Strength and microstructure of CO2 cured low-calcium clinker

Portland cement clinker contains more than 50% tri-calcium silicate (C3S) and is produced at ∼ 1450 °C, which releases about 850 kg CO2 per ton of clinker. Therefore, the use of dicalcium silicate (C2S) or rankinite (C3S2) in cement can be an alternative to reduce CO2 emission due to their low-calcium. In the present study, a novel low-calcium clinker containing C3S2-γ-C2S-C2AS (Ca2Al2SiO7) was synthesized, then the clinker was under carbonation curing. Experimental results show that the low-calcium clinker was synthesized at sintering temperature of 1320 °C, lower 130 °C than that of Portland cement. The clinker with non-hydraulic phases can be fully harden within 24 h and obtain a higher compressive strength. The mainly carbonation products of the clinker were calcite, aragonite and polymerization silica gels, which was attributed to the compressive strength development. In addition, calcium hydroxide and C-S-H were not detected due to the non-hydraulicity properties of C3S2 and γ-C2S. The carbonated clinker samples displayed a denser microstructure and lower pore structure. This study shows that the low-calcium and low sintering temperature clinker can obtain a better performance through carbonation curing.