Sustainable high-performance concrete with crumb rubber and ternary supplementary cementitious materials via experimental microstructural and statistical analysis
In response to growing concerns regarding construction waste management and the depletion of natural resources, this study investigates sustainable concrete mixtures incorporating crumb rubber, shredded rubber, fly ash, silica fume, and marble slurry powder. Twenty concrete mixtures were prepared to examine the combined effects of rubber aggregates and supplementary cementitious materials (SCMs) on mechanical properties, durability performance, and microstructural characteristics. The results show that, although rubber incorporation reduced strength, the use of SCMs partially offset this effect. Compressive, split tensile, and flexural strengths increased by up to 12%, 8%, and 10%, respectively, compared with their respective rubber-modified reference mixes. Durability indicators, including chloride migration and water absorption, were reduced by approximately 15–20%, indicating improved resistance to fluid ingress. These improvements are attributed to the pozzolanic activity and filler effects of the mineral additions, which promoted pore refinement and improved matrix continuity. Microstructural observations revealed denser interfacial transition zones and more uniform hydration products, supporting the observed trends in mechanical and transport behaviour. Regression-based analysis of variance (ANOVA) was used to evaluate the relative influence of the selected variables within the experimental domain, identifying crumb rubber content as the dominant factor affecting mechanical performance, with coefficients of determination ranging from 0.81 to 0.97. The findings demonstrate that carefully proportioned SCM systems combined with controlled rubber incorporation can produce durable and resource-efficient concrete suitable for non-structural and lightly loaded components where serviceability, durability, and waste utilisation are key design considerations.