Effect of Bacteria Inoculums on Compressive Strength

Abstract

The use of bio-concrete is increasing in the present day context and researchers are working on strength and durability characteristics of concrete using bacteria species which have shown calcite precipitation. Three different species of bacteria namely P. Fluorescence, B. Pumilis and B. Subliis that have calcite precipitation properties have been investigated in this study. The investigations were carried first on cement mortar (CM) cubes using these three bacteria species suspension of 20%; 40% and 60% having colony forming units P. Fluorescence (108 CFU/ml), B. Pumilis (106 CFU/ml) and B. Subtilis (108 CFU/ml) respectively. The 40% suspension in all the three cases has shown increased compressive strength as compared to 20% and 60%. The compressive strength measured showed increase (CS) of 18%; 12% for P. Fluorescence; B. Subtilis and decrease of 35% with B. Pumilis respectively. B. Subtilis with optimized 40% suspension having CFU 10x108/ml showed 4.32% ; 5.56%; and 3.81% increase in CS of CC cubes with 3 days; 7 days and 28 days respectively and 5.92% overall increase in CS of CC cubes as compared to the 3 days CS of control cube. ABBREVIATIONSSDW: Sterile Distilled Water; SHC: Self-Healing Concrete; PCR: Polymerase Chain Reaction; BC: Bacterial Concrete; CP: Calcite precipitation; CS: Compressive Strength; CC: Cement Concrete; CM: Cement Mortar; MTCC: Microbial Type Culture Collection; CFU: Colony Forming Unit/ml