Exploring Early Carbonation Properties of Sr4Al6O12SO4 Compound for a Sustainable Alternative to Cement Clinker

Sr4Al6O12SO4 is a compound that can be used as a sustainable alternative to cement clinker for producing low-carbon precast concrete products. In this study, we examine the impact of CO2 curing on early carbonation properties of Sr4Al6O12SO4. The findings indicate that the carbonation potential of Sr4Al6O12SO4 is substantial for use in CO2 sequestration within the construction sector. The carbonation strength and CO2 uptake of the concrete blocks exhibit a positive correlation with extended carbonation duration, achieving a maximum compressive strength of 63 MPa after 48 h of carbonation. Compared with 2 h, the beneficial strength gain at 24 and 48 h is 39.57% and 70.73%, respectively. This strength gain is mainly due to the formation of rich carbonation products and the reduction of porosity and average pore size within the paste matrix. Furthermore, due to its high degree of crystallinity, SrCO3 is identified as the primary crystalline carbonation product, characterized by large micrometer-sized subrounded grain aggregates. The continued formation of SrCO3 encapsulates unreacted species covered by wet gel layers, leading to a thick microstructure that significantly enhances mechanical strength. This study presents a promising way for employing CO2 curing to produce eco-friendly Sr4Al6O12SO4-based construction materials.