Project on Concrete Mix Design for various grades of Concrete

AIM: To calculate the Concrete Mix Design for M35 grade concrete with fly ash

Introduction: mix proportion to concrete by using fly ash as part of replacement OPC for m35 grade of concrete.

Stipulation for proportion

1. Grade od designation: m40
2. Type of cement: OPC 43 grade conforming to IS 8112
3. Type of mineral admixture: Fly ash conforming to IS 3812 (part 1)
4. Maximum nominal size of aggregate: 20mm
5. Minimum cement content: 320kg/m^3 (from table no 5 of IS 456: 2000 – Exposure condition)
6. Maximum water cement contain ratio: 0.45(from table no 5 of IS 456: 2000 – Exposure condition)
7. Workability: 100mm (slump value of 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 contain: 450kg/m^3
13. Chemical admixture type: superplasticizer
14. Data test materials
15. Cement used: OPC 43 grade conforming to IS 8112
16. Specific gravity of cement: 3.15
17. Fly ash: conforming to IS 3812 (part 1)
18. Specific gravity of fly ash: 2.2
19. Chemical admixture: superplasticizer conforming to IS 9103

Specific gravity of:

• Coarse aggregate: 2.74
• Fine aggregate: 2.74

Water absorption:

• Coarse aggregate: 2.74
• Fine aggregate: 2.74

Free surface moisture:

• Coarse aggregate: Nil
• Fine aggregate: Nil

Sieve Analysis:

• Coarse aggregate: conforming to table no 2 of IS 383
• Fine aggregate: conforming to grading zone 1 of table no 4 of IS 383

Procedure:

Step: 1

Target strength for mix proportioning:

F’ ck = f ck + 1.65 S

Where, f’ck = average compressive strength of concrete at 28 days

F'ck = characteristic compressive strength of concrete at 28 days

From table 1 of IS 10262:2009 standard deviation, s = 5N/mm^2

Therefore, target strength = 35+1.65*5 = 43.25N/mm^2

Step: 2

Selection of water cement ratio:

From the table 5 of IS 456:2000 sever exposure, maximum water cement ratio= 0.45

Based experience, adopted water-cement ratio is 0.40

0.40<0.45 hance ok

Step:3

Selection of water contain:

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

Estimated water contain for 100mm slump is = 186+6/100 x 186 =197 liter

As superplasticizers used, the water content can be reduced up to 20% and above

Based on trail water content reduction of 29% is achieved with plasticizer

Hance the arrived water content = 197 x 0.71 = 140 liter

Step:4

Calculation of cement content

Water cement ratio = 0.4

Cement content = 140/0.4 = 350 kg/m^3

From table 5 of IS 456: minimum cement content for sever exposure condition =320kg/m^3

350kg/m^3 > 320kg/m^3, hance ok

Step:5

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

1. Percentage of fly ash need to be decided based on the project requirement and quality of the materials
2. In some case increase in cementitious materials can be warranted. Increase in cementitious materials content and its percentage may be based on experience and trials (this example is with increase of 10% cementitious materials contain)

cementitious materials content = 350 x 1.10 = 385 kg/m^3

water content = 140 kg/m^3

so, water cement ratio = 140/385 = .0364

fly ash @ 30% total cementitious materials content = 385 x 30% = 115kg/m^3

cement OPC = 385-115 =270 kg/m^3

saving of cement by using fly ash =350-270 = 80kg/m^3

fly ash being utilized =115kg/m^3

Step:6

Proportion of volume of coarse aggregate and fine aggregate content:

From table number 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone-1) for water cement ratio = 0.6

In the present case the water cement ratio = 0.40

• Therefore, the volume of coarse aggregate need to be increased to decreased the fine aggregate content
• As water-cement ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02 (at the ratio of -/+0.01 for every 05 change in water cement ration)

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

For pumpable concrete these values are reduced by 10%

Therefore, the volume of coarse aggregate = 0.62 x 0.9 = 0.56

Volume of fine aggregate content = 1 - 0.56 = 0.44

Step:7

Mix calculation

The mix calculation per unit volume of concrete shall be

1. Volume of concrete = 1m^3

2. Volume of cement = mass of cement / specific gravity of cement x 1/1000

= 270/3.15x1/100

=0.086 m^3

3. Volume of fly ash = mass of fly ash / specific gravity of fly ash x 1/100

= 115/2.2 x 1/1000

= 0.052 m^3

4. Volume of water = mass of water / specific gravity of water x 1/100

= 140/1 x 1/1000

= 0.14 m^3

5. Volume of chemical admixture = mass of chemical admixture / specific gravity of chemical admixture x 1/100

= 7.6/1.145 x 1/1000

= 0.006m^3

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

= (1-(0.086+0.052+0.014+0.006)

=0.716m^3

7. 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

8. 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:8

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 =0.364

Trial mix ratio = 1 : 2.24 : 2.285

Result: The Concrete Mix Design for M35 grade concrete with fly ash is = 1 : 2.24 : 2.85

Conclusion:

1. The mix ratio match the workability, durability, minimum strength of m35 grade concrete
2. If it does not satisfy the above criteria two more trials for increase of 10% should be done

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

Aim: To calculate the Concrete Mix Design for M50 grade concrete without fly ash

Introduction: mix proportion to concrete by without using fly ash for m50 grade of concrete.

Stipulation for proportion

1. Grade od designation: m40
2. Type of cement: OPC 43 grade conforming to IS 8112
3. Maximum nominal size of aggregate: 20mm
4. Minimum cement content: 320kg/m^3 (from table no 5 of IS 456: 2000 – Exposure condition)
5. Maximum water cement contain ratio: 0.45(from table no 5 of IS 456: 2000 – Exposure condition)
6. Workability: 100mm (slump value of 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 contain: 450kg/m^3
12. Chemical admixture type: superplasticizer
13. Data test materials
14. Cement used: OPC 43 grade conforming to IS 8112
15. Specific gravity of cement: 3.15
16. Chemical admixture: superplasticizer conforming to IS 9103

Specific gravity of:

• Coarse aggregate: 74
• Fine aggregate: 74

Water absorption:

• Coarse aggregate: 74
• Fine aggregate: 74

Free surface moisture:

• Coarse aggregate: Nil
• Fine aggregate: Nil

Step: 1

Target strength for mix proportioning:

F’ ck = f ck + 1.65 S

Where, f’ ck = average compressive strength of concrete at 28 days

F ck = characteristic compressive strength of concrete at 28 days

From table 1 of IS 10262:2009 standard deviation, s = 5N/mm^2

Therefore, target strength = 50+1.65*5 = 582.5N/mm^2

Step: 2

Selection of water cement ratio:

From the table 5 of IS 456:2000 sever exposure, maximum water cement ratio= 0.45

Based experience, adopted water-cement ratio is 0.40

0.40<0.45 hance ok

Step:3

Selection of water contain:

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

Estimated water contain for 100mm slump is = 186+6/100 x 186 =197 liter

As superplasticizers used, the water content can be reduced up to 20% and above

Based on trail water content reduction of 29% is achieved with plasticizer

Hance the arrived water content = 197 x 0.71 = 140 liter

Step:4

Calculation of cement content

Water cement ratio = 0.4

Cement content = 140/0.4 = 350 kg/m^3

From table 5 of IS 456: minimum cement content for sever exposure condition =320kg/m^3

350kg/m^3 > 320kg/m^3, hance ok

Step:5

Proportion of volume of coarse aggregate and fine aggregate content:

From table number 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone-1) for water cement ratio = 0.6

In the present case the water cement ratio = 0.40

• Therefore, the volume of coarse aggregate need to be increased to decreased the fine aggregate content
• As water-cement ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02 (at the ratio of -/+0.01 for every 05 change in water cement ration)

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

For pumpable concrete these values are reduced by 10%

Therefore, the volume of coarse aggregate = 0.62x0.9 = 0.56

Volume of fine aggregate content = 1-0.56 = 0.44

Step:6

Mix calculation

The mix calculation per unit volume of concrete shall be

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

= 350/3.15 x 1/1000

=0.111 m^3

3. Volume of water = mass of water / specific gravity of water x 1/1000

= 140/1 x 1/1000

= 0.14 m^3

4.Volume of chemical admixture = mass of chemical admixture / specific gravity of chemical admixture x 1/1000

= 7.6/1.145 x 1/1000

= 0.006m^3

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

= (1-(0.111+0.140+0.006)

=0.743m^3

6. mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.743 x 0.56 x 2.74 x 1000

= 1140 kg/m^3

7. mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.743 x 0.44 x 2.74 x 1000

= 896 kg/m^3

Step:7

Cement = 350 kg/m^3

Water = 140 kg/m^3

Fine aggregate = 896 kg/m^3

Coarse aggregate =1140 kg/m^3

Chemical admixture = 7 kg/m^3

Water cement ratio =0.4

Trial mix ratio = 1 : 2.56 : 3.25

Result: The Concrete Mix Design for M50 grade concrete is = 1 : 2.56 : 3.25

Conclusion:

• The mix ratio match the workability, durability, minimum strength of m35 grade concrete
• If it does not satisfy the above criteria two more trials for increase of 10% should be done