Project on Concrete Mix Design for various grades of Concrete

Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash

Answer-

1. A) Design of M50 grade of concrete without flyash-

For the design of M50 grade of concrete, let us assume the following details-

1. Grade of concrete- M50
2. Type of cement – OPC grade 43
3. Maximum size of coarse aggregate- 20mm
4. Minimum cement content – 320 kg/cum
5. Maximum water cement ratio- 0.45
6. Workability – 100mm slump
7. Exposure condition- severe
8. Method of concreting- normal
9. Degree of supervision – good
10. Type of aggregate- crushed angular aggregates
11. Maximum cement content- 450 kg/cum
12. Chemical admixture- superplasticizers
13. Specific gravity of cement – 3.15
14. Specific gravity of fine aggregate- 2.74
15. Specific gravity of coarse aggregate- 2.74
16. Water absorption of fine aggregate- 0.5 percent
17. Water absorption of coarse aggregate – 1 percent
18. Free surface moisture – 0 in both fine and coarse aggregates
19. Zone of fine aggregate- Zone-I

• Target mean strength

Fck’ = Fck + 1.65 x S

Fck for M50 grade of concrete- 50 N/mm2

S : standard deviation of M50 grade of concrete from Table- 8 of IS 456-2000 is 5 N/mm2

So Fck’ = 50 + 1.65x5

= 50 + 8.25 = 58.25 N/mm2

• Selection of water cement ratio

From Table 5 of Is 456-2000, the maximum free water cement ratio for severe exposure condition and maximum 20mm nominal size of aggregate for RCC is 0.45

Based on experience let as adopt the maximum water cement ratio as 0.40, which is less than 0.45 hence ok

• Selection of water content

From Table 2 of Is 10262-2009, the maximum water content for 20mm maximum nominal size of aggregates for slump value of 25-50 mm is given as – 186 Liters.

So water content for the slump value of 100mm is given by 186 + 186 x 0.06 = 197 Litres

As superplasticizers are used which reduces water content upto range of 20 to 30 %. Assuming water reduction of 29%, water content is given by = 197 x 0.71 = 140 Litres

• Calculation of cement content

For the water cement ratio of 0.4, the cement content is given by = 140/0.4 = 350 Kg/cum.

From Table 5 of Is 456-2000, the minimum cement content for severe condition is 320 kg/cum hence ok

• Proportion of volume of coarse aggregate and fine aggregate

From Table 3 of IS 10262-2009, volume of coarse aggregate corresponding to zone -I grade of fine aggregates for 20mm nominal size of aggregates and water cement ratio of 0.50 is 0.6

So for water cement ratio of 0.4, the volume of coarse aggregate is 0.6 + 0.02 = 0.62

And volume of fine aggregate is = 1-0.62 = 0.38

• Mix calculation

1. Volume of concrete- 1 cum
2. Volume of cement = mass of cement / (specific gravity of cement x 1000)

= 350/ 3.15 x 1000

= 0.111 cum

1. Volume of water – 140/1000 = 0.140 cum
2. Volume of plasticizers – 7 / ( 1.145 x 1000) = 0.006 cum
3. Volume of aggregates (Total) = 1- (b+c+d)

= 1- ( 0.111 + 0.140 + 0.006)

= 0.743 cum

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

= 0.743 x 0.62 x 2.74 x 1000

= 1262 kg /cum

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

= 0.743 x 0.38 x 2.74 x 1000

= 773 kg /cum

• Mix proportion

Cement – 350 kg/cum

Fine aggregate- 773 kg/cum

Coarse aggregate- 1262 kg/cum

Water – 140 kg /cum

1. B) Mix Design for M35 grade of concrete with Fly ash

For the design of M35 grade of concrete, let us assume following details-

For the design of M50 grade of concrete, let us assume the following details-

1. Grade of concrete- M35
2. Type of cement – OPC grade 43
3. Type of mineral admixture- fly ash confirming to relevant IS code
4. Specific gravity of fly ash – 2.2
5. Maximum size of coarse aggregate- 20mm
6. Minimum cement content – 320 kg/cum
7. Maximum water cement ratio- 0.45
8. Workability – 100mm slump
9. Exposure condition- severe
10. Method of concreting- pumping
11. Degree of supervision – good
12. Type of aggregate- crushed angular aggregates
13. Maximum cement content- 450 kg/cum
14. Chemical admixture- superplasticizers
15. Specific gravity of cement – 3.15
16. Specific gravity of fine aggregate- 2.74
17. Specific gravity of coarse aggregate- 2.74
18. Water absorption of fine aggregate- 0.5 percent
19. Water absorption of coarse aggregate – 1 percent
20. Free surface moisture – 0 in both fine and coarse aggregates
21. Zone of fine aggregate- Zone-I

• Target mean strength

Fck’ = Fck + 1.65 x S

Fck for M35 grade of concrete- 35 N/mm2

S : standard deviation of M35 grade of concrete from Table- 8 of IS 456-2000 is 5 N/mm2

So Fck’ = 35 + 1.65x5

= 35 + 8.25 = 43.25 N/mm2

• Selection of water cement ratio

From Table 5 of Is 456-2000, the maximum free water cement ratio for severe exposure condition and maximum 20mm nominal size of aggregate for RCC is 0.45

Based on experience let as adopt the maximum water cement ratio as 0.40, which is less than 0.45 hence ok

• Selection of water content

From Table 2 of Is 10262-2009, the maximum water content for 20mm maximum nominal size of aggregates for slump value of 25-50 mm is given as – 186 Liters.

So water content for the slump value of 100mm is given by 186 + 186 x 0.06 = 197 Litres

As superplasticizers are used which reduces water content upto range of 20 to 30 %. Assuming water reduction of 29%, water content is given by = 197 x 0.71 = 140 Litres

• Calculation of cement and fly ash content

For the water cement ratio of 0.4,

the cementitious (Cement + Fly Ash) content is given by = 140/0.4 = 350 Kg/cum.

From Table 5 of Is 456-2000, the minimum cement content for severe condition is 320 kg/cum hence ok

Now as fly ash is being used as part replacement of cement , so cementitious content is generally increased. Let us assume that the cementitious content is increased by 10 %

So cementitious content = 350 x 1.1 = 385 kg/cum

Water content – 140 kg/cum

So water cement ratio = 140/385 = 0.364

Now let us assume that 30 % fly ash is used in total cementitious content

So fly ash content = 385 x 0.3 = 115 Kg/cum

& cement = 385 -115 = 2780 kg/cum

• Proportion of volume of coarse aggregate and fine aggregate

From Table 3 of IS 10262-2009, volume of coarse aggregate corresponding to zone -I grade of fine aggregates for 20mm nominal size of aggregates and water cement ratio of 0.50 is 0.6

So for water cement ratio of 0.4, the volume of coarse aggregate is 0.6 + 0.02 = 0.62

And for pumpable concrete this value should be reduced by 10 %

So volume of coarse aggregate = 0.62 x 0.9 = 0.56

And volume of fine aggregate is = 1-0.56 = 0.44

• Mix calculation

1. Volume of concrete- 1 cum
2. Volume of cement = mass of cement / (specific gravity of cement x 1000)

= 270/ 3.15 x 1000

= 0.086 cum

2. Volume of fly ash = 115 / (2.2 x1000)

= 0.052 cum

1. Volume of water – 140/1000 = 0.140 cum
2. Volume of plasticizers – 7 / ( 1.145 x 1000) = 0.006 cum
3. Volume of aggregates (Total) = 1- (b+c+d+e)

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

= 0.716 cum

1. Mass of coarse aggregate= e 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 /cum

1. Mass of fine aggregate= e 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 /cum

1. Mix proportion

Cement – 270 kg/cum

Fly ash – 115 Kg/cum

Fine aggregate- 863 kg/cum

Coarse aggregate- 1098 kg/cum

Water – 140 kg /cum

Water cement ratio – 0.364