A user-friendly and low-carbon approach to tackle the later-age strength degradation of low-carbon cement : application of dry ice

Abstract

Calcium sulfoaluminate (CSA) cement is recognized as a promising low-carbon alternative to Portland cement for mitigating carbon emissions. However, its widespread application is limited by the degradation of its later-age strength, primarily attributed to the unstable expansion of ettringite, one of its hydration products. This study proposed a user-friendly and low-carbon approach to mitigate this degradation by incorporating dry ice. The incorporation of dry ice enhanced the compressive strength of CSA cement at both early and later ages. At 1 d, specific amounts of dry ice (0.6 wt% ∼ 1.2 wt%) promoted the hydration of ye'elimite, generating more ettringite with smaller crystallite size and densifying the pore structure. By 28 d, the use of large amounts of dry ice (0.8 wt% ∼ 1.2 wt%) effectively alleviated the later-age strength degradation by promoting the carbonation of ettringite, thereby reducing both its crystallite size and content. The formation of calcium carbonate and smaller ettringite crystal could achieve a synergistic effect to fill the pore structure, leading to smaller pore volume and lower porosity.