Design of Concrete Mix by Indian Standard Method

Design Stipulations1 Characteristic Compressive Strength required in the field at 28 days 30 MPa2 Maximum size of Aggregate 20 mm3 Degree of workability 0.8 C.F.4 Degree of quality control Good 35 Type of exposure Severe 4

Test data for materials1 Specific gravity of cement 3.152 Compressive strength of cement at 7 days3 Specific gravity of coarse aggregates 2.604 Specific gravity of fine aggregates 2.605 Water absorption:

Coarse aggregate 0.50%Fine aggregate 1.00%

6 Free (surface) moisture:Coarse aggregate 0.0%Fine aggregate 2.0%

7 Sand confirming grade zone 3

Design ProcedureStep 1 Target mean strength of concrete

S 6.0Target mean strength of concrete 39.9

Step 2 Selection of water cement ratioFree water cement ratio as per Fig. 1 0.50Maximum free water cement ratio as per Table 5 IS 456 0.45Free water cement ratio as per Fig. 2 0.60Water Cement Ratio 0.45

Step 3 Selection of water and sand contentWater content per cubic metre of concrete 186Sand content as percentage of total aggregate by absolute volume 35

Adjustment of values in water content and sand percentage

Sand confirming zone I, II or IV 0 -1.5Increase or decrease in C.F. by 0.1 0 0Increase or decrease in w/c by 0.05 0 -2.00Total 0 -3.5

31.5%Required water content 186

ft = fck+ tS

Water content

Sand Percent

Required sand content as percentage of total aggregate by absolute volume

Step 4 Determination of cement contentWater-cement ratio 0.45Water 186.0 litreCement 413.33333 kg/m3

Step 5 Determination of coarse and fine aggregate contentsVolume of entrapped air 0.02Absolute volume of fresh concrete 0.98Total mass of fine aggregate 543 kg/m3Total mass of coarse aggregate 1180 kg/m3

The mix proportion then becomes:

Water Cement186.0 413 543 11800.45 1 1.313 2.856

Step 6 Actual quantities required for the mix per bag of cementi Cement 50 kg

ii Sand 65.7 kgiii Coarse aggregate 142.8 kgiv Water1 Quantity of water 22.5 litres2

0.71 litres3

1.31 litres4 Actual quantity of water required to be added 21.90 litres

66.98 kg

Actual quantity of CA required 142.08 kg

Therefore the actual quantities of different constituents required for one bag mix are

Water 21.90 kgCement 50.00 kgSand 66.98 kgCoarse Aggregate 142.08 kg

Fine Aggregate

Coarse Aggregate

Extra quantity of water to be added for absorption in case of CA

Quantity of water to be deducted for moisture present in sand

Actual quantity of sand required after allowing for mass of free moisture

Table 1 : Suggested values of Standard Deviation Degree of Workability0.70.80.9

Very Good Good Fair10 2.0 2.3 3.3 Exposure Condition15 2.5 3.5 4.5 Mild20 3.6 4.6 5.6 Moderate25 4.3 5.3 6.3 Severe30 5.0 6.0 7.0 Very severe35 5.3 6.3 7.3 Extreme40 5.6 6.6 7.645 6.0 7.0 8.0

0.005 50 6.4 7.4 8.455 6.7 7.7 8.760 6.8 7.8 8.8

Table 3 : Approximate air content

1020

40

Grade of Concrete

Standard deviation for different degree of control in N/mm2

Nominal maximum size of aggregate

mm

Degree of Workability

Sl. No. Exposure Plain Concrete

Exposure Condition

1 Mild 220 0.60Very severe 2 Moderate 240 0.60

3 Severe 250 0.504 Very severe 260 0.455 Extreme 280 0.40

Table 3 : Approximate air content

3.02.0

1.010 208 4020 186 3540 165 30

< M35 > M35186 180

35 25

Table 7 : Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposure with Normal Weight Aggregates of 20 mm Nominal maximum Size

Minimum Cement Content kg/m3

Maximum Free Water-Cement

Ratio

Table 4 : Approximate Sand and Water Contents per cubic metre of Concrete for grades upto M35

Nominal maximum size of aggregate

mmEntrapped air, as percentage

of volume of concreteNominal

maximum size of

aggregateWater

contentSand as percent

Plain Concrete Plain Concrete

12

- 300 0.55 M 20 3M 15 300 0.50 M 25 4M 20 320 0.45 M 30M 20 340 0.45 M 35M 25 360 0.40 M 40

10 200 2820 180 25

Table 7 : Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposure with Normal Weight Aggregates of 20 mm Nominal maximum Size

Minimum Grade of Concrete

Minimum Cement Content kg/m3

Maximum Free Water-Cement

Ratio

Minimum Grade of Concrete

Table 4 : Approximate Sand and Water Contents per cubic metre of Concrete for grades upto M35

Table 5 : Approximate Sand and Water Contents per cubic metre of Concrete for grades above M35

Nominal maximum size of aggregate

Water content

Sand as percent

Design Mix of High Strength Concrete by ACI Method using Portland Cement and Fly Ash

Design Stipulations1 Specified Compressive Strength Required at 28 days 9000 psi3 HRWR to be used or not (YES=1, NO=0) yes4 LTB5 Sample standard deviation S 1 psi

Test data for materials1 Specific gravity of cement 3.152 Properties of Course aggregate

(i) Bulk specific gravity (based on oven dry) 2.76

(ii) Dry rodded unit weight (DRUW) 101.00

(iii) Water absorption 0.70 %(iv) Grading As per ASTM C33(v) Maximum size of course aggregate 1/2 from table 4.3.2

3 Properties of Fine aggregate(i) Bulk specific gravity (Based on oven dry) 2.59

(ii) Dry rodded unit weight (DRUW) 103.00

(iii) Water absorption 1.10 %(iv) Grading As per ASTM C33(v) Fineness modulus 2.90

4 Fractional volume of 5 Void percent in sand 35.00

6 62.40

7 Type of fly ash used ASTM Class C8 Bulk specific gravity of fly ash 2.649 Moisture content at field

(i) Course aggregate 0.50 percent (ii) Fine aggregate 6.40 percent

Basis of design (FE=Field Experience, LTB=Laboratory Trial batches)

lb/ft3

lb/ft3

Density of water at 40 C lb/ft3

Design ProcedureSlump used 1 to 2 Required average strength used 10400 psiFractional Volume of oven-dry rodded course aggregate 0.68

1854.36 lb

First estimate of mixing water 295 lbVoid content in fine aggregate 36.00 %Mixing water adjustment 8.00

303 lb

Entrapped air content 2 %(i) Maximum w/c+p for concretes made without HRWR NA(ii) Maximum w/c+p for concretes made with HRWR 0.32Weight of cementitious material per yd3 of concrete 946.875 lb

Proportion basic mixture with cement only946.88 lb

The volume per yd3 of all material except sand are as follows:Cement 4.82

Course aggregate 10.77

Water 4.86

Air 0.54

Total Volume 20.98

6.02

972.91 lbCement 946.88 lb

Sand, Dry 972.91 lb

Course aggregate, dry 1854.36 lbWater (including 3 oz/cwt retarding admixture) 303.00 lb

Dry weight of course aggregate per yd3 of concrete

lb/yd3 of concrete

Total mixing water required per yd3 of concrete

Cement content per yd3

ft3

ft3

ft3

ft3

ft3

Required volume of sand per yd3 of concrete ft3

Weight of sand per yd3 of concrete

Cement Sand Course agg w/c ratio1.00 1.03 1.96 0.32

Proportion companion mixtures using cement and fly ash

Companion mixture #1 20 percentCompanion mixture #2 25 percentCompanion mixture #3 30 percentCompanion mixture #4 35 percent

Calculation of the weight of fly ash and Cement

Companion Mixture Cement Fly ash Total, lb1 757.50 189.38 946.882 710.16 236.72 946.883 662.81 284.06 946.884 615.47 331.41 946.88

The volume of cement fly ash and total cementitius material for each companion mxture

Companion Mixture Cement Fly ash1 3.85 1.15 5.002 3.61 1.44 5.053 3.37 1.72 5.104 3.13 2.01 5.14

Calcualtion of volume of fine aggregate for all companion mixture

ComponenetVolume (per cubic yard of concrete. Ft3)

Mix 1 Mix 2 Mix 3 Mix 4

Cementitius mat 5.00 5.05 5.10 5.14

Total, ft3

ft3

ft3

Coarse agg 10.77 10.77 10.77 10.77

water* 4.86 4.86 4.86 4.86

air 0.54 0.54 0.54 0.54

Total volume 21.17 21.21 21.26 21.31

Fine aggregate 5.83 5.79 5.74 5.69

* including 2.5 oz/cwt retarding mixture

The mix proportion per yd3 of concrete for each companion mixture are as follows

Component Mix 1 Mix 2 Mix 3 Mix 4Cement 757.50 710.16 662.81 615.47 lbFly ash 189.38 236.72 284.06 331.41 lbSand, dry 942.83 935.31 927.79 920.27 lbCoarse agg, dry 1854.36 1854.36 1854.36 1854.36 lbwater (including 2.5 oz/cwt retarding mixture 303.00 303.00 303.00 303.00 lbMix Proportion

Calculating the batch mix based on field moisture content

Basic mixture Companion mix 1 Companion mix 2 Companion mix 3 Companion mix 4Component Dry wt batch wt Dry wt batch wt Dry wt batch wt Dry wt batch wt Dry wt batch wtCement 946.88 946.88 757.50 757.50 710.16 710.16 662.81 662.81 615.47 615.47Fly ash - - 189.38 189.38 236.72 236.72 284.06 284.06 331.41 331.41Sand, dry 972.91 1035.17 942.83 1003.17 935.31 995.17 927.79 987.16 920.27 979.16Coarse agg, dry 1854.36 1863.63 1854.36 1863.63 1854.36 1863.63 1854.36 1863.63 1854.36 1863.63water 303.00 233.13 303.00 245.25 303.00 248.28 303.00 251.31 303.00 254.34

ft3

ft3

ft3

ft3

ft3

Component Exposure ConditioPerformance requirement

Foundation Severe Resistance to sulphate

Plinth Column SevereColumn Inner Mild

Outer ModerateSlab, Beams MildShear Wall MildPrestress Concrete Moderate

Slump required: 50 to 100 mm at placing pointTotal quantity of fine: cement + fine agg. (Passing 250 micron sieve) should be in between 350 to 500 kg/m32) The use of admixtures to be made to make a suitable slump and not compromise on W/C ratio3) the coarse aggregate should preferably be 20 mm down strictly.4) the coarse aggregate should preferably be processed through Vertical shaft impactor.5) use of fly ash be made as cement replacement if OPC is used.

Tensile Strength, Elastic Deformation, Shrinkage, Creep, Thermal Expansion

Concrete Grade Cement requirement Aggregate requiremeFor height 90 to 200mM40

M50 OPCM50-M70 OPCM50-M70 OPCM30-M50 OPCM50-M70 OPC Light weight

Total quantity of fine: cement + fine agg. (Passing 250 micron sieve) should be in between 350 to 500 kg/m32) The use of admixtures to be made to make a suitable slump and not compromise on W/C ratio

4) the coarse aggregate should preferably be processed through Vertical shaft impactor.

Portland pozzolana cement, Sulphate resisting Portland cement depending upon concentration of sulphate in ground water or soil.

Other requirements

Superplasticizer for high slump

Max w/c ratio 0.5Min. Cement Content 300 kg/m3Max Cement content 530 kg/m3