Pore Structures of Mortars with Dolomite and Limestone Powders Cured at Various Temperatures

Strength of blended cements mortars with dolomite powder (DM) at different replaced contents, i.e., 10% and 30%, and cured at 20, 40℃ and 60℃ were investigated. Limestone powder (LS) was also used for the comparison. The pore structure of blended cements mortars were examined by mercury intrusion porosimetry (MIP). The results indicate that DM and LS have different effects on the mortar strength at various replacement levels and curing temperatures. At 20℃ and 40℃, LS shows more positive impact on the promotion of the early strength, compared to DM, but this difference decreases with the increase of replacement level and the curing age. Compared to the mortars with LS, increasing the curing temperature to 60℃ gives a stronger promoting effect on the strength of mortars with DM, and the effect is more pronounced with the increase of replacement levels. With the incorporation of dolomite or limestone powders, the porosity of mortars increases. At the replacement level of 10%, DM and LS show similar effects on the pore size distribution of mortars. Compared to the mortars with LS, the mortars with DM cured at 20℃ have a greater porosities and larger pore sizes. When cured at 40℃, the mortars with DM and LS develop the similar porosity and pore size distribution. When the curing temperature is 60℃, the mortars with DM show a lower porosity and better pore size distribution, compared to the mortars with LS. DM gives a superior effect on the pore structure of mortars when the curing temperature increases. DM develops a stronger chemical effect at high curing temperatures and results in the formation of hydrotalcite, which is beneficial to decreasing the porosity, improving the pore structure and promoting the strength of cement mortars.