Project on Concrete Mix Design for various grades of Concrete

CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH

I. Stipulation for proportioning

1. Grade designation: M35.
2. Type of cement: OPC 33 grade conforming to IS 8112.
3. Type of mineral admixture: Fly ash conforming to 3812 (part-1).
4. Maximum nominal size of aggregate: 20mm.
5. Minimum cement content: 340 kg/m^3 (From table-5 of IS-456:2000-exposure condition).
6. Maximum water-cement ratio: 0.45 (From table-5 of IS-456:2000-exposure condition).
7. Workability: 100mm (slump value for pumpable concrete).
8. Exposure condition: Very severe.
9. Method of concrete placing: Pumping.
10. Degree of supervision: Good.
11. Type of aggregate: Crushed angular aggregate.
12. Chemical admixture type: Superplasticizer.
13. Maximum cement content: 450 kg/m^3.

II. Test date for materials

1. Cement used: OPC grade conforming to IS-8112.
2. The specific gravity of cement: 3.15.
3. Fly ash: conforming to IS-3812 (part-1).
4. The specific gravity of fly ash: 2.2.
5. Chemical admixture: Superplasticizer conforming to IS-9103.
6. Specific gravity: coarse aggregate: 2.74, Fine aggregate: 2.74.
7. Water absorption: coarse aggregate: 0.5%, Fine aggregate: 1.0%.
8. Free surface moisture: coarse aggregate: nill, Fine aggregate: nill.
9. sieve analysis: coarse aggregate: Fine aggregate: Conforming grade zone-I of table-4 of IS-383.

III. Target strength for mix Proportioning

f'ck = fck+1.65*5

Where

f'ck = Target average compressive strength at 28 days.

fck = Characteristic compressive strength at 28 days.

S = Standard deviation.

From Table-1 of IS-10262:2009, standard deviation.

S = 5 N/mm^2

Therefore, Target strength = 35+1.65*5

= 43.25 N/mm^2.

IV. Selection of water cement ratio

From Table-5 of IS-456:2000 for very severe exposure, maximum water-cement ratio = 0.45

Based on experience, adopt water-cement ratio as = 0.35

0.35 < 0.45, hence ok.

V. Selection of water content

From the table-2 of IS-10262:2009, maximum water content for 20mm aggregate = 186 litres (for 25mm to 50mm slump range).

Estimated water content for 100mm slump = 186+((6/100)*186)

= 197 litres

As a superplasticizer is used, the water content can be reduced up to 30%

Based on trials water content reduction of 29% is achieved with a plasticizer.

hence the arrived water content = 197*0.71

= 140 litres

VI. Calculation of cement content

Water-cement ratio = 0.35

cement content = 140/0.35

= 400 kg/m^3

From table-5 of IS-456 minimum cement content for very severe exposure condition =

400 kg/m^3 > 340 kg/m^3, hence ok.

Now, to proportion a mix containing fly ash the following steps are suggested:

a. The percentage of fly ash needs to be decided based on project requirements and the quality of materials.

b. In some cases increase in cementitious material can be warranted. An increase in cementitious material content and its percentage may be based on experience and trial ( increasing of 10% cementitious material content).

• Cementitious material content: 400*1.10 = 440 kg/m^3.
• water content : 140 kg/m^3.
• water-cement ratio : 140/440 = 0.318.
• Fly ash at 30% total cementitious material content: 440*30% = 132 kg/m^3.
• Cement (OPC) : 440-132 = 308 kg/m^3.
• Saving of cement while using fly ash: 400-308 = 92 kg/m^3.
• Fly ash being utilized: 132 kg/m^3.

VII. Proportion of volume of coarse aggregate and fine aggregate

From table-3 of IS-10262:2009,

The volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone-I) for the water-cement ratio of 0.50 = 0.60.

In the present case, the water-cement ratio is = 0.35

• Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As the water-cement ratio is lower by 0.10, the proposition of volume of coarse aggregate is increased by 0.02 ( at the rate of +/- 0.05 change in water-cement ratio).

0.50-0.35 = 0.15

(0.15*0.01)/0.05 = 0.03

0.60+0.03 = 0.63

Therefore, the corrected volume of coarse aggregate for the water-cement ratio of 0.63

( Note: if the coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete, these values are reduced by 10%.

Therefore, the volume of coarse aggregate = 0.63*0.9 =0.567

volume of fine aggregate = 1-0.567 = 0.433

VIII. Mix calculation

The mix calculation per unit volume of concrete shall be as follows:

1. Volume of concrete = 1 m^3.
2. Volume of cement = (mass of cement / specific gravity of cement)*(1/1000)

= (308/3.15)*(1/1000)

= 0.0977 m^3.

c. Volume of fly ash = (mass of fly ash / specific gravity of fly ash)*(1/1000)

= (132/2.2)*(1/1000)

= 0.06 m^3.

d. Volume of water = (mass of water / specific gravity of water)*(1/1000)

= (140/1)*(1/1000)

= 0.140 m^3.

e. Volume of chemical admixture = (mass of chemical admixture / specific gravity of chemical admixture)*(1/1000)

= (7.6/1.145)*(1/1000)

= 0.006 m^3.

f. Volume of aggregate ( coarse aggregate and fine aggregate) = a-(b+c+d+e)

= 1-(0.0977+0.06+0.140+0.006)

= 0.6963 m^3.

g. Mass of coarse aggregate = f*volume of coarse aggregate*specific gravity of coarse aggregate*1000

= 0.6963*0.567*2.74*1000

= 1081.75 kg/m^3

h. Mass of fine aggregate = f*volume of fine aggregate*specific gravity of fine aggregate*1000

= 0.6963*0.433*2.74*1000

= 826.10 kg/m^3

IX. mix proportion of trial number-1

Cement = 308 kg/m^3.

Fly ash = 132 kg/m^3.

water = 140 kg/m^3.

Fine aggregate = 826.10 kg/m^3.

Coarse aggregate = 1081.75 kg/m^3.

Chemical admixture = 7 kg/m^3.

Water-cement ratio = 0.318

Trial mix ratio = 1 : 1.87 : 2.45

X. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.

XI. Two more trials having variation of 10% of water-cement ratio in clause-X shall be carried out and a graph between three water-cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.

CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLY ASH

I. Stipulation for proportioning

1. Grade designation: M50.
2. Type of cement: OPC 43 grade conforming to IS 8112.
3. Maximum nominal size of aggregate: 20mm.
4. Minimum cement content: 360 kg/m^3 (From table-5 of IS-456:2000-exposure condition).
5. Maximum water-cement ratio: 0.40 (From table-5 of IS-456:2000-exposure condition).
6. Workability: 100mm (slump value for pumpable concrete).
7. Exposure condition: extreme.
8. Method of concrete placing: Pumping.
9. Degree of supervision: Good.
10. Type of aggregate: Crushed angular aggregate.
11. Chemical admixture type: Superplasticizer.
12. Maximum cement content: 450 kg/m^3.

II. Test date for materials

1. Cement used: OPC 43 grade conforming to IS-8112.
2. The specific gravity of cement: 3.15.
3. Chemical admixture: Superplasticizer conforming to IS-9103.
4. Specific gravity: coarse aggregate: 2.74, Fine aggregate: 2.74.
5. Water absorption: coarse aggregate: 0.5%, Fine aggregate: 1.0%.
6. Free surface moisture: coarse aggregate: nill, Fine aggregate: nill.
7. sieve analysis: coarse aggregate: Fine aggregate: Conforming grade zone-I of table-4 of IS-383.

III. Target strength for mix Proportioning

f'ck = fck+1.65*5

Where

f'ck = Target average compressive strength at 28 days.

fck = Characteristic compressive strength at 28 days.

S = Standard deviation.

From Table-1 of IS-10262:2009, standard deviation.

S = 5 N/mm^2

Therefore, Target strength = 50+1.65*5

= 58.25 N/mm^2.

IV. Selection of water cement ratio

From Table-5 of IS-456:2000 for extreme exposure, maximum water-cement ratio = 0.40

Based on experience, adopt the water-cement ratio as 0.34

0.34 < 0.45, hence ok.

V. Selection of water content

From the table-2 of IS-10262:2009, maximum water content for 20mm aggregate = 186 litres (for 25mm to 50mm slump range).

Estimated water content for 100mm slump = 186+((6/100)*186)

= 197 litres

As a superplasticizer is used, the water content can be reduced up to 30%

Based on trials water content reduction of 29% is achieved with a plasticizer.

hence the arrived water content = 197*0.71

= 140 litres

VI. Calculation of cement content

Water-cement ratio = 0.34

cement content = 140/0.34

= 411.76

From table-5 of IS-456 minimum cement content for very severe exposure condition =

411.76 kg/m^3 > 360 kg/m^3, hence ok.

VII. Proportion of volume of coarse aggregate and fine aggregate

From table-3 of IS-10262:2009,

The volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone-I) for the water-cement ratio of 0.50 = 0.60.

In the present case, the water-cement ratio is 0.34

• Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As the water-cement ratio is lower by 0.10, the proposition of volume of coarse aggregate is increased by 0.02 ( at the rate of +/- 0.05 change in water-cement ratio)

0.50-0.34 = 0.16

(0.16*0.01)/0.05 = 0.032

0.60+0.032 = 0.632

Therefore, the corrected volume of coarse aggregate for the water-cement ratio of 0.632

( Note: if the coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete, these values are reduced by 10%.

Therefore, the volume of coarse aggregate = 0.632*0.9 = 0.5688

volume of fine aggregate = 1-0.5688 = 0.4312

VIII. Mix calculation

The mix calculation per unit volume of concrete shall be as follows:

1. Volume of concrete = 1 m^3.
2. Volume of cement = (mass of cement / specific gravity of cement)*(1/1000)

= (411.76/3.15)*(1/1000)

= 0.130 m^3.

1. Volume of water = (mass of water / specific gravity of water)*(1/1000)

= (140/1)*(1/1000)

= 0.140 m^3.

1. Volume of chemical admixture = (mass of chemical admixture / specific gravity of chemical admixture)*(1/1000)

= (7.6/1.145)*(1/1000)

= 0.006 m^3.

1. Volume of aggregate ( coarse aggregate and fine aggregate) = a-(b+c+d)

= 1-(0.130+0.140+0.006)

= 0.724 m^3.

1. Mass of coarse aggregate = e*volume of coarse aggregate*specific gravity of coarse aggregate*1000

= 0.724*0.5688*2.74*1000

= 1128.36 kg/m^3.

1. Mass of fine aggregate = e*volume of fine aggregate*specific gravity of fine aggregate*1000

= 0.724*0.4312*2.74*1000

= 855.39 kg/m^3.

IX. mix proportion of trial number-1

Cement = 411.76 kg/m^3.

water = 140 kg/m^3.

Fine aggregate = 855.39 kg/m^3.

Coarse aggregate = 1128.36 kg/m^3.

Chemical admixture = 7 kg/m^3.

Water-cement ratio = 0.34

Trial mix ratio = 1: 2.07 : 2.74

X. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.

XI. Two more trials having variation of 10% of water-cement ratio in clause-X shall be carried out and a graph between three water-cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.