Project on Concrete Mix Design for various grades of Concrete
design mix for M35 grade with fly ash
- Cement used=OPC 43 grade
- Grade of concrete = M35
- Maximum nominal size of aggregate = 20mm
- Minimum cement content = 320 kg/m3 (from table 5 IS 456 2000 according to exposure condition)
- Maximum w/c ratio = 0.45(from table 5 of IS 456 2000 according to exposure condition)
- Workability = 100 mm (slump value for pumpable concrete)
- Exposure condition = severe
- Degree of supervision = good
- Type of aggregate = crushed angular aggregate
- Maximum cement content = 450 kg/m3
- Chemical admixture used = super plasticizer
- Specific gravity of cement=3.15
- Specific gravity of fly ash=2.2
- Specific gravity of coarse aggregate=2.74
- Specific gravity of fine aggregate=2.74
- Water absorption
Coarse aggregate=0.5%
Fine aggregate=1.0%
- Sieve analysis:
Coarse aggregate table 2 is IS 383
Fine aggregate = confirming to grading zone 1 of table 4 IS 383 confirming to grading zone 1
1.Target mean strength:
F’ck = fck + 1.65S
where,
F’ck = target average strength @ 28 days
fck = characteristics compressive strength @ 28 days
S = standard deviation, S = 5.0N/mm2 from table 1 of IS 10262:2000
Target strength = 35+1.65*5 = 43.25N/mm2
2.Selection of water cement ratio:
From table 5 of IS 456 maximum water cement ratio for severe exposed condition = 0.45
Based on experience, adopt water cement ratio = 0.40
0.40< 0.45 hence o.k
3.Selection of water content:
From table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25-50 mm slump)
Estimated water content for 100 mm slump = 186+6/100*186
= 197 lit
As super plasticizer is used, the water content can be reduced to 30%
Based on trials water content reduction is 29% is achieved with plasticizer
197*0.7=140 litres.
4.Calculation of cement
Water cement ratio = 0.40
Cementitious material (cement + fly ash) content = 140/0.40 = 350 kg/m3
From table 5 of IS 456 minimum cement content for severe exposure conditions = 320kg/m3
350>320 kg/m3 hence ok.
Now, to proportion a mix containing fly ash the following steps are suggested.
- The percentage of fly ash needs to be decided based on project requirements and quality of materials.
- In some cases, increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial ( this example is with increase of 10% cementitious material content.
Cementitious materials content 350*1.10 = 385 kg/m3
Water content = 140 litres
So water cement ratio = 140/385 = 0.364
fly ash @ 30% total cementitious material content = 385* 30%
= 115 kg/m3
Cement = 385- 115 = 270 kg/m3
Saving of cement while using fly ash = 350-270 = 80 kg/m3
5.Proportion of volume of coarse and fine aggregate
Properties of volume coarse aggregate and fine aggregate content from table 3 of IS 10262 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone 1) for w/c ratio = 0.6
In the present case the w/c ratio = 0.40
Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
So the corrected volume of coarse aggregate for w/c ratio of 0.40 = 0.62
For pumpable concrete these values are reduced by 10%
Volume of coarse aggregate = 0.62*0.9 = 0.56
Volume of fine aggregate = 1-0.56 = 0.44
6.Mix calculation:
The mix calculation per unit volume of concrete shall be as follows:
a] Volume of concrete = 1m3
b]Volume of cement= (mass of cement/sp.gravity of cement)*(1/1000)
= (270/3.15)*(1/1000)=0.086 m3
c]Volume of fly ash = (mass of fly ash/sp.gravity of fly ash)*(1/1000) = (115/2.2)*(1/1000) = 0.052 m3
d]Volume of water = (mass of water/sp.gravity of water)*(1/1000)
= (140/1)*(1/1000)= 0.140 m3
e]Volume of chemical admixture = 0.006 m3
f]Volume of all in aggregate = 1-[0.086+0.052+0.140+0.006] = 0.716 m3
Mass of coarse aggregate = f*volume of C.A*sp.gravity of C.A*1000
= 0.716*0.56*2.74*1000
= 1098kg/m3
Mass of fine aggregate = f*volume of F.A*sp.gravity of F.A*1000
= 0.716*0.44*2.74*1000
= 863kg/m3
7.Mix proportion for trial 1
Cement = 270kg/m3
Silica fume = 115kg/m3
Water = 140kg/m3
Fine aggregate = 863kg/m3
Coarse aggregate = 1098kg/m3
Chemical admixture= 7kg/m3
Water-cement ratio = 0.364kg/m3
The trial mix ratio is = 1: 2.24: 2.85
design mix for M50 grade without fly ash
- Cement used=OPC 43 grade
- Grade of concrete = M50
- Maximum nominal size of aggregate = 20mm
- Minimum cement content = 360 kg/m3 (from table 5 IS 456 2000 according to exposure condition)
- Maximum w/c ratio = 0.40(from table 5 of IS 456 2000 according to exposure condition)
- Workability = 100 mm (slump value for pumpable concrete)
- Exposure condition = extreme
- Degree of supervision = good
- Type of aggregate = crushed angular aggregate
- Maximum cement content = 450 kg/m3
- Chemical admixture used = super plasticizer
- Specific gravity of cement=3.15
- Specific gravity of fly ash=2.2
- Specific gravity of coarse aggregate=2.74
- Specific gravity of fine aggregate=2.74
- Water absorption
Coarse aggregate=0.5%
Fine aggregate=1.0%
- Sieve analysis:
Coarse aggregate table 2 is IS 383
Fine aggregate = confirming to grading zone 1 of table 4 IS 383 confirming to grading zone 1
1.Target mean strength:
F’ck = fck + 1.65S
where,
F’ck = target average strength @ 28 days
fck = characteristics compressive strength @ 28 days
S = standard deviation, S = 5.0N/mm2 from table 1 of IS 10262:2000
Target strength = 50+1.65*5 = 58.25N/mm2
2.Selection of water cement ratio:
From table 5 of IS 456 maximum water cement ratio for extreme exposed condition = 0.40
Based on experience, adopt water cement ratio = 0.40
3.Selection of water content:
From table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25-50 mm slump)
Estimated water content for 100 mm slump = 186+6/100*186
= 197 lit
As super plasticizer is used, the water content can be reduced to 30%
Based on trials water content reduction is 29% is achieved with plasticizer
197*0.7=140 litres.
4.Calculation of cement
Water cement ratio = 0.40
Cementitious material (cement + fly ash) content = 140/0.40 = 350 kg/m3
From table 5 of IS 456 minimum cement content for extreme exposure conditions = 360kg/m3
so, cement content = 360kg/m3
Water content = 140 litres
5.Proportion of volume of coarse and fine aggregate
Properties of volume coarse aggregate and fine aggregate content from table 3 of IS 10262 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone 1) for w/c ratio = 0.6
In the present case the w/c ratio = 0.40
Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
So the corrected volume of coarse aggregate for w/c ratio of 0.40 = 0.62
For pumpable concrete these values are reduced by 10%
Volume of coarse aggregate = 0.62*0.9 = 0.56
Volume of fine aggregate = 1-0.56 = 0.44
6.Mix calculation:
The mix calculation per unit volume of concrete shall be as follows:
a] Volume of concrete = 1m3
b]Volume of cement= (mass of cement/sp.gravity of cement)*(1/1000)
= (360/3.15)*(1/1000)=0.114 m3
c]Volume of water = (mass of water/sp.gravity of water)*(1/1000)
= (140/1)*(1/1000)= 0.140 m3
d]Volume of chemical admixture = 0.006 m3
e]Volume of all in aggregate = 1-[0.114+0.140+0.006] = 0.74 m3
Mass of coarse aggregate = e*volume of C.A*sp.gravity of C.A*1000
= 0.74*0.56*2.74*1000
= 1135kg/m3
Mass of fine aggregate = e*volume of F.A*sp.gravity of F.A*1000
= 0.74*0.44*2.74*1000
= 892kg/m3
7.Mix proportion for trial 1
Cement = 360kg/m3
Water = 140kg/m3
Fine aggregate = 892kg/m3
Coarse aggregate = 1135kg/m3
Chemical admixture= 7kg/m3
Water-cement ratio = 0.4kg/m3
The trial mix ratio is = 1: 2.47:3.15