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Số người truy cập: 39,658,387

 Microstructural and permeability changes due to accelerated Ca leaching in ammonium nitrate solution
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Tác giả hoặc Nhóm tác giả: Quoc Tri Phung; Norbert Maes; Diederik Jacques; Geert De Schutter; Guang Ye
Nơi đăng: Concrete Solutions; Số: -;Từ->đến trang: 431-438;Năm: 2014
Lĩnh vực: Khoa học công nghệ; Loại: Bài báo khoa học; Thể loại: Quốc tế
TÓM TẮT
Although Ca leaching in cement-based materials is an extremely slow process, this process is relevant for long-term assessments of the evolution of concrete used in radioactive waste disposal systems. In the present work, an ammonium nitrate solution of 6 mol/l was used to accelerate the leaching kinetics of ce-ment paste. The change of sample mass over time was monitored by weighing, whereas the amount of calci-um ion leached out during the test was followed by ion chromatography. A variety of post-analysis tech-niques like XRD, MIP and BET were used to characterize the microstructural changes and portlandite content, while the degraded front was determined by phenolphthalein spraying. The effect of accelerated leaching on transport properties was studied by measuring changes in water permeability. Results showed that (i) the porosity of the leached samples increased significantly, (ii) the critical pore size was shifted to larger radius and (iii) the BET specific surface area of the leached sample was also significantly increased. These changes resulted in a one to two order increase in water permeability depending on the immersed time.
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ABSTRACT
Although Ca leaching in cement-based materials is an extremely slow process, this process is relevant for long-term assessments of the evolution of concrete used in radioactive waste disposal systems. In the present work, an ammonium nitrate solution of 6 mol/l was used to accelerate the leaching kinetics of ce-ment paste. The change of sample mass over time was monitored by weighing, whereas the amount of calci-um ion leached out during the test was followed by ion chromatography. A variety of post-analysis tech-niques like XRD, MIP and BET were used to characterize the microstructural changes and portlandite content, while the degraded front was determined by phenolphthalein spraying. The effect of accelerated leaching on transport properties was studied by measuring changes in water permeability. Results showed that (i) the porosity of the leached samples increased significantly, (ii) the critical pore size was shifted to larger radius and (iii) the BET specific surface area of the leached sample was also significantly increased. These changes resulted in a one to two order increase in water permeability depending on the immersed time.
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