Immobilization of Bacillus sphaericus with palm oil fuel ash for self-healing in the mortar

Crack in concrete or mortar provides preferential accesses for permeation of liquids and gasses which results in degradation of concrete or mortar and structural failure. Basically, this study has used immobilized Bacillus sphaericus(B.sphaericus) with palm oil fuel ash as self-healing agent in the mortar. The strength of the mortar was improved throughprecipitation of calcium carbonate by B.sphaericuscausing stronger structure due to the binding effect of calcium silicate (C-S-H) gel produced from the pozzolanic reaction. Both self-healing agentswere most likely increased the performance of self-healing in the mortar. In the first phase of this study, the immobilization of both self-healing agentswas studied. This was then followed by embedment of immobilized B.sphaericus with POFA into mortar mixture and the effect of different mortar proportion on flow table diameter, compressive strength, microstructural and atomic percentage. It was found that samples containing bio-based self-healing agent recorded the highest compressive strength of 20.95 MPa. The micrograph of SEM and EDX analysis showed that self-healing occurred when secondary C-S-H gel and calcium carbonate present in particular sample. From the result obtained, embedment of the immobilized B.sphaericus with POFA into mortar mixture could solve the crack issue.