Optimal design of sustainable recycled rubber-filled concrete using life cycle assessment and multi-objective optimization

Abstract

This research studies the use of recycled crumb rubber (CR) as partial replacement for fine aggregates in concrete. Fracture analysis and Life Cycle Assessment (LCA) approach are used to assess 10 different Recycled Rubber-Filled Concrete (RRFC) mixtures by evaluating damage across 22 impact categories using the ReCiPe 2016 methodology. Multi-objective optimization (MOO) is deployed to identify optimal mixture proportions of RRFC using a BPNN-AGE-MOEA model. The MOO process considers concrete characteristic objectives, environmental assessment, and cost, while imposing boundary values for target compressive strength, water-to-cement (W/C) ratio, and CR content. The results show that increasing the CR content increases toughness and energy absorption capacity yet decreases the compressive and tensile strengths. Reducing the W/C ratio and increasing the CR content improved fracture characteristics and crack resistance. It is also found that the mechanical properties and the transportation stage of RRFC manufacturing have a significant effect on the environmental footprint. Careful material selection and transportation strategies can significantly reduce this environmental footprint. The proposed MOO approach using the predictive BPNN model successfully resolved the complex relationship between economic and environmental considerations of mixture design variables. To achieve a balance of environmental impact, affordability, and performance, the study underlines the need for carefully balancing the W/C ratio and CR content. The findings suggest that enhancing fracture properties while limiting the environmental impact is possible, allowing to promote wider application of recycled rubber in concrete.