Project on Concrete Mix Design for various grades of Concrete
CHALLENGE 05
1) Calculation of Concrete Mix Design for M35 Grade Concrete with Flyash:
i) Stipulations for Proportioning:
- Grade of concrete : M35
- Type of cement : OPC 43 grade
- Maximum nominal size of aggregate: 20mm
- Minimum Cement content : 320kg/m³ (from Table 5 of IS456-2000 - Exposure Condition)
- Maximum W/C ratio - 0.45 (from Table 5 of IS 456-2000 - Exposure Condition)
- Workability : 100mm (slump value for pumpable concrete)
- Exposure Condition : Severe (for reinforced concrete)
- Method of concrete placing : Pump
- Type of Concrete : Crushed angular Aggregate
- Maximum cement content : 450kg/m³
- Chemical admixture type : Super Plasticizers.
ii) Test Data for Materials:
- Cement used : OPC 43 grade conforming to IS8112
- Specific gravity of cement : 3.15
- Chemical admixture : Super Plasticizers conforming to IS 9103
- Specific gravity of CA & FA : 2.74
- Water absorption of CA : 0.5%
- Water absorption of FA : 1.0%
- Fine Aggregate : conforming to grading Zone01 of Table 4 of IS 383.
iii) Target strength for Mix Proportioning:
. f'ck = fck+1.65 S
Where,
f'ck = Target average compressive strength at 28days
fck = Characteristic Compressive strength at 28days
S = Standard Deviation
From Table 1 of IS 10262-2009, Standard Deviation,. S = 5N/mm².
Therefore, Target strength = 35+(1.65x5)
f'ck = 43.25 N/mm².
iv) Selection of Water - Cement ratio:
. From Table 5 of IS 456-2000 for severe exposure,
Maximum W/C ratio = 0.45
Based on experience, adopted W/C ratio is 0.40
0.40<0.45, hence ok.
v) Selection of Water Content:
. From Table 2 of IS 10262-2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range).
Estimated water content for 100mm slump
= 186+(6/100*186)
= 197 litre
As super plasticizers is used, the water content can be reduced upto 20% and above
Based on trials water reduction of 29% is achieved with plasticizers.
Hence the arrived water content = 197*0.71
= 140 litre.
vi) Calculation of Cement Content:
W/C ratio = 0.40
Cementcontent = 140/0.40 = 350kg/m³
FromTable 5 of IS 456 minimum Cement content for 'Severe' exposure Condition = 320kg/m³.
- 350kg/m³ > 320kg/m³, Hence ok.
Now, to proportion a mix containing fly ash the following steps are suggested:
a) The percentage of flyash needs to be decided based on project requirements and quality of materials.
b) In some cases increase in cementitious material can be warrented. Increase in cementitious material content and it's percentage may be based on experience and trails (This example is with increase of 10% cementitious material content).
Cementitious material content = 350x1.10
= 385kg/m³
Water content = 140kg/m³
So, Water-cement ratio = 140/385 = 0.363
Flyash @ 30% total cementitious material content = 385 x 30% = 115kg/m³
Cement ( OPC) content = 385 - 115 = 270kg/m³.
Saving of cement while using flyash
= 350 - 270 = 80kg/m³
Fly ash being utilised = 115kg/m³.
vii) Proportion of Volume of CA and FA:
From Table 3 of IS 10262-2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) for W/C = 0.6
In the present case, W/C is 0.40
*Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
*As water - cement ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every 0.05 change in water cement ratio).
Therefore, corrected volume of coarse aggregate for the water - cement ratio of 0.35 = 0.64
For pumpable concrete these values are reduced by 10%.
Therefore, volume of coarse aggregate = 0.64 x 0.9
= 0.576
Volume of Fine aggregate content = 1 - 0.576 = 0.424
viii) Mix Calculations:
The mix calculation per unit volume of concrete shall be as follows:
a) Volume of concrete = 1m³
b) Volume of cement = (Mass of cement/ Specific gravity of cement) x 1/1000
= 270/3.15 x 1/1000
= 0.086m³
c) Volume of flyash = (Mass of flyash/ specific gravity of flyash) x 1/1000
= 115/2.2 x 1/1000
= 0.052m³
d) Volume of Water = (Mass of water / Specific gravity of water) x 1/1000
= 140/1 x 1/1000
= 0.140m³.
e) Volume of chemical admixture = (Mass of chemical admixture / Specific gravity of admixture) x 1/1000
Mass of chemical admixture = 2% of cementitious material
= 350 x (2/100) = 7.0
Volume of chemical admixture = 7.0/1.145 x 1/1000
= 0.006m³.
f) Volume of aggregate ( FA & CA) = (a - (b+c+d+e)).
= (1- (0.086+0.052+0.140+0.006))
= 0.716m³.
g) Mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.716*0.576*2.74*1000
= 1130 kg/m³
h) Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.716*0.424*2.74*1000
= 832 kg/m³.
MIX PROPORTION :
- Cement = 270 kg/m³
- Flyash = 115 kg/m³
- Fine aggregate = 832 kg/m³
- Coarse aggregate = 1130 kg/m³
- Water = 140 kg/m³
- Chemical admixture = 7kg/m³
- Water - cement ratio = 0.40
Mix Ratio for M35 Grade Concrete with Flyash = 1 : 2.16 : 2.94. ( Cement + Flyash : FA : CA)
2) Calculation for Concrete Mix Design for M50 Grade Concrete without Flyash:
i) Stipulations for Proportioning:
- Grade of concrete : M50
- Type of cement : OPC 43 grade
- Maximum nominal size of aggregate: 20mm
- Minimum Cement content : 320kg/m³ (from Table 5 of IS456-2000 - Exposure Condition)
- Maximum W/C ratio - 0.45 (from Table 5 of IS 456-2000 - Exposure Condition)
- Workability : 100mm (slump value for pumpable concrete)
- Exposure Condition : Severe (for reinforced concrete)
- Method of concrete placing : Pump
- Type of Concrete : Crushed angular Aggregate
- Maximum cement content : 450kg/m³
- Chemical admixture type : Super Plasticizers.
ii) Test Data for Materials:
- Cement used : OPC 43 grade conforming to IS8112
- Specific gravity of cement : 3.15
- Chemical admixture : Super Plasticizers conforming to IS 9103
- Specific gravity of CA & FA : 2.74
- Water absorption of CA : 0.5%
- Water absorption of FA : 1.0%
- Fine Aggregate : conforming to grading Zone01 of Table 4 of IS 383.
iii) Target strength for Mix Proportioning:
. f'ck = fck+1.65 S
Where,
f'ck = Target average compressive strength at 28days
fck = Characteristic Compressive strength at 28days
S = Standard Deviation
From Table 1 of IS 10262-2009, Standard Deviation,. S = 5N/mm².
Therefore, Target strength = 50+(1.65x5)
f'ck = 58.25 N/mm².
iv) Selection of Water - Cement ratio:
. From Table 5 of IS 456-2000 for severe exposure,
Maximum W/C ratio = 0.45
Based on experience, adopted W/C ratio is 0.35
0.35<0.45, hence ok.
v) Selection of Water Content:
. From Table 2 of IS 10262-2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range).
Estimated water content for 100mm slump
= 186+(6/100*186)
= 197 litre
As super plasticizers is used, the water content can be reduced upto 20% and above
Based on trials water reduction of 29% is achieved with plasticizers.
Hence the arrived water content = 197*0.71
= 140 litre.
vi) Calculation of Cement Content:
W/C ratio = 0.35
Cementcontent = 140/0.35 = 400kg/m³
FromTable 5 of IS 456 minimum Cement content for 'Severe' exposure Condition = 320kg/m³.
400kg/m³ > 320kg/m³, Hence ok.
vii) Proportion of Volume of CA and FA:
From Table 3 of IS 10262-2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) for W/C = 0.6
In the present case, W/C is 0.35
*Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
*As water - cement ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every 0.05 change in water cement ratio).
Therefore, corrected volume of coarse aggregate for the water - cement ratio of 0.35 = 0.65
For pumpable concrete these values are reduced by 10%.
Therefore,
volume of coarse aggregate = 0.65 x 0.9
= 0.585
Volume of Fine aggregate content = 1 - 0.585 = 0.415
viii) Mix Calculations:
The mix calculation per unit volume of concrete shall be as follows:
a) Volume of concrete = 1m³
b) Volume of cement = (Mass of cement/ Specific gravity of cement) x 1/1000
= 400/3.15 x 1/1000
= 0.127m³
c) Volume of Water = (Mass of water / Specific gravity of water) x 1/1000
= 140/1 x 1/1000
= 0.140m³.
d) Volume of chemical admixture = (Mass of chemical admixture / Specific gravity of admixture) x 1/1000
Mass of chemical admixture = 2% of cementitious material
= 400 x (2/100) = 8
Volume of chemical admixture = 8/1.145 x 1/1000
= 0.007m³.
e) Volume of aggregate ( FA & CA) = (a - (b+c+d)).
= (1- (0.127+0.140+0.007))
= 0.726m³.
f) Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.726*0.585*2.74*1000
= 1164 kg/m³
g) Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.726*0.415*2.74*1000
= 826 kg/m³.
MIX PROPORTION :
- Cement = 400 kg/m³
- Water = 140 kg/m³
- Fine aggregate = 826 kg/m³
- Coarse aggregate = 1164 kg/m³
- Chemical admixture = 8 kg/m³
- Water - cement ratio = 0.35.
MIX RATIO FOR M50 = 1 : 2.065 : 2.91
(Cement:FA:CA)