Microstructural phase evolution and strength development of low-lime calcium silicate cement (CSC) paste incorporating ordinary Portland cement under an accelerated carbonation curing environment.

Low-lime calcium silicate cement (CSC) is a CO 2 -reactive cement that utilizes the carbonation products of low- or non-hydraulic C 2 S, C 3 S 2 , and CS phases under H 2 O- and CO 2 -rich conditions. However, the reactivity and compressive strength of the CSC require further improvement. Therefore, this study aims to investigate the effects of blending ordinary Portland cement (OPC) as a reactive source into CSC on the initial reaction kinetics, phase evolution, and compressive strength development during carbonation curing. To assess the effects of blending CSC and OPC, CSC was substituted by OPC with the incremental ratio of 20 wt%. Notably, the CSC sample with 20 wt% OPC incorporation exhibited the highest compressive strength, which increased by up to 2.5 times compared to the pure CSC paste. Analysis of the microstructural phase evolution revealed that this significant increase in compressive strength was attributed to the strong mechanical interlocks between the rhombic CaCO 3 crystals, which were reinforced by a substantial amount of vaterite. [Display omitted] • Microstructure of blended CSC and OPC pastes under carbonation curing was studied. • Incorporation of OPC enhanced the initial reaction and Ca leaching of the cement paste. • Blending ratio of CSC:OPC= 8:2 was the most favorable for the formation of vaterite. • Vaterite generated on the calcite crystals reinforced the mechanical interlock. • Reinforced mechanical interlock significantly enhanced the compressive strength. [ABSTRACT FROM AUTHOR]