Use of Sewage Effluent as Water Replacement in Microbial Concrete

Abstract

Microbial concrete is made by adding microbes to the standard material of the concrete. These microbes lead toward the formation of calcium carbonate crystals within the pores of the concrete specimen known as microbial induced calcite precipitation (MICP). This results in the formation of denser microstructure of concrete, having high compressive strength, lower initial surface absorption, lower rate of initial and secondary absorption and better corrosion resistance. In this research work, sewage effluent was used in place of fresh water for casting and curing of the specimen. Microbes were mixed with sewage effluent along with nutrient media (NB and CSL) supplemented with calcium chloride and urea. Compressive strength test were performed after 3, 7, 28 and 90 days of curing while the durability tests were performed after 28 days of curing. From the experimental data it was observed that the performance of the microbial concrete produced by using sewage effluent was much better than the conventional concrete mix produced by using sewage effluent only. The relative increase in the 90 days compressive strength of the microbial concrete was 43.13% and 37.02% as compared to the control specimen (S-S) in case of microbial treated NB media and microbial treated CSL media, respectively. The durability properties of the microbial concrete were very much improved as compared to the control specimens. Also, microbial concrete is resistive to corrosion of the reinforcement bar. Corrosion of control specimen takes place after 6 days while the corrosion of microbial concrete takes place after 14 days and 10 days in case of microbial treated NB media and microbial treated CSL media, respectively. Out of microbial treated NB media and microbial treated CSL media, microbial treated NB media is much better. This is because of the cost difference between them. CSL is an industrial by-product, while NB is an expensive laboratory nutrient medium. The experimental results regarding strength and durability properties of the concrete specimens were approximately same for both the nutrient medium. So for huge construction microbial treated CSL media should be economical.