Title: Effect of Bacterial Spore in Surface-Treated Fiber-Reinforced Concrete

Author(s): Davood Mostofinejad, Nasrin Karimi, and Bahareh Tayebani

Publication: Materials Journal

Volume: 119

Issue: 6

Appears on pages(s): 263-272

Keywords: bacteria; compressive strength; electrical resistance; fiber; spore; water absorption

DOI: 10.14359/51737198

Date: 11/1/2022

Abstract:
One way to reinforce concrete is to use steel bars. It is essential to find substitute artificial materials because such bars are prone to corrosion, and reinforcing steel suffers from the penetration of hazardous substances into porous concrete. Several solutions have been proposed in recent years for reducing the pores and microcracks thus created. From these solutions, biological methods have attracted more attention due to their cost-effective and eco-friendly nature. On the other hand, fiber reinforcement may significantly improve concrete tensile strength, crack-related properties, and ductility. In the present study, Bacillus subtilis is used in specimens in which one of the three polypropylene, hooked-end steel, or barchip fibers (at volume percentages of 0.3%, 1%, and 0.75%, respectively) is considered as reinforcement. Moreover, bacterial strains in the culture medium are used in place of concrete mixing water, and bacterial spores in the culture medium are applied as a surface treatment gel. Cylindrical specimens were cast to be used for the compressive strength, water absorption, and electrical resistance tests. With a reduction of 36% in water absorption, the bacterial specimens outperformed their corresponding controls. The compressive strength test revealed an increase of 25.5% in compressive strength in surface-treated specimens relative to the corresponding control ones. The best performance of bacteria was observed in reducing electrical resistance in the concrete specimens reinforced with polypropylene fibers. Overall, the three applications of bacteria were found capable of forming calcite sediments, with greater deposits formed due to bacterial activity than by the spores used in the surface treatment.