Prediction of self-healing ability and compressive strength of bacterial-based self-healing concrete using direct method of ultrasonic pulse velocity test

This study focuses on applying the ultrasonic pulse velocity (UPV) test to understand the self-healing of cracks and predict compressive strength and crack depth in bacterial-based self-healing concrete. After conducting those tests, an equation with an R2 value of 0.85 is derived between the compressive strength and UPV results. Self-healing of crack, UPV test and water absorption tests are conducted on various stages like uncracked specimen (FS), immediately after cracking (CS), and after 28 days and 56 days of self-healing (HS-1 and HS-2). Crack healing was observed using the Digimizer software and the UPV test results. A relationship was developed for calculating the crack depth in the direct method of UPV testing, which matches 95% with the visual observation. The improved results of the UPV and water absorption tests showed that precipitation density improved from 28 to 56 days. The healing capacity of the cracks improved along with the age of the crack, and healing was observed along the internal periphery of the crack. Cracks up to 1.21 mm wide are 100% healed in 56 days. SEM and XRD tests are performed on the precipitation formed, and it was clear that the precipitation was in the form of calcite with a rhombohedral crystal structure.