Exploring morphological effects and multi–scale analysis on the mechanical properties and volume stability of composite mortar

Abstract

This study conducted experimental research on the strength and micro–expansion properties of cement mortar with varying dosages of steel slag powder (SSP) and fly ash (FA) to enhance the application of SSP as a mineral admixture in concrete cementitious material systems. Scanning electron microscopy and X-ray diffractometry were employed to analyze the microscopic morphology and structure of the specimens before and after hydration. The study discussed the impact of the water–to–binder ratio (w/b), curing age, SSP, and FA dosage on the mechanical properties and volume stability of mortar. Then models for predicting the strength and expansion deformation prediction through correlation analyses were proposed. The results indicated that the mechanical strength of the mortar decreased with increasing substitution of the composite admixture, while reducing w/b and increasing SSP dosage improved the resistance to shrinkage, with the resistance shrinkage positively correlated with SSP dosage under the same w/b. Furthermore, correlation analyses revealed that the cement and SSP dosage significantly affected the 28-day strength and 90-day expansion deformation of mortar, and the established models can well describe the strength and expansion deformation of composite mortar incorporating SSP, providing valuable insights for the engineering application of SSP.