| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 98 === In this study, the effects of the pre-treatment temperatures (40, 60, and 80oC) on the crystallization, microstructure, and formation kinetics of xonotlite for C-S-H gels with Ca/Si=1 after steam curing at high temperature were investigated. The results showed that (1) a higher amount of amorphous calcium silicate was observed for the sample pre-treated at 60oC. (2) NMR results found that SiO44- remained as monomer for the sample with the pre-treatment temperature of 60oC and the SiO44- condensed to form silicate chains for the sample pre-treated at 80oC. (3) Based on the results of the micro-pore analysis, the sample pre-treated at 60oC had lower porosity, suggesting that it had more amorphous calcium silicate and poor crystallinity. However, the sample pre-treated at 80oC had the highest porosity, indicating that it had the best crystallinity. (4) The formation mechanism of xonotlite was via dissolution and precipitation. The dissolution of the ordered C-S-H gel after heat pre-treatment at 80oC needed higher activation energy to form xonotlite during steam curing process, which delayed the formation of xonotlite after steam curing for 24 h. However, at higher steam-curing temperatures (200oC), xonotlite formed rapidly independent of the crystallinity of C-S-H gels.
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