A Study on Performance of Standard Grade Bacterial Concrete with Fly Ash

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A Study on Performance of Standard Grade Bacterial Concrete with Fly Ash

Dr. Ravande Kishore1 , P. Srinivas Reddy2, Dr. G.Vijaya Laxmi3

1 Professor, Principal, MIT School of Engineering, Pune

2Assistant Professor, Department of Civil Engineering, Chaitanya Bharathi Institute of Technology (A), Hyderabad

3Assistant Professor, Department of Biotechnology, Chaitanya Bharathi Institute of Technology (A), Hyderabad

Abstract:-Concrete is prone to micro crack formation which is undesirable because they provide an open pathway for the ingress of water and other deleterious substances. Main reason to prevent cracks or limit crack width is to enhance the durability of the structure. Concrete surface treatments with water proofing materials to prevent the access of aggressive substances are a common way to repair concrete structures. These cracks should be repaired to increase the strength and durability of the structure, using either epoxy injections or latex treatment. However, the most common surface treatments include using organic polymers (epoxy, acrylics andpolyurethanes). The characteristics of pore structure of concrete have a direct influence on its durability. One way to avoid costly manual maintenance and repair is to incorporate an autonomous self-healing mechanism in concrete. One such alternative repair mechanism, i.e. a novel technique based on the application of bio mineralization of bacteria in concrete. The bacteria present in the concrete rapidly fill cracks through calcite production. The search for new environmental friendly construction materials like fly ash which can improve the strength and durability of concrete structures has developed interest in self healing bacterial concrete with Fly Ash. The present experimental investigation is carried out to study the mechanical and durability properties of M40 grade concrete using Sporosarcina Pasteurii which would make it, self-healing. The bacterial concentrations were varied by 105, 106 and 107cells/ml. The percentage replacement of fly ash used were 0%, 10%, 20% and 30% by mass of cement. The experiments were carried out to evaluate the effect of Sporosarcina Pasteurii on the compressive strength, split tensile strength, flexural strength, strength loss and weight loss at 7, 28, 56 and 90 days. The test results indicated that inclusion of Sporosarcina Pasteurii with mix 1×106 cells/ml bacteria and 20% fly ash gives optimum performance in terms of compressive strength, split tensile and the mix with 1×107 cells/ml bacteria and 30% fly ash gives optimum performance in terms of strength loss and weight loss and acid durability factor.

Keywords: Concrete, Self healing concrete, Fly Ash, Bacteria, Mechanical properties, Durability.

1.0 INTRODUCTION

Rapid growth and development in the infrastructure can be seen over the past hundred years in the construction activities. In this development concrete plays an important role in the development of the infrastructure in the day-to-day life. Among all the building materials concrete is the artificially made building material which is got special characteristics.

The major drawback of concrete is its low tensile strength due to which microcracks occurs when the structure is subjected to sustained loading and exposed to aggressive environmental conditions results in to decreasing the life of the structure. Entry of harmful chemicals through these cracks may result in concrete deterioration through chemical attack and can also cause corrosion of steel reinforcement. This corrosion leads to increase in crack damage resulting in loss of strength and stiffness of concrete structures. Even though there are many crack repairing techniques to reduce the extent of cracking by available modern technology, There are large number of techniques to repair cracks in concrete such as Grouting,Guniting,Sealing with epoxy's and many more.However,the above mentioned techniques are costly and also in high maintenance cost. In order to overcome this a special type of concrete is developed with the introduction of bacteria in concrete which results in bacterial concrete. This is also called as Self Healing concrete.

In view of the global sustainable development, it is imperative that supplementary cementing materials be used to replace large proportions of cement in the concrete industry. The most available supplementary cementing material worldwide is fly ash, a by-product of thermal power stations. which indicates that there is a potential for the use of much larger amounts of fly ash in concrete, and therefore, for significant reductions in cement production resulting in considerable environmental benefits. To considerably increase the utilization of fly ash that otherwise is being wasted, and to have a significant impact on the production of cement, it is necessary to advocate a use of concrete that will incorporate large amounts of fly ash as a replacement for cement.

An attempt is made to study the properties of bacterial concrete using Sporosarcina pasteurii (Bacillus Pasteuri) along with fly ash as partial replacement to cement.

Bacteria The "Bacterial Concrete" is a concrete which can be made by embedding bacteria in the concrete that are able to constantly precipitate calcite. This phenomenon is called microbiologically induced calcite precipitation. It has been shown that under favorable conditions for instance Sporosarcina pasteurii(Bacillus Pasteruii), a common soil bacterium, can continuously precipitate a new highly impermeable calcite layer over the surface of an already existing concrete layer.

Microbiologically induced calcium carbonate precipitation (MICCP) is comprised of a series of biochemical reactions.In this process, an alkalophilic soil microorganism, Bacillus pasteurii, plays a key role by producing urease that hydrolyzes urea to

2-

2-

ammonia and carbon dioxide.In aqueous environments, the overall chemical equilibrium reaction of calcite precipitation can be decribed as:

[Ca2+]+ [CO3 ] ——--> CaCO3

Possible biochemical reactions in Urea-CaCl2 medium to precipitate CaCO3 at the cell surface can be summarized as follows CO (NH2)2+H2O———>NH2COOH+NH3

2-

2-

2-

2-

NH2COOH+H2O——--> NH3 + H2CO3 2OH+ H2CO3 ——-> CO3 + 2H2O Cell – Ca2++ CO3 ——->Cell CaCO3

Bacterial spores are specialized cells which can endure extreme mechanical and chemical stresses and spores of this specific genus are known to remain viable for up to 200 years. Spores are dormant but viable bacterial spores immobilized in the concrete matrix will become metabolically active when revived by water entering freshly into the concrete.

2.0 RESEARCH SIGNIFICANCE

Cracks in a concrete structure reduces the life and cracks of dimension smaller than that of cement (micro cracks) cannot be filled with chemicals. Crack treatment processes involve harsh materials such as cement and chemicals adding to the pollution of environment. There have been instances of allergic reactions due to chemicals faced by the inhabitants and handlers. Bacteria secretes calcite which fills the cracks and compressive strength and durability of concrete is improved.The environmental impacts of poor disposal of mineral wastes like fly ash, GGBS need to be addressed. Use of fly ash in the manufacture of concrete reduces its interaction with the environment as well plays an important role in imparting strength and durability to the concrete. As there is limited literature available on the study of properties and characteristics of such combination, it is intended to ivestigate in this direction.

    1. MATERIALS

    2. Cement

      Ordinary Portland cement of 53 grade available in local market conforming to specifications of IS: 12269-1987 having specific gravity of 3.06 is used.

    3. Fine Aggregate

Locally available clean, well-graded, natural river sand conforming to specifications of IS 383-1970 having specific gravity of

2.50 is used.

    1. Coarse Aggregate

      Crushed granite angular aggregate of size 20 mm nominal size from local source with specific gravity of 2.65 is used.

    2. Water

      Locally available potable water conforming to IS 456 is used.

    3. Fly Ash

      Fly Ash of class F with 2.32 specific gravity is used

    4. Microorganisms

      Sporosarcina Pasteurii, a soil bacterium which is cultured and grown at laboratory of Biotechnology Department, CBIT, is used in 105,106 and 107cells/ml concentrations.

      Calcium lactate is added by 1% of mass of cement.

    5. Grade designation: M40 grade concrete

    6. Culture of Bacteria

      The pure culture was isolated from the soil sample and 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 glass bottles containing nutrient broth of 13 grams in 1000 ml of distilled water and the growth condition is maintained at 37°C temperature. The medium composition required for growth of culture is Peptone: 5 gm/lit., NaCl: 5 gm/lit., Yeast extract: 3 gm/lit.

    7. Maintenance of Stock Cultures

Stock cultures of Sporosarcina Pasteurii were maintained on nutrient agar slants. The culture was streaked on agar slants with an inoculating loop and the slants were incubated at 37°C. After 2-3 days of growth, slant cultures were preserved under refrigeration (4°C) until further use. Contamination from other bacteria was checked periodically by streaking on nutrient agar plates.

4. 0 EXPERIMENTAL PROGRAM

Table 1: Types of Mix

Mix

Fly Ash (%)

Bacteria (cells/ml)

NC

0

0

105BC

0

1×105

105BCF10

10

1×105

105BCF20

20

1×105

105BCF30

30

1×105

106BC

0

1×106

106BCF10

10

1×106

106BCF20

20

1×106

106BCF30

30

1×106

107BC

0

1×107

107BCF10

10

1×107

107BCF20

20

1×107

107BCF30

30

1×107

    1. Compressive Strength Test

      In the present investigation, compressive strength is determined as per the procedure given in IS 516:1959. Compressive strength is determined on 150 x 150 mm cubes using UTM at a loading rate of 140kg/cm 2/min. Compressive strength = P /A

      P – Maximum load applied on the specimen during the test in Newton

      A – Cross-sectional area calculated from the mean dimensions of the section in mm2

    2. Split Tensile Strength Test

A diametric compressive load will be applied along the length of the sample at a continuous rate until failure occurs. This loading induces tensile stresses on the plane containing the applied load, causing tensile failure of the sample. IS 5816:1999 formed the basis for the development of this procedure. The measured splitting tensile strength of the specimen shall be calculated using the following formula Fct=2P/ dl

P = Maximum load applied on the specimen during the test in Newton l = length of the specimen in mm

d = cross sectional dimension of the specimen in mm

4.3. Durability (Acid test)

The chemical resistance of the concretes was studied through chemical attack by immersing concrete blocks in an acid solution. After 28 days period of curing, the specimens were removed from the curing tank and their surfaces were cleaned with a soft nylon brush to remove weak reaction products and loose materials from the specimen. The initial weights were measured and the specimens were identified with number. The specimens were immersed in 5% H2SO4 and HCL and reading for weight and compressive strengths were recorded for all mix types at 7, 28, 56 and 90 days. The solution was replaced at regular intervals to maintain constant concentration throughout the test period.

Acid Durability Factor (ADF) can be designed as follows. [5]

Acid Durability Factor (ADF) = Sr N / M where, Sr = relative strength at N days, ( % )

N = number of days at which the durability factor is needed. M = number of days at which the exposure is to be terminated.

Acid attack test was terminated at 90 days. So, M is 90 in this case.

    1. TEST RESULTS

    2. Compressive Strength

      Table 1. Compressive strength values

      Mix designation

      Cell concentration ( cells / ml )

      Average cube compressive strength in MPa

      7 days

      28 days

      56 days

      90 days

      NC

      32.44

      48.39

      48.76

      49.10

      105BC

      105

      36.29

      50.88

      52.93

      54.03

      105BCF10

      34.07

      48.07

      51.19

      54.69

      105BCF20

      33.33

      48.71

      54.29

      56.44

      105BCF30

      32.60

      47.81

      50.74

      55.31

      106BC

      36.69

      50.91

      52.80

      55.48

      106BCF10

      34.32

      47.68

      51.33

      55.16

      106BCF20

      106

      34.69

      48.58

      53.81

      57.83

      106BCF30

      32.46

      47.39

      51.27

      55.56

      107BC

      107

      36.28

      50.18

      53.24

      54.21

      107BCF10

      34.21

      47.22

      51.73

      55.03

      107BCF20

      33.25

      48.39

      52.31

      56.47

      107BCF30

      32.06

      47.19

      50.38

      55.55

    3. Split tensile Strength

Figure1 Comparison of Compressive Strength development

Table 2. Split Tensile strength values

Mix designation

Cell concentration( cells / ml

)

Split Tensile strength ( N/mm2)

28 days

90 days

NC

3.76

4.22

105BC

105

3.86

4.47

105BCF10

372

4.49

105BCF20

3.76

4.52

105BCF30

3.92

4.47

106BC

106

3.89

4.45

106BCF10

3.78

4.51

106BCF20

3.94

4.62

106BCF30

3.75

4.49

107BC

107

3.90

4.41

107BCF10

3.69

4.49

107BCF20

3.81

4.49

107BCF30

3.79

4.46

Figure 2: Split Tensile strength values at 28 and 90 days curing

    1. Durability

      1. Acid Test

        Table 3. Percentage weight loss immersed in 5% H2SO4 acid

        Mix designation

        Cell concentration ( cells / ml )

        Percentage weight loss (H2SO4)

        7 days

        28 days

        56 days

        90 days

        NC

        0.53

        1.67

        5.55

        6.91

        105BC

        105

        0.49

        1.78

        4.52

        5.83

        105BCF10

        0.50

        1.71

        3.82

        5.80

        105BCF20

        0.93

        1.83

        4.58

        5.89

        105BCF30

        1.02

        1.79

        5.02

        6.00

        106BC

        106

        0.60

        1.69

        4.46

        5.60

        106BCF10

        1.12

        1.78

        5.30

        5.80

        106BCF20

        1.17

        1.77

        5.00

        5.55

        106BCF30

        1.09

        1.79

        4.92

        5.89

        107BC

        107

        0.55

        1.71

        4.34

        5.61

        107BCF10

        0.72

        1.94

        4.24

        5.64

        107BCF20

        0.98

        1.95

        4.85

        5.57

        107BCF30

        0.49

        1.61

        4.80

        5.61

        Mix designation

        Cell concentration( cells / ml )

        Percentage strength loss (H2SO4)

        7 days

        28 days

        56 days

        90 days

        NC

        4.34

        7.65

        11.19

        13.66

        105BC

        105

        3.83

        7.24

        10.71

        12.48

        105BCF10

        4.04

        7.83

        9.11

        11.03

        105BCF20

        3.28

        7.45

        9.51

        11.17

        105BCF30

        3.34

        6.79

        8.19

        10.15

        106BC

        106

        5.81

        8.35

        8.89

        10.91

        106BCF10

        4.31

        7.46

        8.63

        11.18

        106BCF20

        3.39

        7.68

        9.09

        10.76

        106BCF30

        5.47

        7.73

        8.83

        10.58

        107BC

        107

        5.81

        7.74

        8.89

        11.11

        107BCF10

        3.25

        8.15

        9.51

        10.32

        107BCF20

        3.41

        7.12

        6.43

        11.37

        107BCF30

        5.53

        7.43

        8.83

        10.21

        Mix designation

        Cell concentration( cells / ml )

        Percentage strength loss (H2SO4)

        7 days

        28 days

        56 days

        90 days

        NC

        4.34

        7.65

        11.19

        13.66

        105BC

        105

        3.83

        7.24

        10.71

        12.48

        105BCF10

        4.04

        7.83

        9.11

        11.03

        105BCF20

        3.28

        7.45

        9.51

        11.17

        105BCF30

        3.34

        6.79

        8.19

        10.15

        106BC

        106

        5.81

        8.35

        8.89

        10.91

        106BCF10

        4.31

        7.46

        8.63

        11.18

        106BCF20

        3.39

        7.68

        9.09

        10.76

        106BCF30

        5.47

        7.73

        8.83

        10.58

        107BC

        107

        5.81

        7.74

        8.89

        11.11

        107BCF10

        3.25

        8.15

        9.51

        10.32

        107BCF20

        3.41

        7.12

        6.43

        11.37

        107BCF30

        5.53

        7.43

        8.83

        10.21

        Figure 3. Percentage weight loss after immersion in 5% H2SO4 Table 4.Percentage strength loss after immersion in 5%H2SO4

        Mix designation

        Cell concentration( cells / ml )

        Acid Durability Factor(H2SO4)

        7 days

        28 days

        56 days

        90 days

        NC

        7.44

        28.73

        55.26

        86.34

        105BC

        105

        7.48

        28.86

        55.56

        87.52

        105BCF10

        7.46

        28.68

        56.56

        88.97

        105BCF20

        7.52

        28.79

        56.31

        88.83

        105BCF30

        7.52

        29.00

        57.12

        89.85

        106BC

        106

        7.33

        28.51

        56.69

        89.09

        106BCF10

        7.44

        28.79

        56.86

        88.82

        106BCF20

        7.51

        28.72

        56.56

        89.24

        106BCF30

        7.35

        28.71

        56.73

        89.42

        107BC

        107

        7.33

        28.70

        56.69

        88.89

        107BCF10

        7.53

        28.57

        56.30

        89.68

        107BCF20

        7.51

        28.89

        58.22

        90.68

        107BCF30

        7.35

        28.80

        56.73

        90.21

        Mix designation

        Cell concentration( cells / ml )

        Acid Durability Factor(H2SO4)

        7 days

        28 days

        56 days

        90 days

        NC

        7.44

        28.73

        55.26

        86.34

        105BC

        105

        7.48

        28.86

        55.56

        87.52

        105BCF10

        7.46

        28.68

        56.56

        88.97

        105BCF20

        7.52

        28.79

        56.31

        88.83

        105BCF30

        7.52

        29.00

        57.12

        89.85

        106BC

        106

        7.33

        28.51

        56.69

        89.09

        106BCF10

        7.44

        28.79

        56.86

        88.82

        106BCF20

        7.51

        28.72

        56.56

        89.24

        106BCF30

        7.35

        28.71

        56.73

        89.42

        107BC

        107

        7.33

        28.70

        56.69

        88.89

        107BCF10

        7.53

        28.57

        56.30

        89.68

        107BCF20

        7.51

        28.89

        58.22

        90.68

        107BCF30

        7.35

        28.80

        56.73

        90.21

        Figure 4.Percentage strength loss after immersion in 5%H2SO4 Table 5 Acid Durability Factor after immersion in 5%H2SO4

        Figure 5. Acid Durability Factors after immersion in 5%H2SO4 at 28 days

        Figure 6. Acid Durability Factors after immersion in 5%H2SO4 at 90 days

        6.0 MICROSTRUCTURE

        Scanning Electron Microscope (SEM): The microstructure of the fly ash-based bacterial concrete with different calcium contents was observed by SEM. It was notable that the Figure 7 of normal concrete matrix was not homogeneous and contained small pores and cracks. Figure 8, indicates normal concrete sample which had no depositions of calcium carbonate whereas Figure 9 shows good amount of calcium carbonate deposition on the surface and less number of pores are seen in comparison to the samples of normal concrete. Figure 10, shows a reasonable amount of calcium carbonate content along with fairly good amount of silica and this is due to addition of fly ash in the concrete. And it is consistent with the values of higher compressive strength for bacterial concrete and bacterial concrete with fly ash compared to normal concrete. From the micrographs of figure 9 and figure 10, it can be seen that increase in calcite content in white colour formed on the surface and fly ash particles resulted in a more compact and denser matrix filling the voids and cracks in the concrete improving the pore structure of the concrete. Due to reaction of silica with free lime at later age forms calcium silicate hydrate compound. Because of this hydrated compound the values of compressive strength for bacterial concrete with addition of fly ash are higher at 90 days compared to normal concrete.

        Fig.7: SEM Image of Normal Concrete @ 90 Days

        Fig.8: SEM Image of Bacterial concrete @ 90 Days

        Fig.9: SEM Image of Bacterial concrete with Fly Ash @ 90 Days with Bacteria & Fly Ash

        7.0 DISCUSSIONS

        In M40 grade concrete the compressive strength is increased by maximum of 17.80% at 90 day for 106BCF20 when compared to conventional concrete as fly ash has the property of gaining strength over longer period and it is observed that compressive strength is decreasing with increase in fly ash content.

        The maximum splitting tensile strengths obtained as 4.6 Mpa at the age 90 days for 106BCF20. Increase in compressive strength and split tensile strength values is due to the reason that the density of the concrete has been increased due to filling of cracks with calcium carbonate crystals secreted by the bacteria induced in concrete and fly ash gaining strength at later age.

        It is observed that weight loss percentage for 107BCF30 is 5.61% compared to normal concrete of 6.91% at 90 days of immersion in H2SO4 It is observed that strength loss percentage for 107BCF30 is 10.21% compared to normal concrete of 13.66% at 90 days of immersion in H2SO4 . Acid durability factor is found to be high for bacterial concrete 107BCF20 as 90.68 compared to 86.34 of normal concrete.

        8.0 CONCLUSIONS

        Concrete mix 106BCF20 with 1×106 cells/ml bacteria and 20% Fly Ash has given maximum compressive strength and split tensile strength compared to other mixes.

        Concrete mix 107BCF30 with 1×107 cells/ml bacteria and 30% Fly Ash has shown better performance in durability properties like resistance to acid attack compared to other mixes.

        REFERENCES

        1. Ramakrishnan, V. IMPROVEMENT OF CONCRETE DURABILITY BY BACTERIAL MINERAL PRECIPITATION

        2. Ter Heide, N.et Al (2007) ,EXPERIMENTAL STUDY OF CRACK HEALING OF EARLY AGE CRACKS, Proceedings of the First International Conference on Self Healing Materials 18-20 April 2007, Noordwijk aan Zee, The Netherlands

        3. De Muynck, et. al, IMPROVEMENT OF CONCRETE DURABILITY WITH THE AID OF BACTERIA, Proceedings of the First International Conference on Self Healing Materials 18-20 April 2007, Noordwijk aan Zee, The Netherlands

        4. Henk M. Jonkers et al. 2012, "A TWO COMPONENT BACTERIA-BASED SELF-HEALING CONCRETE", Concrete Repair, Rehabilitation and Retrofitting II Alexander et al (eds) © 2009 Taylor & Francis Group, London, ISBN 978-0-415-46850-3

        5. S. Sunil Pratap Reddy, M. V. Seshagiri Rao, P. Aparna and Ch. Sasikala. PERFORMANCE OF ORDINARY GRADE BACTERIAL (BACILLUS SUBTILIS) CONCRETE, International journal of earth science and engineering, vol. 3, no. 1, 2010, pp 116-124.

        6. C. C. Gavimath et Al. 2012, "POTENTIAL APPLICATION OF BACTERIA TO IMPROVE THE STRENGTH OF CEMENT CONCRETE", International Journal Of Advanced Biotechnology And Researchissn 0976-2612, Vol 3, Issue 1, Page 541 To 544.

        7. Vijeth N Kashyap and Radhakrishna et al. 2013, A STUDY ON EFFECT OF BACTERIA ON CEMENT COMPOSITES, IJRET: International Journal of Research in Engineering and Technology, IC-RICE Conference Issue, Page 356 to 360.

        8. M.V.Seshagiri Rao et Al. BIOENGINEERED CONCRETE-A SUSTAINABLE SELF HEALING CONSTRUCTION MATERIAL, Research Journal of Engineering Sciences, Vol 2(6),45-51 June (2013) ISSN 2278-9472.

        9. Srinivasa Reddy V, STUDIES ON PERMEABILITY OF SELF-HEALING BUILT-IN BACTERIA CONCRETE, International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-1, Issue-6, January 2013

        10. P. R. Wankhede and V. A. Fulari et al. 2014, EFFECT OF FLY ASH ON PROPERTIES OF CONCRETE, International Journal Of Emerging Technology And dvanced Engineering, P, Volume 4, Issue 7 , Page 284 To 289.

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