, United States and Europe.

Validation Exercise at European Level on Natural Chloride Diffusion Test and Natural and Accelerated Carbonation Testing

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:58:37 +0200

The work summarizes the results of the interlaboratory testing made in the committee CEN/TC51/WG12 on the standardized procedures for carbonation (EN 12390 – 10 and part 12) and chloride diffusion (EN 12390-12). The exercise was made by 13 different laboratories on 8 different concrete compositions with w/c ratios of 0.4, 0.5 and 0.6. The results indicated repeatability of 10-22% for natural carbonation (outdoors protected from rain and controlled chamber respectively), of around 5% for accelerated carbonation (at 4% of CO2 concentration), and 23% in the Apparent diffusion coefficient for natural chloride diffusion and 13% for the chloride surface concentration.

Link between Durability Defects and Construction Failures

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:58:28 +0200

Over thirty years ago enthusiastic and dedicated materials scientists and structural engineers initiated a series of research projects and draft International Standards which has now revolutionised the design approach to durability of concrete structures. Concrete mix design is dominated by the contractual requirement for the concrete supply not to exceed specified limiting values of the nationally favoured durability criteria. The specifying Authorities are striving to ensure that structures achieve their design service life (ideally 100 years+). Concrete research and development is their primary hope. During the 1990s, the concrete construction industry was also working hard to develop better specifications and contract management procedures to address the pressing problems of not only durability but also safety. Central to all the work of the construction industry was the principle that all concreting operations were ‘special processes’ (as universally acknowledged for welding processes), and therefore they had to be documented, trialled, verified and implemented in compliance with the process control requirements of ISO 9001:1987/1994. Procedures had to be prepared, approved and implemented for all processes which were identified as being potentially ‘adverse to quality’ (which included most processes involved in concreting and prestressing operations (including grouting)). The critical question to answer in preparing a procedure is HOW the process will be carried out and verified. However, equally critical questions may be WHEN, WHERE and BY WHOM. The Project Specification must ask these questions in the tender documents and the Owner and/or his Designer must satisfy themselves that all the identified problems have been resolved – both technical and administrative – before relevant design/construction commences. These questions must be answered by all subcontractors, including designers and checkers of falsework structures. Example are given, based on recent fatal bridge collapses largely caused by Owner and Designer failings to control subcontracting of temporary works design and checking.

Electrical Resistivity Measurements on Hardened Concrete Exposed to Various Curing Conditions

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:58:12 +0200

Evaluating concrete quality and performance, especially determining the resistance of concrete to fluid and ion ingress, is fundamental to estimating concrete’s durability and predicting the service life of concrete structures. Both bulk and surface electrical resistivity tests have gained increasing interest as rapid and repeatable indicators of concrete’s resistance to fluid ingress. In this study, concrete electrical resistivity was measured at the ages of 56 and 91 days on specimens from five concrete mixtures exposed to different curing environments and storage solutions. Both bulk and surface resistivity of concrete in each curing condition are compared, and the effect of curing methods on electrical resistivity is discussed. The results show that conditioning in a highly-conductive storage solution, such as a simulated pore solution, led to a lower concrete resistivity measurement than when stored in saturated limewater. The effect of mixture compositions on measured resistivity revealed that for the same cementitious materials, the electrical resistivity increased as the w/cm ratio decreased, and a linear correlation between the w/cm ratio and concrete electrical resistivity was obtained.

Application of Service Life Planning to Existing Buildings – Perspectives on Condition Appraisal, Performance and Cost

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:57:57 +0200

ISO 15686 on Service Life Planning of Constructed Assets provides guidance which is applicable to both new and existing constructed assets and their parts. However, there has been limited exposition of the applicability of the guidance to existing buildings. This paper provides perspectives on practical application of the principles to condition assessment (survey and appraisal) of the long-term performance of existing buildings, in particular in respect of the building envelope and how maintenance interventions and life cycle costs are predicted or estimated. The authors are currently actively involved through CIB W080 and ISO TC59/SC14 in preparing for the revision of the ISO 15686 standards to take account of experience over the last 20 years, including the development of the factor method and its applicability, and guidance on life cycle costing of existing buildings. The paper will develop key themes from the series of ISO 15686 standards, which are particularly relevant to assessment of existing buildings and other constructed assets.

Prediction and Ranking of Moisture Severity of Climate Years Using Supervised Projection to Latent Structures Applied to Tall Wood Buildings

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:57:40 +0200

Hygrothermal simulation tools are commonly used to assess the moisture performance of building envelope components. Owing to the computational costs required to complete simulations over the long-term, one approach to reduce simulation time when undertaking hygrothermal design analysis is to select representative year(s) amongst sets of long-term climate data. To properly select these moisture reference year(s), a method is required to rank or predict the moisture severity of climate years for sets of long-term climate data. Several methods are used in the literature for this purpose, but none seems to be sufficiently accurate. In this study, the supervised projection to latent structures, also known as partial least squares regression, was trained and validated on data obtained from hygrothermal simulations of tall wood building wall assemblies for several cities across Canada. Models developed at the city level, for a given greenhouse gas emission scenario or time period, or encompassing historical and future time periods, showed comparable scores for ranking. In respect to prediction of the moisture severity of climate year sets, models developed at the city level were shown to be more accurate.

Opportunity-Based Maintenance of Buildings’ Envelope

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:57:26 +0200

More than half of the building’s life-cycle costs correspond to maintenance costs. Nevertheless, maintenance actions are, generally, conditioned by subjective criteria and carried out at inopportune times, which implies that one third of the maintenance costs are improperly incurred. Buildings are multi-component systems and, therefore, the adoption of opportunistic maintenance policies allows reducing the maintenance costs and the number of interventions, while maximizing the service life and the efficiency of the resources available. In this study, an opportunistic maintenance plan is proposed for the buildings’ envelope, combining the maintenance needs of four elements: rendered facades; ceramic claddings; window frames; and pitched roofs ceramic claddings. For this purpose, a condition-based maintenance model is used. The maintenance model is based on stochastic degradation models for the individual components of the system. The optimization of these policies will identify the best maintenance schedule and combination of maintenance activities, finding the optimal trade-off between disruption of the buildings’ use, maintenance costs and their service life. The application of these opportunistic maintenance policies in the building envelope elements allows mitigating the degradation of these elements over the buildings’ life cycle and, consequently, increasing the economy, quality, and aesthetic perception of our cities. This methodology will change the way that maintenance plans are defined, and interventions are prioritized.