An Investigation into the Thermo-Physical, Mechanical, and Microstructural Properties of Cement Mortar Incorporating Hybrid Waste Slags

This study investigates the mechanical and thermal properties of cement mortars incorporating two types of waste slags: ferrochrome (FeCr) slag aggregate was used as a replacement for sand at ratios of 25, 50, 75 and 100 wt%, and ground granulated blast furnace slag (GGBS) was used as a partial replacement for cement at a ratio of 25 wt%. Compressive strength, volume of permeable voids (VPV), drying shrinkage, and thermal conductivity tests were conducted after 28 days of curing. The microstructure characteristics were examined by scanning electron microscopy. The experimental results revealed that FeCr waste aggregates could satisfactorily replace natural fine sand in cement mortars up to 25 wt% without a remarkable degradation of compressive strength. Furthermore, increasing the replacement ratios of FeCr aggregates by over 25 wt% resulted in a noticeable decrease in thermal conductivity and an increase in the permeable void content of cement mortars. The increased VPV of FeCr slag-blended mortars led to a significant increase in drying shrinkage. The integration of GGBS with FeCr aggregates led to enhanced compressive strength and reduced VPV and drying shrinkage, thus contributing to an improved microstructure.

Automated summary

The study shows that FeCr waste slag can replace natural fine sand in cement mortars without reducing compressive strength. Increasing FeCr aggregate replacement ratios decreases thermal conductivity and increases permeable void content, leading to significant drying shrinkage. Integrating GGBS with FeCr aggregates enhances compressive strength, reduces VPV and drying shrinkage, and improves microstructure.