Project on Concrete Mix Design for various grades of Concrete
1.Aim and introduction:
To calculate a mix design for M35 grade concrete with fly ash.
Procedure:
Grade designation:M35
Type of cement:OPC53
Maximum nominal size of aggregate:20mm
Exposure type:Severe Exposure
Minimum cement content:340kg
Workability:100mm slump
Method of concrete placing:Pumping
Types of aggregate:Crushed angular
Maximum cement content:450kg
Chemical admixture:Superplasticizer
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
Mineral admixture:Fly ash
Specific gravity of flyash:2.2
Target strength:
f'ck=fck+1.65S
s=standard deviation (S=5, from table 1 of IS10262:2009)
=35+1.65*5
f'ck=43.25N/mm^2
Selection of water cement ratio:
From table 5 IS456:2000 exposed for severe condition ,maximum water-cement ratio is 0.45
Selection of water content:
From table 2 of IS456:2000
Maximum water content for 20mm aggregate is=186L
for 25-50mm above slump for every 25mm 3% is increased
Water content=186+(6/100*186)=197.16L
Superplasticizer is used water content can be reduced 20%
=197.16-(29/100*197.16)=139.98~140L
Calculation of cement content:
Water cement ratio 0.40
Cementitious material(cement+fly ash)content=140/0.40=350kg
350kg>340kg Hence ok.
Fly ash is used therefore cementitious material is increased by 10%
Cementitious material content =350*1.1=385kg/m^3
Water content 140L
Water-cement ratio=140/385=0.36
Fly ash @30% total cementitious material content=385*30%=115.5kg/m^3~115kg/m^3
Cement content=385-115=270kg/m^3
Saving cement by using fly ash=350-270=80kg/m^3
Fly ash utilized=115kg/m^3
Volume of coarse aggregate and fine aggregate :
From table 3 of IS10262 20mm size aggregateand fine aggregate for water-cement ratio is 0.4=0.62
we have water-cement ratio0.4
volume of coarse aggregate increases by decresing fine aggregate
As water-cement ratio is lower by 0.10,the proportion of the volume of coarse aggregate is increased by0.02
the corrected proportion of volume of Coarse aggregate the water-cement ratio of 0.4=0.62
For pumpable concrete it can be reduced by 10%
volume of coarse aggregate =0.62*0.9=0.56
volume of fine aggregate=1-0.56=0.44
Mix calculations:
volume of concrete=1m^3
volume of cement=270/3.15*1/1000=0.086m^3
volume of fly ash=115/2.2*1/1000=0.052m^3
volume of water=140/1*1/1000=0.140m^3
volume of chemical admixture=7.6/1.145*1/1000=0.006m^3
volume of aggregate=[a-(b+c+d+e)]=[1-(0.086+0.052+0.140+0.006)]=1-0.284=0.716m^3
Mass of coarse aggregate=f*volume of CA*Specific gravity of CA*1000=0.716*0.56*2.74*1000=1098.63kg/m^3
Mass of fine aggregate=f*volume of FA*Specific gravity of FA*1000=0.716*0.44*2.74*1000=863.20kg/m^3
Mix proportioning:
Cement=270kg/m^3
Fly ash=115kg/m^3
Water=140kg/m^3
Fine aggregate=863kg/m^3
Coarse aggregate=1098kg/m^3
Chemical admixture=7.16kg/m^3
water-cement ratio=0.40
Trial mix ratio=1:2.24:2.85.
2.Aim and introduction:
To calculate a mix design for M50 grade concrete without fly ash.
Procedure:
Grade designation:M50
Type of cement:OPC53
Maximum nominal size of aggregate:20mm
Exposure type:Extreme
Minimum cement content:360kg
Workability:100mm slump
Method of concrete placing:Pumping
Types of aggregate:Crushed angular
Maximum cement content:450kg
Chemical admixture:Superplasticizer
Specific gravity of cement:3.12
Specific gravity of fine aggregate:2.74
Specific gravity of coarse aggregate:2.56
Target strength:
f'ck=fck+1.65S
s=standard deviation (S=5, from table 1 of IS10262:2009)
=50+1.65*5=58.25N/mm^2
Selection of water cement ratio:
From table 5 IS456:2000 exposed for extreme condition ,maximum water-cement ratio is 0.35
Selection of water content:
From table 2 of IS456:2000
Maximum water content for 20mm aggregate is=186L
for 25-50mm above slump for every 25mm 3% is increased
Water content=186+(6/100*186)=197.16L
Superplasticizer is used water content can be reduced 20%
=197.16-(29/100*197.16)=139.98~140L
Calculation of cement content:
Water-cement ratio=0.35
Cement content=140/0.35=400kg/m^3
For extreme exposure 360kg/m^3
400kg>360kg hence ok
Volume of coarse aggregate and fine aggregate :
From table 3 of IS10262 20mm size aggregateand fine aggregate for water-cement ratio is 0.5=0.62
we have water-cement ratio0.35
volume of coarse aggregate increases by decresing fine aggregate
As water-cement ratio is lower by 0.10,the proportion of the volume of coarse aggregate is increased by0.02
the corrected proportion of volume of Coarse aggregate the water-cement ratio of 0.35=0.65
For pumpable concrete it can be reduced by 10%
volume of coarse aggregate =0.65*0.9=0.585
volume of fine aggregate=1-0.585=0.415
Mix calculations:
volume of concrete=1m^3
volume of cement=400/3.12*1/1000=0.128m^3
volume of water=140/1*1/1000=0.140m^3
volume of chemical admixture=8.2/1.145*1/1000=0.007m^3
volume of aggregate=[a-(b+c+d)]=[1-(0.128+0.140+0.007)]=1-0.284=0.725m^3
Mass of coarse aggregate=e*volume of CA*Specific gravity of CA*1000=0.725*0.585*2.74*1000=1162.10kg/m^3
Mass of fine aggregate=e*volume of FA*Specific gravity of FA*1000=0.725*0.4165*2.56*1000=770.24kg/m^3
Mix proportioning:
Cement=400kg/m^3
Water=140kg/m^3
Fine aggregate=770.24kg/m^3
Coarse aggregate=1162.10kg/m^3
Chemical admixture=7kg/m^3
water-cement ratio=0.35
Trial mix ratio=1:1.925:2.9.