Integrated Life-Cycle and Multi-objective Optimization of Recycled Concrete with Rubber Particles and Recycled Coarse Aggregate for Low-Carbon Construction

The construction sector, as a major source of carbon emissions, must transition to low-carbon materials to achieve dual-carbon targets. Rubber recycled coarse aggregate concrete (RRAC), which replaces natural aggregates with waste tires and demolition debris, presents a promising solution for conserving natural resources and reducing carbon emissions. Compared with existing RRAC studies, this study quantitatively assesses the carbon mitigation benefits of RRAC and seeks to optimize its performance under multiple constraints. Systematic experimentation and analysis were conducted to examine the effects of varying proportions of rubber particles and recycled coarse aggregates on mechanical strength, durability, and carbon intensity, with the goal of identifying optimal mix ratios that balance these key parameters. A life-cycle assessment (LCA) framework, adopting a cradle-to-gate perspective, was employed to quantify the carbon emissions associated with RRAC production. Taguchi–grey relational analysis method was then used to develop a multi-response optimization model that simultaneously considers mechanical properties, durability indices, and emission levels. The results showed that RRAC achieves substantial reductions in carbon emissions—ranging from 4.3% to 34.3%—compared with conventional concrete (NC), with the highest reduction observed at 15% rubber content and 100% RCA, where carbon emissions were minimized. Furthermore, the analysis identified specific mix ratios of rubber and recycled aggregates that deliver superior integrated performance. These findings clarify the synergistic carbon-reduction mechanisms inherent in the combined use of rubber and recycled aggregates and establish a robust methodological framework for multi-objective optimization in the design of low-carbon building materials.