Other materials, such as fly ash and polyvinyl alcohol (PVA) fibers, have been explored in conjunction with bacteria to enhance concrete's durability and self-healing capabilities. Combining autogenous and autonomous self-healing techniques using B. subtilis bacteria, fly ash, and PVA fibers has shown promising results in improving compressive and flexural strength while reducing water absorption and sorptivity. Studies have demonstrated that the inclusion of B. subtilis bacteria significantly improves concrete's self-healing capability, leading to substantial strength recovery and reduced permeability, especially in wet and dry curing cycles. In another study, the incorporation of fly ash improved the compressive strength of mortar specimens, with enhancements of up to 19% compared to control specimens, indicating the potential of supplementary materials to enhance the biocementation process. PVA fibers have also been shown to enhance crack repair and strength recovery in self-healing concrete. The combination of bacteria and PVA fibers can lead to a higher calcium carbonate concentration on the inner crack surface, potentially due to the absorption property of PVA fibers accelerating the precipitation of carbon dioxide and the generation of calcium carbonate , - .