Effects of Additives on the Hydration of Cement Paste with Large Water Solid Ratio (W/S=1) and the Microstructure of the Hardened Cement Paste

摘要

Ordinary Portland cement(OPC), low heat Portland cement(LHC) and Eco-cement(EC) pastes in the presence of various additives such as limestone powder, granulated blast furnace slag, silica fume or fly ash with large water solid ratio (W/S=1) were prepared by using special viscosity thickener and polycarboxylic acid type superplasticizer. These pastes were cured for 1day to 4years in water at 20C. Hydration process and microstructure were discussed by hydration rate and pore structure in the hardened pastes. Obtained results were summarized as follow. In the paste with large water solid ratio, hydration rate of cement was larger than that with generally used water cement ratio, because it was not affected by the decreasing effect of densification of microstructure by formation of hydrates. Belite in the cements was almost hydrated within the 182days of curing. The morphology of hydrates was changed considerably with the kind of cement. And the morphology of the hydrates largely affected on the pore structure of the pastes. The large pore around 500nm in diameter was only observed in the hardened EC pastes of 1 years of curing. In the addition of lime stone powder, monocarbonate hydrate was produced and the amount of pore between 10-104nm in the hardened pastes were larger than that without additives. In the addition of slag, the amount of pore between 10-104nm in the hardened pastes was less than that without additives, the pore structure in the hardened pastes was changed considerably with the kind of cement. In the addition of silica fume, ettringite remained in the hardened paste for 4years of curing, pore size and the amount of pore between 10-104nm in the hardened pastes were small or less than that without additives.