Project on Concrete Mix Design for various grades of Concrete
PROJECT : 1
* AIM :
To Calculate the Concrete Mix Design for M35 grade concrete with fly ash and M50 grade concrete without Fly ash.
* PROCEDURE :
1.To Calculate the Concrete Mix Design for M35 grade concrete with fly ash :
STEP 1 : Data Required for Concrete Mix Design
Grade of Concrete : M35
Type of Cement : OPC 43 Grade confirming to IS 8112
Type of mineral admixture : Fly Ash confirming to IS 3812 (PART 1)
Maximum Nominal size of Aggregate : 20mm
Minimum cement content : 320 Kg/m3 (From Table 5 of IS 456 : 2000 - EXPOSURE CONDITION)
Maximum water - cement ratio : 0.45 (Table 5 of IS 456-2000 EXPOSURE CONDITION)
Exposure Condition : Severe (For Reinforced Concrete)
Workability : 100mm (Slump value for pumpable concrete)
Method of concrete placing : Pumping
Degree of supervision : Good
Type of Aggregate : Crushed Angular Aggregates
Maximum cement content : 450 Kg/m3
Chemical admixture : Super Plasticizer
STEP 2 : Test Data for Materials :
Cement used : OPC 43 Grade
Specific gravity of cement : 3.15
Fly Ash : Confirming to IS 3812 PART 1
Specific gravity of fly ash : 2.2
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Water absorption of coarse aggregate : 0.5%
Water absorption of fine aggregate : 1.0%
Free surface moisture of Coarse aggregate : Nil
Free surface moisture of Fine aggregate : Nil
Sieve analysis of Coarse aggregate : Confirming to Table 2 of IS 383
Sieve analysis of Fine aggregate :Confirming to Grading Zone II of Table 4 of IS 383
STEP 3 : Target Mean Strength
ft = fck + 1.65s
Where,
ft = target average compressive strength at 28 days
fck = Characteristics compressive strength at 28 days
s = standard deviation
s = 5 N/mm2 ( From table 1 of IS 10262 : 2009)
ft = 35 + 1.65 x 5 = 43.25 N/mm2
Target Mean Strength = 43.25 N/mm2.
STEP 4 : Selection of Water - Cement Ratio
The maximum water - cement ratio to design M50 grade concrete can be found from table 5 of IS 456- 2000.
Maximum W/C ratio = 0.45
Adopted water - cement ratio for M35 grade is 0.44
0.44 < 0.45 ,Hence Ok.
Adopted W/C ratio = 0.44.
STEP 5 : Selection of Water content
From Table 2 of IS 10262 : 2009,maximum 186 litre ( for 25 to 50 mm water content for 20mm slump range)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from50mm slump.So a 6% is to be added to it.
186 + (6/100)*186 = 197 litre.
Estimated water content for 100mm slump
As Super plasticizer is used water content reduction of 20% is achieved, Hence the arrived water content is,
197 * 0.8 = 158 litre.
Water content = 158 litre.
STEP 6 : Calculation of Cement content and Fly ash required.
Adopted W/C Ratio = 0.44
Total cementitious ( Cement + Fly ash )Material = 158/0.44 = 359 Kg/m3
Water content / Water-cement ratio,
The cementitious content has to be increased in order to attain good workability and strength. The increment required is determined on the basis of experience and research .Here we are increasing cementitious content by 10%.
Final cementitious content = 359 X 1.10 = 395 Kg
395 Kg/m3 > 320 Kg/m3 hence Ok.
New water cement ratio = 158/395 = 0.4
Fly ash content is taken as 30% of the total cementitious content = 395 X 0.3 = 118.5 Kg/m3
Cement required = 395 - 118 = 277 Kg/m3
Cement quantity saved due to fly ash addition = 350 - 277 = 73 Kg/m3
Cementitious material, cement, and flyash required is 395 Kg/m3, 277 Kg/m3, and 118 Kg/m3 and the W/C Ratio is 0.4.
STEP 7 : Volume of Coarse Aggregate and Fine Aggregate Content
From Table 3 of IS 10262:2009 Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone II) for W/C ratio 0.50 is
In our case the water cement ratio is 0.44.
Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. The W/C ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02.
Corrected proportion of volume of coarse aggregate for w/c ratio 0.44 is 0.632.
For pumpable concrete these values should be reduced up to 10%.
0.632 X 0.9 = 0.568.
Volume of Coarse aggregate = 0.568
Volume of Fine aggregate = 1 - 0.568 = 0.431.
STEP 8 : Mix Calculations
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement)/(specific gravity of cement) X 1/1000 = (277/3.15) X (1/1000)
= 0.087m3
c) Volume of flyash = (Mass of Fly ash )/(Specific gravity of cement) X 1/1000 = (118/2.2) X (1/1000)
= 0.053m3
d) Volume of water = (Mass of water)/(specific gravity of water) X 1/1000 = (158/1)X(1/1000) = 0.158m3
e) Volume of chemical admixture = (7.6/1.145) X (1/1000) = 0.006m3
f) Volume of all in aggregate = [ 1 - (0.087 + 0.053 + 0.158 + 0.006) ] = 0.696m3
g) Mass of coarse aggregate = 0.696 X 0.568 X 2.74 X 1000 = 1077 Kg/m3
h) Mass of Fine aggregate = 0.696 X 0.431 X 2.74 X 1000 = 822 Kg/m3
STEP 9 :Mix Proportions
Cement = 277 Kg/m3
Fly ash = 118 Kg/m3
Water = 158 Kg/m3
Fine aggregate = 822 Kg/m3
Coarse aggregate = 1077 Kg/m3
Chemical admixture = 7.18 Kg/m3
Water - Cement Ratio = 0.4
Mix Proportion = [ 1 : 2.08 : 2.72 ] .
2. To Calculate the Concrete Mix Design for M50 grade concrete without fly ash.
STEP 1 : Data Required For Concrete Mix Design
Grade of Concrete : M50
Type of Cement : OPC 53 Grade (confirming to IS BIS 12269 - 1987)
Nominal size of aggregate : 20mm
Minimum cement content : 320 kg/m3
Maximum water - cement ratio : 0.45
Workability : 100mm (slump value for pumpable concrete)
Exposure condition : Severe (for reinforced concrete)
Method of concrete placing : Pumping
Degree of supervision : Good
Type of aggregate : Crushed Angular Aggregates
Maximum Cement content : 450 Kg/m3
Chemical admixture : Super Plasticizer
STEP 2 : Test Data For Materials
Specific gravity of cement : 3.15
Specific gravity of coarse aggregate : 2.74
Specific gravity of Fine aggregate : 2.64
Water absorption of coarse aggregate : 0.5%
Water absorption of fine aggregate : 1.0%
Free surface moisture of coarse and fine aggregates : Nil
Sieve analysis Fine aggregate : Confirming to Grading Zone II of Table 4 of IS 383.
STEP 3 :Target Mean Strength
ft = fck + 1.65s
s = 5 N/mm2 ( From table 1 of IS 10262:2009)
ft = 50 + 1.65 X 5 = 58.25 N/mm2
Target Mean Strength = 58.25 N/mm2.
STEP 4 : Selection of Water-Cement Ratio
Maximum Water-Cement Ratio = 0.45
Adopted water-cement ratio is 0.44.
STEP 5 : Selection of Water Content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate,
186 litre (for 25 to 50 mm slump range )
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. so a 6% is to be added to it,
186 + (6/100)*186 = 197 litre.
If super plasticizer is used , the water content can be reduced up to 20% and above.
197 X 0.8 = 158 litre.
Water Required = 158 litres.
STEP 6 : Calculation of Cement Content
Adopted W/C Ratio = 0.44
Cement Content = 158/0.44 = 359 Kg/m3
359 Kg/m3 > 320 Kg/m3 , Hence Ok.
Cement Required = 359 Kg/m3.
STEP 7 : Volume of Coarse aggregate and Fine aggregate content
From Table 3 of IS 10262:2009 Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone II) for W/C ratio 0.50 is
In our case the water cement ratio is 0.44.
Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. The W/C ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02.
Corrected proportion of volume of coarse aggregate for w/c ratio 0.44 is 0.632.
For pumpable concrete these values should be reduced up to 10%.
0.632 X 0.9 = 0.568.
Volume of Coarse aggregate = 0.568
Volume of Fine aggregate = 1 - 0.568 = 0.431.
STEP 8 : Mix Calculations
a) Volume of concrete = 1 m3
b) Volume of cement = (359/3.15) X (1/1000) = 0.114 m3
c) Volume of water = (158/1) X (1/1000) = 0.158 m3
d) Volume of chemical admixture = (7.6/1.145) X (1/1000) = 0.006 m3
e) Volume of all in aggregate = [ 1 - ( 0.114 + 0.158 +0.006) ] = 0.722 m3
f) Mass of coarse aggregate = 0.722 X 0.568 X 2.74 X 1000 = 1123 Kg/m3
g) Mass of fine aggregate = 0.722 X 0.431 X 2.64 X 1000 = 821 Kg/m3
STEP 9 : Mix Proportions
Cement = 359 Kg/m3
Water = 158 Kg/m3
Fine aggregate = 821 Kg /m3
Coarse aggregate = 1123 Kg/m3
Chemical admixture = 7.18 Kg/m3
Water Cement Ratio = 0.44
Mix Proportion = [ 1: 2.28 : 3.12 ].
* RESULTS :
Mix Proportion by weight of M35 grade of concrete with fly ash is (1 : 2.08 : 2.72) and its water-cement ratio was found to be 0.4.
Mix Proportion by weight of M50 grade of concrete without fly ash is (1 : 2.28 : 3.12) and its water-cement ratio was found to be 0.44 .