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A Sustainable Environmental Study on Corn Cob Ash Subjected to Elevated Temperature

Komalpreet Singh1*, Jaspal Singh1and Sarvesh Kumar1

1Department of Civil Engineering, PAU Ludhiana, Ludhiana, Punjab India

DOI:http://dx.doi.org/10.12944/CWE.13.1.13

Rapid increase in greenhouse gas induces mischievous impact on environment. In this study, carbon dioxide emission can be reduced to some extent by replacing some amount of cement with corn cob ash. The performance of concrete at high temperature was also studied. This paper investigates the effect of elevated temperature on strength property of ordinary concretes of grade M25, containing Corn Cob Ash (CCA) at various replacement levels of cement. The cube samples were subjected to high temperature of 1500C, 3000C, 4500C and 6000C for 2 hour duration in a muffle furnace. The samples were tested for compressive strength after air cooling to the room temperature. It can be seen that at normal temperature, compressive strength of the concrete decreases as the CCA content increases. The compressive strength of concrete increased significantly for all the mixes including control mix when the temperature was raised to 3000C. The recommended maximum replacement content of cement with CCA and elevated temperature was 10% and 3000C respectively.


Cement; Compressive Strength; Concrete; Corn Cob Ash; Elevated Temperature

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辛格K,辛格J,Kumar S. A Sustainable Environmental Study on Corn Cob Ash Subjected to Elevated Temperature. Curr World Environ 2018;13(1). DOI:http://dx.doi.org/10.12944/CWE.13.1.13

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辛格K,辛格J,Kumar S. A Sustainable Environmental Study on Corn Cob Ash Subjected to Elevated Temperature. Curr World Environ 2018;13(1). Available from://www.a-i-l-s-a.com/?p=1050


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Article Publishing History

Received: 2017-11-10
Accepted: 2017-12-26

Introduction

Carbon dioxide gas (CO2) available in earth’s atmosphere is about 0.04%. In change in amount of CO2creates adverse effect on environment. CO2emission occurs due to combustion of fossil fuels, cement production and deforestation which causes global warming. The cement production contributes large amount of global CO2emission generated from calcinations of lime stone and combustion of fuels in a kiln. In order to control carbon dioxide emission, it is necessary to minimize the production and use of cement to some extent by partial replacing it with other environment friendly material. The agricultural waste used as a partial replacement of cement is one of the best solution to minimize water, land and air pollution. The waste agriculture products which possess pozzolanic properties have been studied were rice husk ash,1saw dust ash2and corn cob ash.3Corn is one of the most important crop in India after wheat and rice. Worldwide production of corn is about 1070 million metric tons in 2016-17. United States of America was the largest producer of corn in 2016-17 and contributes about 36% of the total production of corn in the world. India is at 7thplace in the production of corn. India produces about 26 million metric ton of corn for the year 2016-17.

Corncob is a waste product obtained during production of corns, with approximately about 170-190 kg corn cob generated for every 1000 kg of corn produced.4For the purpose of removal of heavy metal from waste water5corn cob has also been used and its ash is used as ingredient to ordinary Portland cement concrete.6Corn cob ash (CCA) is obtained by burning of corn cob waste. CCA has about 70% of combined content of SiO2and CaO. Investigators and researchers have various opinion on the properties of concrete in account of effect of temperature in the range of 100-3000C7-9and the compressive strength of concrete above 3000C goes on decreasing. The serious deterioration has found at 600°C, at this stage concrete loses almost half of its original strength.10-11Concrete containing CCA is used in structures under normal temperature conditions. Properties of CCA concrete under ambient temperature conditions have received considerable research attention. However, the behaviour of CCA concrete at elevated temperature has not sufficiently been covered. Compressive strength of CCA concrete under elevated temperatures needs to be studied. The present study investigates the effect of elevated temperature on the compressive strength of CCA concrete.

Materials Used

Ordinary Portland Cement (OPC)

Ordinary Portland cement 43 grade was conforming to BIS: 811212was used. The physical properties of ordinary Portland cement are given in Table 1.

Table 1: Properties of OPC 43 grade cement

Characteristics

Experimentally Values Obtained

Values specified by BIS 8112

Standard consistency

31%

-

Specific Gravity

3.15

-

Initial Setting time (min)

152

not less than 30

Final Setting time (min)

249

not more than 600

Compressive Strength
3 days
7 days
28 days


23.60 MPa
34.84 MPa
46.55 MPa


23 MPa
33 MPa
43 MPa


Coarse and Fine Aggregates

所使用的粗骨料是碎石nominal size of 20 mm. Locally available river sand having nominal size of 4.75 mm was used. The sand was conforming to grading zone II as per BIS: 383.13Table 2 shows the physical properties of coarse and fine aggregates.

Table 2: Physical Properties of Coarse and Fine Aggregates

Property

Fine aggregate

Coarse aggregate

Specific Gravity

2.74

2.68

Fineness modulus

2.73

6.62

水absorption %

0.5

1


Corn Cob Ash (CCA)

To prepare CCA, first corn cobs were broken down into small pieces which helps in enhancement of combustibility and reduction in carbon content that affects the pozzolanic properties. CCA was produced by burning of pieces of corn cob in furnace at about 7000C up to 5 hours. The chemical composition of CCA is shown in Table 3.

Table 3: Chemical Composition of CCA

Chemical Components

Value

SiO2

64.56%

CaO

12.0%

Fe2O3

5.12%

Al2O3

9.42%

MgO

3.01%


Methods

Concrete Mixes and Mix Proportions

Control mix C1 was designed as per BIS: 1026214for M25 grade of concrete. Then four mixes were casted at various replacement levels of OPC (0%, 5%, 10%, 15% & 20%) with CCA and are designated as C2, C3, C4 and C5. The water/cement (w/c) ratio in all the mixes was kept at 0.45. Mix proportions of concrete mixes are given in Table-4.

Table 4: Mix Proportions of Concrete Mixes

Mixes

CCA
%

CCA
(kg/m3)

W/C
Ratio


(l/m3)

Cement
(kg/m3)

Coarse aggregate
(kg/m3)

Fine aggregate
(kg/m3)

M1

0%

0

0.45

191.58

425.73

1100.22

719.16

M2

5%

21.2

0.45

191.58

404.53

1100.22

719.16

M3

10%

42.57

0.45

191.58

383.16

1100.22

719.16

M4

15%

63.86

0.45

191.58

361.87

1100.22

719.16

M5

20%

85.14

0.45

191.58

340.59

1100.22

719.16


Preparation of Test Cubes

All the specimens were casted in accordance with BIS: 51615. After casting, the cubes were wrapped in plastic sheets and kept at room temperature for 24 hours. The cubes were removed from the moulds after 24 hours of casting and submerged into water for curing till the time of the test.

Compressive Strength of CCA Concrete at Elevated Temperature

The cubes were heated in a muffle furnace at 1500C, 3000C, 4500C, and 6000C for 2 hours after 28 days curing. The cubes were allowed to cool at room temperature naturally. The compressive strength was performed on cubes of size 100 mm X 100 mm X 100 as per BIS: 516.18Loading rate of 2.5kN/s was applied for compressive strength test.

Results and Discussions

The test results of compressive strength of CCA concrete subjected to different elevated temperature is given in Table 5. The effect of elevated temperature of CCA concrete on compressive strength is shown in Figure 1. It was observed that the compressive strength of all mixes increases up to elevated temperature of 3000C. Beyond the temperature of 300oC, the compressive strength decreases significantly for all mixes. The compressive strength of mixes M1, M2, M3, M4 and M5 at elevated temperature of 1500C was increased by 3.01%, 1.20%, 3.29%, 2.55% and 1.19% respectively, as compared to normal temperature.

Table 5: Average Compressive Strength of CCA Concrete at Elevated Temperature

Mix

28 days Compressive strength at room temperature (MPa)

Compressive strength at elevated temperature (MPa )

1500C

3000C

4500C

6000C

M1

36.43

37.53

41.43

32.33

12.40

M2

32.47

32.86

36.75

29.00

11.12

M3

27.33

28.23

31.76

22.73

10.06

M4

23.07

23.66

25.63

20.56

10.50

M5

20.15

20.39

23.03

16.68

09.13

Figure 1: Compressive strength of CCA concrete at elevated temperature

Figure 1: Compressive Strength of CCA Concrete at Elevated Temperature
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The increase in compressive strength at elevated temperature of 3000C with reference to normal temperature for mixes M1, M2, M3, M4 and M5 was 13.72%, 13.18%, 16.20%, 11.09% and 14.29% respectively. This may be due to the evaporation of the free moisture content which accelerates the hydration and hence increases the compressive strength till the temperature of 3000C. The reduction in compressive strength at elevated temperature of 4500C with reference to normal temperature for mixes M1, M2, M3, M4 and M5 was respectively 11.25%, 10.68%, 16.83%, 10.87% and 17.22%. Same trend has been observed at elevated temperature of 6000C, with percentage reduction (65.96%, 65.75%, 63.19%, 54.48% and 54.68%) for different mixes (M1, M2, M3, M4 and M5) respectively. For temperatures higher than 3000C, the strength of CCA concrete starts decreasing. This decrease is attributed to the fact that chemically-bound water starts to disintegrate and evaporate at this stage.

The coefficient of determination ‘R2’ of Mixes M1, M2, M3, M4 and M5 are shown in Figure 2, 3, 4, 5 and 6 respectively. In these equations y is value of compressive strength obtained with respect to temperature ‘x’. The comparison between values of R2is shown in Table-6.

It is clear from the values obtained from the regression analysis that regression lines of mixes M1 to M5 approximates shows the real data points. The values of R2obtained for the mixes M1 to M5 are nearer to the 1 which indicates that the regression line perfectly fits the data.

Figure-2: Coefficient of determination of mix M1

Figure 2: Coefficient of determination of mix M1
点击他re to View figure

Figure-3: Coefficient of determination of mix M2

Figure 3: Coefficient of Determination of Mix M2
点击他re to View figure

Figure-4: Coefficient of determination of mix M3

Figure 4: Coefficient of Determination of Mix M3
点击他re to View figure

Figure-5: Coefficient of determination of mix M4

Figure 5: Coefficient of determination of mix M4
点击他re to View figure

Figure-6: Coefficient of determination of mix M5

Figure 6: Coefficient of determination of mix M5
点击他re to View figure



Table 6: Values of R2of the Mixes Shown in Table-6

Mix

28 days Compressive strength at room temperature (MPa)

Coefficient of determination (R2)

M1

36.43

0.9912

M2

32.47

0.9902

M3

27.33

0.9709

M4

23.07

0.9890

M5

20.15

0.9547


Conclusion

From this study following conclusions are drawn:

It was noticed that the compressive strength of all mixes increases up to elevated temperature of 3000Beyond this temperature, compressive strength decreases significantly for all mixes. High rise in compressive strength was noted at 300oC w.r.t compressive strength of concrete under normal temperature. The result shows that all reaction providing strength to the concrete gets completed at about temperature of 300oC. The compressive strength of normal concrete subjected to temperature of 300oC at 28 days curing age was noted 13.72 % higher than that of concrete at normal temperature.

The optimum content of CCA is recommended as 10% corresponding to elevated temperature of 3000C

The regression analysis shows that the values of R2obtained for the mixes M1 to M5 are nearer to the unity which indicates that the regression line perfectly fits the data.

Acknowledgements

This research was carried out and supported by the authors of this paper. We thanks our colleagues and staff of Punjab agricultural university Ludhiana who provided insight and expertise that greatly assisted the research. We thank Punjab agricultural university Ludhiana to provide world quality infrastructure and instruments to carry out our research.

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