Bio-Self-Healing of Cementitious Mortar Incubated within Clay Soil

Abstract

The use of bacteria-based self-healing concrete for substructures in ground conditions is an area of increasing interest for enhancing the durability and longevity of infrastructure. In line with this objective, the present study investigates the bio-self-healing performance of a cementitious material embedded in clay soil with varying chemical exposures and water saturation regimes. Laboratory experiments were conducted on pre-cracked mortar specimens with Bacillus subtilis encapsulated in perlite. The specimens were incubated in the soil with different pH and sulphate levels, representing three exposure classes (based on Eurocodes). The crack healing ratio was evaluated through visual inspection and capillary-water absorption—before and after soil incubation. Findings showed that all inoculated specimens exhibited healing ratios noticeably larger than those of the control specimens, which mainly experienced small autogenous healing. Of note, the best healing performance was observed when the soil was fully saturated and pH-neutral. From the design perspective of bio-concrete, this study emphasizes the consideration of groundwater regime as well as acidity and sulphate of the soil.