International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 02 | Feb 2021 www.irjet.net p-ISSN: 2395-0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1197 PERMEABILTY PROPERTIES OF SELF HEALING CONCRETE PRODUCED WITH BACTERIA (BACILLUS SUBSTILIS) AND PUMICE AS A CARRIER Goh, D.J. 1 , Anowai, S.I. 2 , Katyen, A.M. 3 &Ehi, J.O. 4 1 Lecturer, Department of Building, University of Jos, Nigeria 2 Lecturer, Department of Building, University of Jos, Nigeria 3 Lecturer, Department of Architecture, University of Jos, Nigeria 4 Graduate, Department of Building, University ofJos, Nigeria ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract -Concrete is one of the most commonly used building materials in the construction industry. Many researchers have researched into methods of improving the properties of concrete to overcome the observed limitations of concrete especially in terms of durability and permeability. Microbiologically Induced Calcite Precipitation (MICP) is a technique that comes under a broader category of science called bio-mineralization with the ability to heal cracks in construction materials including concrete. This study investigated the effects of self-healing concrete produced with bacteria (Bacillus Subsilis) with pumice as micro-organism carrier material on the permeability properties of concrete in terms of porosity, water absorption and sorptivity. A Mix ratio of 1:2:3 (cement: fine aggregate: coarse aggregate) was adopted in this study. Pumice coarse aggregates were soaked in the bacteria solution until bubble formation stopped then drained and allowed to achieve a surface dry condition.150mm x 150mm x 150mm cubes of concrete samples were cast with the addition of bacteria in pumice as a carrier material partially replacing 20% of coarse aggregates. The results showed a 64.3% and 36% reduction in porosity with 41.07% and 33.0% reduction in water absorption for uncracked and cracked samples and 18.98% reduction in sorptivity. This indicates a substantial positive effect of the bio-based self-healing agent on the permeability properties of concrete. Hence to increase the resistance of concrete to ingress of fluids and harmful chemical, self-healing concrete can be produced with Bacillus Substilis bacteria with pumice as a carrier material. Key Words: Self-healing concrete, biomeneralization, Bacillus substilis, Sorptivity, Porosity, water absorption. 1. INTRODUCTION Concrete is one of the most commonly used building materials in the construction industry and thus great interest has been invested by numerous researchers in effort to produce concrete with better properties that will overcome the limitations of concrete in terms of strength, durability, permeability and resistance to cracking [1]. Improving the lifespan of concrete structures will indirectly improve the sustainability of the environment [2]. The major shortcoming of concrete is that it cracks when subjected to tension. Crack formation in concrete and mortar could be a development that may hardly be fully avoided. Tiny cracks formed on the surface of the concrete make the whole structure vulnerable due to seepage of water into the concrete, promoting corrosion of steel reinforcement thus reducing the life span of the structure [3]. Whereas larger cracks will doubtless hamper a structures' integrity requiring immediate repair actions to be taken, smaller cracks like crack with dimension between 0.1mm to 0.2mm do not have an effect on strength properties of concrete structures but they do contribute to material porousness allowing the penetration of harmful substance [4]. Ingress of aggressive chemicals like chlorides, sulfates and acids could result on the long run in concrete matrix degradation and premature corrosion of the embedded steel reinforcement and so hamper the structures' sturdiness in the future [5]. The concept of self- healing of cracks by biological means is an area of great interest to researchers due to its natural approach and environmental friendliness. Cracks in concretes are sealed due to stimulation of metabolic activity of bacteria by water leading to the precipitation of insoluble Calcium Carbonate on crack surfaces [6]. Self- healing concrete based on bacteria also has potential of improving the durability of concrete [7]. Autogenic and autonomic mechanisms are the two processes of self-healing in cementitious materials. Autogenic refers to the process where the cementitious material heals cracks using its own basic innate constituents. If cracking of the concrete occurs, unreacted cement grains may become exposed to moisture penetrating the crack causing the hydration process to start again and hydration products may fill up and heal the crack. This inherent self-healing mechanism is known since long as autogenous healing [3]. Autonomous self- healing is defined as a purposely designed self-healing mechanism where cementitious healing agent can be used in the presence of water as a prerequisite for the self- healing process to happen [3]. A cementitious healing agent requires water in order to become effective, else healing will not occur. The water may penetrate into a crack from external sources or alternatively water- saturated porous lightweight aggregate particles can be added to the concrete mixture. These porous particles may release water when a crack occurs and moisture gradients