Project on Concrete Mix Design for various grades of Concrete
1) 1. Properties.
Grade of concrete :M35
Type of concrete OPC 43 grade comparing to grade IS 8112
Type of mineral admixture : Fly ash comparing to IS 3812 (Part 1)
Maximum nominal size of aggregaten: 20mm
Minimum cement content 320kg/m^3 (from table 5 of IS 456:2000- Exposure Conditions)
Maximum water-cement ratio: 0.45 (from table 5 of IS 456:2000 - Exposure Condition )
Workability : 100mm ( slump value for pumpable concrete)
Exposure condition : Severe (for reinforced concrete)
Method of concrete placing : : pumping
Degree of supervision : Good
Type of aggregate : Crushed angular aggregate
Maximum cement content : 450kg/m^3
Chemical adimixture type : Superplasticizer
2. Test data for materials
Cement used : OPC 43 grade conforming to IS 8112
Specific gravity of cement : 3.15
Fly ash : Conforming to IS 3812(part 1)
Specific gravity of fly ash :2.2
Chemical adimixture : Superplasticizer conforming to IS 9103
Specific gravity of : Coares aggregate : 2.74
Fine aggregate : 2.74
Water absorption : Coarse aggregate : 0.5%
Fine aggregate : 1.0%
surface moisture : Coarse aggregate : Nill
Fine aggregate : Nill
Sieve Analysis : Coarse aggregate : 100
Fine aggregate : Conforming to grading Zone 1 of Table 4 of IS 383.
3. Target strength of mix propertion : fc'k=fck+1.655
where,fc'k=Target average compresive strength at 28 days .
fc'k = Characteristic compressive strength at 28 days
S = Standard deviation
From table no 1 of IS 10262:2009 , Standard devation S= 5 N/mm^2
Therefore, Target Strength = 35+1.65*5
=43.25 N/mm^2
4. Selection of water cement ratio : From table 5 of IS 456:2000 for sever exposure, maximum water-cement ratio=0.45
Based on exposure, adopt water cement ratio as 0.40 0.40<0.45, hence ok
5. Selection of water content
From table 2 of IS 10262:2009, maximum water content for 20mm aggregate = 186 liter ( for 25mm to 50mm slump range )
Estimated water content for 100mm slump = 186+6/100*186
= 197 liters
As superplastisizer is used the water content can be reduced upto 30%
Based on trials water content reduction of 29% is achived with plasticizer .
Hence the arrived water content = 197 * 0.71
= 140 liters
6. Calculation of cement content
water cement ratio = 0.4
Cementitious material ( cement + fly ash ) content = 140/0.4
= 350 Kg/m^3
From table 5 of IS 456 minimum cement content for seiver exposure condition = 320 kg/m^3
350kg/m^3>320k/m^3, hence ok
Now, to prepare a mix containing a fly ash the following steps are suggested
a) The percentage of fly ash need to be devided based on project requirement and quality of materials.
b) In some cases increase in cementitious material can be warranted. Increase in cementent and its percentage may be based on experiance and trail ( this example is with increase of 10% cementitious material content )
Cementitonus material cement = 350*1.10=385 kg/m^3
water content = 140 kg/m^3
So, water-cement ratio = 140/385
= 0.363
Fly ash @30% total cement material content = 385*30%=115 kg/m^3
cement (OPC) = 385-115 = 270 kg/m^3
saving of cement while using fly ash = 350-270 = 80kg/m^3
Fly ash being utilized = 115kg/m^3
7. Propertion of volume of coarse aggregate and fine aggregate content:
from table 3 of IS 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 0.40
As the water cement ratio is lower by 0.10 the propertion of volume of coarse aggreggate is increased by 0.02
Therefore, corrected volume of coarse aggregate for the water cement ratio of 0.40=0.62
For pumpable concrete the values are reduced by 10%
Therefore , volume of coarse aggregate = 0.62*0.9=0.56
Volume of fine aggregate content = 1-0.56=0.44
8. Mix calculation :
The mix calculation per unit volume of concrete shall be as follows :
a) Volume of concrete= 1m^3
b) Volume of cement = mass of cement/specific gravity of cement*1/1000
= 350/3.15*1/1000
= 0.111m^3
c) volume of water = mass of water /specific gravity of water *1/1000
= 140/1*1/1000
= 0.140m^3
d) Volume of chemical adimixture = Mass of chemical admixture / specific gravity of admixture*1/1000
= 7.6/1.145*1/1000
= 0.006 m^3
e) Volume of aggregate (FA & CA) = (a-(b+c+d))
= (1-(0.111+0.140+0.006))
=0.743 m^3
f) Mass of coarse aggregate = e* volume of coarse aggregate *specific gravity of coarse aggregate*1000
= 0.743*0.56*2.74*1000
= 1140 kg/m^3
g) Mass of fine aggregate = e*volume of fine aggregate*specific gravity of fine aggregate*1000
= 0.743*0.44*2.74*1000
= 896 kg/m^3
9. Mix propertion of trial Number 1:
Cement =350kg/m^3
water = 140kg/m^3
finee aggregate = 896kg/m^3
coarse aggregate = 1140 kg/m^3
chemical admixture = 7 kg/m^3
water - cement ratio = 0.4