EXPERIMENTAL STUDY ON STRENGTH OF SELF-HEALING CONCRETE

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1 Conference on Recent in EngineeringCivil Engineering, - SSRG Journal of Civil (ICRTCETM-07) Special Issue (ICRTCETM-07) - April 07 EXPERIMENTAL STUDY ON STRENGTH OF SELF-HEALING CONCRETE M.Monishaa, Mrs.S.Nishanthi. Student of final year M.E. in Structural Enigneering &Dr.Sivanthi Aditanar College of Engineering, Tiruchendur.Tamilnadu, India. mmonishaa9894@gmail.com Assistant Professor Department of Civil Engineering Dr. Sivanthi Aditanar College of Engineering, Tiruchendur.Tamilnadu, India. nishagct@gmail.com Abstract In this paper an overview of new development obtained in experimental study on self-healing concrete. Strength and durability of concrete is mainly affected due to the formation of cracks. Micro cracks are the main cause for structural failure. While larger cracks affect structural integrity, micro cracks result in durability problems. Ingress of water and chemicals can cause premature matrix degradation and corrosion of embedded steel reinforcement. Also concrete fails due to insufficient tensile strength. In order to overcome this, an attempt is made in Bacterial concrete with non-pathogenic, spore forming, calcite mineral precipitating bacterium Bacillius subtilis. M0 grade concrete is prepared with different bacterial cell concentration of 04, 05 and 06 cells per millilitre of water and polyethylene fibre kept at constant as 0.4%. The overall development of strength and durability of self-healing concrete using Bacillius subtilis and polyethylene fibre has investigated and compared with control concrete. The optimum strength is obtained at 05 cells concentration and polyethylene fibre were bridging over the crack and crystallization products became easy to be attached to a large number of polyethylene fibre. The optimum strength is obtained at 05 cells concentration, which increases the compressive strength by.%, split tensile strength by.4% and flexural strength by 6.04%. The percentage of increment in strength clearly shows that the self-healing concrete is advantageous. Key Words: Bacillius subtilis JC, Calcium carbonate precipitating, Crack, Strength and Durability properties *** INTRODUCTION regain the strength of concrete. In concrete Concrete is the most common material used for all structures, repair of cracks usually involves types of construction. Due to its strength and applying a cement slurry or mortar which is durability, concrete became inevitable. The only bonded to the damaged surface. Repairs can defect in the use of concrete is that it is weak in particularly be time consuming and expensive. For tension. Since the concrete is weak in tension the crack repair, a variety of techniques is available Possibility of formation of crack is more. Apart like impregnation of cracks with epoxy based from this, freeze thaw action and shrinkage also fillers [], latex binding agents such as acrylic, leads cracking in concrete. Durability of concrete polyvinyl acetate, butadiene styrene, etc. But is highly affected due to cracks and it leads traditional repair systems have a number of corrosion of reinforcing bars. So it is very disadvantageous aspects such as different thermal essential to find the suitable repair mechanism for expansion coefficient compared to concrete and ISSN : Sense Research Group

2 Conference Journal on Recent in Civil Engineering, Technology and (ICRTCETM-07) SSRG of Civil Engineering(ICRTCETM-07) 07 also have impact on environment and health. Ca (OH) + CO CaCO + HO () Therefore, bio based calcite precipitation has been The bacterial degradation of urea locally proposed as an alternative and sustainable, increases the ph and promotes the microbial environmental friendly crack repair technique []. deposition of Calcium carbonate in a calcium rich Bacterially induced calcium carbonate environment. Through this process, the bacterial precipitation has been proposed as an alternative cell is coated with a layer of calcium carbonate and environmental friendly crack repair technique. [6]. It mimics the process by which bone fractures Microbial calcite precipitation is mainly due to in the human body are naturally healed by unrealistic osteoblast cells that mineralize to reform the bone activity and carbonate bio mineralization of bacteria. The strains of the [7]. bacteria genus Bacillus were found to thrive in the A. Selection of Bacteria high-alkaline tolerance, Due to high internal ph, relative dryness and lack temperature range, ph range and extracellular of nutrients the common bacteria cannot survive products are important taxonomic criteria which in the concrete environment. The ph of cement are used in different species in the genus Bacillus and water when mixed is, which is not suitable [4]. for organisms to survive. Researchers found that environment [].Salt In our study, bacterial species Bacillius only the strains of bacterial genus bacillius are Subtilis is used to improve the strength of suitable to thrive in this high alkaline concrete. Researchers have shown that the environment. It is also found that, bacillus is the microbiologically induced endospore forming only genus that is able to form spore in the hostile bacteria is able to heal cracks effectively. The environment. Such spores have extremely thick principle behind in bacterial crack healing cell walls that enable them to remain unbroken for mechanism is that the bacteria should able to up to 00 years while waiting for a better transform soluble organic nutrients into insoluble. environment to germinate. They would become Inorganic calcite crystals which seal the cracks activated when the concrete starts to crack. The [5]. process of mineral precipitation lowers the ph of When cracks appear in a concrete structure the highly alkaline concrete to values in the range and water starts to seep in through, the spores of (ph 0 to.5) where the bacterial spores become the bacteria starts microbial activities on contact activated. with the water and oxygen. In the process of B. Polyethylene Fiber precipitating calcite crystals through nitrogen Polyethylene is a polymer. Many no. of ethylene cycle, the soluble nutrients are converted to monomers join with each in the synthesis of insoluble CaCO. The CaCO solidifies on the polyethylene. Polyethylene is a hard, stiff, strong cracked surface, thereby sealing it up. and a dimensionally stable material that absorbs CaO + HO very little water. It has good gas barrier properties Ca (OH) () ISSN :Sense 48 Research - 85 Group

3 SSRG Civil Engineering(ICRTCETM-07) 07 Conference onjournal Recent of in Civil Engineering, (ICRTCETM-07) and good chemical resistance against acids, for concrete. Bacterial count is measured using greases and oils. It can be highly transparent and haemocytometer under microscope. The culture of colorless but thicker sections are usually opaque bacteria is described in the following figures. and off-white. It has a round cross section and mixed with the concrete at contents of up 4% by volume or a continuous network of fibrillated fiber to produce high fiber content composite. Fig. Incubation of bacillus subtilis bacteria II.Test On Bacteria Concentration of cells is measured by Haemocytometer and Gram staining method is Fig. Polyethylene fiber Properties of Polyethylene fiber used to determine the morphology of the bacterial Density 0.97 g/cc strains. Fiber Diameter 0.0 mm Length 6 mm Tensile strength 580 Mpa Elastic modulus 7 Gpa Test To determine Result Haemocytometer Cell 05 cells/ml of test concentration bacterial solution. MATERIALS AND METHODS Gram staining Morphology Gram positive Urease test Calcite Color change precipitation yellow to I. Culture of Bacteria The bacteria used in this study are Bacillius subtilis. The bacteria are cultured in mass on the pink culture medium. The culture medium is prepared using nutrient broth which consist of Peptone - CaCO test Quantity of gram, Glucose - gram, Beef extract - gram and calcite Sodium chloride-0.8 gram. The culture medium is precipitation mg/l sterilized in autoclave at C at the pressure of 5lps.The bacteria is then introduced, mass cultured and diluted as per requirements. Staining Table. Various test on bacteria is done to find the suitability and morphology of bacteria. Only gram positive bacteria are suitable ISSN : Sense 48 -Research 85 Group 47887

4 Conference onjournal Recentof in Civil Engineering, (ICRTCETM-07) SSRG Civil Engineering(ICRTCETM-07) 07 III. Properties of Materials Bacteria 05cells per SHC The cement used in this study is OPC, 5 millimeter of water and 0.4% grades Chettinad cement which satisfies IS: of Polyethylene Fiber The fine aggregate of zone II with specific gravity.6, fineness modulus. and moisture 4 Bacteria 06cells per millimeter of water and 0.4% of Polyethylene Fiber. content.5% is used and they are found as per IS: The coarse aggregate of 0 mm size with specific gravity.85, fineness modulus.69 and Table Details of specimen s. EXPERIMENTAL PROCEDURE moisture content 0.6 % is and they are found as per: The slump test was carried out on fresh concrete to check the workability of all concrete mixes. It Distilled water is used for this study. The properties of water are satisfied as per 05 can be tested as per IS: part, part and IS: a. Compression test: IV. Mix Design Concrete mix proportion is designed as per IS and the mix ratio is :.6:.84 with The compressive strength of concrete is tested on cubes using compression testing machine. The rate of 40 kg/cm/min as per IS 56: 964 and the water cement ratio the ultimate loads were recorded. V. Details of specimen About 4 cubes of size 50X50x50mm were The bearing surface of machine was wiped cast to test the compressive strength on 7th and off clean and the surface of the specimen was th 8 day. sample of cylinders of size cleaned. The specimen was placed in machine and 50x00mm and prism of size 00x00x500mm the axis of the specimen was carefully aligned at were cast to find the split tensile and flexural the center of loading frame. The load was applied strength respectively. The details of specimen are at a constant rate of 40 kg/cm/min until the given in table. specimen fails and the maximum load applied on SI. No. Mix Description specimen was recorded. ID The compressive strength of the Control concrete Bacteria 04cells per concrete was calculated using the following millimeter of water and 0.4% formula and the results are tabulated. Compression strength = of Polyethylene Fiber. ISSN :Sense 48 Research - 85 Group

5 onjournal Recent of Civil Engineering, (ICRTCETM-07) SSRG Conference Civil in Engineering(ICRTCETM-07) 07 Where, P - Load in (N) A Area in (mm) Fig.4 Experimental Setup for Split Tensile Strength Test c. Flexural test: Flexural strength is measured using universal Fig. Experimental setup for Compressive testing machine. The flexural strength is the strength test ability of a beam or slab to resist failure in bending. It is measured by loading un-reinforced b. Split tensile test: concrete beams with a span three times the depth Split tensile strength of concrete is tested on (usually 00 x 00 x 500 mm). The flexural cylinder using compression testing machine. The strength is expressed as Modulus of rupture in split tensile strength test for cylinders was carried N/mm².Modulus of Rupture is about to 0 out as per IS 56: 964. Specimen was kept percent of compressive strength. However, the horizontally between the loading surfaces of a best correlation for specific materials is obtained universal testing machine and the load was by laboratory tests. The specimens are subjected applied until failure of the cylinder. The failure to external curing are tested after the 8 days. load was noted and strength was calculated using The flexural strength test for beam the following formula. was carried out as per IS 56:964.Specimen was Split Tensile Strength = kept horizontally between the loading surfaces of a universal testing machine and the load was Where, applied until failure of the cylinder. The failure P = Ultimate load (N) load was noted and shorter length from crack to support strength was measured. Then flexural L = Length of cylinder (mm) D = Diameter of cylinder (mm) Research ISSNSense : Group strength was calculated using the following formula

6 Conference on Recent in Civil Engineering, - SSRG Journal of Civil Engineering(ICRTCETM-07) Special Issue (ICRTCETM-07) - April 07 When a mm specimen, whereas the workability of specimens and SHC are nearer to control R = specimen. The observation on fresh concrete shows that there occurs little bleeding in the When 0 < a mm concrete specimen.it is found that there is R = an increase in slump with the increase in concentration Where, of bacterial cells. Thus the workability of concrete is increased with the R - Modulus of rupture in N/mm increase in bacterial concentration. The result of slump test reveals that all the concrete mixes have P - Maximum Load in N medium workability. L - Span in m a - Shorter length from crack to support in mm Mix Slump (mm) b - Average width in mm, 5 d - Average depth in mm. 60 SHC Slump (mm) Table. Slump Value of Specimens Fig.5 Experimental Setup for Flexural Strength 0 Test 0 4. RESULT AND DISCUSSION SHC workability Graph..Variation of Slump value A. Workability B. Compressive Strength Graph..shows the variation of workability in terms of slump value. The slump values lies between 5 and 69. From the results, Among all mixes the maximum workability is obtained for Sense Research Group ISSN : Graph..shows the variation of compressive strength of concrete on 7 days and 8days. The results showed that the strength of Self-healing concrete has marginally higher than the control

7 Conference on Recent in EngineeringCivil Engineering, - SSRG Journal of Civil (ICRTCETM-07) Special Issue (ICRTCETM-07) - April 07 concrete. The maximum strength is obtained for strength of SHC concrete is.%. The increment in strength is due to the growth of filler material within the concrete and the dead cells present in the concrete. The presence of dead cells Compressive strength (N/mm²) SHC concrete. The percentage of increment in SHC Description of Mix 8 DAYS also reduces the porosity and crack formation in 7 DAYS concrete. Compressive Strength (N/mm) Mixes Average Graph.. Variation of Compressive strength of concrete % Increase in strength C. Split Tensile Strength Graph..shows the variation of split tensile SHC SHC and are increased compared to the control concrete. Maximum strength is obtained strength of concrete. The results showed that the tensile strength of Self-healing concrete of, on SHC concrete and the percentage of Table4. Compressive strength of concrete cubes at 7 days control concrete. Higher bacterial concentration in concrete leads to more decomposition of urea, Compressive Strength (N/mm) Mixes increment in strength is.4% compared with which contains higher concentration of Ca+. This Average % Increase in strength helps to improve the strength. Split tensile Strength (N/mm) Mixes Average % Increase SHC SHC Table5. Compressive strength of concrete cubes at 8 days in strength Table6. Split tensile strength of cylinders for 8 days ISSN : Sense- Research Group

8 Flexural strength (N/mm²) Split tensile strength (N/mm²) SSRG Journal Civil Engineering(ICRTCETM-07) 07 Conference on Recentof in Civil Engineering, (ICRTCETM-07) 0 SHC 8 DAYS Description of Mix SHC Description of Mix 8 DAYS Graph.. Variation of Split tensile strength of concrete D. Flexural Strength Graph.4. Variation of Flexural strength of concrete Graph.4. shows the variation of flexural strength 5. CONCLUSION of concrete. The percentage of increment in strength compared to control specimen is Microbial concrete technology has proved 6.04%.It is increased with the addition of to be better than many conventional bacterial cell. This was due to the reason that technologies because of its eco-friendly bacillus subtilis has more calcium precipitation to nature, self-healing abilities and increase heal crack in concrete. The results showed that the in durability of various building materials. flexural strength of Self-healing concrete of The overall development of strength and, SHC and are increased than the durability of Self-healing concrete by control. using Bacillius subtilis bacteria and polyethylene fibre has investigated and Mixes Flexural Strength (N/mm ) Average compared with control concrete. % Increase The greatest improvement of 05cells/ml in strength for all ages. The showed that a.% 6. increase in 8 day compressive strength, - split tensile strength by.4% and flexural SHC strength by 6.04% was achieved. The more CaCO precipitations, the better the self-healing effect will be. The concentrations of bacteria and Ca + will greater the amount of precipitated CaCO. Tables7. Flexural strength of prisms at 8 days Polyethylene fiber can be increased its mechanical properties of the concrete. ISSN Sense : 48Research - 85 Group

9 Recent of Civil Engineering, (ICRTCETM-07) SSRG Conference onjournal Civil in Engineering(ICRTCETM-07) 07 This process results in the precipitation of [6] IS 06:009 Indian Standard code of substantially higher amounts of calcium Recommended Guidelines for Concrete Mix carbonate inside the crack to be healed. Design, Bureau of Indian Standards, New Delhi. The reason for this can be explained by the [7] IS 456:000 Indian Standard Code of Plain strictly chemical processes in the control and Reinforced Concrete Code of Practice, and additional biological processes in the Bureau of Indian standards, New Delhi. Self-healing concrete. [8] IS 8:970 Indian Standard Code of Coarse Optimum strength is obtained on SHC and Fine Aggregates from Natural Sources for concrete specimen. Bacillus subtilis strain Concrete, Bureau of Indian Standards, New can improve the characteristics of cement Delhi. composites. [9] Seshagiri Rao M.V., Srinivasa Reddy V., Hafsa 6. REFERENCES [] Bang S.S., Galinat J.K. and Ramakrishnan V., Calcite precipitation induced by polyurethaneimmobilized Bacillus pasteurii. Enzyme Microb. Technol., pp ,00. [] DE Belie N., and DE Muynck W., crack repairs in concrete using biodeposition taylor &francis London,009.Raijiwala D.B., M., Veena P. and Anusha P, Bioengineered Concrete A Sustainable SelfHealing Construction Material,Research Journal of Engineering Sciences., Vol. (6),pp. 455,0. [0] Shetty M.S. (00), Concrete Technology Theory and Practice, S.Chand and Company ltd, New Delhi. Bacterial Concrete: A Self-Healing Concrete, [] The ICFAI University Journal of Structural concrete miracle? Concr. Int., 4, pp 76 8,00 Engineering, Vol. I (), pp. 56-6,008. [] De Muynck W., Cox K., De Belie N. and Verstraete W., Bacterial carbonate precipitation as an alternative surface treatment for concrete, Constr. Build. Mater.Vol., pp ,008. Neville, A. Autogenous healing A [] Vijeth N Kashyap and Radhakrishna A Study on the effect of Bacteria on Cement Composites, Journal of Research in Engineering and Technology, pp 56-60, 0. [4] Holt J., Bergey s Manual of Determinative Bacteriology, 9th ed. Williams & Wilkins, Baltimore, 994. [5] Henk M. Jonkers and Erik Schlangen., A two component bacteria-based self-healing concrete Concrete Repair, Rehabilitation and Retrofitting Vol.,pp 5-0,009. ISSN : Sense Research Group