Effect of Crushed Sand and Bacillus Subtilis on the Cantabro Loss of Bacterial Concrete

Abstract

Bacterial concrete has emerged as a remedial measure for healing cracks in structures such as bridges, RCC buildings, RCC pipes, canal linings and pavements. Crack formation is an extremely common occurrence in concrete structures, and allows water and different chemicals to enter the concrete through cracks, diminishing its strength. In addition, it has consequences on the reinforcement once it comes into contact with water, CO2 and other chemicals. The repair of cracks within concrete requires regular maintenance and special kinds of treatment, which can be very expensive. In bacterial concrete, particular types of microorganism can be extremely useful for refurbishing cracks in existing concrete structures. In this research, an experimental investigation was made to prevent cracks in concrete using Bacillus subtilis bacteria and calcium lactate. Bacillus subtilis bacteria with calcite lactate were used at varying percentages of 5%, 10% and 15% cement weight for M40 grade concrete. The fine aggregate used in all the mixes was crushed rock sand. A Cantabro loss test was conducted for all the mixes after 3, 7, 14 and 28 days of curing. An empirical relation between flexural and compressive strength is proposed in the form of ft = 0.66 ?fck for river sand mixes and  ft = 0.89fck0.46for crushed rock sand. An empirical relation is also proposed between Cantabro loss and flexural strength for bacterial concrete.

Keywords

• Bacillus subtilis
• Bacterial concrete
• Cantabro loss
• Compressive strength
• Flexural strength
• Split tensile strength