Project on Concrete Mix Design for various grades of Concrete

• Aim:- Concrete mix design for M35 grade concrete with fly ash to reduce the cement usage and to make the concrete more environment friendly-
• Procedure:

• Stipulations for proportioning

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 8112
4. Maximum nominal size of aggregate = 20mm
5. Maximum cement content = 320 kg/cu.m (from table-5 of IS-456:2000; exposure condition = severe)
6. Maximum water-cement ratio: 0.45 (from table-5 of IS-456:2000; exposure condition = severe)
7. Workability = 100mm (slump value for pumpable concrete 75-100 mm)
8. Exposure condition: Severe (for reinforced concrete)
9. Method for concrete placing: Pumping
10. Degree of supervision: Good
11. Type of aggregate: Crushed angular aggregate
12. Maximum cement content: 450 kg/cu.m
13. Chemical admixture type: Superplasticizer

• Test data for materials

1. cement used: OPC 43 grade conforming to IS 8112
2. specific gravity of cement: 3.15
3. fly ash: conforming to IS 3812 (part-I)
4. specific gravity of fly ash: 2.2
5. chemical admixture: superplasticizer conforming to IS 9103
6. specific gravity of: coarse agregate = 2.74 & fine agregate = 2.74
7. water absorption: coarse sgregate = 0.5% & fine agregate = 1.0%
8. free surface moisture: coarse agregate = nil & finr agregate = nil
9. sieve analysis

• Target strength for Mix proportioning

  f’_ck = f_ck + 1.65 S = 50 + 1.65 * 5 = 58.25 N/sq.mm

• Selection of water-cement ratio: From Table-5 of IS 456:2000 for severe exposure, maximum water-cement ratio = 0.45. Based on experience, the adopted water-cement ratio is 0.40. And 0.40 < 0.45, hence OK.
• Selection of water content: From table-2 of IS 10262:2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range).

1. Therefore, estimated water content for 100mm slump = 186 + 0.06 * 186 = 197 litres.
2. As a super-plasticizer is used, the water content can be reduced to 20% and above.
3. Based on trials water content reduction of 29% is achieved with a plasticizer.

hence, the arrived water content = 197 *0.71 = 140 litres.

• Calculation of cement content

1. water-cement ratio = 0.4
2. cementious material(cement + fly ash) content = 140/0.4 = 350 kg/cu.metre
3. from table-5 of IS 456:2000 minimum cement content for, 'severe' exposure condition = 320 kg/cu.metre. 350 kg/cu.metre > 320 kg/cu.metre, hence OK.

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

1. The percentage of fly ash needs to be decided based on project requirements and the quality of materials.
2. 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 (this project is with an increase of 10% cementitious material content)

1. cementitious material content = 350*1.10 = 385kg/cu.metre
2. water content = 140 kg/cu.metre

So, water-cemet ratio = 140/385 = 0.364

1. Fly ash @30% total cementitious material content = 385*30% = 115 kg/cu.metre
2. Cement (OPC) = 385-115 = 270 kg/cu.metre
3. Saving of cement while using fly ash = 350-270 = 80 kg/cu.meter
4. Fly ash being utilized = 115 kg/cu.meter

• Proportion of volume of coarse aggregate and fine aggregate content:

1. From table-3 of IS 10262:2009, the volume of coarse aggregate corresponds to 20mm size aggregate content.
2. As, the water-cement ratio is lower by 0.10, the proportion of the 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, the corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62.

(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.)

1. For pumpable concrete these values are reduced by 10%
2. Therefore, volume of coarse aggregate = 0.62 * 0.9 = 0.56
3. Volume of fine aggregate = 1 - 0.56 = 0.44

• Mix calculations: The mix calculation per unit volume of concrete shall be as follows.

1. Volume of concrete = 1 cu.meter
2. Volume of cement = (mass of cement/sp.gr. of cement) * 1/1000 = (270/3.15) * 1/1000 = 0.086 cu.metre
3. Volume of fly ash = (mass of fly ash/sp. gr. of fly ash) * 1/1000 = 0.052 cu.meter
4. Volume of water = (mass of water/sp.gr. of water) * 1/1000 = 140/1 * 1/1000 = 0.140 cu.metre
5. Volume of chem. admixture = (mass of chem. admixture/sp.gr. of chem. admixture) * 1/1000 = 7.6/1.145 * 1/1000 = 0.006 cu.metre
6. Volume of aggregate (FA & CA) = (a-(b+c+d+e)) = (1-(0.086+0.052+0.140+0.006)) = 0.716 cu.metre
7. Mass of coarse aggregate = e * vol. of coarse aggregate * sp.gr. of coarse aggregate * 1000 = 0.716*0.56*2.74*1000 = 1098 kg/cu.metre
8. Mass of fine aggregate = e * vol. of fine agregate * sp.gr. of fine aggregate * 1000 = 0.716*0.44*2.74*1000 = 863 kg/cu.metre

• Mix proportions for trial number 1:

1. cement = 270 kg/cu.metre
2. fly ash = 115 kg/cu.metre
3. water = 140 kg/cu.metre
4. Fine aggregate = 863 kg/cu.metre
5. coarse aggregate = 1098 kg/cu.metre
6. Chem. admixture = 7 kg/cu.metre
7. Water-cement ratio = 0.364

• RESULT:-
• Therefore, trial mix ratio = 1 : 2.24 : 2.85
• 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.
• Two more trials having variations of 10% of water-cement ratio in clause-X shall be carried out and a graph between their water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.

• Aim:- Concrete mix design for M50 grade concrete without fly ash
• Procedure:

• Stipulations 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. Maximum cement content = 320 kg/cu.m (from table-5 of IS-456:2000; exposure condition = severe)
5. Maximum water-cement ratio: 0.45 (from table-5 of IS-456:2000; exposure condition = severe)
6. Workability = 100mm (slump value for pumpable concrete 75-100 mm)
7. Exposure condition: Severe (for reinforced concrete)
8. Method for concrete placing: Pumping
9. Degree of supervision: Good
10. Type of aggregate: Crushed angular aggregate
11. Maximum cement content: 450 kg/cu.m
12. Chemical admixture type: Superplasticizer

• Test data for materials

1. cement used: OPC 43 grade conforming to IS 8112
2. specific gravity of cement: 3.15
3. chemical admixture: superplasticizer conforming to IS 9103
4. specific gravity of: coarse agregate = 2.74 & fine agregate = 2.74
5. water absorption: coarse sgregate = 0.5% & fine agregate = 1.0%
6. free surface moisture: coarse agregate = nil & finr agregate = nil
7. sieve analysis

• Target strength for Mix proportioning

  f’_ck = f_ck + 1.65 S = 50 + 1.65 * 5 = 58.25 N/sq.mm

• Selection of water-cement ratio: From Table-5 of IS 456:2000 for severe exposure, maximum water-cement ratio = 0.45. Based on experience, the adopted water-cement ratio is 0.40. And 0.40 < 0.45, hence OK.
• Selection of water content: From table-2 of IS 10262:2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range).

1. Therefore, estimated water content for 100mm slump = 186 + 0.06 * 186 = 197 litres.
2. As a super-plasticizer is used, the water content can be reduced to 20% and above.
3. Based on trials water content reduction of 29% is achieved with a plasticizer.

hence, the arrived water content = 197 *0.71 = 140 litres.

• Calculation of cement content

1. water-cement ratio = 0.4
2. cement content = 140/0.4 = 350 kg/cu.metre
3. from table-5 of IS 456:2000 minimum cement content for, 'severe' exposure condition = 320 kg/cu.metre. 350 kg/cu.metre > 320 kg/cu.metre, hence OK.

• Proportion of volume of coarse aggregate and fine aggregate content:

1. From table-3 of IS 10262:2009, the volume of coarse aggregate corresponds to 20mm size aggregate content.
2. As, the water-cement ratio is lower by 0.10, the proportion of the 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, the corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62.

(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.)

1. For pumpable concrete these values are reduced by 10%
2. Therefore, volume of coarse aggregate = 0.62 * 0.9 = 0.56
3. Volume of fine aggregate = 1 - 0.56 = 0.44

• Mix calculations: The mix calculation per unit volume of concrete shall be as follows.

1. Volume of concrete = 1 cu.meter
2. Volume of cement = (mass of cement/sp.gr. of cement) * 1/1000 = (350/3.15) * 1/1000 = 0.111 cu.metre
3. Volume of water = (mass of water/sp.gr. of water) * 1/1000 = 7/1.145 * 1/1000 = 0.006 cu.metre
4. Volume of chem. admixture = (mass of chem. admixture/sp.gr. of chem. admixture) * 1/1000 = 7/1.145 * 1/1000 = 0.006 cu.metre
5. Volume of aggregate (FA & CA) = (a-(b+c+d)) = (1-(0.111 + 0.140 + 0.006)) = 0.743 cu.metre
6. Mass of coarse aggregate = e * vol. of coarse aggregate * sp.gr. of coarse aggregate * 1000 = 0.743*0.56*2.74*1000 = 1140 kg/cu.metre
7. Mass of fine aggregate = e * vol. of fine agregate * sp.gr. of fine aggregate * 1000 = 0.743*0.44*2.74*1000 = 896 kg/cu.metre

• Mix proportions for trial number 1:

1. cement = 350 kg/cu.metre
2. water = 140 kg/cu.metre
3. Fine aggregate = 896 kg/cu.metre
4. coarse aggregate = 1140 kg/cu.metre
5. Chem. admixture = 7 kg/cu.metre
6. Water-cement ratio = 0.4

• RESULT:-

• Therefore, trial mix ratio = 1 : 2.56 : 3.26
• 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.
• Two more trials having variations of 10% of water-cement ratio in clause-X shall be carried out and a graph between their water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.