Phase Composition of Hydrated DSP Cement Pastes

Abstract

Cement pastes densified with small particles (DSP) containing up to 48% silica fume by weight of cement, and hydrated to up to 180 d at room temperature, have been analyzed using TMS‐GPC, TGA, and 29 Si NMR to quantitatively estimate the amount of unreacted cement, Ca(OH) 2 , and residual silica fume, respectively. Using a mass balance approach, the CaO/SiO 2 and H 2 O/SiO 2 molar ratios of the C‐S‐H in the samples were calculated. For samples containing silica fume, the values of CaO/SiO 2 lie between 0.9 and 1.3, depending on the degree of hydration and silica fume content, whereas for samples without silica fume they were 1.6. Silicate polymerization analysis using TMS‐GPC suggests that the molecular structure of the C‐S‐H is similar to that formed in conventional hydration. No cross‐linking species were found, but the fraction of higher polymers (above octamer) increases as the CaO/SiO 2 ratio decreases.