Experimental Study on Structural Behavior of Self Healing Concrete

Abstract

The Cracking of concrete is a common phenomenon without immediate and proper treatment, cracks in concrete structures tends to expand further and eventually require costly repairs. Even though it is possible to reduce the extent of cracking by available modern technology, remediation of cracks in concrete has been the subject of research for many years. Cracks and fissures are a common problem in building structures, pavements, and historic monuments. Cement mortar durability is the function of its internal pore structure and distribution, porosity, and its permeation properties. Research has shown that some specific bacterial species isolated from soil can tolerate harsh and challenging alkaline environment and can be used in remediating cracks in cement mortar structures. This state-of-the-art microbial based crack healing mechanism is one such phenomenon on which studies were carried out to investigate the role of calcite mineral precipitation in improvement of durability in bacteria integrated cement mortar. The primary goal of this study is to explore the potential of biomineralization microbial calcium carbonate deposition in cement mortar, to develop sustainable construction materials. The idea has led to the conception of energy efficient and sustainable construction material called ‘Bacterial Cement mortar’. This paper primarily focuses on the studies related to the characterization of bacteria produced calcium carbonate crystals using various nano characterization techniques such as Scanning Electron Microscope (SEM), X-ray diffraction (XRD), and Thermo gravimetric analysis (TGA) to validate that cracks/pore were sealed up by calcite crystals grown due to complex metabolic mechanism of nitrogen cycle by Bacillus subtilis JC3. In concrete, cracking is a common phenomenon developed due to relatively low tensile strength. High tensile strength may be developed in concrete due to external loads, imposed deformations, plastic shrinkage, plastic settlement and expensive reaction. Proper and immediate treatment should be done to prevent expansion of cracks which may eventually be of higher cost. For crack repair, a variety of traditional repair systems are available which possess several disadvantages aspect such as different thermal expansion coefficient, environmental and hazards of health. Bacterially induced calcium carbonate precipitation has been proposed as an alternative and environmentally friendly crack repair technique. It is found that microbial mineral precipitation as a result from metabolic activities of favorable bacteria in concrete improved the overall behavior of concrete. It is expected that further development of this technique will result in a more durable, sustainable, and crack free concrete that can be used efficiently for construction in wet atmosphere where corrosion of reinforcement affects the durability, permeability, and strength of concrete.