Project on Concrete Mix Design for various grades of Concrete
Design Mix for M35 Grade concrete with Fly Ash
Introduction:
The design mix is preferred for largescale projects and for the grades of concrete M30 and above. Concrete mix design shall be commenced well in advance atleast 60days prior to start the project.
Code of References:
The concrete mix design shall be designed based on the few available codes such as Indian, British and American standards as below:
IS 456:2000 - Code of Practice-Plain and Reinforced Concrete
IS 10262:1982 - Reccomended Guidelines for Concrete mix design
IS 10262: 2009 - Guidelines for Concrete Mix Design
IS 3812 (Part 1) : 2003 specification for Fly Ash
BS EN 206-1 : 2000 - Concrete, Specification, Production, Performance and confirmity.
BS EN 8500 Part 1 and 2 - This is a suplimentary with BS 206-1 for the sampling, testing and specification for the mix production.
ACI 211. 1-91 : Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete.
Materials and Data considered:
Cement - Considered for OPC 43 Grade
Coarse Aggregate - Maximum size 20mm; Sp. gravity = 2.74
Fine Aggregates - Grading zone 2; Sp. gravity = 2.74
Fly Ash
Chemical Admixture: Super plastizizer
Exposure condition - Severe (Reinforced concrete)
Workability : Pumpable concrete 100mm slump required
Mix Design -M35
Step-1: Target Mean Strength - f'ck =fck+1.65S
= 35+1.65*5 =43.25N/mm^2
Step -2: Water -Cement Ratio
Reference to IS 456, Table 5 - W/C Ratio is 0.45 for severe exposure condition
Based on experience w/c ratio considered as 0.4
Minimum Cement Content is 340Kg/m^3
Step-3: Selection of Water Content
Reference to IS 10262, Table 2, the maximum water content (20mm max. size of aggregates)
is 186lit (25 to 50mm slump)
For Slump 100mm = 186+ (6/100)*186 = 197.16 lit
For adding admixture super plastisizer, the water content can be reduced more than 20%, it is considered to reduce 30% from the above water content.
Therefore, =197 - (0.3*197) = 138lit.
Step-4: Calculation of Cement Content
Water-Cement ratio = 0.4
Cement+Fly Ash = 138/0.4 = 345Kg/m^3
Hence, it is ok 345>340Kg/m^3
Fly Ash : Fly ash quantity to be decided based on the project requirement and trials. It normally added from 20% of Cemetatious materials.
It is advised to increase 10% of cement = 345*1.1 = 379.5Kg/m^3
Water content = 138lit
Water - Cement ratio = 138/379.5 = 0.363
Fly ash @ 30% of weight of Cement = 379.5*0.3 = 114 Kg
Cement OPC = 379.5-114 = 265.5Kg
Savings of Cement = 345-265.5 = 79.5Kg.
Fly ash quantity = 114Kg.
Step -5: Proportion of C.A and F.A
Reference to IS 10262, Table-3, volume of C.A and F.A for Zone-2, 20mm size and water-cement ratio 0.45 is 0.60.
Present case water-cement ratio considered is 0.4, therefore, the C.A has to be increased by 0.02
Corrected value for C.A for w/c ratio 0.4 = 0.62
For pumpable concrete = 10% F.A has to be increased and 10% of C.A has to be reduced to balance the quantity.
Volume of C.A =0.62*0.9 = 0.56
Volume of F.A = 1-0.56 = 0.44
Step 6: Mix calculation
a. Volume of Concrete = 1m^3
b. Volume of Cement = (Mass of Cement/Sp. gravity of Cement)*1/1000
= (265.5/3.15)*(1/1000) = 0.084m^3
C. Volume of Fly Ash = (Mass of Fly Ash/Sp.gravity of Fly Ash)*(1/1000)
= (114/2.2)*(1/1000) = 0.052
d. Volume of water = (138/1)*(1/1000) = 0.138m^3
e. Volume of Chemical Admixture @2% of wt. of Cement = (6.9/1.145)*(1/1000) = 0.006m^3
f. Volume of C.A and F.A
= a - (b+c+d+e) =1-(0.109+0.138+0.006) =0.747m^3
Volume of C.A = 0.747*0.56 = 0.418m^3
Mass of C.A = 0.418*2.74*1000 = 1145Kg/m^3
Volume of F.A = 0.747*0.44 = 0.328m^3
Mass of F.A = 0.328*2.74*1000 = 899Kg/m^3
Mix Proportion for Trial 1:
1. Cement = 265.5Kg/m^3
2. Fly Ash = 114Kg/m^3
3. Chemical Admixture = 6liters/m^3
4. Fine Aggregates = 899Kg/m^3
5. Coarse Aggregates = 1145Kg/m^3
6. Water content = 138 liters
7. Water-Cement ratio = 0.363
Mix design proportion is 1: 2.3: 3
Two more trials to be conducted to confirm the required workability and strength with different W/C ratio.
Design Mix for M50 Grade Concrete without Fly Ash
Introduction:
The design mix is preferred for largescale projects and for the grades of concrete M30 and above. Concrete mix design shall be commenced well in advance atleast 60days prior to start the project.
Code of References:
The concrete mix design shall be designed based on the few available codes such as Indian, British and American standards as below:
IS 456:2000 - Code of Practice-Plain and Reinforced Concrete
IS 10262:1982 - Reccomended Guidelines for Concrete mix design
IS 10262: 2009 - Guidelines for Concrete Mix Design
BS EN 206-1 : 2000 - Concrete, Specification, Production, Performance and confirmity.
BS EN 8500 Part 1 and 2 - This is a suplimentary with BS 206-1 for the sampling, testing and specification for the mix production.
ACI 211. 1-91 : Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete.
Materials and Data considered:
Concrete Mix Design = M50 Grade
Cement - Considered for OPC 43 Grade
Coarse Aggregate - Maximum size 20mm; Sp. gravity = 2.74
Fine Aggregates - Grading zone 2; Sp. gravity = 2.74
Chemical Admixture: Super plastizizer; Sp.Gravity = 2.2
Exposure condition - Severe (Reinforced concrete)
Workability : Pumpable concrete 100mm slump required
Mix Design -M50
Step-1: Target Mean Strength - f'ck =fck+1.65S
= 50+1.65*5 =58.25N/mm^2
Step -2: Water -Cement Ratio
Reference to IS 10262:1982, Fig-2, curve F considered for target mean strength 58.25N/mm^2
W/C Ratio is 0.35 for severe exposure condition
Step-3: Selection of Water Content
Reference to IS 10262, Table 2, the maximum water content (20mm max. size of aggregates)
is 186lit (25 to 50mm slump)
For Slump 100mm = 186+ (6/100)*186 = 197.16 lit
For adding admixture super plastisizer, the water content can be reduced more than 20%, it is considered to reduce 30% from the above water content.
Therefore, =197 - (0.3*197) = 138lit.
Step-4: Calculation of Cement Content
Water-Cement ratio = 0.35
Cement = 138/0.35 = 395 Kg/m^3
Step -5: Proportion of C.A and F.A
Reference to IS 10262, Table-3, volume of C.A and F.A for Zone-2, 20mm size and water-cement ratio 0.35 is 0.60.
Present case water-cement ratio considered is 0.35, therefore, the C.A has to be increased by 0.02
Corrected value for C.A for w/c ratio 0.35 = 0.62
For pumpable concrete = 10% F.A has to be increased and 10% of C.A has to be reduced to balance the quantity.
Volume of C.A =0.62*0.9 = 0.56
Volume of F.A = 1-0.56 = 0.44
Step 6: Mix calculation
a. Volume of Concrete = 1m^3
b. Volume of Cement = (Mass of Cement/Sp. gravity of Cement)*1/1000
= (395/3.15)*(1/1000) = 0.125 m^3
c. Volume of water = (138/1)*(1/1000) = 0.138m^3
d. Volume of Chemical Admixture @2% of wt. of Cement = (7.9/1.145)*(1/1000) = 0.007 m^3
e. Volume of C.A and F.A
= a - (b+c+d) =1-(0.125+0.138+0.007) =0.73mm^3
Volume of C.A = 0.73*0.56 = 0.40 m^3
Mass of C.A = 0.40*2.74*1000 = 1096 Kg/m^3
Volume of F.A = 0.73*0.44 = 0.321 m^3
Mass of F.A = 0.321*2.74*1000 = 880 Kg/m^3
Mix Proportion for Trial 1:
1. Cement = 395 Kg/m^3
2. Chemical Admixture = 7 liters/m^3
3. Fine Aggregates = 880 Kg/m^3
4. Coarse Aggregates = 1096 Kg/m^3
5. Water Content = 138 liters
6. Water-Cement ratio = 0.35
Mix design proportion is 1: 2.2: 2.77
Two more trials to be conducted to confirm the required workability and strength with different W/C ratio.