International Journal of Engineering Science Invention Research & Development; Vol. I Issue IV October 2014 www.ijesird.com e-ISSN: 2349-6185 S.Soundharya and Dr.K.Nirmalkumar ijesird, Vol. I (IV) October 2014/162 Strength Improvement Studies on Self-Healing Characteristics of Bacterial Concrete (Review Paper) S.Soundharya 1 and Dr.K.Nirmalkumar 2 1 Student of Final Year M.E. Structural Engineering, Kongu Engineering College, Perundurai 2 Professor, Department of Civil Engineering, Kongu Engineering College, Perundurai Erode, Tamil Nadu, India ABSTRACT-The application of concrete is rapidly increasing worldwide and therefore the development of sustainable concrete is urgently needed for environmental reasons. As present, about 7% of the total atmospheric carbon-dioxide (CO 2 ) emission is due to cement production and its mechanisms that would contribute to a longer service life of concrete structures and it makes the material not only more durable but also sustainable. Cracks are common failures in concrete. Cracks may develop due to addition of excess of water during mixing of concrete, or may be due to shrinkage or creep. In this paper, the following notable points regarding development of a two component self-healing system, characterization studies done with different bacterial species, variation in compressive strength of concrete upon bacterial cell concentrations, physical properties of self-healing concrete, potential of bacteria to act as a self-healing agent etc., are observed and identified from the other research works. A specific group of alkali-resistant spore forming bacteria preferably of genus Bacillus are selected and added to concrete or mortar paste for development of self-healing capacity in structures. Keywords :Crack remediation, Characterization Studies, Compressive strength, Spore formation 1. INTRODUCTION Concrete is a strong and relatively cheap construction material and is therefore presently the most used construction material worldwide. Though concrete has a massive production, it exerts a negative effect on the environment. It is estimated that cement production alone contributes to about 7% of global anthropogenic CO 2 emissions [2]. In the construction sector, concrete is considered as one of the most important building materials around the world. Advancement in concrete technology is in its strength improvement and its enhancement in durability, using pollution-free and natural methods. This needs to be taken care of at the design stage itself [3]. Autogenous crack-healing capacity of concrete has been recognized in several recent studies. Mainly microcracks with widths typically in the range of 0.05 to 0.1 mm have been observed to become completely sealed particularly under repetitive dry/wet cycles. The mechanism of this autogenous healing is chiefly due to secondary hydration of non- or partially reacted cement particles present in the concrete matrix [1]. The development of a self-healing mechanism in concrete that is based on a potentially cheaper and more sustainable material then cement could thus be beneficial for both economy and environment. The main goal of the present research therefore was to develop a type of sustainable self-healing concrete using a sustainable self-healing agent. It was reported that the effect of bio-deposition improves the durability of cement mortar/concrete specimens. It was also observed that deposition of CaCO 3 crystals decreased the water absorption of the sample depending on the inherent porosity of the specimen leading to a decrease in the carbonation rate by about 25–30% [3]. Another aspect of concrete is its liability to cracking, a phenomenon that hampers the material’s structural integrity and durability. The effects of durability problems reflect so much on the money spent for maintenance and repair of concrete structures [2]. Cracking of concrete is a common phenomenon. Without immediate and proper treatments, cracks in concrete