Performance evaluation of bacterial self-healing rigid pavement by incorporating recycled brick aggregate

Concrete is the most widely used construction material in the world. Surely, it is extensively employed in the construction of rigid pavements. Repetitive loads on the pavement cause cracks which allow the ingress of harmful compounds and thus reduce the durability of concrete. Hence, this research presents an ecofriendly solution to impart self-healing capability to concrete by using bacteria as a healing agent and Recycled Brick Aggregate (RBA) as an immobilizer for bacterial spores. Utilization of RBA is considered to offer a sustainable resource consumption. The bacteria used in this study is Bacillus subtilis and the calcium source used is calcium lactate. Specimens were prepared for four mixes, mix 1 was control mix, mix 2,3 and 4 contained 30%, 50% and 70% RBA respectively. The number of bacterial spores was kept same in mix 2,3 and 4 which was 106 cells/ml. The results showed slight reduction in compressive and flexural strength with the increasing percentage of RBA in the mix. Self-healing tests were also conducted which showed that samples containing 50% RBA and bacterial spores showed maximum crack healing of up to 0.92 mm with strength recovery of 69% when samples were cracked after 7 days and crack healing of 0.68 mm with strength recovery of 57% when samples were cracked after 28 days. Moreover, XRD and SEM analysis also confirmed the calcite precipitation.