Analysis of the Stability and Reactivity of Carbonated Steel Slag Powder as a Supplementary Cementitious Material

In order to address the poor volume stability and low reactivity of steel slag powder (SS) as a supplementary cementitious material (SCM), this study investigates a microbial-assisted carbonation method for its enhancement. Using untreated SS as a control, we compared the performance and microstructure of carbonated steel slag powder (CSS) and bio-mineralized steel slag powder (BSS). Results indicate that, compared to CSS, BSS exhibits a more significant reduction in the content of f-CaO and f-MgO (from 6.25% and 3.19% to 0.8% and 1.36%, respectively) and a greater improvement in 7-day and 28-day activity indices (from 59% and 72% to 78% and 87%), leading to markedly enhanced volume stability and reactivity. Calculations show that each ton of BSS can sequester 114.2 kg of CO2, and it achieves a cement replacement ratio exceeding 30%. The utilization of BSS as an SCM not only addresses the inherent technical challenges of steel slag powder but also creates dual environmental benefits through emission reduction and active carbon sequestration, demonstrating significant potential for advancing the low-carbon transition in the construction materials industry.