Assessment of Bacterial Encapsulation Techniques for Self Healing of Cracks in Cement Mortar

Abstract

Concrete is recognized as a significant construction material due to its high strength and mouldability. At the same time, it exhibits high porosity and brittleness, which tends to produce micro cracks during loading and drying shrinkage. Subsequently, these cracks lead to the ingress of pollutants along with moisture and air, thereby resulting in the corrosion of installed reinforcement. In this way, the structure loses its integrity, strength, and durability, ultimately affecting its life span. Bacterial concrete made with calcite precipitating bacteria, precipitates calcite inside pores of the mortar matrix due to oxygen and moisture, reduces porosity and increases density. The ingress of pollutants that can harm the quality of cement mortar can be arrested. Also, subtle cracks can be healed by embedding suitable bacteria and nutrients in convenient capsules that can withstand stresses during fresh and hardened states of cement mortar. Using these capsules as a fine aggregate helps the concrete heal its micro-cracks more efficiently than adding the bacteria directly into the concrete. The current research explores the feasibility of using bacillus megaterium MTCC 8510 for assessing crack healing efficiency and performance in cement mortar by the direct addition and by using encapsulation techniques. The strength and durability parameters of the cement mortar prepared with the direct addition of bacteria into the mix has revealed that bacillus megaterium MTCC 8510 can improve strength up to 16.97 percent. The healing capacity of bacteria was also experimented by spraying the bacterial solution on the cracks directly. The direct spraying of bacteria resulted in 94.73 percent of the healing surface crack area. The current study also uses three different encapsulation techniques using light weight aggregates like expanded perlite, expanded vermiculite, and sodium alginate polymer. Upon encapsulation of bacteria into these materials, another coating was done using cement to ensure the sealing performance...