Project on Concrete Mix Design for various grades of Concrete
Q = Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash ?
- Mix Design for M35 grade concrete
- Stipulations for Mix Design Concrete
Grade designation : M 35
Type of cement : OPC 53 grade confirming to IS 8112
Maximum nominal size of aggregate : 20 mm
Minimum cement content : 340 kg/m3
Maximum water-cement ratio : 0.45
Workability : 50-100 mm (slump)
Exposure condition : Very Severe (for reinforced concrete)
Method of concrete placing : Pumping
Degree of supervision : Good
Type of aggregate : Crushed angular aggregate
Maximum cement content : 450 kg/m3
Chemical admixture type : Super Plasticizer
- Test Data for Materials (to be determined in the laboratory)
Specific gravity of cement : 3.12
Specific gravity of Coarse aggregate : 2.74
Specific gravity of Fine aggregate : 2.56
- Target Strength for Mix Proportioning
ftarget = fck + 1.65 x S.
Explanation of terms:
‘ftarget‘ is the target average compressive strength at 28 days,
‘fck‘ is the characteristic compressive strength at 28 days, and
's’ is the standard deviation
As per the table I of IS: 10262-2009 , standard deviation, s = 5.0 N/mm2
Therefore, target strength = 35 + 1.65 x 5.0 = 43.25 N/mm2.
- Selection of Water/Cement Ratio
From Table 5 of IS 456:2000,
Maximum water-cement ratio = 0.45
- Selection of Water Content
From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.
Estimated water content for 100 mm slump =186+(6/100) x 186 =197 liter.
(Note: If Super plasticizer is used, the water content can be reduced upto 20% and above.)
Based on trials with Super plasticizer water content reduction of 25% has been achieved, Hence the arrived water content = 197-[197 x (25/100)] = 147 litres.
- Calculation of Cement Content
Water-cement ratio =0.45
Cement content = 147/0.45 = 350kg/m3
From Table 5 of IS 456, minimum cement content for ‘Very Severe‘ exposure condition = 340 kg/m3
350 kg/m3 > 340 kg/m3, hence, O.K.
Now, to proportion a mix containing fly ash the following step are suggested.
a) the percentage of fly ash needs to be decided based on the project requirements and quality of material.
b) in some cases increase in cementitious material can be warranted. Increase in cementitious material content and it's persentage may be based on experience and trial (this is with the increase of 10% cementitious material content).
Cementitious material content= 350x1.10 = 385 kg/m³.
Water content= 147kg/m³.
So, water/cement ratio = 147/385 = 0.381.
Fly ash @30% total cementitious material content= 385x30% = 115 kg/m³.
Cement (OPC) = 385-115= 270 kg/m³.
Saving of cement while using fly ash = 350-270 = 80 kg /m³
Fly ash being utilised= 115kg/m³
- The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content
From Table 3 of IS 10262, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 = 0.62.
In the present case, the water-cement ratio is 0.45. Therefore, the volume of coarse aggregate is required to be increased to reduce the fine aggregate content.
As the water-cement ratio is lower by 0.10, the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.45 = 0.63.
NOTE – In case the coarse aggregate is not angular one. then also the volume of coarse aggregate may be required 10 be increased suitably, based on experience.
For pumpable concrete, these values should be reduced by 10 percent.
Therefore, volume of coarse aggregate = 0.63 x 0.9 = 0.567.
Volume of fine aggregate content =1 – 0.567 = 0.433
- Mix Calculations
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement/Specific Gravity of Cement) X (1/1000)
= (270/3.12) X (1/1000)
= 0.086 m3
c) Volume of fly ash = (Mass of flyash/specific gravity of flyash) X (1/1000)
= (115/2.2)x(1/1000)
= 0.052m³
d) Volume of water = (Mass of water/specific gravity of water) X (1/1000)
= (147/1) X (1/1000)
= 0.147 m3
e) Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)
= (7/1.145) X (1/1000)
= 0.006 m3
f) Volume of all aggregate = (a-(b+c+d))
= 1 – (0.112 + 0.147+0.006)
= 0.735 m3
g) Mass of coarse aggregate = Volume of all aggregate X volume of coarse aggregate X Specific gravity of coarse aggregate X 1000
= 0.735 x 0.567 x 2.74 x 1000
= 1141.88 kg
h)Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000
= 0.735 x 0.433 x 2.56 x 1000
= 814.73 kg
- Concrete Mix Proportions
Cement = 270 kg/m3
Water = 147 kg/m3
Super plasticizer = 7 kg/m3
Fine aggregates = 814.73 kg/m3
Coarse aggregate = 1141.88 kg/m3
W/c = 0.45
Concrete Mix Ratio Obtained
The Mix Ratio of M35 as obtained is 1 : 3.01 : 4.22 (Cement : Fine aggregate : Coarse aggregate)
This is the procedure for mx design calculation of M35 grade concrete using flyash.
Mix Design for M50
- Stipulations for Concrete Mix Design
Grade designation : M50
Type of cement : OPC 53 grade confirming to IS 8112
Maximum nominal size of aggregate : 20 mm
Minimum cement content : 360 kg/m3
Maximum water-cement ratio : 0.35
Workability : 50-75 mm (slump)
Exposure condition : Extreme (for reinforced concrete)
Method of concrete placing : Pumping
Degree of supervision : Good
Type of aggregate : Crushed angular aggregate
Maximum cement content : 450 kg/m3
Chemical admixture type : Super Plasticizer
- Test Data for Materials
The following data are collected by performing standard tests in a laboratory.
Specific gravity of cement : 3.12
Specific gravity of Coarse Aggregate : 2.74
Specific gravity of Fine Aggregate : 2.56
Procedure for Concrete Mix Design of M 50 Concrete
- 1. Target Strength for Mix Proportioning
ftarget = fck + 1.65 x s
ftarget denotes the Target Average Compressive Strength at 28 days,
fck denotes the Characteristic Compressive Strength at 28 days,
‘s’ stands for Standard Deviation
According to the table 1 of IS: 10262-2009 ,
standard deviation, s = 5.0 N/mm2
Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm2
- 2. Selection of Water/Cement Ratio
From Table 5 of IS 456 : 2000,
Maximum water-cement ratio = 0.35
- 3. Selection of Water Content
From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.
Estimated water content for 100 mm slump =186+(6/100) x 186 =197 litres.
(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)
Based on trials with Super plasticizer water content reduction of 27% has been achieved, Hence the arrived water content = 197 – [197 x (27/100)] = 143 litres.
- 4. Calculation of Cement Content
Water-cement ratio = 0.35
Cement content = 143/0.35 = 410 kg/m3
From Table 5 of IS 456, minimum cement content for ‘Extreme exposure’ condition = 360 kg/m3
410 kg/m3 > 360 kg/m3, hence, O.K
- 5. Proportion of Volume of Coarse Aggregate and Fine Aggregate Content
From Table 3 of IS 10262. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.
In the present case, the water-cement ratio is 0.35. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).
Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.
NOTE – 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 pumpable concrete, these values should be reduced by 10 percent.
Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.
Volume of fine aggregate content =1 – 0.585 =0.415
- 6. Mix Calculations
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)
= (410/3.12) X (1/1000)
= 0.131 m3.
c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)
= (143/1) X (1/1000)
= 0.143 m3
d) Volume of Superplasticizer = (Mass of Superplasticizer / Specific gravity of admixture) X (1/1000)
= (8.2/1.145) X (1/1000)
= 0.007 m3
e) Volume of all aggregate = (a – (b + c + d))
= 1 – (0.131 + 0.143+0.007)
= 0.719 m3
f) Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000
= 0.719 x 0.585 x 2.74 x 1000
= 1152.48 kg
g) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000
= 0.719 x 0.415 x 2.56 x 1000
= 763.86 kg
- 7. Concrete Mix Proportions
Cement = 410 kg/m3
Water = 143 kg/m3
Super plasticizer = 7 kg/m3
Fine aggregates = 763.86 kg/m3
Coarse aggregate = 1152.48 kg/m3
W/c = 0.35
The Mix Ratio of M50 as obtained is 1 : 1.86 : 2.81 (Cement : Fine aggregate : Coarse aggregate)
This is the procedure for mx design calculation of M50 grade concrete