Investigating the bacterial sustainable self-healing capabilities of cracks in structural concrete at different temperatures
Yasmine Elmenshawy, Mohamed A.R. Elmahdy, Mohamed Moawad, Ahmed A. Elshami, Seleem Ahmad, Kaori Nagai
Abstract
Structural cracks are the major cause of structural failure and significantly impact their strength and durability. Bacterial self-healing concrete as a sustainable structural Smart material offers potential advantages by autonomously repairing cracks, reducing repair costs, and eliminating human intervention. Most self-healing concrete bacteria have optimal growth temperatures around 25-37°C. Their metabolic activity can decline at higher temperatures, potentially affecting their ability to produce calcium carbonate and heal cracks. This study aimed to investigate the effectiveness of heat-resistant bacteria strains in self-healing concrete under high temperatures. The study examined the impact of temperature, bacteria type, and content on self-healing concrete properties at four different temperatures: room temperature, 60°C, 120°C, and 200°C. Several tests were performed to test the effectiveness of the bacteria strains, including compressive strength tests, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This study showed significant improvement in the mechanical strength of the concrete, particularly at 60°C by 91.2% for compressive strength and 95.95% for indirect tensile strength. The SEM and EDS tests also revealed the presence of calcium carbonate, which suggests that the bacteria were actively involved in the self-healing process. However, as the temperature increased to 200°C, there was a noticeable decrease in strength compared to 60°C, but the compressive strength at room temperature remained higher, indicating that heat-resistant strains of bacteria may not be effective at higher temperatures.