Effect of Starting Materials on the Synthesis of Tobermorite

Abstract
The effect of starting materials on the synthesis of tobermorite was studied using29Si MAS and CPMAS NMR Spectroscopy. Three Q2 and one Q3 peak were identified during the crystallization of tobermorite from C-S-H. C-S-H, which had a Ca/Si ratio >1, crystallized readily because this C-S-H consists of dimer and short chains of silica tetrahedra. This occurred whenever quartz was used as a starting material. C-S-H, which had a Ca/Si ratio <1 was harder to crystallize because this C-S-H consists of long and cross-linked chains of tetrahedra. The latter was observed when amorphous silica was used as a starting material.