Project on Concrete Mix Design for various grades of Concrete
2:To Calculate the Concrete Mix Design for M50 grade concrete without fly ash:
A) M35 grade concrete with Fly ash.
STEP 1: Stipulations for Concrete design mix
Grade designation: M35
Type of cement: OPC 43 Grade confirming to
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- Exposure condition)
Maximum water-cement ratio: 0.45
Workability : 100 mm
Maximum cement content: 450 kg/m3
Chemical admixture type : Super Plasticizer
STEP 2: TEST DATA FOR MATERIALS
Cement used: OPC 43 Grade conforming
Specific gravity of cement : 3.15
Specific gravity of fly ash : 2.2
Chemical admixture: Super Plasticizer
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Water absorption of coarse aggregate: 0.5%
Water absorption of fine aggregate : 1%
Sieve analysis: Coarse aggregate
STEP 3: TARGET STRENGTH FOR MIX Proportioning
f’ck =fck + 1.65s
s = standard deviation
s = 5 N/mm2.
= 35 + 1.65 x 5 = 43.25 N/mm
Target mean strength = 43.25 N/mm2
STEP 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
Maximum W/C ratio =0.45
Based on experience adopted water cement ratio is .44
0.44<0.45, hence ok
Adopted W/C ratio=0.44
STEP 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
Estimated water content for 100 mm slump
186+ (6/100)*186 = 197 litre.
Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content
197*0.8 = 158 litre
Water required 158 litres
B) M50 grade concrete without Fly ash
STEP 1: Stipulations for Concrete design mix
Grade designation: M50
Type of cement : OPC 53 Grade
Maximum nominal size of aggregate: 20mm
Minimum cement content :. 320 kg/m3
Maximum water-cement ratio: 0.45
Workability:100 mm
Maximum cement content :. 450 kg/m3
Chemical admixture type: Super Plasticizer
STEP 2: TEST DATA FOR MATERIALS
Cement used : OPC 53 Grade
Specific gravity of cement: 3.15
Specific gravity of coarse aggregate: 2.74
Specific gravity of fine aggregate: 2.64
Water absorption of coarse aggregate: 0.5%
Water absorption of fine aggregate: 1.0%
STEP 3: TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65s
Where
·standarard Deviation, s = 5 N/mm2
50 + 1.65 x 5 = 58.25 N/mm2
Target mean strength = 58.25 N/mm2
STEP 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 for severe exposure.
Maximum W/C ratio =0.45
Based on experience adopted water cement ratio is .
0.44<0.45, hence ok
Adopted W/C ratio=0.44
STEP 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)
50mm slump. So a 6% is to be added to it
Estimated water content for 100 mm slump
186+ (6/100)*186 = 197 litre.
Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content
197 X 0.8 = 158 litre
Water required: 158 litres
EP 6: CALCULATION OF CEMENT REQUIRED
Adopted w/c Ratio: 0.44
Cement Content :. 158/0.44 = 359 kg/m3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure condition
320kg/m3
359 kg/m3 > 320 kg/m3 hence ok.
Cement required is 359 kg/m3
STEP 7: VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 in
0.62.
In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).
Therefore, 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 x 0.9 =0.568.
Volume of fine aggregate content
1 – 0.576 =0.431
Volume of fine aggregate and coarse aggregate is 0.431 and .568 respectively
STEP 8: MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete : 1m3
b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000
(359/3.15) X (1/1000) =0.114m3
c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000
(158/1) X (1/1000) = 0.158m3
d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
(7.6/1.145) X (1/1000) =0.006 m3
e) Volume of all in aggregate = [a-(b+c+d)]
[1-(0.114+0.158+0.006)] = 0.722m3
f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
0.722x 0.431x 2.64 x 1000 = 821 kg/m3
STEP 9: MIX PROPORTIONS
Cement :. 359 kg/m3
Water: 158 l/m3
Fine aggregate :. 821 kg/m3
Coarse aggregate 20mm : 1123 kg/m3
Chemical admixture :. 7.18kg/m2
Water-cement ratio : 0.44
Mix Proportion By weight : 1:2.28:3.1
RESULTS:
Mix Proportion by weight of M35 grade of concrete with fly ash is 1:2.08:2.72 and its water-cement ratio was found to be 0.4.
Mix Proportion by weight of M50 grade of concrete without fly ash is 1:2.28:3.12 and its water-cement ratio was found to be 0.44.