Project on Concrete Mix Design for various grades of Concrete
1. Concrete mix design for M35 grade concrete with fly ash:
- Target strength for the mix proportion:
Target strength Fck= fck+ 1.65 s
= 35+ 1.65* 5 (As per table 2 of IS 456 2000)
=43.25 N/mm2
- calculation of the water-cement ratio
For very severe exposure W/C as per table 5 of IS 456:2000 is 0.45.
Let's assume 0.40.
- Water content:
For 20mm maximum nominal size coarse aggregate, 186 kg of water is taken for the slump value of 25-50 mm. The slump value is 100 mm.
so the water content is increased by 3% for every 25mm increase in slump value.
so it will be 197 litres.
so the water content reduction of 29% can be achieved with plasticizers.
197* 0.71 = 140 litres.
- calculation of cement content
The water-cement ratio is 0.40 and the water content is 140 litres. cement content = 140/0.4= 350 kg/m3.
350 kg/m3 is greater than 340kg/m3. hence 350 is acceptable.
- calculation of cement and fly ash content:
the calculation of fly ash as per project requirements and the increase in cementitious materials are the other factors to be considered.
Let us assume an increase in 10% of the cementitious material content.
Thus the cement content becomes 385 kg/m3.
Also, the water-cement ratio varies = 140/ 385= 0.364
Fly ash @ 30% of the total cementious content gives the value of 115 kg/m3.
Thus the cement content is 385- 115 = 270 kg/m3.
- The proportion of volume of coarse aggregate and fine aggregate:
from table 3 of IS 10262:2009 for 20 mm size aggregate 0.60 volume of coarse aggregate is taken which belongs to zone 1.
But the water-cement ratio we have calculated is 0.40 which is lower by 0.10 when compared to 0.5.
thus the volume of coarse aggregate needs to be increased by 0.02. for every 0.05 variation in the water-cement ratio, 0.01 percent is raised. Thus the volume of coarse aggregate for the present condition is 0.62.
for pumpable concrete, this value is reduced by 10%.
thus the volume of coarse aggregate is taken as 0.56(0.62*90/100)
since total aggregate = (volume of coarse + fine aggregate)
volume of fine aggregate = 1 - 0.56 =0.44
- Mix calculation
Volume of concrete = 1m3
The volume of cement = (Mass of cement / specific gravity of cement) * (1/1000)
= 270 / 3.15 *1/1000
=0.086 m3
Volume of Fly ash = (Mass of fly ash / specific gravity of fly ash) * (1/1000)
= 115/2.2 *1 /1000
=0.052 m3
Volume of water = (Mass of water / specific gravity of Water) * (1/1000)
= (140/1)* (1/1000) =0.14 m3
chemical admixture = (Mass of chemical admixture / specific gravity of chemical admixture) * (1/1000)
= (7.6/1.45) *1/1000
=0.006 m3
Volume of coarse and fine aggregate is 1 - (0.086+ 0.052 + 0.140 + 0.006) = 0.716 m3
Mass of coarse aggregate = (Volume of total aggregate * volume of coarse aggregate specific gravity of coarse aggregate * 1000)
= (0.716*0.56*2.74*1000)
= 1098 kg/m3
Mass of fine aggregate = (Volume of total aggregate * volume of fine aggregate specific gravity of fine aggregate * 1000)
= (0.716*0.44*2.74*1000)
= 863 kg/m3.
- Mix proportion
cement = 270 kg / m3
Fly ash = 115 kg /m3
water = 140 kg /m3
fine aggregate = 863 kg/ m3
coarse aggregate = 1098 kg/ m3
chemical admixture = 7 kg/ m3
W/C ratio = 0.364
Final mix ratio = 1:2.2:2.8
2. Concrete mix design for M50 grade concrete without fly ash:
- Target strength for the mix proportion:
target strength Fck= fck+ 1.65 s
= 50+ 1.65* 5 (As per table 2 of IS 456 2000)
=58.25 N/mm2
- calculation of the water-cement ratio
For very severe exposure, W/C as per table 5 of IS 456:2000 is 0.45.
Let's assume 0.45.
- Water content:
For 20mm maximum nominal size coarse aggregate, 186 kg of water is taken for the slump value of 25-50 mm. The slump value is 100 mm.
so the water content is increased by 3% for every 25mm increase in slump value.
so it will be 197 litres.
so the water content reduction of 29% can be achieved with plasticizers.
197* 0.71 = 140 litres.
- calculation of cement content
The water-cement ratio is 0.40 and the water content is 140 litres. cement content = 140/0.45= 311 kg/m3.
311 kg/m3 is less than 340kg/m3. hence 340 is acceptable.
- The proportion of volume of coarse aggregate and fine aggregate:
from table 3 of IS 10262:2009 for 20 mm size aggregate 0.60 volume of coarse aggregate is taken which belongs to zone 1.
But the water-cement ratio we have calculated is 0.45 which is lower by 0.10 when compared to 0.5.
thus the volume of coarse aggregate needs to be increased by 0.01. for every 0.05 variation in the water-cement ratio, 0.01 percent is raised. Thus the volume of coarse aggregate for the present condition is 0.62.
for pumpable concrete, this value is reduced by 10%.
thus the volume of coarse aggregate is taken as 0.56(0.61*90/100)
since total aggregate = (volume of coarse + fine aggregate)
volume of fine aggregate = 1 - 0.54 =0.46
- Mix calculation
Volume of concrete = 1m3
The volume of cement = (Mass of cement / specific gravity of cement) * (1/1000)
= 340 / 3.15 *1/1000
=0.107 m3
Volume of water = (Mass of water / specific gravity of Water) * (1/1000)
= (140/1)* (1/1000) =0.14 m3
volume of chemical admixture = (Mass of chemical admixture / specific gravity of chemical admixture) * (1/1000)
= (7/1.45) *1/1000
=0.004 m3
Volume of coarse and fine aggregate is 1 - (0.107+ 0.14 + 0.004) = 0.749 m3
Mass of coarse aggregate = (Volume of total aggregate * volume of coarse aggregate specific gravity of coarse aggregate * 1000)
= (0.749*0.54*2.74*1000)
= 1108 kg/m3
Mass of fine aggregate = (Volume of total aggregate * volume of fine aggregate specific gravity of fine aggregate * 1000)
= (0.716*0.46*2.74*1000)
= 902 kg/m3.
- Mix proportion
cement = 340 kg / m3
water = 140 kg /m3
fine aggregate = 902 kg/ m3
coarse aggregate = 1108 kg/ m3
chemical admixture = 7 kg/ m3
W/C ratio = 0.364
Final mix ratio = 1:2.6:3.2