376 | Page Study on Characteristic Compressive Strength of concrete with Fly ash as partial replacement of cement Rehan Ali Khan 1 , Shahbaz Ahmad 2 , Moizuddin Siddiqui 3 1 HoD, 2,3 Lecturer, Civil Engg. Deptt. Integral University , Campus Shahjahanpur ABSTRACT Experimental study is conducted on partial replacement of cement with Rosa Thermal Fly Ash in different grades of concrete. Cubes were casted with 15%, 20%, 25%, 30% and 35% flyash replacement in design mix concrete. It is observed that at 15% fly ash, rate of gain of strength is maximum in different grades of concrete ( M20, M25, M30, M35 ). In M35 Grade Concrete, its strength decreases with increase in flyash quantity. After curing of concrete cube for 56 days, the rate of gain of strength is almost equal to that of 28 days curing strength. I. INTRODUCTION Fly ash is the notorious waste product of coal based electricity generating thermal power plants, known for its ill effects on agricultural land, surface and sub-surface water pollution, soil and air pollution and diseases to mankind. Fly ash particles are almost totally spherical in shape, allowing them to flow and blend freely in mixtures. That capability is one of the properties making fly ash a desirable admixture for concrete. These materials greatly improve the durability of concrete through control of high thermal gradients, , depletion of cement alkalis, resistance to chloride and sulphate penetration, and continued micro structural development through a long-term hydration and pozzolanic reaction Fig: 1.1 II. OBJECTIVES In this paper work, objective is to develop engineering database on the mechanical properties and to determine the necessary level of fluidity, generally termed as of fly ash concrete incorporating RTPS fly ash and Ordinary Portland Cement, and it is compared with controlled concrete. Also four grades (M20, M25, M30 and M35) of concrete are targeted to select optimum percentage of cement replacement by Fly ash as cementitious material, for obtaining maximum possible 28 days compressive strength. 1. Preliminary laboratory test of fine aggregates, coarse aggregate for mix design.
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376 | P a g e
Study on Characteristic Compressive Strength of concrete with Fly ash as
partial replacement of cement
Rehan Ali Khan1, Shahbaz Ahmad
2, Moizuddin Siddiqui
3
1HoD,
2,3Lecturer, Civil Engg. Deptt. Integral University , Campus Shahjahanpur
ABSTRACT
Experimental study is conducted on partial replacement of cement with Rosa Thermal Fly Ash in different
grades of concrete. Cubes were casted with 15%, 20%, 25%, 30% and 35% flyash replacement in design mix
concrete. It is observed that at 15% fly ash, rate of gain of strength is maximum in different grades of concrete (
M20, M25, M30, M35 ). In M35 Grade Concrete, its strength decreases with increase in flyash quantity. After
curing of concrete cube for 56 days, the rate of gain of strength is almost equal to that of 28 days curing
strength.
I. INTRODUCTION
Fly ash is the notorious waste product of coal based electricity generating thermal power plants, known for its ill
effects on agricultural land, surface and sub-surface water pollution, soil and air pollution and diseases to
mankind. Fly ash particles are almost totally spherical in shape, allowing them to flow and blend freely in
mixtures. That capability is one of the properties making fly ash a desirable admixture for concrete. These
materials greatly improve the durability of concrete through control of high thermal gradients, , depletion of
cement alkalis, resistance to chloride and sulphate penetration, and continued micro structural development
through a long-term hydration and pozzolanic reaction
Fig: 1.1
II. OBJECTIVES
In this paper work, objective is to develop engineering database on the mechanical properties and to determine
the necessary level of fluidity, generally termed as of fly ash concrete incorporating RTPS fly ash and Ordinary
Portland Cement, and it is compared with controlled concrete.
Also four grades (M20, M25, M30 and M35) of concrete are targeted to select optimum percentage of cement
replacement by Fly ash as cementitious material, for obtaining maximum possible 28 days compressive strength.
1. Preliminary laboratory test of fine aggregates, coarse aggregate for mix design.
377 | P a g e
2. Mix design and proportioning for ingredients.
3. Modification and correction in mix proportioning during concrete production to meet workability
requirement.
4. Modification and correction in mix proportioning during concrete productions for moisture content of fine
aggregates.
5. Water to binder (cement plus fly ash) ratio was kept 0.50, 0.46, 0.42 and 0.38 for M20, M25, M30 and M35
grade concrete respectively.
6. 150 mm size cubes were casted, cured in water tank and weighed for unit weight before compression testing
for the determination of mechanical properties of concretes at 7 days and 28 days .
7. Super plasticizer dose was calculated for each grade of concrete for same W/C ratio to obtain slump value
80-120mm.
8. Test result interpretation for optimum selection of suitable part replacement of Fly ash as cementitious
material.
9. Compressive strength test and analysis for the determination of mechanical properties of concrete at 7 days
and 28 days from the date of casting of the test specimen.
III. CHARACTERISTICS OF FLY ASH
Table: 1.1
Characteristics Value Characteristics Value
Moisture (%) 0.09 Total:
SiO2 + AL2O3+ Fe2O3 (%)
87.73
Loss on Ignition (%) 7.03 Na2O (%) 0.44
Fineness > 45mic 27.53 K2O (%) 1.53
Fineness > 75mic 14.30 MgO (%) 1.45
Free CaO (%) 0.00 SO3 (%) 0.25
Total CaO (%) 2.25 Chloride (%) 0.00
SiO2 (%) 58.46 P2O5 (%) 0.16
AL2O (%) 21.47 TiO2 (%) 0.93
Fe2O3 (%) 7.81 Specific Gravity 2.36
Source: “Low cost high performance concrete using low quality fly ash” by Aires Camões, Patrício Rocha, J.C.
Pereira, J.B. de Aguiar, Syed Jalali .
Table: 1.2 Loss on ignition of Fly ash
Fly Ash L.O.I.
(%)
Total „as received‟ 7
Particles > 75μm 26.5
Particles < 75μm (enhanced fly
ash)
3.5
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Source: “Low cost high performance concrete using low quality fly ash” by Aires Camões, Patrício Rocha, J.C.
Pereira, J.B. de Aguiar, Said Jalali.
IV. DESIGN OF CONCRETE MIX
As stated earlier Mix Designing Methods according to Indian Bureau of Standard (IS456-2000) is adopted as a
general guideline to arrive at mix proportioning for four grade of concrete (M20, M25,M30 and M35) with
super plasticizer.
Table: 1.3 Test of 53 grade OPC Cement
S.No Test Conducted Results Requirement as per IS:12269-
1987(RA1999)
1. Brand of Cement J P
2. Type of Cement 53 Grade-
OPC
3. Normal Consistency 29.0% Not Specified
4. Initial Setting Time 140 Minutes Shall not be less than 30 min.
5. Final Setting Time 220 Minutes Shall not be less than 600 min.
6.
Compressive Strength After
3 Days 44.6 Mpa Shall not be less than 27.0 Mpa
7 Days 55.0 Mpa Shall not be less than 37.0 Mpa
28 Days 59.0 Mpa Shall not be less than 53.0 Mpa
7. Fineness (by Blain‟s air permeability
method)
326.0 m2/Kg Shall not be less than 225.0m2/Kg
8. Soundness (by Le-Chatelier‟s method) 1.0mm Shall not be more than 10mm
9. Ratio of % of Alumina to that of Iron
Oxide
1.22 Not less than 0.66
10. Insoluble Residue 0.51 Not more than 3%
11. Magnesia (%) 1.11 Not more than 6%
12. Total loss of Ignition (%) 1.60 Not more than 4%