Feasibility study of using carbonated and ultrasound treated electric arc furnace slag as a nano-enhanced supplementary cementitious material

Abstract

As a primary by-product of the electric arc furnace (EAF) steelmaking process, the relatively low carbonation capacity of EAF slag limits its use as a carbon-sequestering construction material. To address this limitation, this study proposed a two-step chemical-physical modification approach. First, a gas-solid carbonation process was applied, where humidity, temperature, CO₂ concentration, and carbonation duration were adjusted to specifically promote the growth of aragonite whiskers. Next, the carbonated EAF slag underwent liquid-phase ultrasound treatment, and the resulting liquid-solid mixture was used to prepare cement paste. The effect of the two-step modification was evaluated by characterizing the physical properties, microstructural evolution, and phase transformation of the EAF slag. The study further elucidated the feasibility of using modified EAF slag as a supplementary cementitious material (SCM) by examining its nucleation morphology, hydration products, and impact on hydration kinetics. Ultrasound treatment uniformly dispersed the aragonite whiskers, which acted as nanomaterials to fill the pores in the cement paste. Additionally, the exposed silica-rich surface facilitated the nucleation of C-S-H during hydration. The refined pore structure of the hardened paste ultimately resulted in a 30–50 % improvement in compressive strength compared to the untreated group and a 10–20 % increase compared to the pure ordinary Portland cement group. This study offers a novel perspective on utilizing EAF slag as an environmentally beneficial SCM, uncovering its potential properties while addressing the objectives of the CCUS strategy.