The effect of the cooling process of ferrochrome slag waste on its performance as a sustainable supplementary cementitious material

This study presents a comprehensive experimental research study to investigate the feasibility of utilizing mechanically activated ferrochrome slag (FCS) as a supplementary cementitious material (SCM) for manufacturing eco-friendly mortar, aiming to address the pressing need to reduce the energy-intensive production of ordinary Portland cement (OPC). Two types of slag, air-cooled (AC-FCS) and water-cooled (WC-FCS), were used to partially replace ordinary Portland cement (OPC) at substitution levels of 5% to 35% (in 5% increments) to determine the effect of the cooling process of FCS on the mortar performance. The examination includes key parameters such as flowability, fresh and hardened density, porosity, compressive strength, flexural strength, ultrasonic pulse velocity (UPV), microstructural study of the blended mortar, rapid chloride permeability and mechanical performance at elevated temperatures. Chemical composition, crystallinity and amorphousness of the FCS samples were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests. The research is filling the gap of comparative evaluation of mechanically activated AC-FCS and WC-FCS as supplementary cementitious materials in the cement mortar. The analysis confirmed that FCS exhibits pozzolanic characteristics similar to Class F fly ash. Mortars containing up to 15% WC-FCS had comparable or higher 28-day compressive strength than the control mix. The optimum performance was observed at 10% WC-FCS, where compressive strength rose by 16% along with better chloride resistance and thermal performance. The findings highlight WC-FCS as an effective SCM, fostering circular economy goals in the construction sector.