Project on Concrete Mix Design for various grades of Concrete

Calculate the Concrete Mix Design for M35 grade concrete with fly ash

Aim: To calculate the design mix ratio for M35 grade concrete with Fly Ash as an admixture.

Introduction: To design mix ratio of M35 grade of concrete with Fly Ash as an admixture. In the building industry, the use of fly ash is a part replacement of cement in motor & concrete.

Step I: Stipulated for proportioning

1. Grade designation = M35
2. Type of cement: OPC 43 Grade
3. Type of mineral admixture: Fly ash Conforming of IS 8112
4. Maximum nominal size of aggregate: 20mm
5. Minimum cement content: 320kg/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: Severe (for reinforced concrete)
9. Method of concrete placing: Pumping
10. Degree of supervision: Good
11. Type of aggregate: Crushed angular aggregate
12. Maximum cement content: 450kg/m^3 (As per para 8.2.4.2 of IS 456:2000)
13. Chemical admixture type: Superplasticizer

Step II: Test data for materials

1. Cement used: OPC 43 Grade.
2. Specific gravity of cement: 3.15
3. Fly Ash: Conforming to IS 3812 (part 1)
4. Specific gravity of Fly Ash: 2.2
5. Chemical admixture: superplasticizer
6. Specific gravity of:
1. Coarse aggregate: 2.74
2. Fine aggregate: 2.74
7. Water absorption:
1. Coarse aggregate: 0.5%
2. Fine aggregate: 1.0%
8. Free surface moisture:
1. Coarse aggregate: Nil
2. Fine aggregate: Nil
9. Sieve analysis:
1. Coarse aggregate:Should be followed as per Table (2) IS 383:1970
2. Fine aggregate: Conforming to grading zone (I) of Table (4) IS 383:1970

Step III: Target strength for mix proportioning:

• f’ck = fck + 1.65 x S (From Table 1 IS 10262:2009)
• f’ck = 35 + 1.65 x 5
• f’ck = 43.25 N/mm^2

Step IV: Selection of water cement ratio:

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

Based on experience adapted water cement ratio is = 0.40

0.40 < 0.45, hence ok

Step V: Selection of water cement ratio:

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

Estimated water content for 100 mm slump = 186+6/100 x 186 = 197 litre

Superplasticizer is used the water content can be reduced upto 20% and above.

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

Hence the arrived water content = 197*0.71=140. litre

Step VI: Calculation of cement content:

Water cement ratio = 0.40

Cementitious meterial (Cement + Fly ash) content = 140/0.40 = 350kg/m^3

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

1. The percentage of fly ash needs to decided based on project requirement & quality of materials.
2. In some cases increase in cemtitious material can be warranted. Increase in cementitious material content & its percentage may be based on experience & trail (This example is with increase of 10% cementitious material content)

• Cementitious Material Content = 350 x 1.10 = 385 kg/m^3
• Water Content = 140 kg/m^3
• Water Cement Ratio = 140/385 = 0.363
• Fly ash @ 30% Total Cementitious material = 385 x 30% = 115 kg/m^3
• Cement (OPC) = 385-115 = 270 kg/m^3
• Saving of cement while using fly ash = 350 - 270 = 80 kg/m^3
• Fly Ash being Utilized = 115 kg/m^3

Step VII: Proportion of volume of coarse aggregate and fine aggregate:

From Table 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water cement ratio of 0.5 = 0.6

In present case the water cement ratio is 0.40.

• Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As water cement ratio is lowered by 0.10, proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of +/- 0.01 for every +/- 0.05 change in water cement ratio).

Therefore, corrected volume of coarse aggregate for the water cement ratio of 0.40 = 0.62

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

For pumpable will concrete these values are reduced by 10%

Therefore

volume of coarse aggregate = 0.62 x 0.9 = 0.56

Volume of fine aggregate content = 1 - 0.56 = 0.44

Step VIII. Mix calculations:

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

a.Volume of concrete = 1m^3

b.Volume of cement = [(Mass of cement/ Specifi Gravity of Cement)x1/1000]

= 270/3.15X1/1000

= 0.086 m^3

c.Volume of Fly Ash = [(Mass of Fly Ash/ Specifi Gravity of Fly Ash)x1/1000]

=115/2.2X1/1000

= 0.052 m^3

d.Volume of water = [(Mass of Water/ Specifi Gravity of Water)x1/1000]

= 140/1X1/1000

= 0.140 m^3

e.Volume of chemical admixture = [(Mass of chemical admixture/ Specifi Gravity of chemical admixture)x1/1000]

= 7.6/1.145X 1/1000

= 0.006 m^3

f.Volume of aggregate (FA & CA) = (a-(b+c+d+e))

= (1-(0.086+0.052+0.140+0.006)

= `0.716 m^3`

g.Mass of coarse aggregate = f x Volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= (0.716 x 0.56 x 2.74 x 1000)

= 1098 Kg/m^3

h.Mass of fine aggregate = f x Volume of fine aggregate x specific gravity of fine aggregate x 1000

= (0.716 x 0.44 x 2.74 x 1000)

= 863 Kg/m^3

Step IX: Mix proportion for Trial number 1:

• Cement = 270 Kg/m^3
• Fly Ash 115 Kg/m^3
• Water = 140 Kg/m^3
• Fine aggregate = 863 Kg/m^3
• Coarse aggregate = 1098 Kg/m^3
• Chemical admixture = 7 Kg/m^3
• Water cement ratio = 0.363

Trial mix ratio = 1:2.24:2.85

Step 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 revoked for the actual water content and checked for durability requirements

Step XI: Two more trials having variation of 10% of water cement ratio in clause X shall be carried out a graph between 3 water cement ratios & corresponding strengths shall be plotted to work out the mix proportion for the given target strength for field trials, However durability is met.

Calculate the Concrete Mix Design for M50 grade concrete without fly ash

Aim: To calculate the design mix ratio for M50 grade concrete.

Introduction: To design mix ratio of M50 grade of concrete without using any admixutres.

Step I: Stipulated for proportioning

1. Grade designation = M50
2. Type of cement: OPC 53 Grade
3. Maximum nominal size of aggregate: 20mm
4. Minimum cement content: 320kg/m^3 (from Table 5 of IS 456:2000 - Exposure Condition)
5. Maximum water cement ratio: 0.45 (from Table 5 of IS 456:2000 - Exposure Condition)
6. Workability: 100mm (slump value for pumpable concrete)
7. Exposure condition: Severe (for reinforced concrete)
8. Method of concrete placing: Pumping
9. Degree of supervision: Good
10. Type of aggregate: Crushed angular aggregate
11. Maximum cement content: 450kg/m^3 (As per para 8.2.4.2 of IS 456:2000)
12. Chemical admixture type: Superplasticizer

Step II: Test data for materials

1. Cement used: OPC 53 Grade.
2. Specific gravity of cement: 3.15
3. Chemical admixture: superplasticizer
4. Specific gravity of:
1. Coarse aggregate: 2.74
2. Fine aggregate: 2.74
5. Water absorption:
1. Coarse aggregate: 0.5%
2. Fine aggregate: 1.0%
6. Free surface moisture:
1. Coarse aggregate: Nil
2. Fine aggregate: Nil
7. Sieve analysis:
1. Coarse aggregate:Should be followed as per Table (2) IS 383:1970
2. Fine aggregate: Conforming to grading zone (I) of Table (4) IS 383:1970

Step III: Target strength for mix proportioning:

• f’ck = fck + 1.65 x S (From Table 1 IS 10262:2009)
• f’ck = 50 + 1.65 x 5
• f’ck = 58.25 N/mm^2

Step IV: Selection of water cement ratio:

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

Based on experience adapted water cement ratio is = 0.35

0.35 < 0.45, hence ok

Step V: Selection of water cement ratio:

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

Estimated water content for 100 mm slump = 186+6/100 x 186 = 197 litre

Superplasticizer is used the water content can be reduced upto 20% and above.

Based on trials water content reduction of 27% is achieved for plasticizer.

Hence the arrived water content = 197*0.73=143. litre

Step VI: Calculation of cement content:

Water cement ratio = 0.35

Cement content = 143/0.35 = 410kg/m^3

From Table 5 of IS 456:2000 minimum cement content for severe exposure condition = 320 kg/m^3

410 kg/m^3 > 320 kg/m^3, Hence Ok.

Step VII: Proportion of volume of coarse aggregate and fine aggregate:

From Table 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water cement ratio of 0.5 = 0.6

In 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 water cement ratio is lowered by 0.10, proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of +/- 0.01 for every +/- 0.05 change in water cement ratio).

Therefore, corrected volume of coarse aggregate for the water cement ratio of 0.40 = 0.63

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

For pumpable will concrete these values are reduced by 10%

Therefore

volume of coarse aggregate = 0.63 x 0.9 = 0.57

Volume of fine aggregate content = 1 - 0.57 = 0.43

Step VIII. Mix calculations:

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

a.Volume of concrete = 1m^3

b.Volume of cement = [(Mass of cement/ Specifi Gravity of Cement)x1/1000]

= 410/3.15X1/1000

= 0.130 m^3

c.Volume of water = [(Mass of Water/ Specifi Gravity of Water)x1/1000]

= 143/1X1/1000

= 0.143 m^3

d.Volume of chemical admixture = [(Mass of chemical admixture/ Specifi Gravity of chemical admixture)x1/1000]

= 7.6/1.145X 1/1000

= 0.006 m^3

e.Volume of aggregate (FA & CA) = (a-(b+c+d))

= (1-(0.130+0.143+0.006)

= 0.721 m^3

f.Mass of coarse aggregate = e x Volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= (0.721 x 0.57 x 2.74 x 1000)

= 1126 Kg/m^3

g.Mass of fine aggregate = e x Volume of fine aggregate x specific gravity of fine aggregate x 1000

= (0.721 x 0.43 x 2.74 x 1000)

= 850 Kg/m^3

Step IX: Mix proportion for Trial number 1:

• Cement = 410 Kg/m^3
• Water = 143 Kg/m^3
• Fine aggregate = 850 Kg/m^3
• Coarse aggregate = 1126 Kg/m^3
• Chemical admixture = 7 Kg/m^3
• Water cement ratio = 0.35

Trial mix ratio = 1:2.1:2.75

Step 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 revoked for the actual water content and checked for durability requirements

Step XI: Two more trials having variation of 10% of water cement ratio in clause X shall be carried out a graph between 3 water cement ratios & corresponding strengths shall be plotted to work out the mix proportion for the given target strength for field trials, However durability is met.