Mechanical and microbiological characterization of Portland cement mixtures with waste tire rubber

Abstract Concrete is a mixture of sand, gravel, water, and cement, the latter serving as the binder that promotes and maintains the cohesion of the aggregates. Numerous studies have investigated the properties of concrete, particularly the incorporation of rubber as a fine aggregate to assess its mechanical performance. The strength of concrete depends largely on how well the cement adheres to the aggregates; poor adhesion results in weak concrete. The present study aims to evaluate the efficiency of the bond between cement and rubber, in order to assess the feasibility of using rubber particles, either as fine or coarse aggregate. So, cement-based samples were prepared by incorporating millimeter-sized rubber particles sourced from discarded tires. Mechanical tests in flexion and compression were carried out to assess the influence of rubber on the fracture behavior of cement. Additionally, microbiological tests were conducted under two environmental conditions, varying temperature (°C) and relative humidity (%), to determine whether the presence of rubber promotes microbial growth in both humid and dry environments. Results indicate that rubber particles alter the fracture pattern of the cement, slowing the propagation and separation of fragments once a crack is initiated. This behavior could help prevent sudden catastrophic failures, potentially allowing additional time for evacuation during structural emergencies. Furthermore, the samples showed no signs of microbial development or reproduction under the tested environmental conditions. The results suggest that the use of rubber as an aggregate in concrete is potentially feasible.