Project on Concrete Mix Design for various grades of Concrete
Ans. Data collection
Grade of concrete = M35
Exposure condition = moderate
grade of cement=M33(OPC)
fck=35N/mm^2
std. Deviation for M35= 5N/mm^2
I. Target mean strength of concrete
ft=fck+1.65*S
ft=35+1.65*5
ft=43.25 N/mm^2
Target mean strength of concrete=43.25 N/mm^2
II. Selection of w/c ratio
From the table 5 of IS 456: 2000
Maximum w/c ratio 0.50 for exposure condition Moderate
Adopted w/c ratio = .45
III. Selection of water content:
From table 2 of IS 10262: 2009,
maximum water content for 20mm aggregate = 186l (for 25mm to 50mm slump range)
For addititional slump 3% may be added for every 25mm slump
Estimated water content for 100 mm slump
=186+(6/100)X186
=197L
As superplasticizer is used, the water content can be reduced up to 20% and above based on trails water content reduction of 29% is achieved with plasticizer
Hence the arrived water content=197X0.71
=140L
IV. Calculation of cement content:
w/c ratio=0.45
Cement content=140/0.45=311.11 Kg/m^3
we can take 311 kg/m^3
From Table -5 of IS 456: 2000 minimum cement content for 'moderate' exposure condition= 300Kg/m^3
311Kg/m^3>300Kg/m^3 hence ok
To proportion a mix containing fly ash, the following steps are to be followed.
1. The % of fly ash need to be decided based on project requrement and quality of materials
2. Increase in cementitous material content is by 10%
cementitious material content=311*1.10=342 Kg/m^3
Water content=140L
w/c ratio=140/342 =0.40
Fly ash at 30% of cement=342*(30/100)= 102.6 Kg/m^3~103 kg/m^3
cement=342-103=239 Kg/m^3
Saving of cement using fly ash=311-239=72 Kg/m^3
V. Proportion of volume of CA and FA concrete
From table 3 of IS 10262:2009, volume of CA corresponding to 20mm size aggregate and FA (zone1) for w/c ratio 50 is 0.60
in the present case the water cement ratio is 0.45
- There fore the volume of CA need to be increased to decrease the FA content
-As w/c ratio is lower by 0.05, the proportion of volume of CA is increased by 0.01 (at the rate of -/+ 0.01 for every +-0.05 charge in w/c ratio
Therefore, corrected volume of CA for the w/c ratio of 0.45=0.61
(Note: if CA is not a angular types then also the volume of CA may be required to be increased suitably based on experience)
For pumpable concrete these value are reduced by 10%
Therefore, volume of CA=0.61X0.9=0.55
volume of FA content=1-0.55=0.45
VI. Mix calculation:
a) volume of concrete=1m^3
b) volume of cement =239/3.15 X 1/1000
=0.075 m^3
c) volume of fly ash =103/2.2 x 1/1000
= 0.046 m^3
d) volume of water =140/1 X 1/1000
=0.140 m^3
e) volume of chemical admixture =6.8/1.145 X1/1000
=0.006m^3
f) volume of aggregate(FA & CA) =(a-(b+c+d+e))
=(1-(0.075+0.046+0.140+0.006))
=0.733 m^3
g) mass of CA =0.733 X 0.55 X 2.74 X 1000
=1124 Kg/m^3
h) mass of FA = 0.733 x 0.45 x 2.74 x 1000
=906Kg/m^3
mix proportion for trial noumber 1:
Cement = 239 kg/m^3
Fly ash = 103 kg/m^3
Water = 140 kg/m^3
FA = 903 kg/m^3
CA = 1124 kg/m^3
chemical Adnixture= 6.8 kg/m^3
w/c ratio = 0.4
Trial mix ratio =1:3.77 :4.70
FOR M50 GRADE CONCRETE WITHOUT FLY ASH
Data collection--
Grade of concrete =M50
Exposure condition = moderate
Grade of concrete = M33 (OPC)
f'ck= 50 N/mm^2
Std deviation for M50= 5N/mm^2
I. Target mean strength of concrete
=50+1.65X5
=58.25 N/mm^2
II. Selection of water cement ratio
From Table 5 IS 456: 2000
maximum w/c ratio for 'moderate' exposure condition is 0.50
adopted w/c ratio = 0.45
III. Selection of cement content:
it can be calculated from w/c ratio
minimum cement content is taken from Table-5 of IS 456:2000
W=186 kg
w/c=0.45
C=186/0.45
=413.33 kg/m^3
Estimated water content for 100 mm slump
=186+6/100X186
=197L
As superplasticizer is used, the water content can be reduced up to 20% and above based on trails water content reduction of 29% is achieved with plasticizer
Hence the arrived water content=197X0.71
=140L
IV. calculation of cement content:
w/c ratio=0.45
cement content=140/0.45=311 Kg/m^3
hence ok from table 5 IS 456
V. Proportion of volume of CA and FA concrete
From table 3 of IS 10262:2009, volume of CA corresponding to 20mm size aggregate and FA (zone1) for w/c ratio .50 is 0.60
in the present case the water cement ratio is 0.45
- There fore the volume of CA need to be increased to decrease the FA content
-As w/c ratio is lower by 0.06, the proportion of volume of CA is increased by 0.01 (at the rate of -/+ 0.01 for every +-0.05 charge in w/c ratio
Therefore, corrected volume of CA for the w/c ratio of 0.45=0.62
(Note: if CA is not a angular types then also the volume of CA may be required to be increased suitably based on experience)
For pumpable concrete these value are reduced by 10%
Therefore, volume of CA=0.61X0.9=0.55
volume of FA content=1-0.55=0.45
VI. Mix calculation:
a) volume of concrete=1m^3
b) volume of cement=311/3.15 X 1/1000
=0.099 m^3
c) volume of water=140/1 X 1/1000
=0.140 m^3
d)volume of chemical admixture=6.22/1.145 X1/1000
=0.005m^3
e) volume of aggregate(FA & CA)=(a-(b+c+d))
=(1-(0.099+0.140+0.005))
=0.756 m^3
f) mass of CA =0.756 X 0.55 X 2.74 X 1000
=1139.29 Kg/m^3
g) mass of FA = 0.756 x 0.45 x 2.74 x 1000
=932.18 Kg/m^3
VII. Mix proportion for trial number1:
Cement = 311 kg/m^3
Water = 140kg/m^3
FA = 932 kg/m^3
CA = 1139 kg/m^3
Chemical admixture = 6.22 kg/m^3
W/C ratio = 0.40
Trial mix Ratio = 1: 2.99: 3.66