Project on Concrete Mix Design for various grades of Concrete
Concrete mix design for M35 grade concrete with flyash
Target mean strength for mix proportions:
f'ck=fck+1.65*S
=35+1.65*5=43.25N/mm^2
Selection of water cement ratio:
From table 5 of IS 456:2000 for severe condition
maximum water cement ratio =0.45
Based on experience adopted water cement ratio is 0.40
0.40<0.45,hence ok
Selection of water content:
from table 2 of IS 10262:2009,
max water content for 20mm aggregate=186 litre (For 25mm to 50 mm slump range)
Estimated water content for 100 mm slump =186+6/100*186=197 litre.
As flyash is using,the water content can be reduced upto 20% and above
Based on trials water content reduction of 29% is achieved with flyash
Hence the arrived water content =197*0.71=140 litre
Calculation of cement content:
water cement ratio=0.4
cement content =140/0.4=350 kg/m^3
From table 5 of IS 456 minimum cement content for severe exposure condition 320kg/m^3
350kg/m^3>320kg/m^3,hence ok.
Now to proportion a mix containing flyash the following steps are suggested:
a) The percentage of flyash needs to be decided based on project requirement and quality of materials.
b) In some cases icrease in cementitious material can be warranted.
Cementitious material content=350*1.10=385 kg/m^3
water content =140kg/m^3
so,w/c ratio =140/385=.364
Flyash @ 30 % total cementitious materail content=385*30%=115kg/m^3
cement =385-115 =270 kg/m^3
saving of cement while using flyash 350-270=80kg/m^3
Flyash being utilized =115 kg/m^3
Proportion of volume of CA & FA
From table 3 of IS 10262:2009,volume of CA corresponding to 20 mm size aggreate FA for w/c ratio of 0.5=0.6
In the present case the w/c is=0.4
Therefore the volume of CA needs to be increased to decrease the FA content.
Corrected volume of CA for the w/c ratio of 0.4=0.62
therefore volume of CA =0.62*0.9=0.56
volume of FA content =1-0.56=0.44
Mix calculations
The mix calculation per unit volume of concrete shall be as follows:
Volume of concrete =1m^3
Volume of cement=Mass of cement/sp. gr. of cement*1/1000=270/3.15*1/1000=0.085m^3
Volume of water=mass of water/sp gr of water*1/1000=140/1*1/1000=0.140M^3
Volume of chemical admixture=7/1.145*1/1000=0.006m^3
Volume of aggregate=1-(0.085+0.140+0.006)=0.769m^3
Mass of coarse aggregate=0.769*0.56*2.74*1000=1140kg/m^3
Mass of fine aggregate=0.769*0.44*2.74*1000=896kg/m^3
Mix proportions for trial no
cement=270kg/m^3
Flyash=115kg/m^3
water=140kg/m^3
FA=896kg/m^3
CA=1149kg/m^3
w/c ratio=0.364
Concrete mix design for M50 grade concrete without flyash
Target strength for mix proportions:
f'ck=fck+1.65*S=50+1.65*5=58.25N/mm^2
selection of water cement ratio:
From table 5 of IS 456:2000 for severe exposure,
max water cement ratio=0.45
Based on experience,adopted w/c ratio is 0.40.
0.40<0.45,hence ok.
Selection of water content:
from table 2 of IS 10262:2009,
max water content for 20 mm aggregete=186 litre
As superplasticizer is used,the water content can be reduced upto 20% and above
Baseed on trials water content reduction of 29% is achieved with plasticizer
Hence the arrived water content=186*0.71=132litre
Calculation of cement content:
w/c ratio=0.4
cement content=132/0.4=330 kg/m^3
from table 5 of IS 456:2000 min cement content for severe exposure condition=320kg/m^3
330kg/m^3>320kg/m^3,Hence ok.
Proportion of volume of CA & FA
From table 3 of IS 10262:2009,volume of CA corresponding to 20mm size aggregate & FA for w/c artio of 0.5=0.6
In the preseent case the w/c ratio is =0.4
Therefore the volume of CA needs to be increased to decrease the FA content.
As w/c ratio is lower by0.10,the proportion of volume of CA is increased by 0.02
Therefore corrected volume of CA for the w/c ratio of 0.40 is 0.62.
volume of FA content=1-0.62=0.38
Mix calculations:
The mix calculation per unit volume of concrete shall be as follows:
Volume of concrete=1m^3
Volume of cement=330/3.15*1/1000=0.105m^3
Volume of water=132/1*1/1000=0.132m^3
Volume of chemical admixture=7/1.145*1/1000=0.006m^3
Volume of aggregate=1-(0.105+0.132+0.006)=0.757m^3
Mass of CA=0.757*0.62*2.74*1000=1285kg/m^3
Mass of FA=0.757*0.38*2.74*1000=788.2kg/m^3
Mix proportions for trial number
cement=330kg/m^3
water=132kg/m^3
FA=788.2kg/m^3
CA=1285kg/m^3
chemical admixture=7kg/m^3
w/c ratio =0.4
Trial mix ratio=1:2.39:3.89