A study on the flexural behaviour and self-healing of fibre reinforced bacterial concrete beams

Abstract

This study investigates reinforced concrete (RC) beams’ flexural behaviour, focusing on their strength and self-healing properties. The research explores how these beams respond under load and how they can recover from damage over time. The study aims to contribute valuable insights into concrete technology and structural engineering by analysing flexural behaviour and self-healing mechanisms. As the most crucial material for building construction, concrete inevitably develops cracks in its structures. These structural cracks diminish the lifespan of concrete elements and weaken their strength and durability. Traditional repair methods are commonly employed to address these cracks. However, these conventional rehabilitation techniques often incur high maintenance expenses and exacerbate environmental and health challenges. To tackle this, researchers have turned to the self-healing mechanism of calcite-precipitating bacteria. These bacteria automatically repair micro-cracks by filling them with calcite through a process known as Microbiologically Induced Calcite Precipitation (MICP). The resulting bacterial concrete possesses self-healing capabilities, allowing it to rectify cracks and maintain structural integrity while reducing maintenance costs. This innovative approach also extends the overall lifetime of concrete structures. Self-healing concrete promises to create more sustainable and durable structures, benefiting the environment and human health. An experimental and analytical study was conducted on the flexural behaviour of RC beams with the addition of steel fibres and Bacillus licheniformis bacteria. A total of six beams were examined, each with dimensions of 150 mm x 180 mm x 2500 mm. Two of these six RC beams were selected for the self-healing process. Steel fibres (ranging from 0.2 to 1.2%) and concentrated bacteria dosages (3%, 5%, and 7%) were added to the concrete mix based on the weight of the cement. The experimental study revealed that the optimal percentages for steel fibres and bacteria were 1% and 5%, respectively. Adding steel fibres and bacteria significantly enhanced the strength properties of the concrete. The flexural behaviour of the RC beams was investigated with various shear reinforcement spacings, including 100 mm and 80 mm. The main objectives of this study were to explore the load-carrying capacity, load-deflection behaviour, ductility, stiffness, and mode of failure related to self-healing in the RC beams. Notably, the inclusion of Bacillus licheniformis bacteria led to an improvement in the flexural behaviour of the RC beams. Additionally, a finite element model was developed and analyzed using ANSYS software. The results from the finite element model closely aligned with the experimental findings. Remarkably, the Bacillus licheniformis bacteria facilitated the healing of the RC beams within 112 days, making them a practical recommendation for crack healing applications.