Mechanical Properties of Self-Healing Concrete (Bio-Concrete) Modified with Limestone Powder

Abstract

Many advantages over conventional concrete have been demonstrated by the use of bio-concrete, which is created by adding microorganisms to conventional concrete. Research on the durability and strength of bio-concrete that uses limestone powder as a filler instead of regular Portland cement is lacking. The aim of this study is to examine the mechanical properties of bio-concrete made with bacillus subtils as the healing agent and limestone powder as a supplementary cementitious material (SCM) at percentage replacement levels of 0%, 5%, 10%, and 15%. The materials used in this study were bacillus subtils as the bacteria, regular Portland cement and limestone powder as the binders, fine and coarse aggregates. The mechanical tests carried out were sulphate attack, alkaline attack, splitting tensile strength, compressive strength and flexural strength tests. The samples were subjected to water ponding for three days to induce an initial crack width of no more than 0.3 mm. The samples' microstructure were characterized using XRF, SEM-EDS, and XRD as well. Based on the data collected, the weight loss, strength, and crack closure indices for each sample were calculated and compared to the control sample. In comparison to the control, it was found that the bacteria's presence decreased the samples' crack width as the curing age rose. In addition, the strength, durability, and microstructure of the self-healing concrete were enhanced by the bacteria and limestone powder, particularly when the concrete contained 10% limestone powder. Based on this study, it can be inferred that bacillus subtils can cause concrete to self-heal by forming spores that reduce or completely seal cracks in the concrete. In addition, including limestone powder can result in concrete that heals more effectively.