138 EXPERIMENTAL STUDY ON THE BEHAVIOUR OF SELF HEALING CONCRETE BY USING BACILLUS SUBTILIS Thivya.J 1, Chandrasekaren.M 2 1 Assistant Professor, Department of Civil Engineering, University College of Engineering-Dindigul, Tamilnadu 2 PG Student (Structural Engineering), Department of Civil Engineering, Anna University Regional Campus-Madurai, Tamilnadu Abstract is the most critical element applied in public buildings and is often difficult to service, yet requires lengthy service periods. Recent research has shown that specific species of bacteria can actually be useful as a tool to repair cracks in already existing concrete structures. This new concrete, that is equipped to repair itself, presents a potentially enormous lengthening in service-life of public buildings and also considerably reduces the maintenance costs. The objective of the present investigation is to study the potential application of bacterial species i.e. Bacillus subtilis JC3 to improve the strength of cement concrete. The aim of this research project is the development of a new type of concrete in which integrated bacteria promote self-healing of cracks. Various test such as compressive strength test, split tensile strength test and flexural strength test will be carried out. The strength properties will be compared with the conventional concrete after the curing period of 7, 14 and 28 days. The grade of concrete used in this project is M25. The bacteria Bacillus Subtilis in solution form is added to the concrete by 3 ml, 6 ml and 9 ml per litre of water. Keywords: Bacteria, Bacillus subtilis JC3, Self-Healing. 1. INTRODUCTION In concrete, cracking is a common phenomenon due to relatively low tensile strength. Without immediate and proper treatment, cracks tend to expand further and eventually require costly repair techniques. Durability of concrete is also impaired by these cracks, since they provide an easy path for the transport of liquids and gases that potentially contain harmful substances leading to corrosion of reinforcement. Cracks are therefore precursors to structural failure. For crack repair, a variety of techniques are available but traditional repair systems have a number of disadvantageous aspects such as differential thermal expansion coefficient compared to concrete and environmental hazards. Therefore, bacterial induced calcium carbonate precipitation has been proposed as an environmental friendly crack repair technique. Humans have the ability to precipitate minerals in the form of bones and teeth continuously. This ability is not only confined to human beings, even certain bacteria can continuously precipitate calcium carbonate (CaCo3).This phenomenon is called microbiologically induced calcite precipitation. is a composite building material comprised of aggregate and binder (cement). finds good use in all types of building construction.fly ash and silica fume can be used in concrete mix because of its light weight and high thermal insulation. Durability of concrete is another major aspect of concern. There are different methods which would thereby improve the concrete durability and these include e (a) Chemical methods : By applying epoxy coating which there by reduces steel siloxane can be used as these materials combine with siliceous portions of cement and aggregates (b) Physical methods : use of Pozzolans like silica fume, fly ash can improve the concrete durability by enhancing impermeability and chemical durability. Sulphate resistance in concrete can be improved by incorporating supplementary cementing materials. Permeability is one of the most important properties of durability.use of supplementary cementing materials such as fly ash and silica fume improve the microstructure of the concrete matrix resulting in the impermeability of concrete. Once impermeability in enhance, concrete becomes more durable against sulphate resistance and resistance due to chemicals, etc. For that reason, it enhances the chemical durability. (c) Development of Self-healing bacterial concrete: A novel technique for the remediation of damaged structural formations has been developed by employing a selective bacterial plugging process, in which metabolic activities promote precipitation of calcium carbonate in the form of calcite. Bacteria can affect the carbonate precipitation both through local geochemical conditions and by serving as potential, nucleation sites for mineral formation. Ca 2+ is one of the most adundant cations while carbonate ions (HCO 3- and CO 2 3) are some of the some of the most abundant anions in most subsurface waters. In order to produce the most mineral mass, utilizing elements already present in subsurface is a more efficient method than adding another chemical.a variety of ions can non-specially get deposited on bacterial cell surface at the nucleation site.
139 2. BACILLUS SUBTILIS JC3 Researchers with different bacteria proposed different bacterial concretes. The various bacteria used in the concrete are Bacillus pasteurii, Bacillus sphaericus, E.coli etc. In the present study an attempt was made by using the bacteria Bacillus subtilis strain no. JC3. The main advantage of embedding bacteria in the concrete is that it can constantly precipitate calcite. This phenomenon is called microbiologically induced calcite precipitation (MICP). Calcium carbonate precipitation, a widespread phenomenon among bacteria, has been investigated due to its wide range of scientific and technological implications. Bacillus subtilis JC3 is a laboratory cultured soil bacterium and its effect on the strength and durability is studied here. Bacillus subtilis JC3 researchers with different bacteria proposed different bacterial concretes. The various bacteria used in the concrete are Bacillus pasteurii, Bacillus sphaericus, E.coli etc. In the present study an attempt was made by using the bacteria Bacillus subtilis strain no. JC3. Calcium carbonate precipitation, a widespread phenomenon among bacteria, has been investigated due to its wide range of scientific and technological implications. Bacillus subtilis JC3 is a laboratory cultured soil bacterium and its effect on the strength and durability is studied here. Micro organisms (cell surface charge is negative) draw cations including Ca 2+ from the environment to deposit on the cell surface. The following equations summarize the role of bacterial cell as a nucleation site. Ca 2+ + Cell -----> Cell- Ca 2+ Cell- Ca 2+ +CO3 2- -----> Cell-CaCO3 3. MATERIAL PROPERTIES AND DESCRIPTION 3.1. Cement Ordinary Portland cement of 53 grade available in local market is used in the investigation. The cement used has been tested for various properties as per IS: 4031-1988 and found to be confirming to various specifications of IS: 12269-1987 having specific gravity of 3.16. 3.2. Fine Aggregate Locally available clean, well-graded, natural river sand having fineness modulus of 2.59 conforming to IS 383-1970 was used as fine aggregate. 3.3. Coarse Aggregate Crushed granite angular aggregate of size 20 mm nominal size from local source with specific gravity of 2.67 was used as coarse aggregate. 3.4. Water Locally available potable water conforming to IS 456 is used. 3.5. Microorganisms In this study Bacteria Bacillus Subtilis is used. The micro-organism used for manufacturing of microbial concrete should be able to possess long term effective crack sealing mechanism during its lifetime serviceability. The principle behind bacterial crack healing mechanism is that the bacteria should be able to transform soluble organic nutrients into insoluble inorganic calcite crystals which seals the cracks. For effective crack healing, both bacteria and nutrients incorporated into concrete should not disturb the integrity of cement sand matrix and also should not negatively affect other important fresh and hardened properties of concrete. Only spore forming gram positive strain bacteria can survive in high ph environment of concrete sustaining various stresses. Figure 3.1 Bacillus Subtilis Table 3.1 Properties of Bacteria Type Phase Gram Positive Liquid ph 7-8 Temperature Room Temperature 3.6. Mix Design The mix proportion for ordinary grade concrete (M25) is designed using IS: 10262-1982. Materials required for 1 cubic meter of concrete in ordinary grade concrete is: Mix Proportion 1: 1.713: 2.64: 0.45 4. RESULTS AND DISCUSSION 4.1. Compressive Strength Compressive strength is most important property of the hardened concrete. The concrete cubes were casted, cured and tested accordance with the IS standard and 7, 14, & 28 days.
Compressive Strength 2inN/mm Tensile of Strength of in N/mm 2 International Journal of Advanced Engineering Research and Technology (IJAERT) 140 Table 4.1 Compressive Strength of DAY 7 th 14 th 28 th PERCENTAGE In In In N/mm 2 N/mm 2 N/mm 2 CONVENTIONAL 16.22 20.66 25.50 0.3% 18.67 21.80 26.67 0.6% 19.78 22.44 27.19 0.9% 21.11 23.11 27.87 4.2. Split-Tensile Strength After curing of cylinders for respective days it was placed in testing machine having a maximum capacity of 1000 KN. The load is applied on the cylinder specimens. The cylinder specimen was failed at ultimate load which was noted from dial gauge reading. From the result, it was found that the split tensile strength was increased at addition of 0.9% of bacteria when compared to the conventional mix. Table 4.2 Split-Tensile Strength of concrete DAY 7 th 14 th 28 th PERCENTAGE In In In N/mm 2 N/mm 2 N/mm 2 CONVENTIONAL 2.76 3.60 3.82 0.3% 2.86 3.78 4.08 Figure 4.1 Compressive Strength of Compressive strength result of concrete are listed in table. The highest compressive strength value is 27.87Mpa which is obtained at 28 days by addition of 0.9% of bacteria by weight of concrete when compared to the conventional mix. Fig 4.1 shows that the compressive strength of concrete for various mixes. Figure was drawn between compressive strength and curing periods for the various mixes. 30 25 20 15 10 5 0 7 Days 14 Days 28 Days 0.6% 2.93 3.94 4.36 0.9% 3.14 4.12 4.54 Based on the result, the highest split tensile strength value is 4.54Mpa which is obtained at 28 days. 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Figure 4.2 Chat for compressive strength Figure 4.3 Chat for split tensile strength Fig 4.3 shows that the split tensile strength of concrete for various mixes.
Flexural Strength of 2inN/mm International Journal of Advanced Engineering Research and Technology (IJAERT) 141 4.6 4.4 4.2 4 3.8 3.6 3.4 28 Days Figure 4.4 Split-Tensile Strength of concrete 4.3. Flexural Strength of concrete Figure 4.5 Chat for flexural strength After curing of prism specimens, which are placed in testing machine having a maximum capacity of 100 KN. The load is applied on the prism specimens. The specimen is failed at ultimate load which is noted from dial gauge bacterial concrete which is compared to the conventional reading. Table 4.3 Flexural Strength of concrete DAY 28 TH PERCENTAGE In N/mm 2 0 3.88 0.3 % 4.07 0.6 % 4.24 0.9 % 4.54 From the result flexural strength is increased at addition of 0.9% of bacterial concrete. Flexural strength is the property of the hardened concrete. The concrete prisms were cast, cured and tested accordance with the IS standard for 28 days flexural strength result of concrete are listed in table 3.3. Based on the result, the highest flexural strength value is 4.54Mpa which is obtained at 28 days. Fig 4.5 shows that the flexural strength of concrete for various mixes. Figure 4.6 Flexural Strength of concrete 5. CONCLUSION Experimental investigations were conducted to determine the Characteristics and Strength of concrete by addition of bacteria with water. specimens were casted and tested to determine the Compressive strength, Split tensile strength and Flexural strength. Based on the test results it was inferred, which percentage gave better results than the conventional concrete with respect to 7, 14 and 28 days Compressive strength, Split tensile strength and Flexural strength when added bacteria.
142 According to the comparative studies undertaken it is clear that with 0.6% and 0.9% addition of bacteria a maximum compressive strength of 27.87 and 27.19 N/mm2 which is more than the conventional concrete was obtained. The other results showed a progressive increase for each percentage. Further increment of concentration of Bacillus Subtilis to the percentages could further increase the strength of concrete. Microbial technology have proved to be better than conventional technologies because of its eco-friendly nature, self healing abilities and very convenient for usage. The optimum percentage obtained is 0.9%. REFERENCES [1] S.Sunil Pratap Reddy, M.V.Seshagiri Rao, P.Aparna and CH.Sasikala, (2010), Performance of Ordinary Grade Bacterial (Bacillus Subtilis) ISSN 0974-5904, Vol. 03, No. 01, pp. 116-124. [2] Kim Van Tittelboom, Nele De Belie, Willem De Muynck and Willy Verstraete, Use of bacteria to repair cracks in concrete, Cement and Research 40 (2010) 157 166. [3] M.V. Seshagiri Rao, V. Srinivasa Reddy, M. Hafsa, P. Veena and P. Anusha," Review Paper Bioengineered - A Sustainable Self- Healing Construction Material " Research Journal of Engineering Sciences ISSN 2278 9472 Vol. 2(6), 45-51, June (2013). [4] Jagadeesha Kumar.B.G, Prabhakara.R, Pushpa.H, (2013) Effect of Bacterial Calcite Precipitation on Compressive Strength of Mortar Cubes International Journal of Engineering and Advance, 8958, Volume-2, Issue-3. [5] Ashwija.K.C. and Jayaprakash Narayan.K.S Experimental Study on The Strength Variation of Using Bacteria International Journal of Advanced Biotechnology and Research ISSN 0976-2612, Vol 3, Issue 1, 2012, pp 541-544. [6] Prof. M.Manjunath, Prof. Santosh, A.Kadapure, Ashwinkumar, A.Kalaje (2014), An Experimental Investigation on the Strength and Durability Aspects of Bacterial with Fly Ash Civil and Environmental Research ISSN 2224-5790 (Paper) ISSN 2225-0514 (Online) Vol.6, No.6.