Abstract
The effect of organic retarders on the nucleation mechanism of calcium silicate hydrate (C-S-H) is still under debate. In this study, the effects of organic admixtures Dextrin, citric acid (CA), and citric acid modified chitosan (CAMC) on the early formation of C-S-H were investigated. The results indicated that the C-S-H formation followed a non-classical nucleation mechanism: amorphous silicate droplets formed first and then crystallized into thin foil-like tobermorite-type C-S-H. The –COOH group affected the Ca/Si ratio of the C-S-H product and reduced the particle reaction driving force, which is the main reason for the transition of the synthesis process from endothermic to exothermic. The formation of hydration products was not inhibited by nucleation disruption, Ca complex precipitation, or encapsulation of silicate spheres; instead, it was by the reduction of free Ca2+ normally involved in the formation process.
Published Version
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