Development of ultra-high-performance concrete with low environmental impact integrated with metakaolin and industrial wastes

Industrial waste contributes to serious environmental issues. However, these issues can be solved by utilizing them as building materials. This paper investigated the effects of substituting the cement with a variety of industrial wastes and metakaolin (MK) on ultra-high-performance concrete (UHPC) properties. The industrial wastes used in this study include silica fume (SF), granulated blast-furnace slag (GGBS), and fly ash (FA). The prepared mixtures were created by varying the amounts of Portland cement, GGBS (30-50%), FA (20-30%), or MK (15-25%), while maintaining a constant amount of SF of 15%. The mechanical, durability, and micro-structural characteristics of the mixtures were investigated. This study also uses life cycle assessment to estimate the reductions in embodied energy consumption, life cycle cost, and carbon footprint associated with integrating metakaolin and industrial waste. The results indicated that the inclusion of 15%MK led to an increase in the compressive, flexural, and splitting tensile strengths. Also, the chloride permeability resistance was enhanced. The mechanical properties and chloride-ion permeability resistance of the ternary mixtures with 50%GGBS and 25%MK were the lowest compared to other mixtures. These results were supported by SEM micrographs and EDX analysis for the UHPC structure, which demonstrate the high-density microstructure and extremely thin interfacial transition zone thickness. The inclusion of industrial waste and metakaolin can lower environmental impact of UHPC without compromising the mechanical performance. Also, the environmental assessment shows that the UHPC containing industrial waste has a lower impact on the environment, which means they could make cleaner products in the near future.