Project on Concrete Mix Design for various grades of Concrete

Concrete Mix Design for M35 grade concrete with fly ash:

1. Grade designation: M35
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: 320 Kg/m^3 (From Table 5 of IS 456:2000)
6. Maximum water-cement ratio: 0.45 From Table 5 of IS 456:2000)
7. Workability: 100mm slump
8. Exposure condition: Severe
9. Method of concrete placing: Pumping
10. Degree of supervision: Good
11. Type of aggregate: Crushed angular aggregate
12. Maximum cement content: 450 kg/m^3
13. Chemical admixture type: Superplasticizer

Test data for materials:

1. Cement used is OPC 43 conforming to IS 8112 and Specific gravity of cement is 3.15
2. Fly ash conforming to IS 3812 (part 1) and the Specific gravity of fly ash is 2.2
3. Chemical admixture superplasticizer conforming to IS 9103
4. Specific gravity of CA: 2.74 and FA: 2.74
5. Water absorption of CA: 0.5%. FA : 1.0%
6. Free surface moisure is nil for both CA and FA.

Target strength for mix proportioning

Where,

• f'ck = average compressive strength for 28 days
• fck = characteristic compressive strength for 28 days._.
• S = Standard deviation is 5.0 M35 (from table 8 of IS:456-2000)
• Target mean strength f’ck= 35 + 1.65×5 = 43.25 N/mm^2

Selection of water cement ratio:

From table 5 of IS 456:2000 for severe exposure maximum w/c ratio is = 0.45. Based on experience adopted w/c ratio is 0.40. 0.40 < 0.45 hence ok.

Selection of water content:

From Table 2 of IS:10262 – 2009, for 20 mm maximum size aggregate - Maximum water content for 25 mm to 50 mm slump = 186 litres

Estimated water content=186+6/100 x 186 = 197 litres

As superplasticizer is used as admixture, the water content can be reduced up 30% or more. Based on trials with superplasticizer water content reduction of 29 percent has been achieved. Hence, water content =197 x 0.71 =140 litres

Calculation of cement content

Water-cement ratio = 0.40

Cementitious material(cement + fly ash content) = 140/0.4= 350kg/m^3

From Table 5 of IS 456, minimum cement content for ‘severe’ exposure condition = 320 kg/m^3 350 kg/m3 > 320 kg/m^3, hence, cement content adopted = 350 kg/m^3.

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

• Percentage of fly ash needs to be decided based on project requirement and quality of materials.
• In some cases increases of cementitious materials can be warranted. Increase in cementitious material content and its percentage can be based on experience and trial(in this case 10%)

Cementitious material content= 350 x 1.10 = 385 kg/m^3

Water content = 140 kg/m^3

Water cement ratio= 140/385 = 0.364

Fly ash @ 30% cementitious material content = 385 x 30%= 115 kg/m^3

Cement (OPC) = 385-115 = 270 kg/m^3

Saving of cement while using fly ash = 370-270 = 80 kg/m^3

Fly ash being utilized = 115 kg/m^3

Proportion of volume of coarse aggregate and fine aggregate content:

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

In the present case the w/c ratio is 0.40

therefore coarse aggregate should be increased to decrease the fine aggregate content.

As water-cement ratio is lower by 0.10 the proportion of volume of CA is increased by 0.02 (at the rate of 0.02 for every 0.05 change in water cement ratio).

Therefore corrected volume for coarse aggregate for w/c ratio of 0.40 =0.62

it is pumpable concrete so value is reduced by 10%

therefore volume of coarse aggregate = 0.56

volume of fine aggregate = 1- 0.56 = 0.44

Mix calculations:

1. volume of concrete = 1 m^3
2. volume of cement = 0.086 m^3
3. volume of fly ash = 0.052 m^3
4. volume of water = 0.140 m^3
5. volume of admixture = 0.006 m^3
6. volume of aggregate (FA&CA) = (a-(b+c+d+e) = 0.716 m^3
7. mass of coarse aggregate= f x vol of coarse aggregate x specific gravity of CA x 1000= 1098 kg/m^3
8. mass of fine aggregate = e x vol of fine aggregate x specific gravity of FA x 1000 = 863 kg/m^3

Mix proportions for trial 1

Cement = 270 kg/m^3

Fly ash = 115 kg/m^3

Water = 140 kg/m^3

FA = 863 kg/m^3

CA = 1098 kg/m^3

Chemical admixture = 7 kg/m^3

Water cement ratio = 0.364

Trial mix ratio = 1: 2.24 :2.85.

Concrete Mix Design for M50 grade concrete

1. Grade designation: M50
2. Type of cement: OPC 43 grade
3. Maximum nominal size of aggregate: 20mm
4. Minimum cement content: 320 Kg/m^3 (From Table 5 of IS 456:2000)
5. Maximum water-cement ratio: 0.45 From Table 5 of IS 456:2000)
6. Workability: 100mm slump
7. Exposure condition: Severe
8. Method of concrete placing: Pumping
9. Degree of supervision: Good
10. Type of aggregate: Crushed angular aggregate
11. Maximum cement content: 450 kg/m^3
12. Chemical admixture type: Superplasticizer

Test data for materials:

1. Cement used is OPC 43 conforming to IS 8112 and Specific gravity of cement is 3.15
2. Chemical admixture superplasticizer conforming to IS 9103
3. Specific gravity of CA: 2.74 and FA: 2.74
4. Water absorption of CA: 0.5%. FA : 1.0%
5. Free surface moisure is nil for both CA and FA.

Target strength for mix proportioning

Where,

• f'ck = average compressive strength for 28 days
• fck = characteristic compressive strength for 28 days._.
• S = Standard deviation is 5.0 M50 (from table 8 of IS:456-2000)
• Target mean strength f’ck= 50 + 1.65×5 = 58.25 N/mm^2

Selection of water cement ratio:

From table 5 of IS 456:2000 for severe exposure maximum w/c ratio is = 0.45. Based on experience adopted w/c ratio is 0.40. 0.40 < 0.45 hence ok.

Selection of water content:

From Table 2 of IS:10262 – 2009, for 20 mm maximum size aggregate - Maximum water content for 25 mm to 50 mm slump = 186 litres

Estimated water content=186+6/100 x 186 = 197 litres

As superplasticizer is used as admixture, the water content can be reduced up 30% or more. Based on trials with superplasticizer water content reduction of 29 percent has been achieved. Hence, water content =197 x 0.71 =140 litres

Calculation of cement content

Water-cement ratio = 0.40 Cement content = 140/0.40 =350 kg/m^3 From Table 5 of IS 456, minimum cement content for ‘severe’ exposure condition = 320 kg/m^3 350 kg/m3 > 320 kg/m^3, hence, cement content adopted = 350 kg/m^3.

Proportion of volume of coarse aggregate and fine aggregate content:

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

In the present case the w/c ratio is 0.40

therefore coarse aggregate should be increased to decrease the fine aggregate content.

As water-cement ratio is lower by 0.10 the proportion of volume of CA is increased by 0.02 (at the rate of 0.02 for every 0.05 change in water cement ratio).

Therefore corrected volume for coarse aggregate for w/c ratio of 0.40 =0.62

it is pumpable concrete so value is reduced by 10%

therefore volume of coarse aggregate = 0.56

volume of fine aggregate = 1- 0.56 = 0.44.

Mix calculations:

1. volume of concrete = 1 m^3
2. volume of cement = 0.111 m^3
3. volume of water = 0.140 m^3
4. volume of admixture = 0.006 m^3
5. volume of aggregate (FA+CA) = (a-(b+c+d) = 0.743m^3
6. mass of coarse aggregate= e*vol of coarse aggregate*specific gravity of CA*1000= 1140 kg/m^3
7. mass of fine aggregate = e*vol of fine aggregate*specific gravity of FA*1000 = 896 kg/m^3

Mix proportions for trial 1

Cement = 350 kg/m^3

Water = 140 kg/m^3

FA = 896 kg/m^3

CA = 1140 kg/m^3

Chemical admixture = 7 kg/m^3

Water cement ratio = 0.4

Trial mix ratio = 1: 2.56: 3.26.