Project on Concrete Mix Design for various grades of Concrete
1) Data required:
Grade designation: M35
Type of cement: OPC 43 grade conforming to IS 8112
Type of miniral admixture : Fly ash
Maximum nominal size of aggregate: 20mm
Maximum free water content ratio : 0.45
Exposure type: Severe
Minimum cement content: 320 kg/m^3
Workability: 75mm slump
Degree of supervision : Good
Method of concrete placing: pumping
Type of aggregate: Crushed angular
Maximum cement content: 450 kg/m^3
Chemical admixture : Super plasticizer
Water absorbtion for Coarse aggregate : 0.5 percent
Water absorbtion for Fine aggregate : 1 percent
Free (surface) moisture - nil
Specific gravity of cement: 3.15
Specific gravity of fine aggregate: 2.74
Specific gravity of coarse aggregate: 2.74
Coarse and fine aggregate: Grade 1
Target strength strength for mix proportioning :
f'ck = fck + 1.65s
s = 5 (From table 1 of IS 10262 2009)
f'ck = 35 + 1.65 x 5 = 43.25 N/mm^2
Selection of water-cement ratio
From table 5 of IS456 2000 for severe exposure,
maximun water cement = 0.45
Based on experience, adopt water cement ratio as 0.40
0.40 < 0.45 Hence OK
Selection of water content :
From table 2 of IS 10262 : 2009
maximum water content for 20mm aggregate = 186 L
Estimated water content for 75mm slump = 186 + 3/100 x 186 = 191 L
As superplasticizer is used,the water content can be reduced upto 30%,
191 x 0.71 = 135 L
Calculation of cement content : water cement ratio - 0.4
Cementious material (cement and fly ash) content = 135/0.4 = 337 kg/m^3
From table 5 of IS456 2000 Minimum cement for severe exposure condition = 320 kg/m^3
Now to proportion a mix containing fly ash the following steps are suggested :
a) The percentage of fly ash needs to be decided based on project requirement and quality of materials
b) In some case increase in cementitious material can be warranted
Cementitious material content = 337 x 1.10 = 337 kg/m^3
Water content = 140 kg/m^3
So, water cemeent ratio = 140/337 = 0.415
Fly ash @ 30% total cementitious = 337 x 30% = 101 kg/m^3
material content = 101 kg/m^3
Cement (opc) = 337 - 101 = 236 kg/m^3
Saving of cement while using fly ash = 337 - 236 = 101 kg/m^3
Fly ash being utilized = 101 kg/m^3
Proportion of volume of Coarse aggregate and fine aggregate content : from table 3 of Is10262
Volume of Coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) water cement = 0.6
In the present case the water cement ratio is 0.4
Volume of coarse aggregate = 0.62 x 0.9 = 0.56
Volume of fine aggregate = 1 - 0.56 = 0.44
Mix calculation :
a) Volume of concrete = 1m^3
b) Volume of cement = (Mass of cement/specific gravity)x(1/1000)
337/3.15 x 1/1000 = 0.106 m^3
c) Volume of fly ash = (mass of fly ash/specific gravity of fly ash) x (1/1000)
101/1 x 1/1000 = 0.101 m^3
d) Volume of water = (Mass of water/specific gravity)x(1/1000)
140/1 x 1/1000 = 0.14
e) Volume of aggregate (fine aggregarte and coarse aggregate) = a - (b+c+d)
[1 - (0.106 + 0.101 + 0.14)]
1 - 0.347 = 0.65 m^3
Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
0.65 x 0.56 x 2.74 x 1000 = 997 kg
Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000
0.65 x 0.44 x 2.74 x 1000 = 784 kg
Mix proportion :
Cement = 337 kg/m^3
Fly ash = 101 kg/m^3
Water content = 140 kg/m^3
Fine aggregate = 784 kg/m^3
Coarse aggregate = 997 kg/m^3
Water cement ratio = 0.415
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2)Data required :
Grade designation : M50 grade
Type of cement : OPC 53 grade
Maximum nominal size of aggregate: 20mm
Exposure type: Severe
Minimum cement content: 320 kg/m^3
Workability: 50mm slump
Method of concrete placing: pumping
Type of aggregate: Crushed angular
Maximum cement content: 450 kg/m^3
Chemical admixture : Super plasticizer
Specific gravity of cement: 3.15
Specific gravity of fine aggregate: 2.56
Specific gravity of coarse aggregate: 2.74
Target strength:
f'ck = fck + 1.65s
s = 5 (From table 1 of IS 10262 2009)
f'ck = 50 + (1.65 x 5) = 58.25 N/mm^2
Selection of water cement ratio:
For severe exposure condition maximum w/c = 0.45 (From table 5 IS 456:2000)
Selection of water content:
Maximum water content = 186lit
Super plasticizer reduces 29% of water content.
New water content = (71/100)*186 = 134.19
Calculating cement content:
Water/cement = 0.4
cement = 134.19/0.4 = 335.47 > 320kg/m^3 Hence OK
Cement content = 335 kg/m^3
Proportioning of volume of coarse and fine aggregate:
Volume of coarse aggregate for w/c 0.3 = 0.38 =x
0.05 = 0.01
0.14 = x
x = 0.01 x 0.14/0.05 = 0.028
Volume of coarse aggregate = 0.6+0.028 = 0.628 x 0.9 = 0.56 (Since the concrete is pumpable the volume of coarse aggregate is reduced by 10%)
Volume of fine aggregate = 1 - 0.56 = 0.44
Volume of coarse aggregate = 0.56
Volume of fine aggregate = 0.44
Mix calculations:
a. Volume of concrete = 1m^3
b. Volume of cement = (Mass of cement/specific gravity)x(1/1000)
335/3.15 x 1/1000 = 0.106 m^3
c. Volume of water = (Mass of water/specific gravity)x(1/1000)
134.19/1 x 1/1000 = 0.134 m^3
d. Super plasticizer is upto 2% of mass of total cementitious content
6.7/1.15 c 1/1000 = 0.006 m^3
e. Volume of aggregate = a - (b+c+d) = 1-(0.106+0.134+0.0060 = 0.754 m^3
f. Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate
0.754 x 0.56 x 2.73 x 1000 = 1152kg
g. Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate
0.754 x 0.44 x 2.61 x 1000 = 866kg
Mix proportion :
Cement = 335
Fine aggregate = 866
Coarse aggregate = 1152
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