Project on Concrete Mix Design for various grades of Concrete
AIM: To calculate the concrete mix design for M35 grade concrete with fly ash and M50 grade cocnrete without fly ash.
OBJECTIVE: The objective of this project is to produce a mix design for M35 grade concrete containing fly ash and M50 grade concrete. The mix will be prepared as per IS METHOD: Concrete mix proportioning guidelines from IS 10262:2009.
TARGET MEAN STRENGTH:
f’ck =fck + 1.65s
Where
f’ck = target average compressive strength at 28 days
fck = characteristics compressive strength at 28 days, and
s = standard deviation.
CEMENT CONTENT:
Cement content = water content/water cement ratio.
VOLUME CALCULATIONS:
(a) Volume of concrete
(b) Volume of cement = Mass of cement / Specific Gravity of Cement]x 1/1000
(c) Volume of water = Mass of water / Specific Gravity of water x 1/1000
(d)Volume of chemical admixture = Mass of admixture / Specific Gravity of admixture x 1/1000
(e) Volume of all in aggregate =a-(b+c+d)
(f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
(g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000.
M35 GRADE CONCRETE WITH FLY ASH:
Grade=M35
Type of cement=opc 43 grade
Type of mineral add mixture=fly ash
Nominal size of aggregate=20mm
Cement content=320kg/m3 (from IS 456-2000)
Water cement ratio=0.45(from IS 456-2000)
Specific gravity of cement=3.15
Specific gravity of fly ash=2.2
Chemical admixture=suoper plasticizer
Specific gravity of coarse aggragate=2.74
Specific gravity of fine aggragate=2.74
TARGET STRENGTH FOR MIX PROPORTIONING:
fck =fck + 1.65s
Where,
f’ck = target average compressive strength at 28 days
fck = characteristics compressive strength at 28 days, and
s = standard deviation
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.
35 + 1.65 x 5 = 43.25 N/mm2
Target mean strength = 43.25 N/mm2
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
Based on experience adopted water cement ratio is .44
0.44<0.45, hence ok
Adopted W/C ratio=0.44
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
Estimated water content for 100 mm slump
186+ (6/100)*186 = 197 litre.
197*0.8=158 liters
Water required is 158 liters
CALCULATION OF CEMENT AND FLY ASH REQUIRED:
Adopted w/c Ratio
0.44
Total cementitious (Cement + fly ash)requirement =
Water content/ Water Cement ratio
158/0.44 = 359 kg/m3
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
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions
320 kg
395 kg/m3 > 320 kg/m3 hence ok.
Cementitious material content
395
New water cement ratio
158/395 =0.4
Fly ash content is taken as 30% of the total cementitious content
395 X .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
VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
Volume of coarse aggragate 20mm size and fine aggragate for water cement ratio of 0.50
0.62
In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06.
corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44
0.632
0.632*0.9=0.568
Volume of fine aggregate content 1 – 0.568 =0.431.
Volume of fine aggregate and coarse aggregate is 0.431 and 0.568.
MIX CALCULATIONS:
The mix calculations as per unit volume of concrete shall be as follows:
a) Volume of concrete 1 m3
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 fly ash = [Mass of fly ash] / [Specific Gravity of fly ash] x 1/1000
(118/2.2) X (1/1000) =0.053
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 = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
(7.6/1.145) X (1/1000) =0.006 m3
f) Volume of all in aggregate =
[a-(b+c+d+e)]
[1-(0.087+0.053+0.158+0.006)] = 0.696m3
g) Mass of coarse aggregate= f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
0.696x 0.568 x 2.74 x 1000 = 1077 kg/m3
h) Mass of fine aggregate= f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
0.696x 0.431x 2.74 x 1000 = 822 kg/m3.
MIX PROPORTIONS:
Cement=277 kg/m3
Fly ash=118 kg/m3
Water=158 l/m3
Fine aggregate=822 kg/m3
Coarse aggregate 20mm=1077 kg/m3
Chemical admixture=7.18 kg/m3
Water-cement ratio (lowest W/C ratio is selected)=0.4
Mix Proportion By weight=1:2.08:2.72 .
TO CALCULATE THE CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLY ASH:
Grade designation=M50
Type of cement=OPC 53 Grade confirming to IS BIS 12269 - 1987
Maximum nominal size of aggregate=20 mm
Minimum cement content=320 kg/m3 (Table 5 of IS 456:2000- Exposure condition)
Maximum water-cement ratio=0.45 (Table 5 of IS 456:2000 Exposure condition)
Type of aggregate=Crushed Angular Aggregates
Maximum cement content=450 kg/m3
Chemical admixture type=Super Plasticizer
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%
TARGET STRENGTH FOR MIX PROPORTIONING:
fck =fck + 1.65s
Where
· fck = target average compressive strength at 28 days
· fck = characteristics compressive strength at 28 days, and
· s = standard deviation
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.
50 + 1.65 x 5 = 58.25 N/mm2
Target mean strength = 58.25 N/mm2
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 for severe exposure.
Maximum W/C ratio =0.45
Based on experience adopted water cement ratio is .44
0.44<0.45, hence ok
Adopted W/C ratio=0.44
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
Estimated water content for 100 mm slump
186+ (6/100)*186 = 197 litre.
197 X 0.8 = 158 litre
Water required is 158 liters.
CALCULATION OF CEMENT REQUIRED:
Adopted w/c Ratio=0.44
Cement Content=158/0.44 = 359 kg/m3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions=320kg/m3
359 kg/m3 > 320 kg/m3 hence ok.
Cement required is 359 kg/m3
Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate for water-cement ratio of 0.50 is
0.62.
0.632 x 0.9 =0.568.
Volume of fine aggregate content
1 – 0.576 =0.431
Volume of fine aggregate and coarse aggregate is 0.431 and 0.568 .
MIX CALCULATIONS:
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete 1 m3
b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000=(359/3.15) X (1/1000) =0.114m3
c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000=(158/1) X (1/1000) = 0.158m3
d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000=(7.6/1.145) X (1/1000) =0.006 m3
e) Volume of all in aggregate ==[a-(b+c+d)]
[1-(0.114+0.158+0.006)] = 0.722m3
f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000=0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000=0.722x 0.431x 2.64 x 1000 = 821 kg/m3.
MIX PROPORTIONS:
Cement=359 kg/m3
Water=158 l/m3
Fine aggregate=821 kg/m3
Coarse aggregate 20mm=1123 kg/m3
Chemical admixture=7.18kg/m3
Water-cement ratio=0.44
Mix Proportion By weight=1:2.28:3.12
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.