Impact of Hemp Fiber on Mechanical and Durability Characteristics of Bacterial-Based Cement Mortar

Abstract

Natural fibers are currently highly valued due to the need for environmentally friendly alternatives. Integrating self-healing bacteria with natural fiber-reinforced mortar creates a unique and sustainable building material that enhances strength and facilitates crack repair. This study evaluates the performance of natural fiber and bacteria in improving the mechanical properties and durability of impaired mortars. The methodologies adopted include a bio-based approach incorporating directly added bacteria and a bio-based strategy utilizing bacteria and fiber reinforcement. Bacteria were identified from a suitable environment and directly added to the cement mortar, along with varying percentages of hemp fibers (0, 0.25, 0.5, and 1). Intentionally induced cracks, subjected to 80% peak compressive stress, undergo water curing with regular monitoring. The effects of hemp fiber content and pH value of acid attack on the mass loss of tested concrete were investigated. The results indicate that the Bacillus strain, Bacillus licheniformis, achieves higher values in compressive strength and lower values of sorptivity tests by 26% and approximately 7%, respectively, with the incorporation of 0.5% hemp fibers leading to a 25–30% increase in 28-day compressive strength. Microstructural investigation reveals that microbial-induced precipitation of various calcium carbonate polymorphs densifies the porous microstructure of the cement matrix. The process was analyzed using SEM imaging to observe bacterially induced carbonate crystals, while FTIR spectroscopy was employed to reveal the variety of CaCO<inf>3</inf> crystals formed and to predict the bonding mechanisms responsible for calcium carbonate formation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.