Project on Concrete Mix Design for various grades of Concrete
A: Calculation of grade M35 with fly ash.
Grade designation: M35
Type of cement: OPC 43 grade
Maximum Nominal size of aggregate: 20mm.
Minimum cement content: 340 kg/m^3. (IS 456: 2000)
Maximum w/c ratio: 0.45 (IS 456:2000)
Workability: 100mm slump.
Exposure condition: Very Severe.
Maximum Cement content: 450 kg/m^3
Admixture: Fly Ash.
Test data for materials:
- Cement used: OPC 43 Grade.
- Sp gravity of cement: 3.15.
- Fly ash Sp. gravity: 2.5
- Sp. gravity of Coarse aggregate: 2.74
- Sp. Gravity of Fine aggregate: 2.74
- Sieve Analysis: Confirming to grading of Zone 1.
1. Target Mean strength (f'ck):
Standard deviation (S) = 5 N/mm^2 (Table 2 IS 10262:2019)
f'ck = 35 + 1.65(5)
f'ck = 43.25 N/mm^2
2. Selection of w/c ratio:
From table 5 IS 456 : 2000
For very severe exposure condition w/c ratio is 0.45
Based on experience adopted w/c ratio is 0.40
0.40 < 0.45 ... hence OK
3. Selection of water content:
From table 4 IS 10262:2019 Maximum water content for 20mm aggregate size 186 litres (for 25-50mm slump range)
So, for 100mm slump range we need to add 3% for every 25mm increase in slump range.
Therefore for 100mm slump range ; 186 + 6% * 186 = 197 litres.
By using Fly Ash as an admixture water content can be reduced upto 10% and based on trials water content reduction is achieved of about 20% with Fly Ash;
197*0.80 = 158 litres.
4. Calculation of cement content:
w/c = 0.4
Cement content = 158/0.4 = 395kg/m^3
from table 5 IS 456:2000 minimum cement content for very severe exposure condition is 340kg/m^3
395 > 340 kg/m^3. ... hence OK.
5. Volume of Coarse Aggregate and Fine Aggregate:
From table 5 IS 10262:2019, Volume of Coarse aggregate correspoding to 20mm aggregate size aggregate and fine aggregate (Zone 1) for w/c ratio 0.6.
In this case w/c ratio is 0.40, therefore volume of coarse aggregate needs to be increased to decrease the Fine aggregate content.
As w/c ratio is lower by 0.10 the proportion the proportion of volume of coarse aggregate is increased by 0.02 (@ of +/- 0.01 for every +/- 0.05 change in w/c ratio)
Therefore corrected volume of coarse aggregate for w/c ratio of 0.40 is 0.62.
For pumped concrete values are reduced by 10%.
Volume of coarse aggregate = 0.62 * 0.90 = 0.56.
Volume of Fine aggregate = 1 - 0.6 = 0.44.
6. Mix calculatons:
The mix calculations per unit volume of concrete shall be;
a. Volume of concrete = 1m^3
b. Volume of cement = Mass of cement/ Sp gravity of cement * 1/1000
= 395/3.15 * 1/1000 = 0.125m^3
c. Volume of water = Mass of water/ Sp gravity of water * 1/1000
= 158/1 * 1/1000 = 0.158m^3
d. Volume of admixture = Mass of Fly ash/ Sp gravity of fly ash * 1/1000
Mass = 2% of cementitious material = 395*2% = 7.9kg/m^3
Volume = 7.9/2.5 * 1/1000 = 0.003m^3.
e. Volume of total aggregate = (a - (b+c+d))= (1-(0.125+0.158+0.003))= 0.714m^3.
f. Mass of coarse aggregate = e * Volume of CA * Sp gravity of CA * 1000
= 0.714 * 0.56 * 2.74*1000
= 1095.56 kg/m^3.
g. Mass of Fine aggregate = e * Volume of FA * Sp. gravity of FA * 1000
= 0.714 * 0.44 * 2.74 * 1000
= 860.8 kg/m^3.
7. Mix proportions:
Cement = 395 kg/m^3.
Water = 158 kg/m^3.
Fly ash = 7.9 kg/m^3.
FA = 860.8 kg/m^3.
CA = 1095.56 k/m^3.
w/c ratio = 0.40
B : Calculation for M50 grade concrete.
Grade designation: M50.
Type of cement: OPC 43 grade
Maximum size of agregate: 20mm.
Maximum w/c ratio : 0.40
Workability: 100mm.
Exposure condition: Extreme.
Minimum Cement content: 360kg/m^3
Maximum Cement content : 450kg/m^3
Admixture: Superplastisizer
Test data for materials;
Specific gravity for Coarse aggregate: 2.74
Specific gravity for Fina Aggregate: 2.74
Sieve Analysis: Zone 1
Specific gravity of cement: 3.15
1. Target mean strength.
f'ck = fck + 1.65(S)
Standard deviation = 5 (Table 1 IS 10262:2019)
f'ck = 50 + 1.65(5)
f'ck = 58.25Mpa
2. Selection w/c ratio:
From table 5 IS456:2000
Maximum water cement ratio for extreme exposure is 0.40
and adopted water cement ratio is 0.40
3. Selection of water content:
From table 2 IS10262:2009, the maximum water content for 25mm to 50mm slump = 186kg = 186lit.
For additional slump 3% may be added for every 25mm slump. For 100mm slump 6% must be added i.e = 186 +6/100*186= 197lit.
By use of superplasticizer water content can be reduced upto 20%, and based on experience 29% reduction in water content is adopted
therefore; 197*0.71 = 140lit
4. Calculation of Cement content:
w/c = 0.4
W= 140 lits
C = 140/0.4 = 350kg/m^3.
Here minimum cement content required is 360kg/m^3.
Hence cement content is C = 360 kg/m^3.
5. Volume of CA and FA.
From Table 3 IS 10262:2009 Volume of aggregate corressponding to 20mm size aggregate and fine agggregate (Zone 1) for w/c ratio of 0.6
In this case w/c ratio is 0.4,
So, the volume of CA needs to be increased to decrease the FA content.
As w/c ratio is lower by 0.10 the proportion of volume of CA is increased by 0.02 (@ +/- 0.01 for every +/- 0.05 change in w/c ratio)
Corrected Volume of coarse aggregate for the w/c ratio of 0.40 = 0.62
For pumpable concrete values are reduced by 10%.
Therefore, Volume of CA = 0.62*0.9 = 0.56
Vol of FA = 1- 0.56 = 0.44.
6. Mix Calculations:
The mix calculations per unit volume shall be;
a. Volume of concrete = 1m^3.
b. Volume of Cement = Mass of cement/ Sp gravity of cement *1/1000 = 360/3.15 * 1/1000 = 0.11m^3
c. Volume of water = Mass of water/ Sp gravity of water * 1/1000 = 140/1 * 1/1000 = 0.14m^3
d. Volume of admixture = Mass / sp gravity of admixture
mass = 2% of cementitious material = 2% * 360 = 7.2kg/m^3.
Vol = 7.2/1.15 * 1/1000 = 0.004 m^3.
e. Vol of Total aggregate = (a - (b+c+d)) = (1-(0.11+0.14+0.004)) = 0.746m^3
f. Mass of CA = e*vol of CA * Sp gravity * 1000 = 0.746*0.56*2.74*1000 = 1144.66 kg/m^3.
g. Mass of FA = e* vol of FA * Sp gravity * 1000= 0.746*0.44*2.74*1000 = 899.37 kg/m^3.
7. Mix proportions:
Cement: 360kg/m^3.
Water : 140lit.
FA: 899.37 kg/m^3.
CA : 1144.66 kg/m^3.
Superplasticizer: 7.2 kg/m^3.
W/c ratio: 0.4