Enhancement mechanism of micro-iron ore tailings on mechanical properties and hydration characteristics of cement-steel slag system

Abstract

The limited cementitious activity of steel slag (SS) powder restricts its large-scale utilization as a replacement material for Portland cement and even more so for inert iron ore tailings (IOT). The micro-IOT (MIOT) were utilized as additives to improve the compressive strength and hydration degree of a binary system containing SS and PC. Compressive strength, flowability, and setting time were measured. The mechanism of MIOT on the hydration properties and microstructure of the cement–SS binary system was investigated using XRD, TG, FTIR, SEM, and MIP. The results revealed that the 28-d compressive strength of composite mortar S20M10 (20% SS and 10% MIOT) with MIOT added to the cement–SS system was 50.32 MPa, which was 93.41% of that of the cement samples and 16.16% higher than the compressive strength of the cement-SS system. Wet grinding of IOT lowered the crystallinity and surface binding energy, increased the reactivity, and facilitated the participation of MIOT in the hydration reaction with the reactive silica-alumina phases in SS, producing more C–S–H. The formation of carbonate AFm phases in the composite system improved the strength. MIOT in suitable dosage can limit the maximum possible pore and porosity of the composite system, increasing the structure's complexity and making the hardened slurry denser. This study provides a solution for IOT activity activation and promotes high-value utilization of SS and IOT.