Documents published in Scipedia

• Study on Shrinkage Properties of Repairing Mortar Modified by Basalt Fiber

  S. Yang, P. Xu

  DBMC 2023.

  
  

  Abstract

  In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four factors, i.e., silica powder, sodium silicate, basalt fiber and a U-type expansive agent, were used to measure the length change ratio. The results show that the shrinkage value of modified repairing mortars have been greatly reduced. Compared with the control specimen without any additives, the shrinkage value of the modified repairing mortar with the silica powder of 3 %, the sodium silicate of 1.0 %, the basalt fiber of 0.2 % and the U-type expansive agent of 10 % at 60d drops by 42.5%. Based on experimental results, the shrinkage prediction model of modified repairing mortar has been established. The model can be used to predict the shrinkage value of the modified repairing mortar with similar compositions.

  Abstract
  In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four [...]

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• Experimental Study on Improvement of Interfacial Bond Properties of Carbon Fiber Reinforced Cement Matrix Composites by Nano Silica

  J. Liu, J. Hong, Y. Gong, B. Yi, D. Zhang

  DBMC 2023.

  
  

  Abstract

  The fiber reinforcement efficiency of carbon fiber reinforced cement matrix composites (CFRCM) is limited by the low permeability of mortar to internal filaments in the fibers, leading to premature failure of the composites due to low bond strength. In this paper, three kinds of nano-silica materials were used to improve the bond properties of carbon fiber bundles to cement-based matrix by coating and electrophoretic deposition. It is found that different methods have different positive or negative effects on the improvement of bond properties, and the effects are different under different embedded lengths. The modification principle is due to the high impregnation of nano silica particles on the fibers and the reaction of volcanic ash of the particles, which promotes the formation of calcium silicate hydrate gel inside the fibers. Relevant research needs further exploration.

  Abstract
  The fiber reinforcement efficiency of carbon fiber reinforced cement matrix composites (CFRCM) is limited by the low permeability of mortar to internal filaments in the fibers, [...]

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• Electrical Joule Heating and Early Strength of Mineral-impregnated Carbon Fibre Reinforcement (MCF)

  W. Dong, M. Liebscher, B. Yang, J. Zhao, V. Mechtcherine

  DBMC 2023.

  
  

  Abstract

  Mineral-impregnated carbon fibre reinforcement (MCF) has attracted increasing attention due to its low-cost, easy manufacturing, high temperature and chloride resistance, when it replaces traditional steel reinforcement for concrete construction. Considering its excellent electrical conductivity, this paper investigates the effect of electrical Joule heating on the temperature increase, mechanical and microstructural characteristics of MCF. Different duration of electrical heating ranging from 0.5h, 1h, 2h, 4h to 8h had been explored. In addition, the effect of water spray treatment on the electrically heated MCF will be conducted. For the MCF reference without electrical heating, it is not hardened and the early flexural strength can’t be obtained. The temperature of MCF under the voltage of 15 V gradually increases to 100.5 °C and then keeps stable. The highest early flexural strength of MCF immediately tested after heating reached 290.8 MPa when the electrical heating time is 8h, and with the water spray treatment. Interestingly, the water spray treatment seems to benefit the strength development, with the less generated micro pores around the interfaces of carbon fibres to cement matrix. The results indicate that the rapid hardening MCF subjected to electrical heating can work as self-heating elements or rapid production and transportation of MCF for concrete structures.

  Abstract
  Mineral-impregnated carbon fibre reinforcement (MCF) has attracted increasing attention due to its low-cost, easy manufacturing, high temperature and chloride resistance, [...]

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• Developing Multifunctional Ultra-High Performance Concrete via Incorporating Hybrid Steel Wires and Fibers

  S. Dong, X. Wang, B. Han

  DBMC 2023.

  
  

  Abstract

  Stainless steel wires (SSWs) with micro diameter and stainless steel fiber (SFs) with millimeter diameter were incorporated together to develop multifunctional ultra-high performance concrete (UHPC) in this study. The addition of 0.2 vol.% of SSWs can already improve interface between matrix and SFs, reduce the microcracks in UHPC caused by shrinkage and initial load, increase SFs’ distribution and orientation with their high flexibility, thus enhancing the flexural toughness and resulting in the occurrence of multiple cracking flexural failure mode of UHPC with less than 2.0 vol.% SFs. The hybrid SWs and SFs reinforced UHPC possesses low electrical resistivity and can sense its initial cracking, residual flexural loading and cracking development by the measured fractional change in electrical resistivity. This is mainly coming from the inhibition effect of SWs on microcracks and the extensively conductive pathway formed by both SWs and SFs. The multiple cracking failure mode under flexural load and the self-sensing capacity to monitor crack initiation and propagation of UHPC with low content hybrid wires and fibers is important to develop multifunctional UHPC, thus providing a new approach for maintaining sustainable development of infrastructures.

  Abstract
  Stainless steel wires (SSWs) with micro diameter and stainless steel fiber (SFs) with millimeter diameter were incorporated together to develop multifunctional ultra-high [...]

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• Study on Performance of Negative Temperature and High Strength Bed Mortar Material for Wind Power Engineering

  L. Tongwei, Z. Jie, C. Guisheng, W. Linmao, Y. Maoqian

  DBMC 2023.

  
  

  Abstract

  As the development process of affordable wind power projects accelerates, the height of tower hub shows a trend of development to 150m above. The technology of steel and concrete is widely applied. Bed mortar material, as the bonding material between precast concrete rings, is the key material to ensure the lifting speed of steel and concrete tower for wind power. In this study, the basic formula of negative temperature and high strength bed mortar material was explored, and its working performance and strength development under different curing conditions were further studied. The results show that the developed bed mortar material has excellent thixotropy and it is still operable at 50min. Under the condition of negative temperature curing, the early strength of bed mortar material is high, and the late strength develops well. Curing at ultra-low temperature of -15℃, the strength of -1d is 35.4MPa, and the strength of -7+21d is over 90MPa. In the outdoor natural curing environment of alternating positive and negative temperatures, the strength of 1d reaches 51.1MPa, the strength of 60d is 113.2MPa. The performance of bed mortar material far meets the requirements of the strength grade of 80MPa which is used in winter construction of wind power engineering.

  Abstract
  As the development process of affordable wind power projects accelerates, the height of tower hub shows a trend of development to 150m above. The technology of steel and concrete [...]

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• Effect of Alkali-free Accelerator Containing Nano-silica on the Durability of Shotcrete

  W. Liya, W. Kaiyu, C. Guisheng, Y. Maoqian, Y. Guangnuan

  DBMC 2023.

  
  

  Abstract

  The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance tests and frost resistance tests. The results show that under the same conditions, the C30 shotcrete with nanosilica-containing alkali-free accelerator has a lower electrical flux and a greater impermeability rating than P10. The C30 shotcrete with nano-silica-containing alkali-free accelerator maintains a mass loss rate of about 0.4% after 200 freeze-thaw cycles, a 10.5% decrease in relative dynamic modulus of elasticity, a compressive strength loss rate of less than 20%, the bubble spacing coefficient and the average bubble diameter increased by 20.9% and 60.5% respectively, showing good frost resistance performance. This indicates that alkali-free accelerator containing nano-silica can improve the durability of shotcrete. In addition, a comparison was also made between ordinary accelerator shotcrete with nano-silica, and when 5% nano-silica was added, the properties of shotcrete were comparable to those of 2% nano-silica alkali-free accelerator shotcrete.

  Abstract
  The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance [...]

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• Combining Wood Protection Options to Enhance Resistance against Decay and Improve Fire Safety of Engineered Wood Products like CLT

  J. Van Acker, W. Li, X. Jiang, M. Durimel, L. De Ligne, B. Parakhonskiy, A. Skirtach, J. Van den Bulcke

  DBMC 2023.

  
  

  Abstract

  Bio-based building products are considered key in our future socio-economic environment, since they are a very relevant nature-based solution (NbS) to climate change. The statement of President von der Leyen (European commission) to turn the construction sector into a carbon sink is critical in this respect: bio-based materials should be used on a larger and more targeted scale in the future. The long-term use of materials is therefore very important since we need to improve the lifespan of renewable materials to increase its carbon sink potential. Hence wood is increasingly considered as a main building material. Service life aspects are critical in relation to the EU Construction Products Regulation (CPR). Traditional treatments to protect against fungal decay and the impact of fire are not always performing adequately and often environmental impact has been an important consideration. The option to enhance wood properties using innovative technologies can be combined with better definition of the expectations and requirements. Besides focusing on combined innovative treatments of the wood matrix, also envelope treatments similar to the use of coatings can be envisaged. This all should lead to an increased use of timber and engineered wood products for green building. This paper mainly focusses on the increased use and high potential of CLT (Cross Laminated Timber) and options to use hardwoods and modified wood (like TMT) in relation to moisture dynamics to come to fit-for-purpose material properties even under more hazardous circumstances.

  Abstract
  Bio-based building products are considered key in our future socio-economic environment, since they are a very relevant nature-based solution (NbS) to climate change. The [...]

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• Capacity of Wood as Flooring Material: Improvement of Thermal Performance of Wood/Phase Change Material Composites

  W. Duk Suh, J. Nam, Y. Uk Kim, Y. Choi, S. Kim, S. Kim

  DBMC 2023.

  
  

  Abstract

  Wood is a biomaterial with good carbon fixation capacity. Phase change materials (PCMs) can impart thermal storage performances to materials. The goal of this study is to improve thermal performance by impregnating PCM into porous wood. The chemical stability of the composites was analyzed to evaluate whether it was appropriate for PCM to be impregnated into wood. Thermal performance of the composites was evaluated through latent heat analysis and thermal conductivity analysis. As a result of the analysis, the composites showed improved thermal performance compared to pure wood. In addition, in order to evaluate the applicability of the composites for floor heating, the dynamic heat transfer test was conducted using specimens as flooring material. As a result, it was confirmed that room temperature maintained the indoor comfort temperature range for longer time in rooms where composite specimens were applied as floor material. Result suggests that the composites can reduce the time for operating heating energy for floor heating. Thus, composites produced in this study proved to have the potential to be used as floor finishing material for floor radiant heating systems.

  Abstract
  Wood is a biomaterial with good carbon fixation capacity. Phase change materials (PCMs) can impart thermal storage performances to materials. The goal of this study is to [...]

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• Transforming low-quality sand into construction materials under 110℃ and Recycling of the Waste Solution

  P. Qiu, Y. Sakai

  DBMC 2023.

  
  

  Abstract

  A strong and eco-friendly material was transformed from low-quality sand via sol-gel method with ethanol as the solvent. 110oC was chosen as a target temperature because it is the average day temperature of the moon, which may be the first place for extraterrestrial development. The appropriate KOH content and ethanol concentration can improve the reaction degree and limit the side reaction. The main results indicated that the highest compressive strength (38 MPa) of the produced material could be obtained by using 20 mass% KOH and 90 V/V% ethanol. According to XRD and FTIR analysis, the formation of sanidine, zeolite, and tetraethoxysilane is the main reason for strength enhancement. Sanidine and zeolite could fill the gap between sand particles and tetraethoxysilane is a good consolidate. Excess ethanol in the waste solution can be reused with recycle rate above 65%. The total carbon emission is 197 kg CO2 eq/m2 after recycling waste solution, which is 35.82% of that produced by normal concrete. Therefore, a tough construction material can be synthesized from lowquality sand, which can partially substitute concrete. This material can address the shortage of raw materials for concrete and can be utilised for extra-terrestrial construction.

  Abstract
  A strong and eco-friendly material was transformed from low-quality sand via sol-gel method with ethanol as the solvent. 110oC was chosen as a target temperature because it [...]

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• Recycling of Silty Waste Soil by CO2 Treatment for Construction Block Manufacture

  Y. Du, Q. Zeng

  DBMC 2023.

  
  

  Abstract

  The poor engineering performance of silty waste soil (SWS) seriously restricts its utilization in new constructions that, in turn, need a large amount of building materials. Meanwhile, traditional sintering technology of clay brick production is prohibited due to its high CO2 emissions. In the present work, a rapid CO2 mineralization method is proposed to treat SWS with active lime after the pressing forming process of building block manufacturing. The optimum mix proportion and pressing forming parameters of SWS blocks are presented. Microstructure of selected SWS block samples is characterized by mercury intrusion porosimetry (MIP) and X-ray computed tomography (XCT), and mineral changes are analyzed by X-rays diffraction (XRD). CO2 emissions from the SWS block production are evaluated considering the entire manufacturing process. Overall, the present study provides a proof-of-concept path that enables recycling of SWS for construction block production with low CO2 emissions.

  Abstract
  The poor engineering performance of silty waste soil (SWS) seriously restricts its utilization in new constructions that, in turn, need a large amount of building materials. [...]

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