Effective Utilization of Fly Ash and Pond Ash in High Strength Concrete

Effective Utilization of Fly Ash and Pond Ash in High Strength Concrete

Romeekadevi. M1, Tamilmullai. K1

Students, MIET Engineering College, Gundur, Tiruchirappalli, Tamil Nadu

Abstract -Due to rapid industrialization and urbanization the demand for usage of cement is increasing at an alarming rate .On the other hand fly ash and pond ash is produced in large amount from thermal plants which causes environmental pollution. To overcome above problems fly ash and pond ash can be effectively utilized with partial replacement of cement in high strength concrete. High-strength concrete mixtures will have a high cementitious material content that increase the heat of hydration and possibly higher shrinkage leading to the potential for cracking. It carries loads more efficiently than normal-strength concrete. These materials impart additional strength to the concrete by reacting with Portland cement hydration products to create additional C-S-H gel, the part of the paste responsible for concrete strength. It requires low water cementitious material ratio of 0.3. These low w/c ratio are only attainable with large doses of high range water reducing admixture. In this experimental investigations showed that partial replacement of cement with fly ash and pond ash can be used for construction which reduces the cement scarcity and overall cost of construction. For M60 grade of concrete is arrived by using cement, fly ash, pond ash, fine aggregate, coarse aggregate and sodium silicate(SS). Tests were carried out for compressive strength, split tensile strength and flexural strength for M60 grade concrete.

Key words: Fly ash, Pond ash, Compressive strength, split tensile strength and flexural strength.

I INTRODUCTION

Concrete is the second most consumed substance on Earth after water. Cement production is growing by 2.5% annually, and is expected to rise from 2.55 billion usages to 3.7-

4.4 billion tons by 2050. The production of cement releases greenhouse gas emissions both directly and indirectly and another major problem is dumping of fly ash and pond ash. Coal ash represents a major environmental problem.In India, every year 100 tons of fly is produced. The prevalent practice is to dump fly ash and pond ash on wastelands, and this has lain to waste thousands of hectares all over the country. These sites are not lined and it leads to seepage, contaminating groundwater and soil. It lowers soil fertility and contaminates surface and ground water as it can leach into the subsoil. When fly ash gets into the natural draining system, it results in siltation and

clogs the system. It also reduces the pH balance and portability of water. To overcome the above problems, our experimental study is done on the partial replacement of fly ash and pond ash in cement to reduce scarcity of cement and the environmental pollution (CO2 emission, ash dumping .etc) which is utilized in high strength concrete. High strength concrete has compressive strength above 60 Mpa .The methods and technology for producing high strength concrete are not substantially different from those required for normal strength concrete. Different trail mixes were made to obtain optimum use of fly ash and pond ash. The target water/cement ratio should be in the range 0.3. Fly ash and pond ash reduces the overall cost of the construction and scarcity of cement. Tests were carried out for compressive strength, spilt tensile strength and flexural strength.

II LITERATURE REVIEW

Arumugam et. al(2011) studied the properties and use of pond ash as fine aggregate in concrete. Combustion of pulverized coal in thermal power plant produces bottom ash, fly ash and vapours. Bottom fly ash is collected at the bottom of the furnace. It is a part of the residue consisting of fused particles. Fly ash is collected from electrostatic precipitator in dry form. Fly ash acts both as a fine aggregate and as a cement. Both fly ash and bottom ash are washed with water and disposal in a slurry form in large ponds. Pond ash differs from fly ash in that it contains relatively coarser particles of size > 45 µm to 150 µm. the researchers studied the workability and compressive strength of concrete having pond ash (as partial replacement of fine aggregate) in various percentage. The properties of fly ash concrete were compared with that of standard concrete.

Pan hao et al.(2005) has given the parameters fitting in the design of High Strength Concrete, mathematical statisitics, linear equations and template thought together successfully and discussed an efficient parameter fitting method based on strength equation model and water consumption equation model.

P. Kumar Mehta reported that the concrete mixtures containing more than 50% fly ash by mass of the cementitious material are more efficient .Mechanisms are discussed by which the incorporation of high volume of fly ash in concrete

reduces the water demand, improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulphate attack, and alkali-silica expansion. For countries like China and India, this technology can play an important role in meeting the huge demand for infrastructure in a sustainable manner.

Catharine W. French Ph . D et al.(1991) evaluated that the Replacement of cement up to 10%by Fly Ash with lime will increase early compressive strength. Studied the use of supplementary cementitious materials such as fly ash and silica fume does not necessarily translate into high strengths. It was shown that benefits from inclusion of fly ash and silica fume in the production of HSC depended on the factors such as mixture proportions, type of aggregate in the mixture and the method of curing. When the strength of the HSC was limited by the failure of the aggregate, further reduction in the w/c ratio will not increase the strength and may cause problems by reducing workability of the mixture.

Mohd Mustafa Al Bakri1 et al.(2010) indicated that the Fly ash-based High Strength concrete is better than normal concrete in many aspects such as compressive strength, exposure to aggressive environment, workability and exposure to high temperature.

H.P. Singh et al.(2008) studied the Utilization of Pond Ash will reduce the problem of storing Thermal waste and also decrease the cost of construction.

S.A. Haldive et al (2013) Energy generation is increasing day by day due to rapid industrialization. Energy generation through thermal power plants is very typical now days. Fly ash (FA) from these thermal plants is available in large quantities in fine and coarse form. Fine fly ash is used in construction industry in some amount and coarse fly ash is subsequently disposed over land in slurry forms. In India around 160 MT fly is produced and only 40% of that is being utilized in different sectors. Balance fly ash is being disposed over land. Currently around 65000 acres of land is occupied by fly ash. It needs one acre of land for ash disposal to produce 1MW electricity from coal. The worldwide requirement of construction aggregate is estimated to be more than 40 billion MT and more than 3 billion MT of raw materials is required for cement production. Fly ash and pond ash utilization helps to reduce the consumption of natural resources. Water permeability of fly ash and pond ash concrete is less than OPC concrete; it would be impermeable in aggressive condition. As pond ash added in fly ash concrete, value of RCPT increases, particularly at 20% pond ash. Overall fly ash and pond ash can be replaced by 20 % and 10% as a partial replacement to cement and river sand in

concrete repectively by compressive strength, water permeability and RCPT.

III EXPERIMENTAL PROGRAMME MATERIALS

The main raw materials required for high strength concrete are Cement (C), Pond ash (PA), Fly ash (FL.A), Coarse aggregates (CA), Fine aggregates (FA), Lime (L) ,Water (W) , Sodium Silicate (SS) and Accelerator(A).

Cement: In this study, ordinary Portland cement of 53 grade is used. OPC is conforming to the code IS12269:1987. The physical properties such as specific gravity, particle size, specific surface area are given in Table-1.The chemical composition of OP cement is given in Table-2

Flyash: Flyash is obtained from Mettur Thermal Power plant. This kind of ash is extracted from flue gases through Electrostatic Precipitator in dry form. This ash is fine material and contains good pozzolanic property. CaO content is less than 5%, so the fly ash is classified as class F. The physical and chemical composition of fly ash material is given in Table 1 and 2.

Pond ash: Pond ash is collected from Mettur Thermal Power Plant. When fly ash and bottom ash or both mixed together in any proportion with the large quantity of water to make it in slurry form and deposited in ponds where in water gets drained away. The physical and chemical composition of pond ash material is given in Table 1 and 2.

LIME: Lime is collected from Pollachi. Lime provides high water retention that allows for maximum early curing of the cementitious materials. It acts as a good binding agent of fly ash and pond ash. The chemical composition of lime is given in Table 2.

Fine Aggregate: Locally available River sand is used for this study. River sand is conforming to IS 383-1970. The physical properties such as specific gravity, bulk density, water absorption, fineness modulus are given in Table 3.

Coarse Aggregate: In this study locally available Crushed angular aggregate of size 20 mm is used. The physical properties of coarse aggregate are given in Table 3.

Water: Potable tap water is used for mixing of concrete and curing of the specimen as well. Quality parameters are given in Table 4.

Sodium silicate: It is the common name for a compound sodium meta silicate (Na 2 SiO3 ) also known as water glass or liquid glass. It is generally obtained as 30% to 40% solution of sodium silicates having a specific gravity of 1.51.8. It is in the form of liquid and it light yellow in colour. The molecular weight of sodium silicate is 184 254.

Accelerator: Accelerating admixture are added to increase the rate of early strength development in

concrete. Table 5 shows the properties of accelerator.

Table-1: Physical properties of the cementitious materials

Table-2: Chemical composition of cementitious materials

Table-3 : Properties of aggregates:

Table-4: quality parameters of water sample

Table-5: Properties of Accelerator

IV MIX DESIGN

The mix design is arrived for M60 grade of concrete by using Erntroy and Shacklock method. Extremely low workability condition is taken for this study. Based on aggregate shape reference number 7 is calculated. w/c ratio and aggregate cement ratio of 0.3and 3 respectively is calculated depends on the workability conditions. By using this above data the mix proportion for M60 grade is arrived and quantities of concrete is also determined. Mix proportion for M60 grade of concrete is 1:0.75:2.25:0.3 (C:FA:CA:W/C). The various mix proportion by replacement of pond ash and fly ash materials and quantities of M60 grade concrete in kg/m3 is given in Table 6 and 7.

Table-6: various mix proportion by replacement for materials

Table -7: Quantities of materials in concrete (kg/m3)

CASTING:

The required raw materials like cement, fly ash, pond ash, lime, coarse aggregates, sand, sodium silicate and accelerator have to be mixed as per mix ratio. Cube, cylinder and beam specimens are cast as per the mix ratio. The details of the specimen are given in table 8.

Concrete cube specimen is used to determine the compressive strength of concrete. Cylinder is used to calculate the split tensile strength of concrete and beam is used for determining the flexural

Concrete cube specimen is used to determine the compressive strength of concrete. Cylinder is used to calculate the split tensile strength of concrete and beam is used for determining the flexural

Table-8: Details of specimen

strength of concrete. The cast specimens are shown in figure 1.

Figure 1: casting of specimen

V TEST FOR COMPRESSIVE STRENGTH:

Compressive strength of concrete is used to conform the grade of concrete. The standard cubes of size 150mm X 150mm X 150mm are cast and cured in a curing tank. Cube strength of concrete is determined at 7 days and 28 days. The specimen was taken out from the curing tank and allowed to dry for few hours. The specimen was placed in compression testing machine of capacity 100 tons. In such a way that the load is applied in cast surface. The load is applied gradually until the sample gets failed. The load at failure has been noted. Figure 2 shows the experimental setup for

compressive strength.

Compressive strength = ultimate load/ cross sectional area. N/mm2

Figure 2: Experimental setup for compressive strength

1. TEST FOR SPLIT TENSILE STRENGTH:

The cylinder specimen of diameter 150mm and height 300mm are cast and cured in a curing tank. The split tensile strength of concrete is determined by using compression testing machine of capacity

100 tons at the end of 28days. The cylindrical specimen is placed horizontally between the loading surface of the compression testing machine and steel plates are placed at top and bottom of the cylindrical specimen. The load is applied until the failure of a cylinder along the vertical diameter. Figure 3 shows experimental setup for split tensile strength of concrete.

Split Tensile strength = 2p/dl N/mm2 Where, p is ultimate load in N,

d is diameter of the cylinder in mm, l is length of the cylinder in mm

Figure 3: Experimental setup for split tensile strength

TEST FOR FLEXURAL STRENGTH

Flexural strength = pl/bd2 N/mm2 Where, p is ultimate load in N,

d is depth of the beam in mm,

b is breadth of the beam in mm, l is length of the beam in mm.

VI RESULTS AND DISCUSSION:

1. COMPRESSIVE STRENGTH:

   Compressive strength of concrete with various mix combination is determined at 7 days and 28 days for M60 grade concrete. Table 9 gives the compressive strength value of M60 grade concrete. Figure 5 shows the comparision of compressive strength with various mixes.

   Table-9: Test result of compressive strength

   Proportions	Compressive strength(N/mm2)
   	7th day	28th day
   A	43.2	61.5
   B	41.94	62.5
   C	39.75	60.2
   D	37.89	59.5

   Compressive Strength in MPa

   Compressive Strength in MPa

   COMPARISON OF COMPRESSIVE STRENGTH

   70

   60

   50

   40

   The size of beam specimen is 500 mm x 100 mm x 100 mm are cast and cured at 28 days. The flexural strength of the concrete is determined by using universal testing machine of capacity 100 tons. The specimen is placed in universal testing machine in such a manner that the single point load is to be applied to the upper most surface of the beam specimen. The load is to be increased until the specimen fails and the maximum load applied to

   30

   20

   10

   0

   A B C D

   Mixes

   7th day

   28th day

   the specimen during the test is recorded. Figure 4 shows experimental setup for flexural strength of concrete.

   Figure 4: Experimental setup for flexural strength

   Figure 5: Comparison of compressive strength values

   The compressive strength value of concrete varies between 37.89 Mpa to 43.2 Mpa at 7 days. The high compressive strength is obtained for the mix A. The compressive strength of concrete varies between 59.5 Mpa to 61.5 Mpa at 28 days. The high compressive strength is achieved for the mix

   B. The mixes A, B , C achieved M60 grade. The mix D attained the strength nearer to 6 Mpa because the pond ash percentage is higher when compared to the other mixes. Mix B has 1.6% and 3.7% higher compressive strength than mix A and C respectively. The compressive strength value is decreased with increase in fly ash and pond ash content. The compressive strength of concrete is increased with increase in cement content.

2. SPLIT TENSILE STRENGTH:

Split tensile strength of concrete with various mix combination is achieved at 28 days for M60 grade concrete. Table 10 gives the split tensile strength value of M60 grade concrete. Figure 6 shows the test results of split tensile strength with various mix combinations.

Table-10: Test Result of Split tensile strength

5.7

5.6

5.5

5.4

5.3

5.2

COMPARISON OF FLEXURAL STRENGTH

5.7

5.6

5.5

5.4

5.3

5.2

COMPARISON OF FLEXURAL STRENGTH

A

MixeBs

C

D

A

MixeBs

C

D

FLEXURAL STRENGTH IN

N/mm2

FLEXURAL STRENGTH IN

N/mm2

Figure 7: mix proportions Vs flexural strength

Split Tensile Strength in MPa

Split Tensile Strength in MPa

5.8

5.6

5.4

5.2

5

4.8

COMPARISON OF SPLIT TENSILE STRENGTH

The Flexural strength value of concrete varies between 5.37 Mpa to 5.65 Mpa at 28 days. The higher Flexural strength is obtained for the mix A. The mix D attained the strength nearer to 60 Mpa because the pond ash percentage is higher when compared to the other mixes. Mix A attained 2.7% and 4% higher Flexural strength value than mix B and C respectively. The Flexural strength of concrete is increased with increase in cement content and decreased with increase in fly ash and pond ash. As per IS code IS 456:2000, theoretical value of flexural strength calculate by using 0.7fck. Experimentally found flexural strength coincides with the theoretical value of 0.7fck.

A Mixes B C D

Figure 6: mix proportions Vs split tensile strength The Split tensile strength value of concrete

varies between 5.12 Mpa to 5.75 Mpa at 28 days. The higher Split tensile strength is obtained for the mix A. The mix D attained the strength nearer to 60 Mpa because the pond ash percentage is higher when compared to the other mixes. Mix A attained 4.3% and 7.7% higher Split tensile strength value than mix B and C respectively. The Split tensile strength of concrete is increased with increase in cement content and decreased with increase in fly ash and pond ash.

C)FLEXURAL STRENGTH:

Flexural strength of concrete with various mix combination is found at 28 days for M60 grade concrete. Table 11 gives the flexural strength value of M60 grade concrete. Figure 7 shows the flexural strength values of concrete with various mix combinations.

Table-11: Test Result of Flexural strength

VII CONCLUSION:

The following points to be drawn from the experimental results,

1. Mix Proportions were arrived for M60 grade concrete.

2. Mix A, B, C and D is arrived by replacing fly ash and pond ash for high strength concrete.

3. Mix A, B and C is achieved the compressive strength value is above 60 Mpa.

4. Effective utilization of cement by fly ash and pond ash decreases the problem of scarcity of cement. In addition to that fly ash and pond ash can also be eco friendly materials.

REFERENCES

1. M.R Taylor et al (1996), Mix Proportion for High Strength Concrete Construction and Building Materials, Vol.10 Issue6, pg 445-450.

2. M.S.Shetty (2007),Concrete Technology , S. Chand Publications

3. N.Krishnaraju, Design of Concrete Mixes, CBS Publishers and distributors.

4. A.Santhakumar (2007), Concrete Technology, Oxford University Press.

5. Pan Hao et al (2005), The Parameters fitting in High Strength Concrete Mix Proportion Experiment Literature search.

6. Catharine W. French Ph.D and Aliera Mokhtarazadesh (1991) High strength concrete-Test procedure on short term strength PCI Journal.

7. Mohd Mustafa Al Bakri, H. Mohammed, H. Kamarudin, I. Khairul Niza and Y. Zarina1 Review on fly ash-based on high strength concrete without Portland Cement in Nov- 2010 Journal of Engineering and Technology Research Vol. 3(1), pp. 1-4, January 2011.

8. H.P. Singh, B.K. Maheshwari , Swami Saran and D.K. Paul Evaluation of Pond Ash in High Strength concrete in The 14 World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China.

9. IS 383:1970 Specification for Coarse and Fine Aggregate.