Evolution of C-S-H morphology at early age: New insights from direct TEM observation
Yu Yan, Guoqing Geng
Abstract
Numerous types of calcium silicate hydrates (C-S-H) gel morphology have been reported. While the mechanisms of C-S-H solidification and morphology development are still largely unclear. This paper systematically studied the development of C-S-H morphology in a white Portland cement (WPC) paste using transmission electron microscope (TEM). As early as 60 s after mixing, C-S-H gel can be observed on the surface of WPC particle. Four typical C-S-H morphologies, namely featureless, fiber-like, blade-like and foil-like, were found in the suspensions. We demonstrated that C-S-H has multiple steps of morphology change, and significant morphological diversity during the precipitation process. The effect of pH value and calcium concentration on the assemblage procedure and final morphology state of C-S-H was also investigated.