Numerical Mesoscale Analysis of Rubber Size, Rubber Content, and Specimen Size Effects on Crumb Rubber Concrete Using BFEM

Crumb rubber concrete (CRC) has emerged as a sustainable solution to the environmental challenges posed by rubber waste. This study introduces an advanced mixed-random-aggregate mesoscale model for CRC based on the Base Force Element Method (BFEM) and the complementary energy principle. The model incorporates different rubber substitution ratios (0%–30%), rubber particle sizes (2 mm and 4 mm), and specimen dimensions (edge lengths of 100, 150, and 300 mm). These parameters are considered to investigate their effects on the mechanical properties and failure mechanisms of CRC. Accordingly, the numerical results include stress–strain responses, elastic modulus, and damage progression patterns. The results indicate that increasing rubber content leads to a pronounced reduction in both tensile and compressive strengths. This drop occurs mainly because rubber particles have a much lower elastic modulus. Thus, they represent stress concentrators and weak points, which accelerate the sample failure. Moreover, for the same replacement ratio, CRC with smaller rubber particles (2 mm) exhibits lower strength than CRC with larger particles (4 mm). This reduction occurs because the finer particles create more interfacial areas, introducing more sites for defect initiation and micro-cracks. In addition, increasing specimen size is associated with reduced strength and elastic modulus, highlighting size-dependent phenomena in CRC. The numerical predictions show good agreement with experimental results reported in the literature.