169

International Journal of Research and Innovation (IJRI)

International Journal of Research and Innovation (IJRI)INVESTIGATION ON MECHANICAL PROPERTIES OF BACTERIAL CONCRETE

WITH FLYASH PARTIAL REPLACEMENT

Vummenthala Anusha1, K. Mythili2 , Venkata Ratnam3.

1 Research Scholar, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India.2 Assistant professor , Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India.3 Associate professor , Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India.

*Corresponding Author:

Vummenthala Anusha, Research Scholar, Department of Civil Engineering, Aurora Scientific Technological and Research Academy,Hyderabad India.

Published: July 25, 2015Review Type: peer reviewedVolume: II, Issue : II

Citation: Vummenthala Anusha, Research Scholar (2015) "INVESTIGATION ON MECHANICAL PROPERTIES OF BACTE-RIAL CONCRETE WITH FLYASH PARTIAL REPLACEMENT "

INTRODUCTION

General The most useful construction material adopted nowadays to the tune of development of infrastructure to the con-tinuously growing population in the world wide and their requirement for the shelter of the population is the ce-ment concrete. The use of concrete is increasing worldwide in a fast track and therefore the development of sustainable concrete is anticipated for environmental reasons and also for the improved strength parameters. As presently about 7% of the total anthropogenic atmospheric CO2 emission is due to cement production. If a mechanism is developed

that would contribute to a longer service life of concrete structures and make the material not only more durable but also more sustainable. One such mechanism that is anticipated in recent years is the ability for self-repair, i.e. the autonomous healing of cracks in concrete. Bacte-rial concrete or self healing concrete would be the correct solution for the construction activities for the durability and strength of structures. If such mixture is combined with a material called ‘fly ash’ the material shall become economical thus saving significant cost.

Fly ash is a finely divided residue resulting from the com-bustion of ground or powdered bituminous coal or sub-bi-tumiNo.us coal (lignite) and transported by the flue gases of boilers fired by pulverized coal or lignite. It is available in large quantities in the country as a waste product from a number of thermal power stations and industrial plants using pulverized coal or lignite as fuel for the boilers. The effective use of fly ash as a pozzolana in the manufac-ture of cement and for part replacement of cement, as an admixture in cement mortar with fly ash and concrete with fly ash and in lime pozzolana mixture, has been es-tablished in the country in recent years. Recent inves-tigations on Indian fly ash have indicated greater scope for their utilization as a construction material. Greater utilization of fly ash will lead to not only saving of scarce construction materials but also assist in solving the prob-lem of disposal of this waste product from thermal power stations. The recent investigations have also indicated the necessity to provide proper collection methods for fly ash so as to yield fly ash of quality and uniformity which are

Abstract

For making it economical, a part of the cement by weight is replaced with a material called ‘fly ash’ which is cheaper in cost and abundantly available. On the other hand the cracks in concrete lead to leakage problems and there is a need to address these problems for future.

In the above context, the objective of the present investigation is to obtain the performance of the concrete by adding microbiologically induced special growth/filler and part of cement replaced by fly ash. One such thought leads to the development of very special concrete known as bacterial concrete where bacteria is induced in the concrete and part of the cement replaced by fly ash. A technique is adopted in the formation of concrete by utilizing microbiologically induced calcite (CaCo3) precipitation. Microbiologically induced calcite precipitation (MICP) is a technique that comes under a broader category of science called Bio-Mineralization. ‘Bacillus Subtilis’, a common soil bacterium can induce the precipitation of calcite.

For the experimental investigation firstly cement mortar blocks are casted using fly ash as partial replacement of ce-ment without bacteria and also with a common soil bacterium called ‘Bacillus Subtilis’ of different concentrations like 104, 105, 106, 107 and 108 cells/ml. The cement mortar blocks are tested for 7 days and 28 days strength. Finally it is observed that the mortar blocks made with 105 cells/ml. concentration of ‘Bacillus Subtilis’ attained good strength when compared with normal mortar blocks.

Therefore, for further experimental investigations ‘Bacillus Subtilis’ culture samples with 105 cells/ml.

From the experimental investigations it is observed that the compressive strength, flexural strength and split tensile strength are on par with the normal concrete strength parameters. The three strength parameters of bacterial concrete are found to be higher than that of the normal concrete.

1401-1402

170

International Journal of Research and Innovation (IJRI) prime requirements of fly ash for use as a construction material. This standard has been prepared to give general guidance towards the suitability of fly ash as a pozzolana and as an admixture for structural mortar and concrete.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 ‘Bacillus Subtilis’, a common soil bacterium, can continuously precipitate cal-cite. The bacterial concrete with fly ash makes use of cal-cite precipitation by bacteria. The phenomenon is called microbiologically induced calcite precipitation (MICP). The MICP is a technique that comes under a broader cat-egory of science called bio-mineralization. It is a process by which living organism or bacteria form inorganic sol-ids. ‘Bacillus Subtilis’, when used in concrete with fly ash, can continuously precipitate a new highly impermeable calcite layer over the surface of the already existing con-crete layer. The precipitated calcite has a coarse crystal-line structure that readily adheres to the concrete with fly ash surface in the form of scales. In addition to the ability to continuously grow upon itself, it is highly insoluble in water.

It resists the penetration of harmful agents like chlorides, sulphates, and carbon dioxide into the concrete with fly ash thereby decreasing the deleterious effects they cause. Due to its inherent ability to precipitate continuously, bacterial concrete with fly ash can be called as a ‘smart bio-material’ for repairing concrete.

Bacterial Concrete using Fly Ash

Bacterial concrete using fly ash is a new concept in which living organism or bacteria called ‘Bacillus Subtilis’ is mixed in water with an ordinary Portland cement, fly ash along with fine aggregate and coarse aggregate.

Concrete with fly ash as a structural material

The most widely used construction material is concrete, commonly made by mixing Portland cement with fly ash, sand, crushed rock and water. The present consumption of concrete in the world is estimated to be around twen-ty thousand million metric tons every year or more than three metric tons for every living human being. The world trends indicate that man consumes no other material ex-cept water in such tremendous quantities.

EXPERIMENTAL PROGRAMME

General Methodology

The present investigation is aimed at arriving the perfor-mance of the bacterial concrete in comparison with the normal concrete using fly ash as partial replacement of cement for M20 and M40 grade concrete, after thor-oughly understanding the parameters influencing the strength improvement which are designed with the help of IS:10262-2009.

The experimental programme is divided into four phases.Phase I: Laboratory setup and procurement of materials.Phase II: Mixing of cement mortar, moulding and curing of cement mortar specimens.Phase III: Mixing of concrete with fly ash as partial re-placement of cement, moulding and curing of concrete specimens.Phase IV: Testing procedure for evaluating the strength parameters of cement mortar and concrete specimens.Phase V: Evaluating test results.

Phase I

Phase I involves establishment of necessary laboratory set up and procurement of required materials.

Laboratory set up

The Concrete Technology Laboratory at University College of Engineering, Osmania University is used for this pro-ject. Universal testing machine and compression testing machine are used to test all the concrete specimens. The curing of the concrete specimens is done by submerging the specimens in storage tanks.

Procurement of materials

The materials used for the investigative study of bacterial concrete using fly ash are given below.• Cement• Fly ash• Fine aggregate• Coarse aggregate• Water• Micro Organisms ‘Bacillus Subtilis’ a model laboratory bacterium is used.

Plate 3.1 Colony morphology of ‘Bacillus Subtilis’ on agar plate (Irregular, dry, white, opaque colonies)

Plate 3.2 Phase contrast micro photograph of ‘Bacillus Subtilis’ (Long rods, 0.6-0.8µm in width and 2.0-3.0 µm in length, gram positive)

Plate 3.3 Microscopic photograph of multiple ‘Bacillus Subtilis’ cultured at Microbiology Department, Osmania University, Hy-derabad (View 1)

171

International Journal of Research and Innovation (IJRI)

Plate 3.4 Microscopic photograph of multiple ‘Bacillus Subtilis’ cultured at Microbiology Department, Osmania University, Hy-derabad (View 2)

Plate 3.5 Microscopic photograph showing the culture of ‘Bacil-lus Subtilis’ cultivated at Microbiology Department, Osmania University, Hyderabad (View 1)

Plate 3.6 Microscopic photograph showing the culture of ‘Bacil-lus Subtilis’ cultivated at Microbiology Department, Osmania University, Hyderabad (View 2)

Liquid form of bacteria ‘Bacillus Subtilis

Phase IIMixing of cement mortar

The following mix cases are considered for both normal cement mortar and bacterial cement mortar using fly ash as partial replacement of cement. The mix propor-tion adopted is 1: 3.Case 1 : Normal or control cement mortar mix with fly ash. Case 2 : Cement mortar mix with fly ash with 104 cells/ml. bacterial solution.Case 3 : Cement mortar mix with fly ash with 105 cells/ml. bacterial solution.Case 4 : Cement mortar mix with fly ash with 106 cells/ml. bacterial solution.Case 5 : Cement mortar mix with fly ash with 107 cells/ml. bacterial solution.Case 6 : Cement mortar mix with fly ash with 108 cells/ml. bacterial solution.

Phase IIIMixing of concrete with fly ash

Two mixes of M20 and M40 grades of concrete are con-sidered for both normal concrete and bacterial concrete using fly ash as partial replacement of cement of 10%, 20% and 30%. The mix design is adopted as per IS: 10262-2009 and mixes are as follows. • Normal mix of concrete with fly ash for M20 and M40 grade as per IS: 10262-2009.• Bacterial mix of same concrete using 105cells/ml of ‘Bacillus Subtilis’ culture for M20 and M40 grade as per IS: 10262-2009.

Slump of concrete being measured in Laboratory

Compaction factor of concrete being measured in the Laboratory

172

International Journal of Research and Innovation (IJRI)

Variation of slump for M20 grade concrete

Variation of compaction factor for M20 grade concrete

From the Figures it can be ascertained that as the fly ash replacement increases, the slump and compaction factors increases gradually for M20 concrete. shows the variation of slump and compaction factors for M40 grade concrete and the same is depicted in the graphs 3.6 and 3.7 respectively.

Workability of M40 concrete (slump and compaction factors)

% fly ash replace-ment

Water cement ratio

Super plasti-cizer

Slump in mm Compaction factor in mm

Without bacteria

With bacteria

Without bacteria

With bacteria

10 0.35 0.8 91 90 0.895 0.910

20 0.35 0.8 102 100 0.905 0.915

30 0.35 0.8 104 102 0.915 0.920

Variation of slump for M40 grade concrete

Variation of compaction factor for M40 grade concrete

From the Figures it can be ascertained that as the fly ash replacement increases, the slump and compaction factors increases gradually for M40 concrete also.

Thirty six cubes, 36 cylinders and 36 prisms are casted as shown in Figure and as explained earlier and are subjected to curing. After each period of curing, the cube, cylinder and prism specimens are tested and the results recorded as per given in the following sections.

Moulds of cement concrete cubes being casted in the Laboratory

Phase IV

Phase IV deals with the testing procedures for evaluating the strength parameters of cement mortar specimens us-ing fly ash and concrete specimens with fly ash with and without bacteria.

Testing procedure

The concrete specimens considered in this investigation programme are subjected to the following tests. Compression test

Compression test is conducted confirming to IS 516-1959, on the concrete specimens, on the Universal Testing Machine (200 MT). In this test, cube is placed with the cast faces not in contact with the platens of testing machine i.e., the position of the cube when tested is at right angles to that as cast. Load is applied at a constant rate of stress equal to 15 MPa/min according to relevant IS code and the load at which the specimen failed is recorded. Thus the compressive strengths of the specimens are obtained and the results of all samples are presented in nest chapter. The compression test-ing machine at the University College of Engineering is shown in Figure.

Compression testing at concrete Laboratory at UCE, OU

173

International Journal of Research and Innovation (IJRI) Summary

The total experimental programme which includes five phases, viz. laboratory set up and procurement of mate-rials, evaluation of physical properties of materials, mix-ing of cement mortar and cement concrete using fly ash as partial replacement for cement, moulding and curing of test specimens and testing procedure for evaluating strength parameters of test specimens are explained in this chapter.

ANALYSIS OF TEST RESULTS AND OBSERVATIONS

Strength Characteristics

Preliminary remarks

This chapter deals with the analysis of experimental tests conducted on hardened mortar specimens and concrete specimens which are casted using fly ash, after attaining the desired age of curing with respect to its compressive strength, flexural strength split tensile strength and pulse velocity. The results are precisely and systematically compiled and presented. They are also represented in graphs for its critical analysis and interpretations.

Properties of Cement Mortar using Fly Ash

Compressive strength

The most common of all the parameters is the compres-sive strength of cement mortar because it is a desirable characteristic of concrete. The compressive strength of cement mortar is quantitatively related to the compres-sive strength of concrete.

7 days compressive strength

Case 1: Normal or control cement mortar with fly ash: The specimens with submerged curing have achieved an average compressive strength of 26.3 MPa.

Case 2: Cement mortar with fly ash with 104 cells/ml of bacterial solution: These specimens have attained an average compressive strength of 28.8 MPa. after the submergedcuring.

Case 3: Cement mortar with fly ash mix added with 105 cells/ml bacterial solution: The specimens with the submerged curing have attained an average compressive strength of 31.6 MPa.

Case 4: Cement mortar with fly ash mix added with 106 cells/ml bacterial solution: The specimens have attained an average compressive strength of 29.3 MPa. after the submerged curing.

Case 5: Cement mortar with fly ash mix added with 107 cells/ml bacterial solutions: The specimens with the submerged curing have attained an average compressive strength of 27.6 MPa.

Case 6: Cement mortar with fly ash mix added with 108 cells/ml bacterial solutions: The specimens have at-tained an average compressive strength of 26.9 MPa. when subjected to sub-merged curing.

28 days compressive strength

Case 1: Normal or control cement mortar with fly ash mix case: The specimens subjected to submerged curing have achieved an average compressive strength of 30.7 MPa.

Case 2: Cement mortar with fly ash mix added with 104 cells/ml bacterial solutions: These specimens have attained an average compressive strength of 32.7 MPa after the submerged curing. Case 3: Cement mortar with fly ash mix added with 105 cells/ml bacterial solution: The specimens with the submerged curing have attained an average compressive strength of 37.2 MPa.

Case 4: Cement mortar with fly ash mix added with 106 cells/ml bacterial solution: An average compressive strength of 33.5 MPa is obtained from the test specimens after the submerged curing.

Case 5: Cement mortar with fly ash mix added with 107 cells/ml bacterial solutions: The specimens with the submerged curing have attained an average compressive strength of 32.5 MPa.

Case 6: Cement mortar with fly ash mix added with 108 cells/ml bacterial solutions: The specimens have at-tained an average compressive strength of 31.7 MPa when they are subjected to submerged curing.

From the above results it can be seen that the 28 days compressive strength is maximum for the concentration of 105cells/ml of bacterial solution, hence the same con-centration of bacterial solution is adopted for concrete specimens.

Properties of Concrete with Fly Ash and Bacteria

Compressive strength

The most important and useful of all the parameters is the compressive strength, because most of the param-eters are quantitatively related to compressive strength.

7 days compressive strength

The average 7 days compressive strengths of concrete with fly ash as partial replacement of cement for M20 and M40 grades of concrete with and without bacte-ria and are tabulated in Table 4.1 and also presented graphical in Figure

28 days compressive strength

The average 28 days compressive strengths of concrete with fly ash as partial replacement of cement for vari-ous grades and proportions is tabulated as below (with and without bacteria) are tabulated in Table 4.1 and also presented graphically in Figures.

174

International Journal of Research and Innovation (IJRI) Compressive strength of M20 and M40 concrete at 7 and 28 days (in MPa)

Con-crete grade

% fly ash replace-ment

Without bacteria With bacteria % increase in strength of bacte-rial fly ash concrete than normal fly ash concrete

7 days 28 days 7 days 28 days 7 days 28 days

M20 10 16.41 26.90 17.55 30.10 6.95 11.90

20 12.90 19.20 13.75 21.45 6.59 11.72

30 10.34 17.82 11.08 20.01 7.16 12.29

M40 10 29.45 48.30 31.85 52.85 8.15 9.42

20 21.84 36.40 23.35 40.40 6.91 10.99

30 18.90 31.50 20.12 33.80 6.46 7.30

Compressive strength of M20 concrete at 7 days

Compressive strength of M40 concrete at 7 days

Compressive strength of M20 concrete at 28 days

Compressive strength of M40 concrete at 28 days

Flexural tensile strength of M20 concrete at 7 days

Flexural tensile strength of M40 concrete at 7 days

Flexural tensile strength of M20 concrete at 28 days

Flexural tensile strength of M40 concrete at 28 day

Split tensile strength of M20 concrete at 7 days

Split tensile strength of M40 concrete at 7 days

175

International Journal of Research and Innovation (IJRI)

Split tensile strength of M20 concrete at 28 days

Split tensile strength of M40 concrete at 28 days

Ultrasonic Pulse Velocity TestsPulse velocity tests

28 days pulse velocity test

(a) Normal or control concrete using fly ash for various proportions of mix with M20 grade is as follows: The cube specimens subjected to submerged curing with 10% fly ash have attained an average pulse velocity of 4390m/sec (Good).The cube specimens subjected to submerged curing with 20% fly ash have attained an average pulse velocity of 4260m/sec (Good).The cube specimens subjected to submerged curing with 30% fly ash have attained an average pulse velocity of 4100m/sec (Good).

(b) Bacterial concrete using fly ash as partial replace-ment in various proportions of mix with M20 grade:The cube specimens subjected to submerged curing with 10% of fly ash have attained an average pulse velocity of 4410/sec (Good).The cube specimens subjected to submerged curing with 20% fly ash have attained an average pulse velocity of 4350m/sec (Good).The cube specimens subjected to submerged curing with 30% fly ash have attained an average pulse velocity of 4230m/sec (Good).

(c) Normal or control concrete using fly ash in various proportions mix with M40 grade: The cube specimens subjected to submerged curing with 10% fly ash have attained an average pulse velocity of 4490m/sec (Good).The cube specimens subjected to submerged curing with 20% fly ash have attained an average pulse velocity of 4380m/sec (Good).The cube specimens subjected to submerged curing with 30% fly ash have attained an average pulse velocity of 4310m/sec (Good).

(d) Bacterial concrete with fly ash mix with M40 Grade: The cube specimens subjected to submerged curing with 10% fly ash have attained an average pulse velocity of 4550m/sec (Good).The cube specimens subjected to submerged curing with 20% fly ash have attained an average pulse velocity of

4470m/sec (Good).The cube specimens subjected to submerged curing with 30% fly ash have attained an average pulse velocity of 4410m/sec (Good).

DISCUSSIONS AND CONCLUSION

Scanning Electron Microscope (SEM) Investigation

To reveal the details of hydrated cement samples, scan-ning electron microscope technique is required. SEM technique is utilized for taking the photographs to find out the presence of ‘Bacillus Subtilis’ bacteria in the concrete samples and also to know about the hydrated structure of normal and bacterial concretes.

A small piece of M20 grade concrete with fly ash and two pieces of M20 grade and one piece of M40 grade bacterial concrete are collected from standard hardened cubes and they are sent to the RUSKA Labs, College of Veterinary Sciences, S.V Veterinary University, Rajendra Nagar, Hyderabad to obtain the SEM photographs of normal and bacterial concrete samples. One SEM photograph of normal concrete (with fly ash) sample, with X300 magnification shows no evidence of presence of bacteria and calcite formation. Similarly three SEM photographs of bacterial concrete (with fly ash) samples (two with 9000 magnification and the other with 9500 magnification) are obtained in which the pres-ence of ‘Bacillus Subtilis’ bacteria is clearly visible. The average length of ‘Bacillus Subtilis’ bacteria observed is around 2.00 µm. The SEM photograph of normal con-crete with X300 magnification and bacterial concrete (with fly ash) with 9000 and 9500 magnifications are depicted .

A SEM photograph of non-bacterial concrete with 10% fly ash for M40 grade in X300 magnification

A SEM photograph of bacterial concrete with 10% fly ash for M20 grade with 9000 magnification.

176

International Journal of Research and Innovation (IJRI)

A SEM photograph of bacterial concrete with 20% fly ash for M20 grade with9500 magnification

A SEM photograph of bacterial concrete with 10% fly ash for M40 grade with 9000 magnification

Conclusions

Based on the present experimental investigations, the following conclusions are drawn.• ‘Bacillus Subtilis’ can be produced from laboratory which is proved to be a safe and cost effective.• The addition of ‘Bacillus Subtilis’ bacteria improve the hy-drated structure of cement mortar.• The compressive strength of cement mortar using fly ash is maximum with the addition of ‘Bacillus Subtilis’ bacteria for a cell concentration of 105 cells/ml of mixing water. Therefore, bacteria with a cell concentration of 105 cells/ml of mixing wa-ter are used in the present investigations.• The addition of ‘Bacillus Subtilis’ and fly ash do not affect the workability aspects of concrete and there is no change in the workability aspects of bacterial concrete when compared to normal concrete without bacteria.• The addition of ‘Bacillus Subtilis’ increases the compressive strength without bacteria for M20 and M40 grade concrete with fly ash, the compressive strength increases up to 7.5% for M20 and 8.00% for M40 grade at 28 days age.

Limitations of the Bacterial Concrete

However this study of bacterial concrete has the following limi-tations. 1. The procurement and maintenance of stock culture is tedious and time consuming. It may also presume that the bacterial concrete is also having the following limitations.1 The bacterial concrete has less resistance to the chemical at-tacks.2. The bacterial concrete offers less resistance the fire acci-dents.

REFERENCES:

1. Chiara Barabesi, Alessandro Galizzi, Giorgio Mastromei, Mila Rossi, Elena, Tamburini and Brunella Perito Pavia, Italy, Micro Organisms-’Bacillus Subtilis’ 2007.2. Leuschner, G.Renata, Lillford, J.Peter―Effect of hydration on molecular mobility in phase-bright Bacillus subtilis spores

Journal of microbiology, 2000.3. Massimiliano Marvasi, T.Pieter, Visscher, Brunella Perito, Giorgio Mastromei and Lilliam Casillas-Martinew―Physiologi-cal requirements for carbonate precipitation during biofilm development of Bacilus Subtilis etfa mutant Journal FEMS Microbiology Ecology 2009.4. J.L.Day, S.S.Bang and V.Ramakrishnan―Microbiologically induced sealant for concrete crack remediation 2003.5. V.Ramakrishnan, S.S.Bang, and R.K.Panchalan, ‘Bacterial Concrete–A self-repairing biomaterial,’ Proceedings of the 10th International Congress on polymers in concrete and ICPI/ICRI International concrete repair workshop, Honolulu, HI, 2001.6. Willem De Muynck, Kathelijn Cox, Nele De Belie, Willy Ver-straete―Bacterial carbonate precipitation as an alternative surface treatment for concrete 2003.7. H.S. Patil, D.B. Raijiwala, Hingwe Prashant and Bhabhor Vi-jay―Bacterial concrete - A self healing concrete, International Journal of Applied Engineering Research, Vol. 3, No. 12, 2008, pp. 1719–1725.8. Ke-Ru-Wu, Bing Chen, Wu Yao, Dong Zhang―Effect of coarse aggregate tupe on mechanical properties of HPC. cement and concrete research, 2001, Vol. 31, pp. 1421-1425.9. P.Ghosh, S.Mandal, B.D.Chattopadhyay and S.Pal―Use of Microorganisms to improve the strength of cement-sand mor-tar 2004.10. C.Raj Kumar―Provisions for cements and mineral admix-ture, ICJ 2001, pp.105-112.11. Edvardsen, C.K Water permeability and self-healing of through cracks in concrete (fly ash), Deutscher Ausschuss fur Stahlbeton, Heft 455, 1996 (in German).12. Reinhardt, H-W. and Joos, M.Permeability and self-healing of cracked concrete (fly ash) as a function of temperature and crack width, C and CR 33, 2003, pp. 981-985.

Author

Vummenthala AnushaResearch Scholar,Department of Civil Engineering,Aurora's Scientific Technological and Research Academy, Bandlaguda,Hyderbad - 500005, India.

Mythili Rao Assistant Professor, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy,Hyderabad India.

Venkata Ratnam, Associate professor,Department of Civil Engineering, Aurora's Scientific Technological and Research Academy,Hyderabad India.