Effect of mineral admixture and natural fiber as partial replacement in self-healing and sustainable concrete.

The manufacture of cement contributes significantly to carbon dioxide (CO2) emissions into the atmosphere. The effects of mineral admixtures (iron dust, glass fines, metakaolin, and limestone fines) make them suitable for reducing carbon emissions as a replacement for cement. All mineral admixtures (MA) are byproducts of primary materials, and natural fiber is included. This study focuses on a sustainable material that does not compromise strength. This paper analyzes the properties of self-healing concrete developed using MA Bacillus tropicus and sisal fiber. Three different percentages of MA, 10%, 20%, and 30%, and 1% of sisal fiber were used by weight of cement. Bacteria were incorporated into the concrete using the direct addition method, in which the healing solution (a combination of a 1:9 bacterial-to-nutrient ratio) was added directly to the concrete. A total of five mixes of concrete control C0, bacterial control CB, 10% MA CB10, 20% MA CB20, and 30% MA CB30 were cast. Thus, 1% sisal fiber was constant for all mixes. The self-healing concrete's (SHC) performance was assessed through sorptivity, porosity, water absorption, acid resistance, crack-healing efficiency (CHE), compressive strength (CS), splitting tensile strength (STS), regain compressive strength (RCS), and microstructural morphology analysis. The economic and environmental benefits are evaluated. A comparative analysis of the experimental results showed positive results up to a 20% replacement after declination, but not to a level below the reference mix. Adding fiber significantly increases tensile strength, achieving a 3 to 13% improvement over the control mix, and supports bacterial survival within the concrete environment. Optimal concrete mixtures of 20% were suggested, and the specimens showed improvements of 15.45% in CS, 12.53% in STS, and 90.96% in RCS compared to control concrete specimens. The recovery ratio can exceed 80% for all mixes except the control specimen. The economic analyses identified reduced maintenance costs and lower carbon emissions. The microstructural analysis confirms the presence of bacteria, as well as calcium carbonate and calcite.