Maiti Fly Ash Concrete

8/11/2019 Maiti Fly Ash Concrete

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FLY ASH CONCRETE MIX DESIGN

By

Dr. S. C. Maiti


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Target 28-Day Compressive Strength of Concrete

= f ck + 1.65 x Standard Deviation

f ck = Characteristic strength of concrete


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CHARACTERISTICS OF MATERIALS

Cement OPC 43 grade

Fly Ash Conforming to Part1 of IS 3812(Fineness : 320 m 2/kg, min.

Lime Reactivity : 4.5 N/mm 2, min.

Loss of ignition : 5%, max)

Superplasticizer Normal or retarding type (as required)

Satisfying the requirements of IS 9103

(approx. 1% by wt of cement)


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AGGREGATES

Coarse Aggregate : 10 mm, 20 mm, 40 mm max. size

Fine Aggregate : Zone II Grading

(Natural or crushed stone)

Silt Content : 3% by weight, max. (natural sand)Silt Content : 15% by weight, max. (crushed stone)


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SUGGESTED STANDARD DEVIATION VALUES(As per IS 456) For Good Quality Control

5.0

M 30M 35M 40M 45M50M 55

4.0

M 20

M 25

3.5M 10M15

Standard DeviationValue (N/mm 2)

Grade of Concrete


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WATER CEMENTITIOUS MATERIALS RATIO

W ratio to be estimated from Fig. 1, for the target 28-

C+F day compressive strength of concrete


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53

47

42

37

33

29

27

0

20

40

60

0.20 0.30 0.35 0.40 0.45 0.50 0.55 0.60

W/C+F (by wt .)

2 8 - d a y

C o m

p r e s s

i v e s

t r e n g

t h o

f c o n c r e

t e ,

M P a

TYPICAL RELATIONSHIP BEWTEEN W/C+F AND 28-DAY COMPRESSIVE STRENGTH OF

SUPERPLASTICISED FLYASH CONCRETE

Fig. 1


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WORKABILITY OF CONCRETE

(i) Medium : 50 60 mm slump

(ii) High : 80 100 mm slump


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ESTIMATION OF MIXING WATER AND SAND CONTENT

(For sand grading: Zone II & crushed rock coarse aggregate**)

303540Sand content*, %

19020021080-100

18019020050-60

40 mm20 mm10 mm

Max. size of aggregateSlump, mm

* For sand of grading Zone I, (+) 1.5% sand

For grading Zone III, (-) 1.5% sand

** For rounded aggregate, the water requirement will be (-) 10 l/m 3 of concrete


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FINE AGGREGATE GRADINGS

(% passing)

0-150-100-100-10150 micron

15-5012-408-305-20300 micron

80-10060-7935-5915-34600 micron

90-10075-10055-9030-701.18 mm

95-10085-10075-10060-952.36 mm

95-10090-10090-10090-1004.75 mm

10010010010010 mm

GradingZone IV

GradingZone III

GradingZone II

GradingZone I

IS SieveDesignation

Note 1: For crushed stone sand, the permissible limit on 150 micron is increased to20%.

Note 2: Fine aggregate conforming to Grading Zone IV should not be used inreinforced concrete, unless tests ascertain the suitability of proposed mixproportions.


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FLY ASH CONTENT

Recommended replacement (% by wt.) : 15-25%

15-20% for good quality of fly ash:

i. Fineness : 320-400 m 2/kg

ii. L.R. : 4.5-5.0 MPa

21-25% for very good quality of fly ash:

i. Fineness : > 400 m 2/kg

ii. L.R. : > 5.0 MPa


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TYPICAL GRADING OF CRUSHED SAND(CRUSHED STONE AGGREGATE)

(IS: 383)

0-10

12-40

60-79

75-100

85-100

90-100

GradingZone III

12.075 micron

0-1021.4*150 micron

8-3031.8300 micron

35-5949.8600 micron

55-9066.21.18 mm

75-10090.42.36 mm

90-10099.24.75 mm

Grading ZoneII

% passingIS SieveSize

* IS: 383 permits upto 20% passing through 150 micron sieve


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DURABILITY REQUIREMENT

(As per IS 456) (For 20 mm MSA)

M 400.40360M 250.40280Extreme5

M 350.45340M 200.45260Verysevere

4

M 300.45320M 200.50250Severe3

M 250.50300M 150.60240Moderate2

M 200.55300-0.60220Mild1

MinimumGrade of

Concrete

MinimumFree

WaterCementRatio

MinimumCement

Contentkg/m 3

MinimumGrade of

Concrete

MinimumFree

WaterCementRatio

MinimumCement

Contentkg/m 3

Reinforced ConcretePlain ConcreteExposureS.No.

For 10 mm MSA + 40 kg/m 3

For 40 mm MSA - 30 kg/m 3


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AIR CONTENT OF CONCRETE

3.010

2.020

1.040

Entrapped Air (%)Max. size of aggregate

(mm)


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ESTIMATION OF SAND CONTENT AND COARSE AGGREGATE

CONTENT, KG PER CUBIC METER OF CONCRETE

V-Vol. of air = W + C + Quantity of Fly Ash + Quantity of Sand X 1

S c Sp. Gr. of Fly Ash p x sp. gr. of sand 1000

V-Vol. of air = W + C + Quantity of Fly Ash + Quantity of coarse aggregate X 1S

cSp. Gr. of Fly Ash (1-p) x sp. gr. of c. aggregate 1000

V = 1 m 3 concrete

W = Weight of water, kg/m 3

C = Weight of cement, kg/m 3

S c = Sp. Gr. of OPC = 3.15

p = Proportion of sand (i.e. sand ratio)

Total aggregate


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COARSE AGGREGATE GRADING (COMBINED)

(As per IS 383)

0-10--2.36

27-360-100-54.75

95-10025-5510-3510

10095-10030-7020

-10095-10040

10 mm MSA20 mm MSA40 mm MSA

% passing for graded aggregateIS sievesize (mm)


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EXAMPLES ON COMBINED GRADING

EXAMPLE 1 (% passing)

0-100.07 + 1.04= 1.1

2.600.124.75

25-552.0 + 32= 32.2

80.123.410.0

95-10055.8 + 40= 95.8

10093.020.0

100.040.0

Desired

gradinglimit

60% of

Fraction I+40% of

Fraction II

Fraction II

(Below 10 mm)

Fraction I

(20-10 mm)

Sieve

size (mm)


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EXAMPLE 2 (% passing)

0.04 + 2.46= 2.5

1.24 + 42.92= 44.1

44.8 + 50= 94.8

-

50% ofFraction I

+50% of

Fraction II

0-100.048 +1.968= 2.01

4.920.084.75

25-551.48 +34.33= 35.8

85.842.4810.0

95-10053.8 + 40= 93.8

10089.7220.0

---100.040.0

Desiredgrading

limit

60% ofFraction I

+40% of

FractionII

Fraction II(Below 10 mm)

Fraction I(20-10mm)

Sievesize

(mm)


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DATA REQUIRED

1. Grade of concrete2. Desired workability of concrete (slump, mm)

3. Durability requirement exposure condition

4. 28-day compressive strength of cement

5. Quality of superplasticiser (% water-reduction)

6. Data on Fly Ash:

Fineness

Lime reactivity

Loss on ignition, %7. Gradings of sand, coarse aggregate (different size fractions)

8. Sp. gr. of sand, coarse aggregate and fly ash

9. Water absorption (%) of sand and coarse aggregate

Maiti Fly Ash Concrete

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