“STRENGTH ANALYSIS OF CLASS F-FLY ASH IN COMBINATION WITH STEEL FIBER”
1Ankit Mishra, 2Prof. Charan Singh Thakur, 3Prof. Anil Sanodiya Department of Civil Engineering, SRGI, Jabalpur, Madhya Pradesh, India
Abstract - The aim of this investigation is to study the variation in strength characteristics of concrete structures, with M20 grade. In each mix containing different percentages of fly ash, is super-imposed by incorporating some proportion of fly ash starting from 0% as normal concrete, i.e. controlled concrete and 10%,20%,30%and 0.25%,and 0.5% steel fiber as test concrete.
Keywords: Concrete, steel fiber, fly ash, structural-characteristics, test concrete.
1 INTRODUCTION
The infrastructure needs our country is increasing day by day & with concrete is a main constituent of construction material in a significant portion of this infra-structural system, it is necessary to enhance its characteristics by means of strength & durability. It is also reasonable to compensate concrete in the form of using waste materials and saves in cost by the use of admixtures such as fly ash, silica fume etc. as partial replacement of cement, one of the many ways this could be achieved by developing new concrete composites.
The composite reinforced with 5 and 10 15,20percentage by wt of fly ash 0.25% 0.5%,0.75% and 1% of steel fiber demonstrated the highest strength compressive strength.
1.1 Fly Ash
Fly ash is a by-product from coal based electricity power plant. The coal used in these power plants is mainly composed of combustible elements such as carbon, hydrogen and oxygen (nitrogen and sulphur being minor elements), and non-combustible impurities (10 to 40%) usually present in the form of clay, shale, quartz, feldspar and limestone.
At high temperature zone in the furnace, the combustible elements of the coal are burnt off, whereas the mineral impurities of the refuse chemically recombine to produce various crystalline phases. The molten ash is entrained in the flue gas and cools dry, when leaving the combustion zone (e.g. from 1500˚c to 2000˚c in seconds), into spherical, glassy particles. Most of these particles fly with the flue gas stream and are therefore called fly
1.2 Points Should be Understood Using fly ash based technology:
1. It is understood that, fly ash is not a waste, but a highly potential 2. Building material.
3. It is learnt that the fly ash has technical edge in enhancing the durability of concrete.
4. It opened up the awareness about the new business opportunities in packing and transportation of fly ash like a cement industry.
5. It is learnt that the use of fly ash is mandatory as per the government directives.
1.3 Reasons for low level utilization of fly ash:
The current low level utilization of the fly ash is mainly due to:
1. Strong myths that fly ash is a inferior building material.
2. Inadequate promotion of the technology.
3. Lack of confidence in the fly ash based technologies.
4. Lack of proper training and demonstration facilities.
5. Higher cost of production of building material using fly ash.
6. Non availability of dry fly ash collection facilities at many stations.
7. Easy availability of land with topsoil at cheap rates for manufacturing
8. Conventional bricks.
9. Lack of proper co-ordination between thermal plants and ash users.
10. Inadequate government policies and codes.
Fly Ash Based Innovative and Commonly Produced Building Products are available in India:
1. Cellular lightweight concrete (CLC) blocks.
2. Fly ash based polymer composites as wood substitute.
3. Fly ash based Portland pozzolana cement.
4. Ready mixed fly ash concrete.
5. Fly ash sand lime gypsum (cement) bricks/blocks.
6. Clay fly ash bricks
1.4 Classifications of Fly Ash:
Astm – C618-93 [1] categorizes fly ash into the following three
Categories
1. Class N fly ash: Raw or calcined natural pozzolanas such as some diatomaceous earths, opaline chart and shale, stuffs, volcanic ashes and pumice come in this category.
Calcined kaolin clay and laterite shale also fall in this category of pozzolanas.
2. Class F fly ash: Fly ash normally produced from burning anthracite or bituminous coal falls in this category. This class of fly ash exhibits pozzolanic property but rarely if any, self-hardening property.
3. Class C fly ash: Fly ash normally produced from lignite or sub bituminous coal is the only material included in this category.
This class of fly ash exhibits pozzolanic property but rarely if any, self hardening property.
1.5 BIS Categorizes Fly Ashes into the following two categories:
1. Class F fly ash: The burning of harder, older anthracite and bituminous coal typically produces class F fly ash. This fly ash is pozzolanic in nature, and contains less than 10% lime (cao).
2. Class C Fly ash: Fly ash produced from the burning of younger lignite or sub bituminous coals are classified as class C fly ash. Fly ash is one of the most extensively used by product materials in the construction field resembling Portland cement (Pfeifer, 1969). It
is an inorganic, noncombustible, finely divided residue collected or precipitated from the exhaust gases of any industrial furnace (Halstead 1986). Most of the fly ash particles are solid particles spheres and some particles, called cenosperes, are hollow (Kosmatka et al. 2002). Also present are plerosheres, which are spheres containing smaller spheres inside.
The particle sizes in fly ash vary from less than 1 mm to more than 100 mm with the typical particle size measuring under 20 mm.
Their surface areas is typically 300 to 500 m²/kg, although some fly ashes can have surface areas as low as 200 m²/kg and as high as 700 m²/kg. Fly ash is primarily silicate glass containing silica, alumina, iron, and calcium. The relative density or specific gravity of fly ash generally ranges between 1.9 and 2.8 and the colour is generally gray or tan (Halstead, 1986).
2 EXPERIMENTAL PROGRAM
Table No. 01 Casting and Curing of M20 Grade of Concrete with 30% Fly
Ash 0.25steel fiber
Sl.
No .
Parti cular Mix
Desi gn
Co de
No.
of Speci
men Curi
ng peri od in day s
Rema rk
1 Cube M30 M7 9 no’s 7, 14,2 8
Cube size 150x1 50x 150m m Table no. 02 Casting and curing of
M20 grade of concrete with 10%
cement replaced by fly ash 0.25 steel fiber.
Sl.
No.
Part icul ar
Mix Desi gn
Co de
No.
of Speci men
Curi ng peri od in Day s
Rema rk
1 Cub
e M30 M8 9 no’s 7, 14,2 8
Cube size 150x1 50x 150m m
Table no. 03 Casting and curing of M20 grade of concrete with 20%
cement replaced by fly ash.0.25%
steel fiber Sl.
No. Parti cular Mix
Design Code No.
of Speci men
Curing period in Days
Remark
1 Cube M20 M9 9 no’s 7, 14,28
Cube size 150X150X 150mm Table No. 04 Casting and curing of
M20 grade of concrete with 30%
cement replaced by fly ash. And 0.25% steel fiber.
Sl . N o.
Partic ular
Mix Des ign
Co de
No.
of Spec ime n
Curin g perio d in Days
Rema rk
1 Cube M20 M10 9
no’s 7, 14,28
Cube size 150X1 50X 150m m Table No. 05 Casting and curing of
M20 grade of concrete with 10%
cement replaced by fly ash. 0.25 steel fiber.
Sl . N o.
Partic ular
Mix Des ign
Co de
No.
of Speci men
Curi ng peri od in Day s
Rema rk
1 Cube M20 M6 9 no’s 7, 14,2 8
Cube size 150X1 50X 150m m 3 TESTING OF MATERIALS:
3.1 Cement:
Ordinary Portland Cement of 53 Grade confirming to IS: 8112-1989 was used in the investigation
Table No. 05 Chemical Composition of OPC
OXIDE PERCENTAGE CONTENT
CAO 60-67
SO2 17-25
AL2O3 3.0-8.0
FE2O3 0.5-6.0
MGO 0.1-4.0
ALKALIES (K20M,
NA20) 0.4-1.3
SO3 1.0-3.0
Table No. 06 Physical Properties of Cement
S.
No. PROPERTIES
CHART RESUL TS
REQUIREMENTS AS PER IS:8112- 1989
1. Specific gravity 3.15 - 2. Finness
(specific gravity) 301m2/
kg Should not be less Than 225m2/kg 3. Normal
consistency 30% - 4. Setting time in
min.
1. Initial setting time
2. Final setting time
130
197 Should not be less than 30min Should not be exceed 600min.
5. Soundness Test: By 1. Le Chatelier 2. Auto clave method.
0.5mm 0.0935
%
Should not exceed 10mm
Should not exceed 0.8%
6. Compressive strength 1. 3– days 2. 7– days 3. 28-days
34.5N/
mm² 45.50N /mm² 65.00N /mm²
Should not less than 27N/mm² Should not be less than 37N/mm² Should not be less than 53N/mm² 7. Temperature
during testing 27 ˚c Min 25 ˚c and Max 29˚c
3.2 Fly Ash:
Fly ash obtained from Satana Thermal Power Plant, M.P with specific Gravity = 2.3.
Table No. 08 Chemical composition of F-fly ash
S.
No. Chemical Analysis
Class F- Fly Ash (%)
ASTM Requirement C618 (%).
1. Silicon dioxide sio2
55.3 - 2. Aluminum
oxide al2o3
25.70 - 3. Ferric
oxide, fe2O3
5.30 - 4. Sio2 + al2o3
+ fe2O3
85.9 70.0 minimum 5. Calcium
oxide, cao 5.60 - 6. Magnesium
oxide mgo 2.10 5.0 maximum 7. Titanium
oxide tio2
1.30 - 8. Potassium
oxide k2o 0.60 - 9. Sodium
oxide nao 0.40 1.5 maximum 10. Sulfur
trioxide so3
1.40 5.0 maximum 11. LOI
(1000˚c) 1.90 6.0 maximum 12. Moisture 0.30 3.0 aximum.
3.3 Fine Aggregate (FA):
Table No. 09: Sieve analysis of fine aggregate S.
No.
IS SIEVE
SIZE
Weight retaine d (gm)
Correc tion
Correct ed weight
Cumul ative weight retaine
d
Cumulative percentage
weight retained
Cumulative percentage
passing
1. 10mm - - - - - -
2. 4.75mm 25 +0.5 25.5 25.5 2.55 97.45
3. 2.36mm 29 +0.58 29.58 55.08 5.508 94.50
4. 1.18mm 209 +4.18 213.18 268.26 26.826 73.18
5. 600µ 317 +6.34 323.34 591.60 59.16 40.84
6. 300µ 350 +7.0 357 948.60 94.86 5.16
7. 150µ 50 +1.0 51.0 999.6 99.96 0.04
3.4 Properties of Fine Aggregate:
Fineness modulus of fine aggregate=
cumulative percentage weight retained/
100
Fineness modulus = 288.864/100 = 2.88
Specific gravity = 2.68 Water absorption = 0.86%
Silt or clay content= 0.5%
Bulk density = 1520kg/m3
Grading = well graded (zone II).
3.5 Coarse Aggregate:
Table No. 10 Sieve analysis of coarse aggregate Sr.
No.
Is sieve
size
Weight
retained (gm) Cumulative weight retained
Cumulative percentage weight retained
Cumulative percentage passing.
1. 63.00 0.00 0.00 0.00 100
2. 40.00 0.00 0.00 0.00 100
3. 20.00 2000 2000 20.00 80.00
4. 12.50 7580 9580 95.80 4.20
5. 10.00 220.0 9800 98.00 2.00
6. 8.00 120.0 9920 99.20 0.80
7. 6.30 40.00 9960 99.60 0.40
8. 4.75 20.00 9980 99.80 0.20
9. pan 20.00 10,000 - 0.00
3.6 Properties of Coarse Aggregate:
Fineness modulus of coarse aggregates = cumulative percentage weight retained/100
Fineness Modulus = 512.40/100
= 5.12 Specific gravity = 2.7 Water absorption = 1.12%
Impact value = 11.76%
Bulk density = 1440kg/m³.
3.7 Water [IS: 456-2000]:
Water used for both mixing and curing should be free from injurious amount of deleterious materials such as acids, alkalies, salts, organic materials etc.
Potable water is generally considered satisfactory for mixing and curing concrete. In present work potable tap water was used.
Slump Cone Test:
Table No. 28 Description of workability and magnitude of slump
Description of workability Slump in mm
No slump 0
Very low 5 – 10
Low 15 – 30
Medium 35 – 75
High 80 – 155
Very high 160 to collapse Table No. 29 Workability of various concrete mixes design for slump cone
test is as follows
Mix design codes Slump cone test in mm.
M1-MIX (normal concrete) 38 M2-MIX (5% fly ash) 42 M3-MIX (0.25% steel fiber ) 43 M4-MIX (0.5% steel fiber ) 46 M5-MIX (1% steel fiber) 48
3.8 Impaction Factor Test:
Table No. 30 Workability of various concrete mix design for compaction
factor test Serial
No.
Mix Design Code
Compaction Factor
1 M7 0.82
2 M8 0.83
3 M9 0.86
4 M10 0.87
5 M11 0.90
3.9 Details of Specimens Used:
150 mm x 150mm x 150mm cube
specimens for Compressive strength.
Figure 1: Mixing of materials and casting
Figure 2 Freshly Placed Specimen
Figure 3 Curing of Specimens
Test for Compressive Strength of Concrete (IS: 516-1959):
Table No: 32 Compressive Strength of Grade M20 as M7, M8, M9, M10,M11
Mix M-7 M-8 M-9 M-10 M-11 Fly as
(%) 30 10 20 30 10
Steel fiber 0.25 0.25 0.25 0.25 0.25 Test age
(days) 3-3SAMPLES COMPRESSIVE STRENGTH (N/mm²)
7 14.1 17.9 15.9 14.7 14.5 14 18.8 22.8 21.2 19.6 19.3
28 23.5 27 26.5 24.5 24.2
4 CONCLUSIONS
Compressive strength, of fly ash based reinforced concrete specimens were higher than the plain concrete (Control Mix) and fly ash concrete specimens at all the ages. The strength differential between the plain concrete specimens and fly ash reinforced concrete specimens became more distinct after at 28 days.
The replacement of cement with 5% fly ash reduced the compressive strength of concrete.
It has been observed that as the percentage of fly ash increases the compressive strength increases initially, on further increase in its percentage reduces its compressive strength.
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