Abstract

Most of the maintenance actions in the construction sector are still reactive and sporadic, based on subjective criteria. Usually, maintenance actions are performed when the building already presents unacceptable degradation levels, and the reactive maintenance actions carried out only correct the anomalies observed, not dealing with the causes, thus leading to additional costs and risks for owners. This study establishes a condition-based maintenance model applied to natural stone claddings. This model has a stochastic nature, in order to deal with the complexity of the degradation phenomena. For that purpose, Petri nets are used, providing an efficient tool to model the deterioration process and the maintenance decisions considered for stone claddings. The maintenance model is a full life-cycle model that encompasses: (i) the stochastic assessment of the degradation condition of the stone claddings, and their expected service life; (ii) and the inspections, maintenance and renewal processes. In this study, three maintenance strategies are considered: (i) major intervention only; (ii) combination of minor and major interventions; and (iii) combination of cleaning operations, minor and major interventions. The impact of the different maintenance strategies in the future performance and remaining service life of stone claddings is analysed, also evaluating the economic impact of each maintenance plan.

Abstract

Abstract

Abstract

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.

Abstract

A well-developed road network provides good services for road consumers. Most roads in the world are flexible types of pavement. Bitumen has viscous-elastic properties and is very sensitive to temperature; it plays a vital role in producing hot mix asphalt and influences the performance of HMA pavement. Flexible pavements are linked to extreme temperatures, causing rutting and fatigue cracking. Pavement distress shortens service life and increases maintenance costs. This research focused on improving pavement resistance to distress by modifying the conventional properties of bitumen using alternative materials such as shredded PET plastic. In this study, two stages were applied. The first stage was collecting samples, and the second stage determined the conventional properties of bitumen by adding 3%, 6%, and 9% of shredded PET plastic to the bitumen. Penetration, ductility, and softening point tests were performed to analyze the conventional behavior of bitumen. Finally, top-down and bottom-up cracks are used to evaluate rutting damage, with 3D-Move analysis software that accounts for moving vehicles under various loads and speeds. From the conventional bitumen test, at 3% PET plastic added to the bitumen has no significant effect on the penetration grade, Ductility, and softening point. However, when 6% and 9% PET by weight of bitumen mixed, the penetration grade, ductility, and softening result become 49.3mm, 45.5mm, 97mm, 85mm, and 57mm and 62^oC, respectively compared with the penetration grade, ductility, and softening point value of unmodified bitumen (66.5mm, 142cm, and 48.9^oC). Besides, the 3D-Move Analysis software results show that asphalt binders with higher PET plastic content best resist the rutting damage, top-down, and bottom cracks.

Abstract

A well-developed road network provides good services for road consumers. Most roads in the world are paved with flexible materials. Bitumen has viscous-elastic properties and is very sensitive to temperature. It plays a vital role in producing hot mix asphalt and influences the performance of HMA pavement. Flexible pavements are associated with extreme temperatures, which can cause rutting and fatigue cracking. Pavement distress shortens service life and increases maintenance costs. This research focused on improving pavement resistance to distress by modifying bitumen's conventional properties with alternative materials, such as shredded PET plastic. In this study, two stages were applied. The first stage was collecting samples, and the second stage determined the conventional properties of bitumen by adding 3%, 6%, and 9% of shredded PET plastic to the bitumen. Penetration, ductility, and softening point tests were performed to analyze the conventional behavior of bitumen. Finally, top-down and bottom-up cracks are used to evaluate rutting damage, with 3D-Move analysis software that accounts for moving vehicles under various loads and speeds. From the conventional bitumen test, adding 3% PET plastic to the bitumen has no significant effect on penetration grade, Ductility, or softening point. However, when 6% and 9% PET by weight of bitumen mixed, the penetration grade, ductility, and softening result become 49.3mm, 45.5mm, 97mm, 85mm, and 57mm and 62oC, respectively compared with the penetration grade, ductility, and softening point value of unmodified bitumen (66.5mm, 142cm, and 48.9oC). Besides, the 3D-Move Analysis software results show that asphalt binders with higher PET plastic content best resist rutting, top-down cracking, and bottom cracks.

Abstract

. Most of European native wood species used outdoors are expected to last less than 10 years if left untreated and exposed to severe environmental conditions such as high humidity and biological agents. However, the current classification of wood’s natural durability based on EN standards does not fully reflect real end-use conditions, often underestimating wood’s performance in use. In addition, the importance of design details and the role they play in enhancing service life, especially in the case of outdoor applications, is often neglected. With the aim of evaluating the positive impact of proper design on wood’s service life, large-scale experimental devices, manufactured according to different designs (water draining / trapping) from six native wood species, were installed in 2009 in two French cities benefiting from different climatic conditions (oceanic / continental). The results of the evaluation carried out after 10 years of natural weathering demonstrated that (1) significant differences in the ability to withstand decay over time exist depending on the selected design details and the climatic conditions encountered in the experimental fields; (2) high variability in the resistance of non-durable spruce and poplar wood against fungal decay was noticed for each tested design, but with an unexpected high percentage of elements performing very well; (3) the moderately durable heartwood of larch, maritime pine and Douglas fir was mostly unaffected by decay even under severe conditions of exposure to rain (decking modules), suggesting these species may have greater value for outdoor applications without any preservative biocidal treatment than previously assumed.

Abstract

Abstract