Impact of Bacillus subtilis bacterium on the properties of concrete Shradha Jena a,⇑ , Bidyadhar Basa a , Kishor Chandra Panda b , Naresh Kumar Sahoo a a Civil Engineering Department, ITER, S‘O’A (Deemed to be University), Bhubaneswar 751030, Odisha, India b Civil Engineering Department, Government College of Engineering, Kalahandi, Bhawanipatna 766002, Odisha, India article info Article history: Received 9 January 2020 Received in revised form 17 February 2020 Accepted 5 March 2020 Available online xxxx Keywords: Bacillus subtilis Compressive strength Split tensile strength Flexural strength abstract The activity life span of concrete sharply decreases with the formation of cracks on its surface which leads to corrosion of concrete. To deal with such problems newer technologies are being adopted for concrete production and one such high-tech concrete is self-healing concrete by Microbiologically Induced Calcite Precipitation (MICP). This kind of concrete can initiate biological activity to deal with its cracks and to recover itself. This research paper throws light on the experimental investigation carried out to evaluate the impacts of Bacillus subtilis bacteria on concrete properties. The experiment has been carried out using six different bacterial concentrations in the concrete mixes, such as 10, 10 2 , 10 3 , 10 4 , 10 5 and 10 6 cells/ml of water. Concrete specimens were left for 7 days, 14 days and 28 days of curing. Tests were conducted for measuring properties like compressive strength, split tensile strength, flexural strength were mea- sured in different interval of curing period. The research showed that concrete having bacterial infusion in all cell concentration have increment in strength in comparison to control mix. Maximum of 32% increase in compressive strength, 14% increase in split tensile strength and 29% increase in flexural strength were observed in the specimen having bacterial concentration of 10 5 cells/ml of water. Microbial calcite precipitation was visualized by Scanning Electron Microscopy (SEM), which showed the growth of filler materials i.e. calcite deposition inside the concrete pores, which results in denser con- crete causing a rise in its strength. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 3rd International Con- ference on Innovative Technologies for Clean and Sustainable Development. 1. Introduction In the current scenarios of never-ending urbanization, concrete plays the role of the most valuable and versatile construction material. In three out of five developed countries, almost 65% of the total built environment is solely made up of concrete infras- tructure. Concrete is indispensable in the all-round development of infrastructure that includes industrial sectors, residencies, facto- ries and business sectors. But concrete has its own loophole, i.e. crack formation. Formed cracks on the surface of concrete make an easy way for entry of water and oxygen along with other chem- icals. Thus, it leads to corrosion of concrete. Corrosion causes decrement in stability and self-life span of concrete. If immediate measures are not considered for dealing with such situations, it might result in a costly repair. Therefore, innovative measures are under consideration for dealing with these situations and one such extra ordinary and out of the box idea is development of self healing concrete by using bacteria species in it. The fact that crystal gets formed by bacteria species is effectively and widely being used in various sectors like oil industries and civil engineering [1]. Some of the examples that can be mentioned are: plugging of rock system for oil recovery enhancement and protection of ornamental stones [2–8]. Carcinogenic bacteria forming calcium carbonate precipitation facilities are used in these applications [9,10]. Researches show that the use of self healing bacteria help with durability and crack formation problems of concrete [11– 15]. The measure drawback of concrete is the formation of huge cracks. Cracks, in turn lead to reinforcement corrosion, which dam- ages internal strength of concrete and is costly for reparation. As cracks cause penetration of water and chloride, they affect the self-life period of concrete adversely. Hence, healing of concrete as soon as possible is quite necessary, so that they do not get the chance to allow water in and cause any damage to concrete. An effective solution to most of these concrete related problems is the most recent and in the talk technology of Self-healing con- crete. Self-healing concrete allows cracks in concrete to be healed https://doi.org/10.1016/j.matpr.2020.03.129 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 3rd International Conference on Innovative Technologies for Clean and Sustainable Development. ⇑ Corresponding author. E-mail address: sjena4203@gmail.com (S. Jena). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: S. Jena, B. Basa, K. C. Panda et al., Impact of Bacillus subtilis bacterium on the properties of concrete, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.03.129