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 Long-term Chemical Degradation of Cement-Based Materials and Its Impact on Transport Properties
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Tác giả hoặc Nhóm tác giả: Quoc Tri Phung
Nơi đăng: Ghent University
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; Số: 3rd Magnel Research Seminar;Từ->đến trang: 44-45;Năm: 2013
Lĩnh vực: Kỹ thuật; Loại: Bài báo khoa học; Thể loại: Quốc tế
TÓM TẮT
Concrete has been considered to be a useful material for a radioactive waste repository in view of its high-pH buffering capacity, low diffusivity and permeability. The use of cement-based materials for both low and high radioactive waste disposals has progressed significantly in recent years. In the high level waste Belgian supercontainer concept, the engineered barriers mainly consist of concrete. The role here is not focused on the retention of the radionuclides but in helping creating beneficial conditions for the waste package integrity for a very long period. Thus, the possibility to assess the service life for structures made of cement-based materials for radioactive waste facilities is of great practical importance because of long-lived activity of radioactive waste. The service life of these structures is directly related to the time necessary for the waste’s radioactivity to reach its natural level, which typically exceeds hundreds or even thousands of years. It is necessary, therefore, to explain how concrete will be degraded, and what properties it will show over hundreds of years after placing. The objective of this research is a phenomenological study of the relationship between chemical degradation and transport properties of cement-based materials at cm3-dm3 scale. Transport properties (permeability, diffusion) are often considered as fundamental parameters for characterizing concrete durability because they govern the penetration of aggressive substances responsible for degradation and, thereby, have an important effect on the durability of cement-based materials. Chemical degradation will alter the concrete microstructural properties as total porosity, pore size distribution, connectivity and tortuosity which are the most important factors influencing transport properties. In this study, processes influencing concrete degradation, solute transport behavior during saturated and steady flow conditions of undegraded and degraded concrete will be investigated. Despite advances in this area, a significant amount of work is still warranted due to limited experimental timeframe available to capture these processes. An improved understanding of these relations via microstructural changes would help to better assess the long-term durability of cement-based materials subjected to chemical degradation.
ABSTRACT
Concrete has been considered to be a useful material for a radioactive waste repository in view of its high-pH buffering capacity, low diffusivity and permeability. The use of cement-based materials for both low and high radioactive waste disposals has progressed significantly in recent years. In the high level waste Belgian supercontainer concept, the engineered barriers mainly consist of concrete. The role here is not focused on the retention of the radionuclides but in helping creating beneficial conditions for the waste package integrity for a very long period. Thus, the possibility to assess the service life for structures made of cement-based materials for radioactive waste facilities is of great practical importance because of long-lived activity of radioactive waste. The service life of these structures is directly related to the time necessary for the waste’s radioactivity to reach its natural level, which typically exceeds hundreds or even thousands of years. It is necessary, therefore, to explain how concrete will be degraded, and what properties it will show over hundreds of years after placing. The objective of this research is a phenomenological study of the relationship between chemical degradation and transport properties of cement-based materials at cm3-dm3 scale. Transport properties (permeability, diffusion) are often considered as fundamental parameters for characterizing concrete durability because they govern the penetration of aggressive substances responsible for degradation and, thereby, have an important effect on the durability of cement-based materials. Chemical degradation will alter the concrete microstructural properties as total porosity, pore size distribution, connectivity and tortuosity which are the most important factors influencing transport properties. In this study, processes influencing concrete degradation, solute transport behavior during saturated and steady flow conditions of undegraded and degraded concrete will be investigated. Despite advances in this area, a significant amount of work is still warranted due to limited experimental timeframe available to capture these processes. An improved understanding of these relations via microstructural changes would help to better assess the long-term durability of cement-based materials subjected to chemical degradation.
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