Experimental Study on Self-Healing Bacterial Concrete By using E-Coli Bacteria

Concrete is an adaptable material having lowered tensile & shear strength. Basically concrete is brittle material and contains lots of micro-cracks present in the body. The elasticity of concrete is fairly constant at low stress levels but starts decreasing at higher stress levels as matrix starts cracking. Concrete has a very low coefficient of thermal expansion and concrete shrinks. All concrete structures will crack to some point, due to shrinkage and tension. Concrete which is under load of forces for long duration of time, creep of concrete may happen. Carbonate- producing bacteria have provide lots of benefits as a promising, natural, environmental friendly novel technique to improvement of concrete characteristics, considerable research has been conducted on utilizing microbial-induced carbonate precipitation to overcome several concrete problems such as crack repair, reduction and modification of porosity, and permeability. Furthermore, bacterial carbonate precipitation (bio deposition) has shown positive influences on compressive strength improvement of concrete, it also reduces water absorption and carbonation of concrete as an alternative surface treatment. As part of metabolism, some bacteria produces enzyme urease which catalyzes the hydrolysis of urea to generate carbonate ions without an associated production of protons which leads to CaCO3 precipitation in presence of calcium ions. Therefore, bacteria cells not only provide a nucleation site for CaCO3 precipitation in presence of calcium ions.