Influence of Calcium Silicate Hydrate Seed on Compressive Strength of CaO-SiO2-H2O Autoclaved System and Its Mechanism Analysis
ZHANG Haidong1,2,WEI Jiangxiong1,2, ZHAO Zhiguang1,2, YU Qijun1,2, LI Fangxian1,2
1 School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640; 2 Low Carbon Technology Engineering Research Center for Building Materials of Guangdong Province, Guangzhou 510640;
Abstract: The effect of calcium silicate hydrate seed on the CaO-SiO2-H2O hydrothermal reaction was studied. Calcium silicate hydrate seed were prepared by hydrothermal synthesis with lime and nano silica under different thermal conditions. Chemical analysis method was used for the determination of reactive degree of fly ash. The effect of calcium silicate hydrate seed on types and morphology of hydration products was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS). The distribution of pore size was investigated by mercury intrusion porosimetry (MIP). The results indicated that the compression strength of CaO-SiO2-H2O autoclaved system increased most obviously when mixed with calcium silicate hydrate and synthesized under the 150 ℃ with calcium silica ratio of 1.0. Calcium silicate hydrate seed promoted dissolution of SiO2PPP from fly ash and decomposition of hydrogarnet, and accelerated the generation of hydration products (mainly C-S-H(B) and tobermorite). Meamwhile, the pore structure was refined and the distribution of the pore size was more uniform with the addition of calcium silicate hydrate. The addition of calcium silicate hydrate caused the number of pores below 50 nm increase and the number of pores above 200 nm decrease, compared with the reference sample.
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2017, Vol. 31 
