Study on Multifractal Characteristics of Cracks and Mechanical Properties in Rubber Recycled Aggregate Concrete

ABSTRACT To study the propagation law of cracks and mechanical properties of rubber recycled aggregate concrete (RRAC) under uniaxial compression, a two‐dimensional computational model of RRAC containing seven phase medium was established by using the Monte Carlo method. A new finite element approach based on the principle of complementary energy, which was referred to as the base force element method (BFEM), was applied for numerical simulation. The stress–strain curves, compressive strength, and failure mode of RRAC under the combined influence of aggregate replacement rate (25%, 50%, 75%, 100%) and rubber content (5%, 10%, 15%, 20%) were investigated. Furthermore, the evolution law of cracks was quantitatively analyzed using fractal dimension (FD) and multifractal spectrum. The simulation findings showed that the first crack forms in the rubber ITZ, and that continuous cracks are primarily found in areas with dense rubber particles and aggregates. When the rubber content and replacement rate rose from 0% to 20% and 100% respectively, the compressive strength dropped by 38.66%, the FD rose by 2.40%, whereas Δ α , Δ f, and I AS dropped by 2.99%, 16.67%, and 8.30%. The amount of major and branching cracks in local areas grew, whereas the degree of complexity dropped. The rubber content of 5% was a boundary point; after that point, the distribution of cracks gradually transformed from discrete and irregular to dense and even. Brittle failure was more likely to occur in RRAC with a high replacement rate. Rubber content had a more significant effect on the cracks propagation than aggregate replacement rate. The multifractal spectrum was superior to FD in truly explicating the evolution process of crack propagation. The outcomes provide quantitative guidance for improving the mix design and comprehending the crack propagation mechanism in RRAC.