Carbon dioxide activated ladle slag binder

The viability of converting steelmaking ladle slag into cementing binder through carbon dioxide activation was studied. Two typical ladle slag materials were examined: one with higher silica content and one with higher alumina content. It was found that ladle slag with higher silica content contained more calcium silicate compounds and less free lime, leading to higher carbonation reactivity in its as-received form. Ladle slag with higher alumina could not be activated directly by carbon dioxide to gain strength. Heat treatment with silica addition was thus developed to produce more calcium silicates and reduce free lime content. Findings reveal that carbonation reactivity is not solely based on chemical compositions of the material, rather, the constituting mineralogical phases. Calcium silicates of any polymorph played a critical role in the formation of the strength-contributing binder matrix activated by carbonation. Strength gain was the result of simultaneous formation of calcium silicate hydrates and calcium carbonates. To produce value-added ladle slag as cementing binder to replace Portland cement, silicon is recommended as deoxidation agent in steel refinery process. The building products based on carbonation activated ladle slag have shown much reduced embodied energy and much reduced natural material consumption.