Experimental and Theoretical Study on Formation Mechanism of Calcium Silicate Hydrate

• 1、State Key Laboratory of Water Resource and Hydropower Engineering Science

Abstract：Structure of calcium silicate hydrate in Portland cement paste was studied by X-ray diffraction, Fourier transform infrared spectroscopy, 29Si MAS NMR respectively and from the viewpoints of several main models for the nanostructure of C-S-H. The research shows that the structure of calcium silicate hydrate in Portland cement paste was different from the crystalline 1.4nm-tobermorite and jennite; C-S-H in cement paste at early age was dimeric and Ca-OH bonds probably occur in it; Formation of Si-OH results from protonation of dimers was critical for increasing the polymerization degree of C-S-H gel; Polymerization between hydrated monomer formed during the hydration process and the protonated dimmers resulted in a few longer silicate chains; The chains of dreierketten with less Ca-OH bonds represent the tobermorite-like strutures and the ones with more Ca-OH bonds represent the jennite-like structures ,however, the chains of dreierketten can not exist in a large number in the paste hydrated for 28 days at 20 C; Al[4] behaved like the hydrated monomer(Q0H) to combine the dimeric C-S-H into aluminosilicate chains.

Keywords： C-S-H microstructure polymerization degree mechanism cement