Performance of Bacillus tropicus on Mechanical, Durable and Crack Remediation Properties in Sustainable Vermiculite Concrete

Sustainable cement-based concrete materials are primarily used for construction, among which vermiculite as lightweight fine aggregate gains more future development prospect. First, a bacterial solution was sprayed over vermiculite and wrapped using calcium sulphoaluminate (CSA) cement to replace with fine aggregate in concrete. Secondly, based on a preliminary test on compressive strength results, 10% of Ground Granulated Blast Furnace Slag (GGBS) and a healing solution proportion of 9:1 was selected for preparing self-healing concrete. The fine aggregate was replaced in concrete using vermiculite in 0%, 5%, 10% and 15% and the findings suggest that bacterial vermiculite replacement should be at most 5% to achieve better results in strength and durable properties. The strength enhancement observed for compressive strength, strength regain, split tensile strength, flexural strength, and ultrasonic pulse velocity were 29.22%, 45.5%, 34.02%, 28.03% and 41.4% respectively. Surface crack healing at 7, 14 and 28 days of BIVC was 38.23%, 58.82% and 79.41%, which is 3–4% lower than internal crack healing. Microstructural analysis by Scanning Electron Microscopy (SEM), X-Ray Diffractometer (XRD), and Energy Dispersive Spectroscopy (EDS) reveals the existence of calcite, and it was formed due to the bio-mineral action of bacteria with available nutrients in sustainable concrete.