Effectiveness of tropical soil bacteria as self-healing agent in concrete

Concrete is one of the most commonly used and popular materials in construction industry. It can be designed to have certain required strength and durability based on its application and surrounding environment. However, one of the setbacks for concrete is that it can suffer from internal micro-cracks during its service life due to various reasons. Thus, in ensuring the long-term performance of concrete, the micro-cracks problem need to be addressed. This paper discusses the possibility and potential use of local tropical soil bacteria as self-healing agent in concrete. The bacteria used in the concrete mix was obtained from UTM soil, Lysinibacilluus sphaerius, isolated and cultured for further testing in concrete to determine its suitability in enhancing the concrete performance. Slump test, compressive strength test and pulse velocity test were conducted to assess the effect of the selected bacteria on concrete properties. The initial results demonstrated the capability and possibility of the selected bacteria strain to be used as healing agent in concrete. The optimun percentage of bacteria found was 4%. The compressive strength and pulse velocity of concrete containing bacteria were found to be better than control concrete by 20% and 2%, respectively. The pores of bacteria concrete were also less than control concrete. These positive effects were most likely attributed to the precipitation of calcium carbonate from bacteria activity in filling the pores in the hardened concrete.