Project on Concrete Mix Design for various grades of Concrete
MIX DESIGN OF M35 GRADE OF CONCRETE WITH FLY ASH
I ) STIPULATIONS FOR PREPARING OF M35 GRADE CONCRETE -
- Grade designation - M35
- Type of cement - OPC53
- Maximum nominal size of admixture - 20mm
- Minimum cement content - 340Kg (As per IS456-2000,Table 5)
- maximum cement content - 450Kg
- Partial replacement of cement by fly ash - 30% (As per requirement.)
- Maximum w/c ratio = 0.45
- Workability = 100mm
- Chemical admixture = PCS type
II) TEST DATA FOR MATERIALS -
- Cement used - OPC53(confirming to IS8112)
- Specific gravity of cement = 3.15
- Mineral admixture = Fly ash
- Specific gravity of fly ash = 2.9
- Chemical Admixture = 0.6%
- Specific gravity of CA and FA= 2.74
- Specific gravity of admixtures PCE based = 1.12
- Water absorbtion = CA is % and FA is 1%
III) TARGET STRENGTH FOR MIX PROPORTION OF M35 GRADE CONCRETE -
Target strength should be greater than the required strength of concrete.The value of standard deviation of concrete is different for different grades. These values are given in Table 1 of IS10262:2009.
So, Fck = fck + 1.65S (where Fck = target compressive strength, fck = strength of concrete after 28 days, S = standard devoiation)
Fck = 35 + (1.65*5)
= 43.25 N/mm2
IV) SELECTION OF WATER CONTENT RATIO -
Maximum water cement ratio = 0.45(Table 5 ,IS456-2000)
Adopted water cement ratio = 0.45
V) SELECTION OF WATER CONTENT -
Maximum water content - 186 Litres.
Above water-content is for 25 to 50mm slump, but we need 100mm slump for our concert as per specification. So we need to increase the water-content to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we to increase water content by 6% to get an additional 50mm slump for our concrete.
So for 100 mm slump water content = 186 + (0.06 * 186)
= 197.16 Litres.
Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete. The amount of water-content to be reduced depends on the type of superplasticizer.
Percentage of reduction in water content = 20%
Water content now = 197.16 - (0.2 * 197.16)
= 157.72 Litres.
Adopted water content = 160 Litres.
VI) CALCULATION OF CEMENT AND FLYASH CONTENT -
Adopted water cement ratio = 0.45
Total cemeticious material = (cement + fly ash)= 160/0.45 = 355.5 kg
Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. The percentage of cementitious content to be increased depends on the experience and research. Here we have increased the cementitious content by 10%.
Final cemetitious content = (0.1*355.5) + 355.5 = 391.6 kg
Adopted cement content = 391.6 > 340 kg
Fly ash required = 0.3* 391.6 = 117.48 kg
So, cement required = 391.6 - 118 = 274.12 kg
Superplasticizers = 0.6 % by weight of cementitious material = 0.6/ 100 * 391.6 =2.35 kg
VII) COARSE AND FINE AGGREGATE -
Coarse aggregate ratio = 0.62 dor w/c ratio = 0.5
Here CA ratio = 0.63(adding 0.01 for every decrease in 0.05 and vice versa)
So, fvolume of fine aggregate = 1 - 0.63
= 0.37
VIII) MIX CALCULATIONS FOR M35 GRADE OF CONCRETE -
- Volume of concrete = 1 cu.m
- Total volume of cement = 275/(3.15*1000)= 0.087 cu.m
- Total volume of flyash = 118/(2.9*1000) = 0.040 cu.m
- Volume of water = 160/(1*1000)= 0.16 cu.m
- Volume of super plasticizers = 2.35/(1.12*1000) = 0.002 cu.m
- Total aggregates requirements = 1 - (2+3+4+5) =0.71 cu.m
- Coarse aggregate = 0.71*0.63*2.74*1000 = 1225.6 kg
- Fine aggregate = 0.71*0.37*2.74*1000 = 719.8 kg
TO FIND THE MIXED RATIO ,DIVIDE ALL THE WEIGHT OF THE MATERIALS BY WEIGHT OF CEMENT =
1:0.4:2.6:4.46(CEMENT : FLYASH : FA : CA).
MIX DESIGN OF M50 GRADE OF CONCRETE WITHOUT FLY ASH -
I ) STIPULATIONS FOR PREPARING OF M50 GRADE CONCRETE -
- Grade designation - M50
- Type of cement - OPC53
- Maximum nominal size of admixture - 20mm
- Exposure condition = extreme(for rcc)
- Minimum cement content - 360Kg (As per IS456-2000,Table 5)
- maximum cement content - 450Kg
- Maximum w/c ratio = 0.35
- Workability = 100mm
- Chemical admixture = PCS type
II) TEST DATA FOR MATERIALS -
- Cement used - OPC53(confirming to IS8112)
- Specific gravity of cement = 3.15
- Chemical Admixture = 0.6%
- Specific gravity of CA and FA= 2.74
- Specific gravity of admixtures PCE based = 1.12
- Water absorbtion = CA is % and FA is 1%
III) TARGET STRENGTH FOR MIX PROPORTION OF M50 GRADE CONCRETE -
Target strength should be greater than the required strength of concrete.The value of standard deviation of concrete is different for different grades. These values are given in Table 1 of IS10262:2009.
So, Fck = fck + 1.65S (where Fck = target compressive strength, fck = strength of concrete after 28 days, S = standard devoiation)
Fck = 50 + (1.65*5)
= 58.25 N/mm2
IV) SELECTION OF WATER CONTENT RATIO -
Maximum water cement ratio = 0.35(Table 5 ,IS456-2000)
Adopted water cement ratio = 0.35
V) SELECTION OF WATER CONTENT -
Maximum water content - 186 Litres.
Above water-content is for 25 to 50mm slump, but we need 100 mm slump for our concert as per specification. So we need to increase the water-content to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we to increase water content by 6% to get an additional 100mm slump for our concrete.
So for 100 mm slump water content = 186 + (0.06* 186)
= 197.16Litres.
Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete. The amount of water-content to be reduced depends on the type of superplasticizer.
Percentage of reduction in water content = 20%
Water content now = 197.16 - (0.2 * 197.16)
= 157.72 Litres.
Adopted water content = 160 Litres.
VI) CALCULATION OF CEMENT CONTENT -
Adopted water cement ratio = 0.35
Total cemeticious material = (cement)= 160/0.35 = 457kg
For extreme exposure the minimum cement content is 360 kg
Adopted cement content = 457 > 360 kg, hence ok.
Superplasticizers = 0.6 % by weight of cementitious material = 0.6/ 100 * 457 =2.74 kg
VII) COARSE AND FINE AGGREGATE -
Coarse aggregate ratio = 0.62 dor w/c ratio = 0.5
Here CA ratio = 0.65(adding 0.01 for every decrease in 0.05 and vice versa)
In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience.
For pumpble concrete these values should be reduced by 10 %
Therefore volume of coarse aggregate = 0.65*0.9 = 0.585
Volume of fine aggregate = 1 - 0.585 = 0.415
VIII) MIX CALCULATIONS FOR M50 GRADE OF CONCRETE -
- Volume of concrete = 1 cu.m
- Total volume of cement = 457/(3.15*1000)= 0.145 cu.m
- Volume of water = 160/(1*1000)= 0.16 cu.m
- Volume of super plasticizers = 2.74/(1.12*1000) = 0.003 cu.m
- Total aggregates requirements = 1. - (2.+3.+4.) =0.692 cu.m
- Coarse aggregate = 0.692*0.585*2.74*1000 = 1109.2 kg
- Fine aggregate = 0.692*0.414*2.74*1000 = 784.97 kg
TO FIND THE MIXED RATIO ,DIVIDE ALL THE WEIGHT OF THE MATERIALS BY WEIGHT OF CEMENT =
1: 1.71 : 2.42(CEMENT : FA : CA).