Reaction and microstructural characteristics of OPC pastes with low-lime calcium silicate cements under carbonation curing

Low-lime calcium silicate cement is one of the promising alternative binders with low CO2 emissions. Ordinary Portland cement and the type of calcium silicate cement in the present study were combined, and the initial setting and flow characteristics of the pastes under carbonation curing condition were examined via flowability and penetration depth tests. In addition, compressive strength, thermogravimetric, and mercury intrusion porosimetry tests were conducted to investigate the reaction and microstructural characteristics of the Portland cement pastes with low-lime calcium silicate cement. The calcium silicate cement used in the present study was synthesized with limestone and silica fume. The content of the calcium silicate cement added to the pastes varied from 0 to 50% by the weight of the Portland cement, and the concentration of gaseous CO2 for the carbonation curing was fixed at 5.0%. The test results showed that initial setting and flowability were dominantly affected by the reaction of the Portland cement. The reaction of low-lime calcium silicate cement occurred between 1 and 3 days of curing, thereby the compressive strength of the pastes with calcium silicate cement of not less than 30 wt % increased as the curing period increased.