The influence of two types of alkali activators on the microstructure and performance of supersulfated cement concrete： mitigating the strength and carbonation resistance

Abstract As a low-carbon cementitious material, the supersulfated cement (SSC) is composed of a thimbleful of cement clinkers and massive industry by-products, i. e: gypsum and slag. However, the concrete made from SSC suffers low strength, poor carbonation resistance, inferior frost resistance, etc. In such a scenario, two types of alkali activators (lactates and sodium hydroxyl) were employed to improve the microstructure and mitigate the performance of supersulfated cement concrete. The results indicate that the incorporation of lactates effectively improves mechanical performance, water impermeability, and carbonation resistance of supersulfated cement concrete. However, the addition of sodium hydroxide failed to result in a performance enhancement of SSC concrete. Furthermore, the mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) were comprehensively utilized to illustrate the microstructure changes of supersulfated cement concrete. It indicates the hydration degree of supersulfated cement was promoted by the addition of lactates, which refined the pore structure of concrete. A more compact matrix conduces to overall performance enhancement. This work may shed new lights on the microstructure optimization of solid-waste-based binding materials and further promote the application of SSC concrete.