Project on Concrete Mix Design for various grades of Concrete
Aim - To calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash.
Introduction - Concrete mix design is used to mix the ingredients like cement, sand and aggregates. The mix design states about taking the proportion of this ingredients, so that we can get the desired strength for the structure. The workability, w/c ratio, durability, compressive strength, setting time all can be acheived by deciding the proportion of materials. Other admixtures are also used to improve the quality of concrete like we are going to use fly ash as an additive for the mix design of M35 grade. In this project we will be calculating the mix design for M35 grade of concrete with fly ash and M50 grade of concrete without fly ash.
Objective - To design M35 grade concrete with fly ash & M50 grade concrete without Fly ash. Using the IS code guidelines from 10262 : 2009.
Part 1 - To calculate the concrete mix design for M35 grade concrete with fly ash.
Basic Data :
Grade - M35
Cement - OPC 43
Admixture used - Fly Ash
Size of aggregate - 20 mm
Minimum cement content - 320 kg/m^3 (Table 5, IS 456:2000, condition-exposure)
Maximum cement content - 450 kg/m^3
Maximum water cement ratio - 0.45 (Table 5, IS 456:2000, condition-exposure)
Workability - 100 mm
Exposure condition - severe
Method of concrete placing - pumping
Chemical admixture - superplasticizer
Type of aggregate - Angular crushed aggregate
Tests on materials :
Cement used - OPC 43 grade
Specific gravity - 3.15
Fly ash - as per IS code
Specific gravity - 2.2
Chemical admixture - superplasticizer
Specific gravity of aggregate - 2.74
Water absorption of CA - 0.5%
Water absorption of FA - 1.0%
Target strength for mix proportioning :
f'ck = fck + 1.65s
= 35 + 1.65x5 = 43.25 N/mm^2
f'ck = target avg compressive strength of 28 days
fck = characteristics compressive strength
s = standard deviation
s = 5 N/mm^2 (from table 10262:2009)
Selection of water-cement ratio :
We take w/c ratio as 0.45 from table 5 IS 456:2000, it gives the maximum w/c ratio for M50 grade of concrete.
We take 0.44
0.44<0.45 , hence ok.
Selection of water content :
From table 5 IS 456:2000, the maximum water content allowed is 186 litres (for 25-50 mm aggregate)
Clause 4.2 suggests 3% of water content should be increase for extra 25 mm slump which may be added over 50 mm slump.
So we have assumed 100 mm slump, we have to add 6% to the 186 litres.
Therefore , 186+11.16 = 197.16 lit say 197 litres
It also states if superplasticizers is used then the water content can be reduced to 20%.
Therefore, 197-39.4 = 157.6 litres say 158 litres.
Calculation of cement and fly ash required :
W/c ratio taken = 0.44
Cement + fly ash = water content/w-c ratio = 158/0.44 = 359 kg/m^3
Increasing cement by 10% = 359+359.9= 395 kg
From table 5 IS 456:2000, the minimum cement content for severe condition is 320kg
395>320kg/m^3 , hence ok.
water cement ratio = 158/395=0.4
Fly ash taken as 30% of the total cementious content = 395x0.3=118.5 kg/m^3.
Cement required = 395-118 = 277kg/m^3
fly ash instead of cement used , so cement quantity is 350-277 = 73kg/m^3.
Volume of CA and FA content :
From table 3 of IS 10262:2009, Volume of CA and FA for 20 mm size aggregate is 0.62.
Now the w/c ratio is 0.44 so we need to increase the volume of CA to decrease the volume of FA. The proportion of CA can be increased by 0.02
Therefore the corrected volume of CA is 0.632
For pumpable concrete the value can be reduced by 10%.
Therefore, 0.632x0.9 = 0.568
Volume of FA content = 1-0.568 = 0.431
MIX CALCULATIONS :
a) Volume of concrete =1 m^3
b) Volume of cement = [Mass of cement]/[specific gravity of cement] x 1/1000 = (277/3.15) x (1/1000) = 0.087m^3.
c) Volume of fly ash = [Mass of fly ash]/[specific gravity of fly ash] x 1/1000 = (118/2.2) x (1/1000) = 0.053m^3
d) Volume of water = [Mass of water]/[specific gravity of water] x 1/1000 = ( 158/1) x (1/1000) = 0.158 m^3
e) Volume of admixture = [Mass of admixture]/[specific gravity of admixture] x 1/1000 = (7.6/1.145) x (1/1000) = 0.00663 m^3
f) Volume of all in aggregate = [a-(b+c+d+e)] = [1-(0.087+0.053+0.158+0.00663)] = 0.696 m^3
g) Mass of CA = f x volume of CA x specific gravity of CA x 1000 = 0.696x0.568x2.74x1000 = 1077 kg/m^3
h) Mass of FA = f x volume of FA x specific gravity of FA x 1000 = 0.696x0.431x2.74x1000 = 822 kg/m^3
MIX PROPORTIONS :
Cement - 277 kg/m^3
Fly ash - 118kg/m^3
Water - 158 litre/m^3
Fine aggregate - 822 kg/m^3
Coarse aggregate - 1077 kg/m^3
Admixture - 7.18 kg/m^3
W/c ratio - 0.4
Mix proportion by weight = 1:2.08:2.72
Two more trials should be done with variation of 10% in w/c ratio and a graph between all the three w/c ratios should be plot out and and then the mix proportion will be acheived.
Part 2 - To calculate the concrete mix design for M50 grade concrete without fly ash.
Basic Data :
Grade - M50
Cement - OPC 53
Admixture used - Fly Ash
Size of aggregate - 20 mm
Minimum cement content - 320 kg/m^3 (Table 5, IS 456:2000, condition-exposure)
Maximum cement content - 450 kg/m^3
Maximum water cement ratio - 0.45 (Table 5, IS 456:2000, condition-exposure)
Workability - 100 mm
Exposure condition - severe
Method of concrete placing - pumping
Chemical admixture - superplasticizer
Type of aggregate - Angular crushed aggregate
Tests on materials :
Cement used - OPC 53 grade
Specific gravity - 3.15
Fly ash - as per IS code
Specific gravity - 2.2
Chemical admixture - superplasticizer
Specific gravity of CA aggregate - 2.74
Specific gravity of FA aggregate - 2.64
Water absorption of CA - 0.5%
Water absorption of FA - 1.0%
Target strength for mix proportioning :
f'ck = fck + 1.65s
= 50 + 1.65x5 = 58.25 N/mm^2
f'ck = target avg compressive strength of 28 days
fck = characteristics compressive strength
s = standard deviation
s = 5 N/mm^2 (from table 10262:2009)
Selection of water-cement ratio :
We take w/c ratio as 0.45 from table 5 IS 456:2000, it gives the maximum w/c ratio for M50 grade of concrete.
We take w/c ratio as 0.44
0.44<0.45 , hence ok.
Selection of water content :
From table 5, IS 456:2000, the maximum water content allowed is 186 litres (for 25-50 mm aggregate)
Clause 4.2 suggests 3% of water content should be increase for extra 25 mm slump which may be added over 50 mm slump.
So we have assumed 100 mm slump, we have to add 6% to the 186 litres.
Therefore , 186+11.16 = 197.16 lit say 197 litres
It also states if superplasticizers is used then the water content can be reduced to 20%.
Therefore, 197-39.4 = 157.6 litres say 158 litres.
Calculation of cement required :
W/c ratio taken = 0.44
Cement content = water content/w-c ratio = 158/0.44 = 359 kg/m^3
Increasing cement by 10% = 359+359.9= 395 kg
From table 5 IS 456:2000, the minimum cement content for severe condition is 320kg
395>320kg/m^3 , hence ok.
Volume of CA and FA content :
From table 3 of IS 10262:2009, Volume of CA and FA for 20 mm size aggregate is 0.62.
Now the w/c ratio is 0.44 so we need to increase the volume of CA to decrease the volume of FA. The proportion of CA can be increased by 0.02
Therefore the corrected volume of CA is 0.632
For pumpable concrete the value can be reduced by 10%.
Therefore, 0.632x0.9 = 0.568
Volume of FA content = 1-0.568 = 0.431
MIX CALCULATIONS :
a) Volume of concrete =1 m^3
b) Volume of cement = [Mass of cement]/[specific gravity of cement] x 1/1000 = (359/3.15) x (1/1000) = 0.114m^3.
c) Volume of water = [Mass of water]/[specific gravity of water] x 1/1000 = ( 158/1) x (1/1000) = 0.158 m^3
d) Volume of admixture = [Mass of admixture]/[specific gravity of admixture] x 1/1000 = (7.6/1.145) x (1/1000) = 0.00663 m^3
e) Volume of all in aggregate = [a-(b+c+d)] = [1-(0.114+0.158+0.00663)] = 0.722 m^3
f) Mass of CA = e x volume of CA x specific gravity of CA x 1000 = 0.722x0.568x2.74x1000 = 1123 kg/m^3
g) Mass of FA = e x volume of FA x specific gravity of FA x 1000 = 0.722x0.431x2.64x1000 = 821 kg/m^3
MIX PROPORTIONS :
Cement - 359 kg/m^3
Water - 158 litre/m^3
Fine aggregate - 821 kg/m^3
Coarse aggregate - 1123 kg/m^3
Admixture - 7.18 kg/m^3
W/c ratio - 0.44
Mix proportion by weight = 1:2.28:3.12
Two more trials should be done with variation of 10% in w/c ratio and a graph between all the three w/c ratios should be plot out and and then the mix proportion will be acheived.
Result :
- Mix proportion for M35 grade of concrete with fly ash is 1:2.08:2.72
- Mix proportion for M50 grade of concrete without fly ash is 1:2.28:3.12