Short Term Study on the Compressive Strength of Microbial Laterized Concrete Cured in Seawater

The effect of bacteria (Bacillus subtilis) on the compressive strength of laterized concrete cured in sea water was investigated. Because of the many variables involved, Taguchi method of experimental design was employed. The variables were water to binder ratio (0.45, 0.50 and 0.55), percentage laterite replacement of fine aggregate (0%, 10% and 20%) and changes in the volume of bacteria culture (0%, 10% and 30%) which depends on the pre-calculated quantity of water required for each test at a cell concentration of 105 colony forming unit per ml. Two curing media (water and sea water) were used with constant mix ratio of 1:2:4. Compressive strengths were determined at 7, 14 and 28 days. Results indicated that maximum compressive strengths for microbial laterized concrete were obtained for the following combinations; 0% laterite replacement with volume of bacterial culture at 20%, 20% laterite replacement with volume of bacterial culture at 30% and 40% laterite replacement with volume of bacterial culture at 10%.