Produce low-CO2 sustainable cement–slag binder incorporating aluminum sulfate

Using slag to produce low-carbon building materials is a sustainable strategy to recycle industrial byproducts. However, with a high clinker substitution rate, the delayed early strength development of slag–cement binders severely limits their applicability in practical engineering. This study investigated the mechanism of action by which aluminum sulfate promotes early strength. Its influence on hydration, microstructure, hydration products, mechanical properties, and CO₂ emissions was investigated. The analysis indicated that aluminum sulfate accelerated the dissolution of C₃S during the induction period, but the precipitation of a large amount of ettringite hindered further hydration. However, this hindering effect decreases as hydration continues. At a 1% dosage, the CO₂ emission per unit strength is the lowest. At a 2% dosage, the early strength can be effectively increased by 38.01%. By comparison, alkali-free aluminum sulfate improves the sustainability and mechanical properties better than an alkaline accelerator (sodium carbonate).