SPECIAL TOPIC: UHPC MATERIAL AND ENGINEERING APPLICATION |
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A Study for Compound Salts Attack on Ultra-high Performance Cement-based Materials: the Stabilities of Chemically Synthesized Friedel Salt and Ettringite in Solutions of Sulfates and Chloride Salts |
GUO Liping1, 2, 3, ZHANG Jian1, CAO Yuanzhang1, ZANG Wenjie1
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1 School of Materials Science and Engineering, Southeast University, Nanjing 211189; 2 Jiangsu Key Laboratory of Construction Materials, Nanjing 211189; 3 Collaborative Innovation Center for Sustainable Civil Engineering Materials & Structures, Nanjing 211189; |
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Abstract Pure Friedel salt (3CaO·Al2O3·CaCl2·10H2O, main corrosion product of cement-based materials by chloride ions) and ettringite (AFt, 3CaO·Al2O3·3CaSO4·32H2O, main corrosion product of cement-based materials by sulfate ions) were chemically synthesized and then characterized via X-ray diffraction and TG-DSC test to investigate their stabilities and transform mechanism. The interaction between different corrosion ions was explored by immersion experiment. The results indicated that sulfates have a significant impact on Friedel salt, as sulfate ions can substitute for chloride ions in Friedel salt and convert Friedel salt into ettringite. Chloride salts can also react with ettringite, leading to ettringite's decomposition. There is an equilibrium between Friedel salt and ettringite, and the inter-transform of them can be achieved under certain conditions. The study verified the interaction effect during the corrosion process of the compound solution of chloride salt and sulfate toward hardened cement paste.
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Published: 10 December 2017
Online: 2018-05-08
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