Low-carbon cement development via synergistic use of lead–zinc smelting slag and magnesium-rich lime mud

Abstract

Lead-zinc smelting slag (LZSS) presents potential as a supplementary cementitious material (SCM); however, its limited intrinsic reactivity and detrimental influence on hydration restrict its widespread application. This study proposes a sustainable strategy for low-carbon cement development by incorporating magnesium-rich lime mud (LM), a by-product of industrial water treatment, to enhance the performance of LZSS-based cement. The influence of LM on cement hydration behavior, mechanical strength development, and phase evolution was comprehensively evaluated. Experimental results revealed that incorporating 5 wt% LM markedly improved compressive strength from early to later curing ages, primarily attributed to the alkaline activation of LZSS and the formation of beneficial hydration products such as carboaluminates and hydrotalcite. In contrast, a higher LM dosage (15 wt%) significantly reduced strength despite enhanced clinker hydration, indicating an optimal LM content threshold. Leaching tests, conducted under neutral water conditions, indicated negligible release of heavy metals from the blended cements, confirming their environmental safety. While hydrotalcite formation may improve resistance to chloride ingress, comprehensive durability evaluation is still needed. Additionally, carbon footprint analysis demonstrated a substantial reduction in the global warming potential (GWP) of the blended cements. Notably, the LM15 formulation achieved a GWP reduction of up to 43 % relative to ordinary Portland cement. These findings highlight the potential of co-utilizing LZSS and LM to improve cement performance, ensure environmental safety, and reduce carbon emissions, thereby advancing the development of low-carbon and resource-efficient cementitious materials.