Project on Concrete Mix Design for various grades of Concrete
1.) Concrete Mix Design for M35 grade with fly ash.
Step - 1st
Stipulation for design mix
a. Grade of Concrete - M35
b. Type of Cement - Ordinary Portland Cement (General Practice)
c. Maximum Nominal size of aggregate - 20mm
d. Minimum cement content - 320kg/m3 (Severe Condition) for RCC
e. Maximum water cement ratio - 0.45 (Severe Condition)
f. Workability - 110mm (If adding flyash which will increase workability of concrete for normal condition)
g. Exposure Condition - Severe Condtion
h. Degree of supervision - Good
i. Maximum Cement Content - 450kg/m3
Step -2nd
Test data on materials
a. Cement - OPC 43 Grade
b. Sp. Gravity of Cement - 3.15
c. Sp. Gravity of flyash - 2.2
d. Chemical Admixture - Sikaplast 5202 NS
e. Specific Gravity of coarse aggregate - 2.68
f. Specific Gravity of fine aggregate - 2.65
g. Water absorption - Coarse aggregate - 0.6%
Fine aggregate - 1%
h. Free surface moisture of coarse aggregate - Nil
i. Free surface moisture of fine aggregate - Nill
j. Sieve analysis -
Coarse aggregate: Conforming to Table 2 of IS :383
Fine aggregate : Conforming to Table 1 of IS : 383
Step- 3rd
Target Mean Strength for Proportioning
F'ck = fck + 1.65 S
Where F'ck - Target mean strength
fck - Charastricts mean strength at 28 days
S - Standard deviation (Table 1st of IS 10262:2009)
So, for M35 grade Standard deviation (S) will be - 5
Hence , F'ck = 35 + 1.65 x 5 = 43.25 N/mm2
Step - 4th
Selection of water cement ratio
From Table 5th of IS 456 : 2000
Maximum water cement ratio = 0.45 for severe conditon
but based on experience adopted = 0.44
Hence, 0.44<0.45
So, Water Cement Ratio will be 0.44
Step -5th
Selection of Water Content
Taking from table-2 of IS 10262 : 2009, Maximum water content for 20mm aggregate
186 litre (for 25 to 50mm slump range)
Increasing 3% for every additional slump of 25mm from 50mm slump
So, for 110mm slump 6% will be increased
Which will be 186 + (6/100)x186 = 197.16 Litre.
If Superplasticizer is used the water content can be reduced upto 20% and above.
So, Water Content - 197x0.8= 157.6 or 158 Litre.
Step -6th
Calculation of Cement Content
We have W/C = 0.44, Where W = 158 Litre
So Cement = 359 Kg/m3
Increasing cement content by 10% for good workability and strength.
= 359 + ( 0.1 x 359 ) = 394.9 or 395 Kg/m3
So, New water cement ratio will be W/C = 158/395 = 0.4
Considering Flyash content 30% of cement content = 395 x 0.3 = 118.5 Kg/m3
So, Final cement required = 395-118= 277Kg/m3
Step -7th
Calculation of Volume of Coarse aggregate & Fine aggregate
Refering from Table 3rd of IS 10262 Vol of Coarse aggregate for 20mm aggregate and Fine aggregate (Zone-1) =0.6
In the present situation W/C = 0.40
So, Vol of Coarse aggregate is required to be increased to decrease the fine aggregate content.
As Water Cement Ratio is lower by 0.1, the proportion of volume of coarse aggregate is increased by 0.02
Therefore, corrected proportion of volume of coarse aggregate for W/C ratio of 0.40 is 0.62
For Pumpable condition these values should be reduced by 10%
Therefore, Volume of of Coarse aggegate = 0.62 x 0.9 = 0.56
Volume of of Fine aggegate = 1.00-0.56 = 0.44
Step -8th
Mix Calculation
a.) Volume of Concrete - 1m3
b.) Volume of Cement - (Mass of Cement/ Sp. Gravity of Cement) x (1/1000)
Therefore, (277/3.25) x (1/1000) = 0.087 m3
c. ) Volume of Flyash- (Mass of Flyash/ Sp. Gravity of Flyash) x (1/1000)
Therefore, (118.5/2.2) x (1/1000) = 0.053 m3
d. ) Volume of Water- (Mass of Water/ Sp. Gravity of Water) x (1/1000)
Therefore, (158/1) x (1/1000) = 0.158 m3
e. ) Volume of Chemical Admixture. - (Mass of Chemical Admixture/ Sp. Gravity of Admixture) x (1/1000)
Assuming 2% by mass of cementitious material - 395 x 0.02 = 7.9
Therefore, (7.9/1.145) x (1/1000) = 0.006 m3
f.) Volume of Aggregate - (a-(b+c+d+e))
Therefore, (1-(0.087+0.053+0.158+0.006) = 0.696 m3
g.) Mass of coarse aggregate - Vol of aggregate x Volume of Coarse aggreagte x Specific gravity of Coarse aggragate x 1000
Therefore, 0.696 x 0.56 x 2.68 x 1000 = 1044.55 Kg/m3
h.) Mass of fine aggregate - Vol of aggregate x Volume of fine aggreagte x Specific gravity of fine aggragate x 1000
Therefore, 0.696 x 0.44 x 2.65 x 1000 = 811 Kg/m3
Step -9th
Final Mix Proportion
a.) Cement - 277 Kg/m3
b.) Flyash - 118.5 Kg/m3
c.) Water - 158 Kg/m3
d.) Fine Aggregate - 811Kg/m3
e.) Coarse Aggregate (20mm) - 1044.55 Kg/m3
f.) Chemical Admixture - 7.9 Kg/m3
g.) Water Cement Ratio - 0.4
h.) Mix Proportion by weight - 1 : 2.92 : 3.77
All material to be batched properly and slump to be measured for three repititions for different trials , dosage of admixture to be adjusted as per workable condition.
Material to be mixed well and filled in concrete cubes for testing in 7 and 28 days respectively.
Two more trials having variations ± 10% of W/C ratio in Step B shall be carried out and graph b/w three W/C and compressive strength to be plotted of given target mean strength of different trials.