Project on Concrete Mix Design for various grades of Concrete
Concrete mix design for M50 grade concrete without flyash-
1. Stipulations for proportioning :
- Grade designation - M50
- Type of cement - OPC 43 grade conforming to IS 8112
- Maximum nominal size of aggregate is 20 mm
- Minimum cement content : 320 kg/m^3 (From table 5 of IS 456 : 2000 - Exposure condition)
- Maximum water-cement ratio : 0.45 (From table 5 of IS 456 : 2000 - Exposure condition)
- Workability : 100 mm (slump value for pumpable concrete)
- Exposure condition : Severe (for reinforced concrete )
- Method of concrete placing - Pumping
- Degree of supervision : Good
- Type of aggregate : Crushed angular aggregate
- Maximum cement content : 450 kg/m^3 (IS 456: 2000 , 8.2.4.2 )
- Chemical admixture type: Superplasticizer
2. Test data for materials:
- Cement used : OPC 43 grade conforming to IS 8112
- Specific gravity of cement : 3.15
- Chemical admixture : Superplasticizer conforming to IS 9103
- Specific gravity of:
- Coarse aggregate : 2.74
- Fine aggregate : 2.74
5. Water absorption: Coarse aggregate - 0.5% and Fine aggregate - 1.0%
6. Free surface moisture in aggregates : Nil
7. Sieve analysis:
- Coarse aggregate- conforming to Table 2 of IS 383
- Fine aggregate- conforming to grading zone I of table 4 of IS 383
3. Target strength for mix proportioning:
f'ck = fck + 1.65 x S where f’ck = target mean compressive strength at 28 days in N/mm^2, fck = characteristic compressive strength at 28 days, in N/mm2,
S = standard deviation, in N/mm2
From Table 2 of IS 10262: 2019, standard deviation , S= 5 N/mm^2, therefore f'ck = 50 + 1.65 * 5 = 58.25 N/mm^2
4. Selection of water-cement ratio:
From figure I of IS 10262: 2019 we get water-cement ratio = 0.29. From table 5 of IS 456-2000 for severe exposure, maximum water-cement ratio = 0.45. We will select the minimum w/c ratio i.e. 0.29.
5.Selection of water content-
From table 4 of IS 10262: 2019, water content for 20 mm aggregate = 186 litre (for 25 mm to 50 mm slump range). For additional slump 3% water content is added for every 25 mm slump.
Therefore estimated water content for 100 mm slump = 186 + (6/100)*186 = 197 litre
As superplasticizer is used , the water content can be reduced up to 20-30 % .Based on trials water content reduction of 29% is achieved with plasticizer. Hence the arrived water content = 197 * 0.71 = 140 litre
6. Calculation of cement content-
Water - cement ratio = 0.29
Cement content = 140/0.29 = 483 kg/m^3
From table 5 of IS 456 minimum cement content for 'severe ' exposure condition = 320 kg/m^3 and 483 kg/m^3 > 320 kg/m^3, hence it's okay. But 483 kg/m^3 exceeds the maximum cement content (450 kg/m^3). Therefore we choose cement content to be 450 kg/m^3
So corrected w/c ratio = 140/450 = 0.31
7. Proportion of volume of coarse aggregate and fine aggregate content :
From table 5 of IS 10262 : 2019, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for w/c ratio 0.5 = 0.60 .In the present case the water-cement ratio is 0.31.
As per IS 10262 : 2019 (5.5.1) ,the proportion of volume of coarse aggregates to that of total aggregates is increased at the rate of 0.01 for every decrease in water-cement/cementitious materials ratio by 0.05 and decreased at the rate of 0.01 for every increase in water-cement ratio by 0.05.
As w/c ratio is lowered by 0.19 ,the proportion of volume of coarse aggregate will be increased.
Volume of coarse aggregate =[{(0.5 - w/c)/0.05} * 0.01 ] + Volume of coarse aggregates from table 5 of IS 10262:2019
=[{(0.5-0.31)/0.05}* 0.01 ] + 0.6
= 0.64
Corrected volume of coarse aggregate for the water-cement ratio of 0.29 = 0.64
For pumpable concrete volume of coarse aggregate is reduced by 10%.
Therefore, volume of coarse aggregate = 0.64 * 0.9 = 0.576
Volume of fine aggregate content = 1- 0.576 = 0.424
8. Mix calculations :
The mix calculation per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m^3
b) Volume of cement = (Mass of cement / Specific gravity of cement) * (1/1000) = (450/3.15) * (1/1000) = 0.143 m^3
c) Volume of water = (mass of water/ specific gravity of water) * (1/1000) = (140/1) * (1/1000) = 0.140 m^3
d) Volume of chemical admixture = (mass of chemical admixture / specific gravity of admixture) * (1/1000) = (9/1.145) * (1/1000) = 0.008 m^3
[Mass of chemical admixture = 2% of cementitious material = 450 x 2/100 = 9 kg (We can also take 1-3 %) ]
e) Volume of aggregates = a - (b + c + d) = 1 - ( 0.143 + 0.140 + 0.008 ) = 0.71 m^3
f) Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.71*0.576*2.74*1000
= 1120 kg/m^3
g) Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.71*0.424*2.74*1000
= 825 kg/m^3
9) Mix proportion for this trial :
Cement = 450 kg/m^3
Water = 140 kg/m^3
Fine aggregate = 825 kg/m^3
Coarse aggregate = 1120 kg/m^3
Chemical admixture = 9 kg/m^3
Water-cement ratio = 0.31
Trial mix ratio = 1 : 1.83 : 2.49
10) 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.
11) Two more trials having variation of 10% of water-cement ratio in Clause 10 shall be carried out and a graph between three 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.
Concrete mix design for M35 grade concrete with flyash-
1. Stipulations for proportioning :
- Grade designation - M35
- Type of cement - OPC 43 grade conforming to IS 8112
- Maximum nominal size of aggregate is 20 mm
- Minimum cement content : 320 kg/m^3 (From table 5 of IS 456 : 2000 - Exposure condition)
- Maximum water-cement ratio : 0.45 (From table 5 of IS 456 : 2000 - Exposure condition)
- Workability : 100 mm (slump value for pumpable concrete)
- Exposure condition : Severe (for reinforced concrete )
- Method of concrete placing - Pumping
- Degree of supervision : Good
- Type of aggregate : Crushed angular aggregate
- Maximum cement content : 450 kg/m^3
- Chemical admixture type: Superplasticizer
- Type of mineral admixture : fly ash conforming to IS 3812 (Part 1)
2. Test data for materials:
- Cement used : OPC 43 grade conforming to IS 8112
- Specific gravity of cement : 3.15
- Chemical admixture : Superplasticizer conforming to IS 9103
- Specific gravity of:
- Coarse aggregate : 2.74
- Fine aggregate : 2.74
5. Water absorption: Coarse aggregate - 0.5% and Fine aggregate - 1.0%
6. Free surface moisture in aggregates : Nil
7. Sieve analysis:
- Coarse aggregate- conforming to Table 2 of IS 383
- Fine aggregate- conforming to grading zone I of table 4 of IS 383
8. Fly ash : conforming to IS 3812 (Part 1)
9. Specific gravity of flyash : 2.2
3. Target strength for mix proportioning:
f'ck = fck + 1.65 x S where f’ck = target mean compressive strength at 28 days in N/mm^2, fck = characteristic compressive strength at 28 days, in N/mm2,
S = standard deviation, in N/mm2
From Table 2 of IS 10262: 2019, standard deviation , S= 5 N/mm^2, therefore f'ck = 35 + 1.65 * 5 = 43.25 N/mm^2
4. Selection of water-cement ratio:
From figure I of IS 10262: 2019 we get water-cement ratio = 0.38. From table 5 of IS 456-2000 for severe exposure, maximum water-cement ratio = 0.45. We will select the minimum w/c ratio i.e. 0.38.
5.Selection of water content-
From table 4 of IS 10262: 2019, water content for 20 mm aggregate = 186 litre (for 25 mm to 50 mm slump range). For additional slump 3% water content is added for every 25 mm slump.
Therefore estimated water content for 100 mm slump = 186 + (6/100)*186 = 197 litre
As superplasticizer is used , the water content can be reduced up to 20% and above .Based on trials water content reduction of 29% is achieved with plasticizer. Hence the arrived water content = 197 * 0.71 = 140 litre
6. Calculation of cement content-
Water - cement ratio = 0.38
cement content = 140/0.38 = 368 kg/m^3
From table 5 of IS 456 minimum cement content for 'severe ' exposure condition = 320 kg/m^3 and 368 kg/m^3 > 320 kg/m^3, hence it's okay.
NOTE- In certain situations, while using part replacement of cement by fly ash, ground granulated blast furnace slag (GGBS), silica fume, and other mineral admixtures, increase in cementitious materials content may be warranted, particularly if fly ash is 20 percent or more. The decision on increase in cementitious materials content and its percentage may be based on experience and trials; or the cementitious materials content so calculated may be increased by 10 percent for preliminary trial.
Cementitious material content = 368 * 1.10 = 405 kg/m^3
Water content = 140 kg/m^3
So, water-cementitious content ratio = 140/405 = 0.346
Fly ash @ 30% total cementitious material content = 405 * 0.3 = 122 kg/m^3
Cement (OPC) = 405-122 = 283 kg/m^3
Saving of cement while using fly ash = 368-283 = 85 kg/m^3
Fly ash being utilised = 122 kg/m^3
7. Proportion of volume of coarse aggregate and fine aggregate content :
From table 5 of IS 10262 : 2019, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for w/c ratio 0.5 = 0.60 .In the present case the water-cement ratio is 0.38.
As per IS 10262 : 2019 (5.5.1) ,the proportion of volume of coarse aggregates to that of total aggregates is increased at the rate of 0.01 for every decrease in water-cement/cementitious materials ratio by 0.05 and decreased at the rate of 0.01 for every increase in water-cement ratio by 0.05.
As w/c ratio is lowered by 0.12 ,the proportion of volume of coarse aggregate will be increased.
Volume of coarse aggregate =[{(0.5 - w/c)/0.05} * 0.01 ] + Volume of coarse aggregates from table 5 of IS 10262:2019
=[{(0.5-0.346)/0.05}* 0.01 ] + 0.6
= 0.631
Corrected volume of coarse aggregate for the water-cementitious content ratio of 0.346 = 0.631
For pumpable concrete volume of coarse aggregate is reduced by 10%.
Therefore, volume of coarse aggregate = 0.631 * 0.9 = 0.568
Volume of fine aggregate content = 1- 0.568 = 0.432
8. Mix calculations :
The mix calculation per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m^3
b) Volume of cement = (Mass of cement / Specific gravity of cement) * (1/1000) = (283/3.15) * (1/1000) = 0.09 m^3
c) Volume of fly ash = (Mass of fly ash / Specific gravity of fly ash) * (1/1000) = (122/2.2) * (1/1000) = 0.055 m^3
d) Volume of water = (mass of water/ specific gravity of water) * (1/1000) = (140/1) * (1/1000) = 0.140 m^3
e) Volume of chemical admixture = (mass of chemical admixture / specific gravity of admixture) * (1/1000) = (8.1/1.145) * (1/1000) = 0.007 m^3
(Mass of chemical admixture = 2% of cementitious material = 405 x 2/100 = 8.1 kg)
f) Volume of aggregates = a - (b + c + d +e) = 1 - ( 0.09 + 0.055 +0.140 + 0.007 ) = 0.708 m^3
g) Mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.708*0.568*2.74*1000
= 1102 kg/m^3
h) Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.708*0.432*2.74*1000
= 838 kg/m^3
9) Mix proportion for this trial :
Cement = 283 kg/m^3
Fly ash = 122 kg/m^3
Cementicious content = 405 kg/m^3
Water = 140 kg/m^3
Fine aggregate = 838 kg/m^3
Coarse aggregate = 1102 kg/m^3
Chemical admixture = 8.1 kg/m^3
Water-cement ratio = 0.346
Trial mix ratio = 405 : 838 : 1102 = 1 : 2.07 : 2.72
10) 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.
11) Two more trials having variation of 10% of water-cement ratio in Clause 10 shall be carried out and a graph between three 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.