Project on Concrete Mix Design for various grades of Concrete
Concrete Mix Design for M35 grade concrete with fly ash
Aim : Concrete Mix Design for M35 grade concrete with fly ash.
Procedure :
Step 1 - Stipulation for proportioning
a) Grade designation : M35
b) Type of cement : OPC 43 grade conforming to IS 8112
c) Type of mineral admixture : Fly ash conforming to IS 3812(part 1)
d) Maximum nominal size of aggregate : 20mm
e) Minimum cement content : 320 Kg/m^3(from table 5 of IS 456 : 2000 - exposure condition)
f) Maximum water-cement ratio : 0.45(from table 5 of IS 456 : 2000 - exposure condition)
g) Workability : 100mm(slump)
h) Exposure condition : severe (For reinforced concrete)
i) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed angular aggregate
l) Maximum cement (OPC) content : 450 Kg/m^3
m) Chemical admixture type : Superplasticizers
Step 2 - Test Data for Materials
a) Cement used : OPC 43 grade conforming to IS 8112
b) Specific gravity of cement : 3.15
c) Fly ash : Conforming to IS 3812(part 1)
d) Specific gravity of fly ash : 2.2
e) Chemical admixture : Superplasticizer conforming to IS 9103
f) Specific gravity of :
1) Coarse aggregate : 2.74
2) Fine aggregate : 2.74
g) water absorption :
1) Coarse aggregate : 0.5 percent
2) Fine aggregate : 1.0 percent
h) Free (surface) moisture :
1) Coarse aggregate : Nil (absorbed moisture also nil)
2) Fine aggregate : Nil
i) Seive analysis :
1) Coarse aggregate : 
2) Fine aggregate : Conforming to grading Zone I of Table 4 of IS 383
Step 3 - Target strength for Mix Proportioning
f'ck = fck + 1.65 S
Where,
f'ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation
From Table 1, Standard Deviation, s = 5 N/mm^2
Therefore, target strength = 35 + (1.65 x 5) = 43.25 N/mm^2
Step 4 - Selection of water cement ratio
From Table 5 of IS 456, Maximum water cement ratio = 0.45
Based on experience, adopt water cement ratio as 0.40
0.40 < 0.45, hence OK
Step 5 - Selection of Water Content
From Table 2, Maximum water content for 20mm aggregate = 186 litre (for 25 to 50 mm slump range)
Estimated water content for 100mm slump = 186 + ((6/100)x186) = 197 litre
As superplasticizer is used, the water content can be reduced upto 30 percent
Based on trials with superplasticizer water content reduction of 29 percent has been achieved.Hence, the arrived water content = 197 x 0.71 = 140 litres.
Step 6 - Cakculation of Cement and Fly ash content
Water cement ratio = 0.40
Cementitious material (cement + fly ash) content = 140/0.40 = 350 Kg/m^3
From Table 5 of IS 456 minimum cement content for 'severe' exposure conditions = 320 Kg/m^3
350 Kg/m^3 > 320 Kg/m^3. Hence, OK.
Now, to proportion a mix containing fly ash the following steps are suggested:
a) Decide the percentage fly ash to be used based on project requirement and quality of materials
b) In certain situations increase in cernentitious material content may be warranted, The decision on increase in cementitious material content and its percentage may be based on experience and trial (see Note).
NOTE - This illustrative example is with increase of 10 percent cement itious material content.
Cementitious material content = 350 x 1.10 = 385 Kg/m^3
Water content = 140 Kg/m^3
So, water cement ratio =140/385 = 0.364
Fly ash @ 30% of total cementitious material content = 385 x 30% = 115 Kg/m^3
Cement (OPC) = 385 - 115 = 270Kg/m^3
Saving of cement while using fly ash = 350 - 270 = 80 Kg/m^3
Fly ash being utilized = 115 Kg/m^3
Step 7 - Proportion of volume of Coarse aggregate and Fine aggregate
From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)for water-cement ratio of 0.50 =0.60.
In the present case water-cement ratio is 0.40. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower hy 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 proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62
NOTE - In case the coarse aggregate is not angular one, then also volume of coarse aggregate may be required to be increased suitably, based on experience.
For pumpable concrete these values should be reduced by 10 percent.
Therefore. volume of coarse aggregate = 0.62 x 0.9 =0.56.
Volume of fine aggregate content = 1 - 0.56 = 0.44.
Step 8 - Mix calculations
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m^3
b) Volume of cement = (Mass of cement/Specific gravity of cement) x (1/1000)
= (270/3.15) x (1/1000) = 0.086 m^3
c) Volume of fly ash = (Mass of fly ash/Specific gravity of fly ash) x (1/1000)
= (115/1) x (1/1000) = 0.052 m^3
d) Volume of water = (Mass of water/Specific gravity of water) x (1/1000)
= (140/1) x (1/1000) = 0.140 m^3
e) Volume of chemical admixture (superplasticizer) @ 2.0% by mass of cementitious material)
= (Mass of chemical admixture/Specific gravity of chemical admixture) x (1/1000)
=(7/1.145) x (1/1000) = 0.007 m^3
f) Volume of all in aggregates = [a-(b+c+d+e)]
= 1-(0.086 + 0.052 + 0.140 + 0.007) = 0.715 m^3
g) Mass of Coarse aggregate = f x volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
= 0.715 x 0.56 x 2.74 x1000 = 1097 Kg
h) Mass of fine aggregate = f x volume of fine aggregate x Specific gravity of fine aggregate x 1000
= 0.715 x 0.44 x 2.74 x1000 = 862 Kg
Step 9 - Mix proportions for trial number 1
Cement = 270 Kg/m^3
Fly Ash = 115 Kg/m^3
Water = 140 Kg/m^3
Fine aggregate = 862 Kg/m^3
Coarse aggregate = 1097 Kg/m^3
Chemical admixture = 7.7 Kg/m^3
Water-cement ratio = 0.364
NOTE - Aggregates should be used in saturated surface dry condition. If otherwise, when computing the requirement of mixing water, allowance shall be made for the free (surface ) moisture contributed by the fine and coarse aggregates. On the other hand, if the aggregates are dry, the amount of mixing water should he increased by an amount equal to the moisture likely to be absorbed by the aggregates . Necessary adjustments are also required to be made in mass of aggregates. The surface water and percen water absorption of aggregates shall be determined according to IS 2386 (Part 3).
Step 10 - The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall he reworked for the actual water content and checked for durability requirements.
Step 11 - Two more trials having variation of ± 10 percent of water-cement ratio in step-10 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall he plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall he met.
Concrete Mix Design for M50 grade concrete without Fly ash
Aim : Concrete Mix Design for M50 grade concrete without Fly ash
Procedure :
Step 1 - Stipulation for proportioning
a) Grade designation : M 50
b) Type of cement : OPC 53 grade confirming to IS 8112
c) Maximum nominal size of aggregate : 20 mm
d) Minimum cement content : 320 kg/m3
e) Maximum water-cement ratio : 0.35
f) Workability : 100 mm (slump)
g) Exposure condition : Extreme (for reinforced concrete)
h) Method of concrete placing : Pumping
i) Degree of supervision : Good
j) Type of aggregate : Crushed angular aggregate
k) Maximum cement content : 450 kg/m3
l) Chemical admixture type : Super Plasticizer
Step 2 - Test Data for Materials
a) Cement used : OPC 53 grade conforming to IS 8112
b) Specific gravity of cement : 3.12
c) Chemical admixture : Superplasticizer conforming to IS 9103
d) Specific gravity of :
1) Coarse aggregate : 2.74
2) Fine aggregate : 2.74
e) water absorption :
1) Coarse aggregate : 0.5 percent
2) Fine aggregate : 1.0 percent
f) Free (surface) moisture :
1) Coarse aggregate : Nil (absorbed moisture also nil)
2) Fine aggregate : Nil
g) Seive analysis :
1) Coarse aggregate :
2) Fine aggregate : Conforming to grading Zone I of Table 4 of IS 383
Step 3 - Target strength for Mix Proportioning
f'ck = fck + 1.65 S
Where,
f'ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation
From Table 1, Standard Deviation, s = 5 N/mm^2
Therefore, target strength = 50 + (1.65 x 5) = 58.25 N/mm^2
Step 4 - Selection of water cement ratio
From Table 5 of IS 456, Maximum water cement ratio = 0.45
Based on experience, adopt water cement ratio as 0.40
0.40 < 0.45, hence OK
Step 5 - Selection of Water Content
From Table 2, Maximum water content for 20mm aggregate = 186 litre (for 25 to 50 mm slump range)
Estimated water content for 100mm slump = 186 + ((6/100)x186) = 197 litre
As superplasticizer is used, the water content can be reduced upto 20 percent
Based on trials with superplasticizer water content reduction of 29 percent has been achieved.Hence, the arrived water content = 197 x 0.71 = 140 litres.
Step 6 - Cakculation of Cement and Fly ash content
Water cement ratio = 0.40
Cementitious material (cement + fly ash) content = 140/0.40 = 350 Kg/m^3
From Table 5 of IS 456 minimum cement content for 'severe' exposure conditions = 320 Kg/m^3
350 Kg/m^3 > 320 Kg/m^3. Hence, OK.
Step 7 - Proportion of volume of Coarse aggregate and Fine aggregate
From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)for water-cement ratio of 0.50 =0.60.
In the present case water-cement ratio is 0.40. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower hy 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 proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62
NOTE - In case the coarse aggregate is not angular one, then also volume of coarse aggregate may be required to be increased suitably, based on experience.
For pumpable concrete these values should be reduced by 10 percent.
Therefore. volume of coarse aggregate = 0.62 x 0.9 =0.56.
Volume of fine aggregate content = 1 - 0.56 = 0.44.
Step 8 - Mix calculations
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m^3
b) Volume of cement = (Mass of cement/Specific gravity of cement) x (1/1000)
= (350/3.15) x (1/1000) = 0.111 m^3
c) Volume of water = (Mass of water/Specific gravity of water) x (1/1000)
= (140/1) x (1/1000) = 0.140 m^3
d) Volume of chemical admixture (superplasticizer) @ 2.0% by mass of cementitious material)
= (Mass of chemical admixture/Specific gravity of chemical admixture) x (1/1000)
=(7/1.145) x (1/1000) = 0.006 m^3
e) Volume of all in aggregates = [a-(b+c+d)]
= 1-(0.111 + 0.140 + 0.006) = 0.743 m^3
g) Mass of Coarse aggregate = f x volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
= 0.743 x 0.56 x 2.74 x1000 = 1140 Kg
h) Mass of fine aggregate = f x volume of fine aggregate x Specific gravity of fine aggregate x 1000
= 0.743 x 0.44 x 2.74 x1000 = 896 Kg
Step 9 - Mix proportions for trial number 1
Cement = 350 Kg/m^3
Water = 140 Kg/m^3
Fine aggregate = 896 Kg/m^3
Coarse aggregate = 1140 Kg/m^3
Chemical admixture = 7 Kg/m^3
Water-cement ratio = 0.4
NOTE - Aggregates should be used in saturated surface dry condition. If otherwise, when computing the requirement of mixing water, allowance shall be made for the free (surface ) moisture contributed by the fine and coarse aggregates. On the other hand, if the aggregates are dry, the amount of mixing water should he increased by an amount equal to the moisture likely to be absorbed by the aggregates . Necessary adjustments are also required to be made in mass of aggregates. The surface water and percen water absorption of aggregates shall be determined according to IS 2386 (Part 3).
Step 10 - The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall he reworked for the actual water content and checked for durability requirements.
Step 11 - Two more trials having variation of ± 10 percent of water-cement ratio in step-10 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall he plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall he met.