Project on Concrete Mix Design for various grades of Concrete
Aim
To Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash
Introduction
Concrete mix design is the method of finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures, therefore concrete mix design can be stated as concrete mix in terms of cement: sand: aggregates.
Formula used
- Target Mean strength
f’ck =fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days, and
- s = standard deviation
2. Cement content
Cement content = water content / water-cement ratio
3. Volume Calculation
- Volume of concrete
- Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000
- Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000
- Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
- Volume of all in aggregate =[a-(b+c+d)]
- Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
- Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:
1 Consideration for Mix design
|
Grade designation |
M35 |
|
Type of cement |
OPC 43 Grade confirming to IS 8112 |
|
Type of mineral admixture |
Fly ash confirming to IS 3812 (Part 1) |
|
Maximum nominal size of aggregate |
20 mm |
|
Minimum cement content |
320 kg/m3 (Table 5 of IS 456:2000) |
|
Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000) |
|
Maximum cement content |
450 kg/m3 |
|
Chemical admixture type |
Super Plasticizer |
2 Required data
|
Cement used |
OPC 43 Grade conforming IS 8112 |
|
Specific gravity of cement |
3.11 |
|
Specific gravity of fly ash |
2.4 |
|
Specific gravity of coarse aggregate |
2.8 |
|
Specific gravity of fine aggregate |
2.7 |
|
Water absorption of coarse aggregate |
0.5% |
|
Water absorption of fine aggregate |
1.0% |
3. Target Strength of mix Proportion
f’ck =fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days, and
- s = standard deviation
f’ck =fck + 1.65s
f'ck=35+1.65*5= 43.25
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm^2.
Target mean strength = 43.25 N/mm^2
4. Selection of Water/Cement ratio
The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000.
Based on experience adopted water cement ratio is .44
0.44<0.45, hence ok
Water/Cement Ratio= 0.44
5. Selection of Water content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate - 186 litre (for 25 to 50 mm slump range)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it - 186+ (6/100)*186 = 197 litre.
Estimated water content for 100 mm slump (Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.) - 197 X 0.8 = 158 litre
Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content
Water required 158 litres
6. Calculation of Cement Required
Adopted w/c Ratio= 0.44
Cement Content= 158/0.44 = 359 KG/M^3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions 320KG/M^3
359 KG/M^3 > 320 KG/M^3 hence ok.
Cement required is 359 KG/M^3
7. Volume of Coarse and Fine aggregrate
From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 is 0.6
corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 - 0.632
For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate 0.632*0.9= 0.568
Volume of fine aggregate content= 1-0.598= 0.431
The Volume of Fine and coarse aggregrate are 0.431 and 0.568
8. Mix Calculations
Volume of concrete= 1 M^3
Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000 = (359/3.11) X (1/1000) =0.116M^3
Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 = (158/1) X (1/1000) = 0.158M^3
Volume of flyash = (Mass of flyash / Specific gravity of flyash )*1/1000 = (115/2.2) *1/1000 = 0.052M^3
Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000= (7.6/1.145) X (1/1000) =0.006 M^3
Volume of all in aggregate = [1-(0.116+0.158+0.052+0.006)] = 0.668M^3
Mass of coarse aggregate= Volume of all in aggregate x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000= 0.668x 0.568 x 2.8 x 1000 = 1062 KG/M^3
Mass of fine aggregate= Volume of all in aggregate x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000= 0.668x 0.431x 2.7x 1000 = 777 KG/M^3
9. Mix Proportions
Cement = 359 KG/M^3
Water = 158 L/M^3
Fine aggregate = 777 KG/M^3
Coarse aggregate = 1062 KG/M^3
Chemical admixture = 7.18 KG/M^3
Water cement ratio = 0.4
Mix proportion = 1:2.16:2.95
10. The slump shall be measured, 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 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 for field trials.
To Calculate the Concrete Mix Design for M50 grade concrete with out fly ash:
1 Consideration for Mix design
|
Grade designation |
M50 |
|
Type of cement |
OPC 43 Grade confirming to IS 8112 |
|
Maximum nominal size of aggregate |
20 mm |
|
Minimum cement content |
320 kg/m3 (Table 5 of IS 456:2000) |
|
Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000) |
|
Maximum cement content |
450 kg/m3 |
2 Required data
|
Cement used |
OPC 43 Grade conforming IS 8112 |
|
Specific gravity of cement |
3.11 |
|
Specific gravity of fly ash |
2.4 |
|
Specific gravity of coarse aggregate |
2.8 |
|
Specific gravity of fine aggregate |
2.7 |
|
Water absorption of coarse aggregate |
0.5% |
|
Water absorption of fine aggregate |
1.0% |
3. Target Strength of mix Proportion
f’ck =fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days, and
- s = standard deviation
f’ck =fck + 1.65s
f'ck=50+1.65*5= 58.25
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm^2.
Target mean strength = 58.25 N/mm^2
4. Selection of Water/Cement ratio
The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000.
Based on experience adopted water cement ratio is .44
0.44<0.45, hence ok
Water/Cement Ratio= 0.44
5. Selection of Water content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate - 186 litre (for 25 to 50 mm slump range)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it - 186+ (6/100)*186 = 197 litre.
Estimated water content for 100 mm slump (Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.) - 197 X 0.8 = 158 litre
Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content
Water required 158 litres
6. Calculation of Cement Required
Adopted w/c Ratio= 0.44
Cement Content= 158/0.44 = 359 KG/M^3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions 320KG/M^3
359 KG/M^3 > 320 KG/M^3 hence ok.
Cement required is 359 KG/M^3
7. Volume of Coarse and Fine aggregrate
From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 is 0.6
corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 - 0.632
For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate 0.632*0.9= 0.568
Volume of fine aggregate content= 1-0.598= 0.431
The Volume of Fine and coarse aggregrate are 0.431 and 0.568
8. Mix Calculations
Volume of concrete= 1 M^3
Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000 = (359/3.11) X (1/1000) =0.116M^3
Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 = (158/1) X (1/1000) = 0.158M^3
Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000= (7.6/1.145) X (1/1000) =0.006 M^3
Volume of all in aggregate = [1-(0.116+0.158+0.006)] = 0.72M^3
Mass of coarse aggregate= Volume of all in aggregate x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000= 0.72x 0.568 x 2.8 x 1000 = 1145 KG/M^3
Mass of fine aggregate= Volume of all in aggregate x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000= 0.72x 0.431x 2.7x 1000 = 838 KG/M^3
9. Mix Proportions
Cement = 359 KG/M^3
Water = 158 L/M^3
Fine aggregate = 838 KG/M^3
Coarse aggregate = 1145 KG/M^3
Chemical admixture = 7.18 KG/M^3
Water cement ratio = 0.44
Mix proportion = 1:2.33:3.20
10. The slump shall be measured, 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 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 for field trials.
Result
Mix Proportion by weight of M35 grade of concrete with fly ash is 1:2.16:2.95 and its water-cement ratio was found to be 0.44.
Mix Proportion by weight of M50 grade of concrete without fly ash is 1:2.33:3.20 and its water-cement ratio was found to be 0.44.