Performance of Self-Healed Alkali-Activated Slag Mortar at Elevated Temperature

Abstract

Microbially induced calcium carbonate precipitation (MICP) is a novel technology aimed at improving the strength and durability of concrete by using micro-organism species. This paper investigated the influence of the bacterial treatment on the strength parameters and microstructures of alkali-activated slag (AAS) mortars at elevated temperatures. Four AAS mortar mixtures containing varying concentrations of Bacillus pasteurii (103, 105, and 107 cells/mL) were investigated at target temperatures of 23°C, 200°C, 400°C, 600°C, and 800°C. After reaching the target temperature, mass loss, compressive strength, and flexural strength tests were carried out on the specimens. Scanning electron microscopy (SEM), X-ray spectroscopy (EDS), and X-ray diffraction (XRD) tests were conducted to compare the microstructure characteristics of bacteria-containing mortars and the control mortar. The results showed a substantial increase of compressive and flexural strength of AAS mortars at ambient and elevated temperatures. In addition, the microstructure analysis indicated that the bacterial specimens produced calcite, leading to crack healing and improvement of mechanical properties; this confirms the functionality and viability of incorporating Bacillus pasteurii in the alkaline environment of AAS mortars.