Influence of copper-impregnated basic oxygen furnace slag on the fresh- and hardened-state properties of antimicrobial mortars

Microbially induced concrete corrosion (MICC) is recognized as one of the main degradation mechanisms of sewer infrastructure worldwide. To help control this problem, a beneficial reuse path for basic oxygen furnace slag (BOFS) has emerged in which the incorporation of copper-laden BOFS particles into cementitious materials inhibits the growth of microorganisms responsible for MICC. This study investigated the effect of substituting fine aggregate with copper-laden BOFS particles (0.30–0.85 mm) on the hydration and microstructural evolution of portland cement mortars. In addition, the fate of copper in the cured cementitious matrix is elucidated and reported herein. As revealed by isothermal calorimetry, the total evolved heat at the end of the testing period (118 h) was similar when up to 40% of the fine aggregate mass was replaced with copper-laden BOFS particles of similar size, while delays in setting times were observed. Analysis of microstructural evolution using quantitative X-ray diffraction (QXRD) showed higher C–S–H contents when fine aggregate was replaced with copper-laden BOFS, indicating copper-laden BOFS exhibited some degree of pozzolanic reactivity. Electron microprobe analysis (EMPA) revealed that, while trace amounts of copper could be detected throughout the cement matrix, copper was predominantly localized in a 100 μm spherical region surrounding BOFS particles. Moreover, strong binding capacity of Fe-rich BOFS particles for copper was observed. Finally, compressive strengths of mixtures analyzed herein were not affected by the presence of copper-laden BOFS.