Characteristics of bacteria based self healing rubberized concrete for sustainable and durable construction

Developing longer-lifespan concrete with minimized surface cracking is crucial for sustainable construction. This study investigates self-healing rubberized concrete incorporating 15% recycled rubber waste as a sand replacement. To enhance strength and flexibility through crack closure, bacteria Sporosarcina Pasteurii and Rhizobium Leguminosarum were introduced at 20% of the water volume. Slump, compressive and flexural strength, SEM, and EDX were the tests performed to identify the effects of bacteria and rubber on the concrete characteristics. The results illustrated that the use of rubber as a partial replacement for sand significantly reduced concrete workability and mechanical performance, with slump, compressive strength, and flexural strength decreasing by up to 77%, 49%, and 47%, respectively. However, incorporating SpP and RL bacteria, particularly at concentrations of 10¹⁰ + 10¹⁰ and 10¹⁴ + 10¹⁰, effectively mitigated these negative effects. The improvement in compressive strength and flexural strength was up to 98.7% and 137.4%, respectively for mixture containing SpP and RL bacteria at concentration 10¹⁰ +10¹⁰ compared to mixture containing 15% rubber only. Complete crack self-healing was achieved in SHRC mixtures after 80 days. Microstructure analysis revealed that the formation of calcium carbonate in large quantities within the concrete matrix, which works to heal cracks and fill voids. Thus, using rubber with bacteria to heal cracks could be a cost-effective solution that helps to increase tire rubber recycling rates.