Comparative performance of alkali activated slag/metakaolin cement pastes exposed to high temperatures |
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| Affiliation: | 1. Department of Materials Science, Technical University of Madrid, E28040 Madrid, Spain;2. Eduardo Torroja Institute for Construction Science (C.S.I.C.), E28033 Madrid, Spain;1. Department of Civil and Environmental Engineering, Clarkson University, 8 Clarkson Avenue, Box 5712, Potsdam, NY 13699, USA;2. Department of Civil and Environmental Engineering, Clarkson University, 8 Clarkson Avenue, Box 5710, Potsdam, NY 13699, USA;1. College of Chemistry and Chemical Engineering and Guangxi Key Lab of Petrochemical Resource Processing and Process Intensification Technology, Guangxi University, Nanning, 530004, PR China;2. College of Chemistry and Materials Science, Guangxi Key Laboratory of Natural Polymer Chemistry and Physics, Guangxi Teachers Education University, Nanning, 530001, PR China;3. Key Laboratory for Green & Advanced Civil Engineering Materials Application Technology of Hunan Province, College of Civil Engineering, Hunan University, Changsha, 410082, PR China;1. Cinvestav Saltillo, Ceramics Engineering Group, Av. Industria Metalúrgica No. 1062, Parque Industrial, Ramos Arizpe, Coahuila, MX, C.P. 25900 Saltillo, Coahuila, Mexico;2. Centro de Investigación y Desarrollo Tecnológico, Universidad Autónoma de Nuevo León Pedro de Alba s/n, Ciudad Universitaria, San Nicolás, N.L., Mexico;1. Building Materials Research and Quality Control Institute, Housing & Building National Research Center, HBRC, Cairo, Egypt;2. Raw Building Materials Technology and Processing Research Institute, Housing & Building National Research Center, HBRC, Cairo, Egypt |
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| Abstract: | This paper presents a study on the effect of temperature exposure of binders of blast furnace slag (BFS) and metakaolin (MK) in BFS-MK weight ratios of 100-0, 50-50, and 0-100 activated with sodium silicate of modulus Ms = SiO2/Na2O = 1 and 5, 10 and 15% Na2O. A blended ordinary CPC-30R Portland cement reference was used. Pastes were subjected to exposure up to 1200 °C and the performance was evaluated in terms of compressive strength, residual strength, volumetric shrinkage, physical appearance and microstructural changes at different temperatures. All the binders retained more than 30 MPa after exposure to 800 °C for 4 h; specimens of MK and CPC-30R experienced the highest strength losses of 42 and 56% respectively, while those of 100-0 and 50-50 showed minor losses of ∼20%. After heating at 1200 °C the samples showed microstructural damage and more than 65% of strength losses. XRD indicated that the 100-0 and 50/50 binders are prone to form crystalline phases as akermanite, nepheline and nosean at temperatures greater than 1000 °C, while 0-100 geopolymeric binders preserved mostly an amorphous structure even at 1200 °C with some traces of mullite. The dehydration of C-A-S-H and N-A-S-H altogether with the crystallization of the binder gel induced the formation of highly porous microstructures. |
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| Keywords: | Alkali-activated composites Slag Metakaolin Structural evolution Thermal stability |
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