Reaction mechanism of dolomite powder in Portland-dolomite cement

The purpose of this study is to provide a better understanding of the reaction mechanism of dolomite powder in Portland-dolomite cement (PDC). The hydration products and microstructure of PDC pastes were investigated by using XRD, TGA, MIP, and SEM, with Portland-limestone cement (PLC) as a comparison. Results show that dolomite exhibited a considerably higher chemical reactivity than limestone as the curing temperature increased. Different from the conventional dedolomitization reaction with brucite formation, the dolomite reaction in PDC at 40 and 60 °C produced hydrotalcite and calcite at the expense of portlandite. Moreover, the formed hydrotalcite was found to result in the decomposition of the Al-bearing products, such as monosulfate, monocarbonate and ettringite, due to its lower solubility. Overall, the reaction of dolomite increased the solid volume, densified the microstructure, and thus resulted in a refined pore structure and a higher long-term compressive strength of PDC compared to PLC.