Project on Concrete Mix Design for various grades of Concrete
1. Mix Design for M50 grade concrete without Fly ash
- Grade designation = M50
- type of cement- OPC 43 grades conforming to is 8112
- maximum nominal size of aggregate = 20mm
- minimum cement content: 400kg/m^3(From table of IS 456:2000 exposure condition)
- maximum water/cement ratio: 0.37 (table 5 of IS 456:2000 exposure condition)
- workability = 100mm (slump value for pumpable concrete)
- exposure condition: moderate for (reinforced concrete)
- method of concrete placing: pumping
- degree of supervision = good
- type of aggregate: crushed angular aggregate
- maximum cement content = 450kg as per para 8.2.4.2 of IS 456
- chemical admixture type - superplasticizers
- specific gravity of cement = 3.15
- specific gravity of CA = 2.74
- specific gravity of FA = 2.74
- water absorption of CA = 0.5%
- water adsorption of FA = 1.0%
- free surface moisture CA = Nill
- free surface moisture FA = Nill
- sieve analysis for CA is taken table 2 IS 383
- sieve analysis for FA is taken table 4 IS 383
target strength for mix proportioning
- f'ck= fck + 1.65S (where f'ck = target average compressive strength at 28 days.)
- fck = characteristic compressive strength deviation
- S = standard deviation.
From table 1 of IS 10262:2009 standard deviation, S = 5N/mm^2
therefore, target strength = 50 + 1.65*5 = 58.25N/mm^2
selection of water-cement ratio
From table 5 of 456 :2000 for severe exposure maximum water cement ratio =0.37
selection water contact from table 2 of IS 10262: 2009 maximum water content for 20mm aggregate= 186lit (for 25mm to 50mm slump range)
estimation water content for 100mm slump = 186 + 6/100*186 =197lit
As superplasticizer is used the water content can be reduced up to 20% and above based on trial water content reduction of 29% is achieved with plasticizer.
hence the arrived water content = 197*0.71=140lite
Calculating Cement content
water cement ratio = 140/0.37 = 378.37kg/m^3
Proportion of volume of coarse aggregate and fine aggregate
from table 2 of 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate zone 1 for water cement ratio = 0.6
in the present case the water/cement ratio is 0.37
Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
as water cement ratio is lower by 0.10, the proportion of volume of course aggregate is increased by 0.02 (at the rate of (-/+0.01) for every -/+0.05 change in water cement ratio)
Therefore, corrected volume of coarse aggregate for the w/c ratio pf 0.37=0.62
note if coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitability based on experience
for pumpable concrete these values are reduced by 10%
therefore, volume of Coarse Aggregate = 0.62*0.9 = 0.56
volume of fine aggregate = 1 - 0.56 =0.44
Mix calculation
volume of concrete = 1m^3
volume of concrete = mass of cement/ specific gravity of cement *1/1000
= 378.37/3.15*1/1000
= 0.12m^3
volume of water = mass of water/specific gravity of water*1/1000
= 140/1*1/1000
= 0.140m^3
volume of chemical admixture = mass of chemical admixture/ specific gravity of admixture*1/1000
= 7.5/1.145*1/1000
= 0.006m^3
volume of aggregate FA & CA
= {a-(b+c+d)}
= {1-(0.12=0.14+0.006)}
=0.728m^3
Mass of Coarse Aggregate
= e * volume of CA* specific of CA*1000
=0.728*0.56*2.74*1000
= 1117.04kg/m^3
mass of fine aggregate
= e*volume of FA* specific of FA*1000
= 0.728*0.4*2.74*1000
=797.8kg/m^3
mix proportion for trial number
- cement = 378.37kg/m^3
- water = 140kg/m^3
- FA = 797.8kg/m^3
- CA =1117.04kg/m^3
- chemical admixture = 7.5kg/m^3
- water/cement ratio = 0.37
- trial mix ratio = 378.3 : 797.8 : 1117.04
=1 : 2.1 : 2.9
2. Mix Design for M35 grade concrete with fly ash
- Grade designation = M35
- type of cement- OPC 43 grades conforming to is 8112
- type of mineral admixture: Fly ash conforming to is 3812
- maximum nominal size of aggregate = 20mm
- minimum cement content: 340kg/m^3(From table of IS 456:2000 exposure condition)
- maximum water/cement ratio: 0.45 (Table 5 of IS 456:2000 exposure condition)
- workability = 100mm (slump value for pumpable concrete)
- exposure condition: very severe
- method of concrete placing: pumping
- degree of supervision = good
- type of aggregate: crushed angular aggregate
- maximum cement content = 450kg as per para 8.2.4.2 of IS 456
- chemical admixture type - superplasticizers
- specific gravity of cement = 3.15
- fly ash conforming to IS 3812
- specific gravity of fly ash :2.2
- specific gravity of CA = 2.74
- specific gravity of FA = 2.74
- water absorption of CA = 0.5%
- water adsorption of FA = 1.0%
- free surface moisture CA = Nill
- free surface moisture FA = Nill
- sieve analysis for CA is taken table 2 IS 383
- sieve analysis for FA is taken table 4 IS 383
target strength for mix proportioning
- f'ck= fck + 1.65S (where f'ck = target average compressive strength at 28 days.)
- fck = characteristic compressive strength deviation
- S = standard deviation.
From table 1 of IS 10262:2009 standard deviation, S = 5N/mm^2
therefore, target strength = 35 + 1.65*5 = 43.25N/mm^2
selection of water-cement ratio
From table 5 of 456 :2000 for severe exposure maximum water cement ratio =0.45
selection water contact from table 2 of IS 10262: 2009 maximum water content for 20mm aggregate= 186lit (for 25mm to 50mm slump range)
estimation water content for 100mm slump = 186 + 6/100*186 =197lit
As superplasticizer is used the water content can be reduced up to 20% and above based on trial water content reduction of 29% is achieved with plasticizer.
hence the arrived water content = 197*0.71=140lite
Calculating Cement content
water cement ratio = 140/0.45 = 311.11kg/m^3
from table of IS456 minimum cement content for very severe condition = 340kg/m^3
340kg/m^3>311.11kg/m^3, H0ence Ok
Now to proportion a mix containing fly ash the following steps are suggested
- The percentage of fly ash needs to be decided based on project requirement and quality of materials
- in some case increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial
- cementitious material content = 340*1.10 =374kg/m^3
- water content = 104kg /m^3
- so, water-cement ratio = 140/374 = 0.374
- fly ash @ 30% total cementitious material content = 374 *30% = 112kg/m^3
- cement OPC = 374-112 =262kg/m^3
- saving cement while using fly ash = 340-262= 78kg/m^3
- fly ash being utilized = 112kg/m^3
Proportion of volume of coarse aggregate and fine aggregate
from table 2 of 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate zone 1 for water cement ratio = 0.6
in the present case the water/cement ratio is 0.45
Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
as water cement ratio is lower by 0.10, the proportion of volume of course aggregate is increased by 0.02 (at the rate of (-/+0.01) for every -/+0.05 change in water cement ratio)
Therefore, corrected volume of coarse aggregate for the w/c ratio pf 0.45=0.62
note if coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitability based on experience
for pumpable concrete these values are reduced by 10%
therefore, volume of Coarse Aggregate = 0.62*0.9 = 0.56
volume of fine aggregate = 1 - 0.56 =0.44
Mix calculation
volume of concrete = 1m^3
volume of concrete = mass of cement/ specific gravity of cement *1/1000
= 262/3.15*1/1000
= 0.083m^3
volume of fly ash = mass of fly ash/ specific gravity of fly ash*1/1000
= 112/2.2*1/1000
= 0.0509m^3
volume of water = mass of water/specific gravity of water*1/1000
= 140/1*1/1000
= 0.140m^3
volume of chemical admixture = mass of chemical admixture/ specific gravity of admixture*1/1000
= 5.24/1.145*1/1000
= 0.004kg/m^3
volume of aggregate FA & CA
= {a-(b+c+d+e)}
= {1-(0.083+0.05+0.14+0.004)}
=0.723kg/m^3
Mass of Coarse Aggregate
= e * volume of CA* specific of CA*1000
=0.723*0.56*2.74*1000
= 1109.37 kg/m^3
mass of fine aggregate
= e*volume of FA* specific of FA*1000
= 0.723*0.4*2.74*1000
=871.64kg/m^3
mix proportion for trial number
- cement = 262kg/m^3
- water = 140kg/m^3
- FA = 871.64kg/m^3
- CA =1109.37kg/m^3
- chemical admixture = 5.24kg
- water/cement ratio = 0.45
- trial mix ratio = 262 : 871.64 : 1109.37
= 1: 3.3 : 4.2