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 to find the mix 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. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage.
EQUATIONS USED:
1) 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 Calculations
- Volume of concrete
- Volume of cement = [Mass of cement] / [Specific Gravity of Cement] * 1/1000
- Volume of water = [Mass of water] / [Specific Gravity of water] * 1/1000 •
- Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] * 1/1000
- Volume of all in aggregate =[a-(b+c+d)]
- Mass of coarse aggregate= e * Volume of Coarse Aggregate * Specific Gravity of Fine Aggregate * 1000
- Mass of fine aggregate= e * Volume of Fine Aggregate * Specific Gravity of Fine Aggregate * 1000
PART 1:To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:
M35 grade concrete with Fly ash
STEP 1: Stipulations for Concrete design mix
| Grade Used | M35 |
| Cement type | OPC 43 |
| Type of admixture | Flyash |
| Max nominal size of aggregate | 20 mm |
| Minimum cement content | 320Kg/m^3 |
| Max w/c ratio | 0.45 |
| Workability | 100 mm (Slump value) |
| Maximum cement content | 450Kg/m^3 |
| Exposure condition | extreme |
Step 2:Target Strength for mix proportioning
f'ck = fck + 1.65S
Where
- f'ck = target average compressive strength at 28 days
- fck = Characteristics compressive strength at 28 days
- S = standard deviation
35 + 1.65 * 5 = 43.25 N/mm^2
Target Mean Strength = 43.25 N/mm^2
Step 3: Selection of water cement ratio
Maximum w/c ratio = 0.45
but adopted w/c ratio is 0.44<0.45
Adopted W/C ratio = 0.44
Step 4: Selection of water content
Maximum water content for 20 mm aggregate = 186 litre (table 2 of IS 10262:2009)
Clause 4.2 suggests increasing of 3% of water content for every eaxtra 25mm slump from 50mm slump.so a 6% is to be added to it
186 + (6/100)*186 = 197 litre
If super plasticizer is used , the water content can be reduced upto 20%, So the arrived water content is
197*0.8 = 158 litre
Water Required 158 Litres
Step 5: Calculation of cement and fly ash required
Adopted w/c ratio = 0.44
Total cement + Fly ash requirement = 158/0.44 = 359kg/m^3
It is also known as cementitious
Total cementitious requirement = 359*1.10 = 395 kg (increasing cementitious content by 10%)
New water cement ratio = 158/395 = 0.4
Fly ash is taken as 30% of the total cementitious content
395*0.3 = 118.5 kg/m^3
Cement required 395 - 118 = 277 kg/m^3
Cementitious material, cement and fly ash required is 395 kg/m^3 and 118 kg/m^3 and the new water -cement ratio is 0.4 respectively
Step 6: Volume of concrete aggregate and fine aggregate content
Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone ll) for water-cement ratio of 0.50 is 0.62
Volume of coarse aggregate for the water-cement ratio of 0.44 is 0.632
For pumpable concrete these values should be reduced upto 10%. Therefore , volume of coarse aggregate
0.632*0.9 = 0.568
Volume of fine aggregate content 1-0.568 = 0.432
Volume of fine aggregate and coarse aggregate is 0.432 and 0.568
Step 7: Mix calculations as per unit volume of concrete are as follows
| a.Volume of concrete | 1m^3 |
| b.Volume of cement= [Mass of cement]/[specific gravityof cement]*1/1000 | (277/3.15)*(1/1000) = 0.087m^3 |
| c.Volume of fly ash= [Mass of fly ash]/[specific gravity of fly ash]*1/1000 | 0.053 |
| d.Volume of water=[Mass of water]/[specific gravity of water]*1/1000 | 0.158m^3 |
| e.Volume of chemical admixture= [Mass of admixture]/[specific gravity of admixture]*1/1000 | 0.006m^3 |
| f.Volume of all in aggregate = [a-(b+c+d+e)] | 0.693m^3 |
| g.Mass of coarse aggregate= f*Volume of coarse aggregate*specific gravityof fine aggregate*1000 | 1077kg/m^3 |
| h.Mass of fine aggregate = f*Volume of fine aggregate*specific gravity of fine aggregate*1000 | 822 kg/m^3 |
Step 8: Mix Proportions
| Cement | 277 kg/m^3 |
| Fly ash | 118 kg/m^3 |
| Water | 158 l/m^3 |
| F.A. | 822 kg/m^3 |
| C.A. | 1077 kg/m^3 |
| Chemical admixture | 7.18 kg/m^3 |
Mix Proportion By Weight = 1:2.08:2.72
Part 2: Calculate the concrete mix design for M50 grade concrete without fly ash
M50 Grade concrete without fly ash
STEP 1: Stipulations for Concrete design mix
| Grade Used | M50 |
| Cement type | OPC 53 |
| Max nominal size of aggregate | 20 mm |
| Minimum cement content | 320Kg/m^3 |
| Max w/c ratio | 0.45 |
| Workability | 100 mm (Slump value) |
| Maximum cement content | 450Kg/m^3 |
| Exposure condition | Severe (for reinforced concrete) |
| Method of concrete placing | pumping |
Step 2:Target Strength for mix proportioning
f'ck = fck + 1.65S
Where
- f'ck = target average compressive strength at 28 days
- fck = Characteristics compressive strength at 28 days
- S = standard deviation
50 + 1.65 * 5 = 58.25 N/mm^2
Target Mean Strength = 58.25 N/mm^2
Step 3: Selection of water cement ratio
Maximum w/c ratio = 0.45
but adopted w/c ratio is 0.44<0.45
Adopted W/C ratio = 0.44
Step 4: Selection of water content
Maximum water content for 20 mm aggregate = 186 litre (table 2 of IS 10262:2009)
Clause 4.2 suggests increasing of 3% of water content for every eaxtra 25mm slump from 50mm slump.so a 6% is to be added to it
186 + (6/100)*186 = 197 litre
If super plasticizer is used , the water content can be reduced upto 20%, So the arrived water content is
197*0.8 = 158 litre
Water Required 158 Litres
Step 5: Calculation of cement Required
| Adopted w/c ratio | 0.44 |
| Cement Content | 158/0.44 = 359 kg/m^3 |
| Minimum cement content for severe exposure condition |
320 kg/m^3 |
359 kg/m^3 > 320kg/m^3 hence ok.
Cement required is 359 kg/m^3
Step 6: Volume of coarse aggregate and fine aggregate content
Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone ll) for water-cement ratio of 0.50 is 0.62
Volume of coarse aggregate for the water-cement ratio of 0.44 is 0.632
For pumpable concrete these values should be reduced upto 10%. Therefore , volume of coarse aggregate
0.632*0.9 = 0.568
Volume of fine aggregate content 1-0.568 = 0.432
Volume of fine aggregate and coarse aggregate is 0.432 and 0.568
Step 7: Mix calculations as per unit volume of concrete are as follows
| a.Volume of concrete | 1m^3 |
| b.Volume of cement= [Mass of cement]/[specific gravityof cement]*1/1000 | (277/3.15)*(1/1000) = 0.087m^3 |
| c.Volume of water=[Mass of water]/[specific gravity of water]*1/1000 | 0.158m^3 |
| d.Volume of chemical admixture= [Mass of admixture]/[specific gravity of admixture]*1/1000 | 0.006m^3 |
| e.Volume of all in aggregate = [a-(b+c+d)] | 0.722m^3 |
| f.Mass of coarse aggregate= f*Volume of coarse aggregate*specific gravityof fine aggregate*1000 | 1123kg/m^3 |
| g.Mass of fine aggregate = f*Volume of fine aggregate*specific gravity of fine aggregate*1000 | 821 kg/m^3 |
Step 8: Mix Proportions
| Cement | 359 kg/m^3 |
| Water | 158 l/m^3 |
| F.A. | 821 kg/m^3 |
| C.A. | 1123 kg/m^3 |
| Chemical admixture | 7.18 kg/m^3 |
Water cement Ratio = 0.44
Mix Proportion By Weight = 1:2.28:3.12
Results:
Mix proportion by weight of M35 grade of concrete with fly ash is 1:2.08:2.72 and its water content was found to be 0.4
Mix proportion by weight of M50 grade concrete without fly ash is 1:2.28:3.12 and its water-cement ratio was found to be 0.44