STUDY ON STRENGTH AND DURABILITY PROPERTIES OF BIO-CONCRETE

    STUDY ON STRENGTH AND DURABILITY PROPERTIES OF BIO-CONCRETE

ABSTRACT

                 The present paper deals with the Bacteria (Bacillus subtilis) to improve the Strength and durability properties of Concrete. Bacillus subtilis is one of the soil Bacterium which is a new methodology in remediating cracks and fissures up to size 0.15mm in concrete by utilizing microbiologically induced calcite (calcium carbonate) precipitation is a technique that comes under a broad category of science called Bio mineralization.The usage of Concrete drastically increasing from day to day life. In spite of much research the cracks in concrete are inevitable the bacterial concrete is the one which is the self –healing property. Here I have made an attempt to incorporate dormant but viable bacteria in the concrete matrix which will contribute to the strength of the concrete. In this project, bacterial concrete is prepared under grade of concrete M20, M30 and M40.The design mix proportioning also carried under IS code provision. For the durability I had testing with H₂SO_4. Testing of specimens are carried at 7 days ,28 days and 90 days of curing by Compression Testing Machine for corresponding specimens. The Compressive Strength, Split Tensile Strength and Flexural Strength of Bacterial Concrete are to be found and it compared with conventional Concrete.

Key words: Bacterial concrete, Beef Extract, compressive strength, flexural strength, Durability.

1. Introduction

     

                        Cement mortar and concrete are the most widely used building material in the construction field. It is difficult to point out another material of construction which is versatile as 

It is the material of choice where strength, permeance, durability, Impermeability are required. Concrete is strong in compression and weak in tension. Cement concrete is one of the seemingly simple but actually complex materials. Many of its complex behaviour are yet to employ this material advantageously and economically. The behaviour of concrete with respect to long-term drying shrinkage, creep, fatigue,cracks and fissures. here the bacterial concrete is the technique which heals the cracks and enhance the strengthening properties. Many of concrete structures face immature degradation problems like carbonation, chloride attack problems and leads to repair or retrofitting of the structures. The usage of these cementitious materials in or combinations of the above is being researched for its variable characteristics are studied. Bacillus subtilis that is rich in soil has been used to generate CaCO3 precipitation. The "Bio-Concrete" is a concrete in which cultured bacteria is

Mixed to prepare concrete. Impeachment of calcium carbonate in concrete enhances properties of concrete. The bacterial concrete can be made by embedding bacteria in the concrete that are able to constantly precipitate calcite. This called microbiologically induced calcite precipitation (MICP). Bacillus subtilis,which can successfully remediate cracks in concrete.

1.1 OBJECTIVE OF STUDY:

                      The main objective of the project is to determine and compared the mechanical properties of Bacterial concrete with conventional concrete such as compressive strength, flexural strength, split tensile strength, and durability studies. The prepared liquid media bacillus subtilis is added to water in concrete as every 5ml, 10ml, 15ml and 20ml for 500ml of water required.

2. Biological requirement (Bacillus subtilis)

                           Bacteria are relatively simple, single celled organisms. The bacteria used were Bacillus subtilis. It is a bacterium with the ability to precipitate calcium carbonate in the presence of any carbonate source. The bacterium is used in this project for the same and for the improvement in the strengths of the concrete test specimens were observed. The microbes are a bacillus species and are completely not harmful to human beings. They precipitate inorganic crystals hence the healing of the cracks takes place in the concrete and it can withstand any temperature conditions. The peptone, beef extract are the ingredients for the growth of Bacteria bacillus subtilis.

2.1 Classification of Bacteria

      Bacteria are the most abundant and metabolically diverse form of life on earth. They growth under the wide range of geochemical conditions in an unparalleled variety of habitats.Basically,microbial life exists wherever there is a liquid water at temperature from -7^▫c to 120^▫c.Bacteria are usually classified on the basis of their shapes, on the results of gram staining method and on the requirement of oxygen for the survival of the bacterium.

Bacteria are mostly simple in form and exbit one of three basic structures: Bacillus (plural,bacilli) straight and rod shaped,coccus (plural,cocci)spherical-shaped, and and also called spirochetes.spirilla bacteria generally do not form associations with other cells and swim singly through their environments.

           

ROD SHAPED

SPIRAL SHAPED

             2.2 Preparation of Bacterial 

                2.2.1 Cutler of bacteria

     The pure culture is maintained constantly on nutrient agar slants. It forms irregular dry white colonies on nutrient agar. Whenever required a single colony of the culture is inoculated into nutrient both of 200ml in500ml conical flask and the growth conditions are maintained at 37 degree temperature and placed in 125rpm orbital shaker.The medium composition required for growth of cultures Peptone, NaCl, beef extract. Primarily 12.5g of Nutrient broth (media) is added to a 1000ml conical flask containing distilled water. It is then covered with a thick cotton plug and is made air tight with paper and rubber band. It is then sterilized using a cooker for about 10-20 minutes. Now the solution is free from any contaminants and the solution is clear orange in colour before the addition of the bacteria Later the flasks are opened up and an exactly 1ml of the bacterium is added to the sterilized flask and is kept in a shaker at a speed of 150-200 rpm overnight. After 24 hours the bacterial solution was found to be whitish yellow turbid solution. After the completion of presence of bacillus subtilis the prepared liquid media should be mixed into the concrete    

  

                                              Fig. Cultured Bacteria (Bacillus subtilis)

3. Mixing Of Concrete

                    

        The mixing process is carried out in electrically operated mixer. The materials are laid inUniform layers, one on the other in the order – coarse aggregate, fine aggregate and cement. Dry mixing is done to obtain a uniform colour. Required amount of bacterial water is added. The workability tests are carried out immediately after mixing of concrete using the compaction factor testing apparatus in accordance with IS: 10510-1983. 5ml,10ml,15ml,20ml reference  of bacteria

 ( Bacillus subtilis) was added to every 500 ml of water while mixing concrete, so the total amount  of bacteria was added to required  liters of water used for mixing cement in concrete.

      3.1 Materials used

                                                  

S.NO	Type of material	Required code
1	Cement	OPC 53 Grade (IS 12269-1987)
2	fine aggregate	ZONE –II (IS 383-1970)
3	coarse aggregate	20 mm Size (IS 383-1970)
4	water	Tap water is used (IS 456-2000)
5	Bacteria (Bacillus subtilis)	Peptone,Nacl,beef extract

         

        3.2 Experimental Results

                     

                  The experimental investigation was conducted as detailed below. All the materials tests were conducted in the laboratory as per relevant Indian Standard codes ASTM. Basic tests were conducted on fine aggregate, coarse aggregate and cement to check their suitability for concrete making. The study aims to investigate the strength related properties of concrete of grade. The proportions of ingredients of the control concrete of grade had to be determined by mix design as per IS code. Workability of fresh concrete was determined by the slump test according to Indian standards. The typical size of cube 150mm×150mm×150mm was used to determine the Compressive strength. Split tensile strength was carried out on the cylinder with 150mm diameter and 300mm height.

3.3 Physical properties of the materials

Table 2

     

Description of Item		Value
Specific gravity of cement		3.15
Setting time	Initial time	50 min
	Final time	217 min
Specific gravity of fine aggregate		2.607
Specific gravity of coarse aggregate		2.866
Sieve Analysis of aggregate		Zone-II

Chemical composition of cement

                               Table 3

Component of cement	% composition
Sio2	21.80
Al2O3	4.80
Fe2O3	3.80
CaO	63.3
SO3	2.20
Mgo3	0.90

4. Mix design

            Mix design can be defined as process of selecting suitable ingredients of concrete such as cement, aggregates, water and determining their relative proportions with the object of producing concrete of required minimum strength, workability and durability as economically as possible. The mix proportions for ordinary grade concrete and standard grade concrete are designed using IS: 10262-2009. Materials required for 1 cubic meter of concrete in ordinary grade concrete and standard grade concrete are shown in table

                      

                                 table 4 (Mix proportions)

Grade of Concrete	Ordinary grade	Standard grade
	M20	M30	M40
Mix proportions	1:2.15:3.80	1:1.83:3.23	1:1.65:2.90
Water cement ratio	0.50	0.42	0.40
Water content (lit)	170	165	170

  

5. RESULTS AND DISCUSSION

 5.1 Compressive strength:

        Compression test has been carried out on concrete cubes with standards confirming to IS 516-1999.All the samples were tested in a 2000 KN capacity Compression testing machine. After 28 days of curing, the cubes were permitted to turn in to dry condition before testing. Plane surfaces of the specimen were between platens of compression testing machine and subjective to loading. The compressive strength of the concrete cubes are given in Table3. In this compressive strength of cubes for M20, M30&M40 grade concrete made with and without bacteria for 7 days & 28 days was tested

Table5 Compressive strength of cubes for M20, M30&M40 grade concrete made with

And without bacteria 7 & 28days

Cell Concentration/ml        of  mixing bacteria	Compressive strength of Concrete in mpa
	7days	%increase	28days	%increase
M20 Control (nil)	19.21	-	27.89	-
5 ml	24.13	25.61	31.37	12.47
10 ml	25.08	30.55	32.89	17.92
15 ml	22.19	15.55	30.79	10.39
20 ml	21.33	11.03	29.40	5.41
M30 Control (nil)	24.32	-	39.26	-
5 ml	29.72	22.20	45.26	15.28
10 ml	32.16	32.16	46.39	18.16
15 ml	30.16	24.01	43.26	10.10
20 ml	28.65	17.80	41.33	5.20
M40 Control (nil)	35.46	-	50.29	-
5 ml	40.76	14.96	53.26	5.90
10 ml	43.26	30.55	58.45	16.22
15 ml	41.46	16.92	56.12	11.59
20 ml	39.32	10.80	55.10	9.60

Table 5 summarizes the 7 days and 28 days compressive strength of the mortar cubes containing different cell concentration of alkaliphilic microorganism (Bacillus subtilus). The greatest improvement in compressive strength occurs at Culture of 10ml for all ages: this increase reaches to 17.92,18.16&16.22 for M20,M30&M40 % at 28 days. This improvement in compressive strength is due to deposition on the microorganism cell surfaces and within the pores of cement–sand matrix, which plug the pores within the mortar. The extra cellular growth produced by the microorganism is expected to contribute more to the strength of cement mortar with a longer incubation period and thus the strength improvement is found to be more at  28 days. Even the dead cells may simply remain in the matrix as organic fibers. Quantification and Characterization was done using Scanning Electron Micrograph analysis, only to be noted that cracks are sealed up by crystalline material grown over the surface due to microbial activity of the bacteria.

5.2 Splitting tensile strength test on concrete cylinders

                     The tensile strength of concrete is one of the basic and important properties. Splitting tensile strength test on concrete cylinder is a method to determine the tensile strength of concrete. The concrete is very weak in tension due to its brittle nature and is not expected to resist the direct tension. Splitting tensile test has been carried out on concrete cylinders with standards confirming to IS 5816-1999

Table 6 Results of the Split Tensile strength Test with and without addition of bacteria for M20, M30 and M40 grade of concrete

Cell concentration/ ml of    mixing bacteria	Tensile strength of Concrete in mpa
	28 days	% Increase
M20 Control (nil)	2.42	--
5 ml	2.65	9.50
10 ml	2.81	16.11
15 ml	2.72	12.39
20 ml	2.56	5.76
M30 Control (nil)	3.43	--
5 ml	3.79	10.49
10 ml	3.92	14.21
15 ml	3.81	11.02
20 ml	3.69	7.50
M40 Control (nil)	4.12	--
5 ml	4.46	8.25
10 ml	5.01	21.60
15 ml	4.76	15.53
20 ml	4.52	9.70

     In M20, M30 and M40 grade concrete the Split Tensile Strength on standard cylindrical specimens at 28 days are given in Table 4 It is observed that with the addition of bacteria there is a significant increase in the spilt tensile strength by 16.11%, 14.21% and 21.60% at  28 days respectively

5.3 Flexural strength test

                    The investigation is carried to study the flexural behaviour of concrete. 3 simply supported beams consisting of balanced section are cast and tested. The cross section of the beam specimen is 100mm x 100mm x 500mm. The beams are cast using with bacteria and without bacteria in M20, M30&M40 grade concrete. The flexural strength of both controlled and bacterial concrete is calculated and the result is tabulated in Table 5. Flexural strength test has been carried out on concrete beams with standards confirming to IS 516-1999

Table 7 Results of the Flexural Tensile Strength test with and without addition of Bacteria for M20,M30&M40grade of concrete.

Cell concentration/ ml of    mixing bacteria	Flexural  strength of Concrete in mpa
	28 days	% Increase
M20 Control (nil)	2.72	--
5 ml	2.90	6.61
10 ml	3.26	19.81
15 ml	3.15	15.80
20 ml	2.96	8.82
M30 Control (nil)	4.36	--
5 ml	4.62	5.96
10 ml	5.11	17.20
15 ml	4.97	13.65
20 ml	4.76	9.17
M40 Control (nil)	5.16
5 ml	5.66	9.68
10 ml	6.43	24.61
15 ml	6.15	19.18
20 ml	5.90	14.34

               Based on the experimental results the Flexural Tensile Strength is as shown in Table 7. It is observed that with the addition of bacteria there is a significant increase in the Flexural Strength by 19.81%, 17.20% and 24.61% at 28 days for M20,M30&M40 Grades respectively.

6. Durability studies:

           

         To study durability characteristics, the specimens are subjected to 5% solution of H2SO4. For determining the resistance of concrete specimens to aggressive environment such as acid attack, the durability factors are proposed by the author, with the philosophy of ASTM C 666–1997, as the basis. In the present investigation, we derived the “Acid Durability Factors” directly in terms of relative strengths. The relative strengths are always with respect to the 28 days value (i.e. at the start of the test). The “Acid Durability Factors” (ADF) can be designed as follows.The addition of Bacillus subtilis bacteria improves the hydrated structure of cement in concrete for a cell Culture of 10 ml of mixing water. So, bacteria of optimum cell culture 10 ml of mixing water was used in the investigation. From the durability studies, the percentage weight loss and percentage strength loss with 5% H2SO4 revealed that Bacterial concrete has less weight and strength losses than the controlled concrete. Durability studies carried out in the investigation through acid attack test 5% H2SO4 revealed that bacterial concrete is more durable in terms of “Acid Durability Factor” than conventional concrete and bacterial concrete is less attacked in terms of “Acid Attack Factor” than conventional concrete.

fig.Acid curing in trays

Table 7 Durability Results of the Compressive Strength test with and without addition of Bacteria for M30 grade of concrete

Grade of Concrete		Days of Immersion	Immersion in 5% H2SO4
			% Weight loss	% Loss in Compressive strength
M30	Controlled	14 days	7.06	8.25
		28 days	16.95	56.42

	Bacterial Concrete
	5 ml	14 days	5.86	7.09
		28 days	12.32	38.43
	10 ml	14 days	5.80	6.01
		28 days	11.68	35.28
	15 ml	14 days	4.85	5.30
		28 days	9.13	29.54
	20 ml	14 days	4.45	4.03
		28 days	9.05	22.61

    6.1 CONCLUSION

Ø  The bacillus subtilis  concrete obtained compressive strength , split tensile strength and porosity results the incorporation of more numbers of bacteria in the cracks of the concrete cube.

Ø  Due to the inclusion of bacteria in concrete, we achieved slight increase in    compressive strength, split tensile strength and flexural strength up to 15% than the conventional concrete.

Ø  From the results it can be concluded that easily cultured Bacillus subtilis can be    safely used in improving the performance and characteristics of concrete.

Ø  By adding the bacillus subtilis the durability strength results fall from 5ml to 20 ml

6.2 ACKNOWLEDGEMENT

   I express my sincere thanks to Coordinator SR.GR.PHANI KUMAR.V, Tech,(GT),Assistant Professor, Departmentof Civil Engineering, Gudlavalleru engineering college for his valuable guidance and timely suggestions during the project work

REFERENCES:

1. Bachmeier KL, Williams AE, Warmington JR, Bang SS.,“Urease activity in microbiologically-induced calcite precipitation.” Journal of Biotechnology 93,2002, pp. 171- 181.
2. Bang, S.S., Galinat, J.K., and Ramakrishnan, “Cal- cite Precipitation Induced by Polyurethane Immobilized Bacillus)Pasteurii,” Enzyme and Microbial Technology, vol.28, 2001, pp. 404–409.
3. De Muynck W., Cox K., De Belie N. and Verstraete W “Bacterial carbonate precipitation as an alternative surface treatment for concrete”, Constr Build Mater, 22, 875-885 (2008).
4. Ghosh P, Mandal S, Chattopadhyay BD, Pal S., “Use of microorganism to improve the strength of cement mortar.” Cement and Concrete Research 35, 2005, pp.1980-1983.
5. H. M. Jonkers and E. Schlangen, “A two component bacteria-based self-healing concrete,” Concrete Repair, Rehabilitation and Retrofitting II, 2009, pp. 215–220.
6. F. Hammes, N. Boon, J. De Villiers, W. Verstraete, S. D. Siciliano, and J. De Villiers, “Strain-Specific Ureolytic Microbial Calcium Carbonate Precipitation,” Applied And Environmental Microbiology, vol.69, no.8, 2003, pp. 4901– 4909.
7.       IS10262,”Recommended Guideline ForConcrete Mix Design”.
     8.      IS 456:2000,”Plain and Reinforced Concrete-Code of Practice”.
     9.      IS 12269-1987 Specification for 53 grade Portland Cement' Bureau of Indian Standards, New Delhi, India.
    10.      Ramachandran, S.K., Ramakrishnan, V., and Bang, S.S. (2001) remediation of concrete using micro-organisms. ACI Materials Journal 98(1):3-9. 

                                

7.      

1.