Engineering properties and stability of high-performance mortar incorporating untreated and treated steel reducing slag aggregate

Abstract

The purpose of this study was to investigate the effect of steel reducing slag aggregate (SRSA) on the mechanical and durability properties of high-performance mortar specimens. Two series of mortar specimens were produced for this study using treated and untreated SRSA. Each type of SRSA was used as a partial-to-complete replacement for natural fine aggregate at the following ratios: 25%, 50%, 75%, and 100%. The water-to-binder ratio (w/b) in all of the specimens was designed at 0.35. The mechanical properties and durability of the specimens were observed using slump flow, fresh unit weight, compressive strength, water absorption and porosity, ultrasonic pulse velocity (UPV), electrical surface resistivity (ESR), thermal conductivity (TC), sulfate attack resistance, and expansion rate. Scanning electron microscopy (SEM) was conducted for the microstructure analysis. The findings indicate that increasing the SRSA content is negatively correlated with mortar strength development and durability, with higher SRSA content reduced mortar compressive strength and durability performance comparing with reference mixture. However, most of the SRSA mortar mixtures exhibited good strength and excellent durability, with high UPV (≥3660 m/s) and ESR (≥20KΩ-cm) values. Notably, compared to the mortar specimens made using untreated SRSA, those made using treated SRSA exhibited better performance and better volume stability.