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Title |
Effect of Na2SO4 on Autogenous Healing in Initial Cracking of Blast Furnace Slag Cement Paste
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Authors |
이승헌(Seung-Heun Lee); 김홍주(Hong-Joo Kim); 임영진(Young-Jin Lim); 김동현(Dong-Hyun Kim); 박병선( Byeong-Seon Park) |
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DOI |
https://doi.org/10.4334/JKCI.2019.31.3.261 |
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Keywords |
자기치유; 고로슬래그 시멘트; Na2SO4; C-S-H; 방해석 autogenous healing; blast furnace slag cement; Na2SO4; C-S-H; Calcite |
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Abstract |
In this study, the autogenous healing properties in initial cracking of blast furnace slag cement paste with 5 % Na2SO4 as an activator for blast furnace slag were investigated. The major autogenous healing products in the cracks were C-S-H, calcite and the addition of Na2SO4 formed 3.7 times more autogenous healing products than no addition. The autogenous healing enhancement effect by Na2SO4 increases the amount of C-S-H generated by accelerating the hydration reaction of un reacted blast furnace slag and cement particles at the crack surfaces. It is considered that Ca(OH)2 formed simultaneously with C-S-H reacted with CO32-(HCO3-) ion in the solution in the crack and CO2 in the air and converted to calcite. Addition of Na2SO4 increased the concentration of Na+ and SO22- ions in solution in crack and precipitated with alkali carbonate and alkali sulfate during water evaporation. In the morphology of autogenous healing products, calcite had a small grain shape, C-S-H had a network shape, alkali carbonate had a large crystal form, alkali sulphate had an elongated plate shape, and Na2SO4 added crystals had grown to form larger without it.
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