Project on Concrete Mix Design for various grades of Concrete
Concrete Mix Design for M-35 Grade of concrete :-
Following steps will be followed:-
Calculation of mix design is based on following conditions :-
a. Taking moderate exposure condition.
b. Nominal size of aggregate as 20 mm
c. Slump required for concrete is 50 mm
d. Type of admixtue - Flyash confirming to IS 3812
e. Sp gravity of cement - 3.15
f. Specific gravity of fly ash - 2.2
g. Specific gravity of coarse & fine aggregate - 2.74
h. As per seive analysis of fine aggregate -Zone 1 is categorized.
1. Calcultion of Target mean strength
Fct = fck +1.65 s ( characteristic strength at 28 Days) & s = Standard deviation as per Table -1 Is 10262
Fct = 35+1.65 *5 = 43.25 MPa
2. Selection of W/c ratio :-
a. As per compressive strength with w/c ratio graph, w.c ratio as per target mean strength of value 43.25 Mpa, w.c ratio come out 0.35
b. w/c ratio as per graph -2 between target mean strength & w.c ratio w/c ratio comes out 0.4
c. As per Table 5 of IS 456-2000 for moderate exposure condition, maximum w/c ratio is 0.5
Therefore, minimum value of the three is the w/c ratio. Taking w/c ratio as 0.35.
3. Selection of Water content
As per Table 2 of IS 10262 -2009
for 20 mm nominal size of aggregate maimum water content is 186 Kg.
4. Calcuation of Cement content
As W/c ratio is 0.35
Cementious material ( cement + flayash) content = 186/0.35 = 531.428 Kg/m3.
As per table 5 of IS 456 -2000, minimum cement content for moderate condition is 300 Kg/m3
5. Estimation of flyash percentage in replacement of cement material
Assuming 30% of cement is replaced by flyash. Therefore
Fly ash content (30% of total cement content) = 0.3*531.428 = 159.428 Kg/m3
Cement Content = 372 Kg/m3
Saving of cement = 531.428-372 = 159.428 Kg/m3.
6. Cacluation of coarse and fine aggregate
As per Table -3 of IS 10262 -2009 for 20 mm maximum nominal size of aggregate for zone 1
Volume of CA over total volume of aggregate is 0.6 for 0.5 w/c ratio
As the w/c ratio is 0.35, Thereofore for every change in w/c ratio by 0.05 there is change of CA/total vol of Aggergate of 0.01
Hence, volume of CA/ Total aggergate is 0.6+0.03 = 0.63
Volume of CA = 0.63
Volume of FA = 0.37
7 Mix Calcualtion
Volume of cement = Mass of cement/ SG of cemet *100
(372/3.15)/1000 = 0.118 cum
Volume of Water = (Mass of water/ SG of water )/1000
(186/1)/1000 = 0.186 cum
Volume of Total Aggregate = 1-0.118-0.186 = 0.696 cum
Volume of CA = Percentage of CA * total volume of aggregate * SG*1000
= 0.63*0.696*2.74*1000
Mass of Corase aggregate = 1201.435 Kg/m3
Volume of FA = Percentage of FA* total volume of aggregate* SG*1000
= 0.37*0.696*2.74*1000
Mass of Fine aggregate = 705.60 Kg/m3
Therefore Mix proportion as per mass for 1st trial
Cement Content = 372 Kg/m3
Fly ash content = 159.428 Kg/m3
Water = 186Kg/m3
Coarse Aggregate = 1201.435 Kg/m3
Fine Aggregate = 705.60 Kg/m3
Calculation of Mix Design M50 grade concrete without Fly ash
Calculation of mix design is based on following conditions :-
a. Taking moderate exposure condition.
b. Nominal size of aggregate as 20 mm
c. Slump required for concrete is 50 mm
d. Sp gravity of cement - 3.15
e. Specific gravity of fly ash - 2.2
f. Specific gravity of coarse & fine aggregate - 2.74
g. As per seive analysis of fine aggregate -Zone 2 is categorize
Following steps will be followed:-
1. Calculation of Targert Mean Strength
fct= fck +1.65 s
fct = 50+1.65*5 = 58.25 MPa
2. Selection of W/C ratio
There for three steps for calculation of W/C ratio:-
1. From Graph for target mena strength of 58.25 MPa value of w/c ratio is 0.3.
2. From Graph 2 for target mean strength of 58.25 MPa value of w/c ratio is 0.35
3. From Table-5 of IS 456-2000 for moderate condition, maximum w/c ratio is 0.5
Based on the three values minimum of the three value is 0.3. Therefore, w/c ratio is taken as 0.3.
3. Calcuation of water content
As per Talbe-2 of IS 10262-2009 for 20 mm nominal size of aggregate, Maximum water content is 186 Kg for 25-50 mm slump requirement.
As the concrete required for Pumping therefor slump required is 100 mm .
As the slump is increased by 25 mm , percentage of water content is increased by 3%
Therefore, water content required now is 186+6%*186 = 197.16 Kg.
Use of superplastisizer is required for control on cement content. Due to application of superplastisizer water content is reduced by 29%.
Hence, corrected water content is = 0.71*197.16 = 139.98 Kg.
4. Calculation of cement content.
Cement content = Water content/W/c ratio = 139.98/0.3 = 466.6 Kg/m3
As per Table -5 of IS 456-2000 minimum cement content required as per moderate exposure condition is 300Kg/m3
5. Volume of CA & FA
As per Table -3 of IS 10262 for 20 mm maxium nominal size of aggregate & for Zone -II of FA,
Vol. of CA over total volume of Aggregate comes out = 0.62
The value of CA is adopted for w/c ratio of 0.5
As the assumed w/c ratio is 0.3 .For every change of w/c ratio by +/- 0.05, changes in aggegate is by +/- 0.02. Therefore, w/c ratio reduced by 4 times 0.05, ratio of aggregate increased by 4 times 0.02.
Corrected ratio becomes = 0.62+0.08 = 0.7
For the case of pumpable concrete value is reduced by 10 %
Therefore Vol of CA = 0.7*0.9
Vol of FA = 0.3*0.9
Now Calculation of Mix calcualtion
1. Volume of Cement Content = (Mass of Cement/ SG of cement)/1000 = (466.6/3.15)/1000 = 0.148
2. Volume of Water = (Mass of water/SG)/1000 = (139.98 /1)/1000 = 0.139
3. Volume of Superplastisizer (2 % by mass of cementious material) = ((0.02*466.6)/1.145)/1000 = 0.008
4. Volume of Total Aggregate = (1-0.148-0.139-0.008) =(1-0.295) = 0.705
Mass of Coarse aggregate = 0.7*0.9*0.705*2.74*1000 = 1216.971 Kg/m3
Mass of Fine Aggregate = 0.3*0.9*0.705*2.74*1000 = 521.55 Kg/m3
Therfore proportion of materials are :-
Cement = 466.6 Kg/m3
Water = 139.98 Kg/m3
CA = 1216.971 Kg/m3
FA = 521.55 Kg/m3
Admixture = 9.33 Kg/m3
W/c ratio = 0.3