Project on Concrete Mix Design for various grades of Concrete
1) Concrete mix design for M35 grade concrete with Fly ash -
AIM - To determine the concrete mix proportions of M35 grade concrete with fly ash by Indian Standards recommended.
REFERENCES -
- IS 10262-2009 - Concrete Mix Proportioning - Guidelines (First Revision )
- IS 456-2000 - Plain and Reinforced Concrete - Code of Practice (Fourth Revision)
INTRODUCTION -
- The process of selecting suitable ingredients of concrete and determining their relative amounts with the objective of producing a concrete of the required, strength, durability, and workability as economically as possible, is termed the concrete mix design.
- The proportioning of ingredient of concrete is governed by the required performance of concrete in two states, the plastic and the hardened states. If the plastic concrete is not workable, it cannot be properly placed and compacted. The property of workability, therefore, becomes of vital importance.
- The compressive strength of hardened concrete which is generally considered to be an index of its other properties, depends upon many factors, e.g. quality and quantity of cement, water and aggregates; batching and mixing; placing, compaction and curing.
- The cost of concrete is made up of the cost of materials, plant and labour. The variations in the cost of materials arise from the fact that the cement is several times costly than the aggregate, thus the aim is to produceas lean a mix as possible.
Requirements of concrete mix design -
- The requirements which form the basis of selection and proportioning of mix ingredients are the minimum compressive strength required from structural consideration.
- The adequate workability necessary for full compaction with the compacting equipment available.
- Maximum water-cement ratio and/or maximum cement content to give adequate durability for the particular site conditions.
- Maximum cement content to avoid shrinkage cracking due to temperature cycle in mass concrete.
PROCEDURE -
Step-1) Data Required -
| 1 | Grade Designation | : M 35 |
| 2 | Type of Cement | : OPC 53 Grade |
| 3 | Type of Admixture | : Fly Ash |
| 4 | Max. nominal size of aggregate | : 20 mm |
| 5 | Min. cement content | : 340 kg/m3 |
| 6 | Max. cement content | : 450 kg/m3 |
| 7 | Max. Water-Cement ratio | : 0.45 |
| 8 | Workability | : 100 mm |
| 9 | Exposure Condition | : Very Severe |
| 10 | Method of Placing | : Pumping |
| 11 | Type of aggregate | : Crushed Angular aggregate |
| 12 | Type of Chemical admixture | : Superplasticizer |
Step-2) Test Data of Material -
| 1 | Specific Gravity of Cement | : 3.15 |
| 2 | Specific Gravity of Fly Ash | : 2.90 |
| 3 | Specific Gravity of Coarse Aggregate | : 2.74 |
| 4 | Specific Gravity of fine aggregate | : 2.74 |
| 5 | Water absorption of Coarse Aggregate | : 0.50% |
| 6 | Water absorption of fine Aggregate | : 1.00% |
| 7 | Sieve analysis fine aggregates confirming | : zone-II |
Step-3) Calculate F(Target) -
f(target)= fck +1.65 x s
Where, f(target) = Targeted average strength at 28 days
fck = Characteristic compressive strength at 28 days
s = standard deviation
F(target) = 35 + 1.65 x 5.0 = 43.25 N/mm2
F(target) = 43.25 N/mm2
Step-4) Selection of W/C ratio -
as per IS 456:2000 Table - 5 , the maximum W/C ratio = 0.45
take W/C ratio = 0.45
Step-5) Selection of Water content -
From IS 456:2000 Table -2,
maximum water content = 186 lit. for 20mm aggregate (For 25 - 50 mm slump range)
Estimated Water content for 100 mm slump = 186 + (6/100) x 186 = 197.16 ~ 197.16 litres
Assume 20 % water content is reduced due to superplasticizer.
Water Content = 197 - (20% of 197) = 157.6 ~ 160 litres.
Therefore, Water content = 160 litres
Step-6) Calculation of Cement and fly ash content i.e. Cementitious Content -
W/C ratio = 0.45
Cementitious Content = 160/0.40 = 355.56~ 356 kg/m3
Cementitious Content = 356 kg/m3
Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. The percentage of cementitious content to be increased depends on the experience and research. Here we have increased the cementitious content by 10%.
Final Cementitious Content = 356 x 1.10 = 391.6 kg/m3
As per IS 456:200 table-5, minimum cement content for extreme exposure is 340 kg/m3.
391.6 kg/m3 > 340 kg/m3, hence ok.
Since 30% of Cement is replaced by fly ash.
Fly Ash Content = 391.6 x 0.30
= 117.48 ~ 118 kg/m3
Cement Content = 391.6 - 117.48
= 274.12 ~ 275 kg/m3
Calculation of Super Plasticizers @ 0.6% to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg/m3
Cement Content = 275 kg/m3
Fly Ash Content = 118 kg/m3
Superplasticizer content = 2.35 kg/m3
Step-7) Calculation of Aggregate content -
From IS 10262:2009, table-3, the volume of coarse aggregate corresponding to 20 mm and fine aggregate zone-II for W/C ratio of 0.50 = 0.62
As the W/C ratio is lowered by 0.05, the proportion of volume of coarse aggregate is increased by 0.01
Corrected volume of coarse aggregate for W/C ratio 0.45 = 0.63
For pumpable concrete, these values lowered by 10%.
Therefore Volume of coarse aggregate = 0.63 x 0.9 = 0.567
Volume of coarse aggregate = 0.567
Volume of fine aggregate = 1-0.567 = 0.433
Volume of fine aggregate = 0.433
Step-8) Mix Calculations -
a. Volume of Concrete = 1 cu.m
b. Volume of Cement = (Mass of Cement / specific gravity of cement) x (1/1000)
= (275 / 3.15) x (1 / 1000)
= 0.087 m3
c. Volume of Fly ash = (Mass of fly ash / specific gravity of fly ash) x (1/1000)
= (118 / 2.90) x (1 / 1000)
= 0.041 m3
d. Volume of Water = (Mass of water / specific gravity of water) x (1 / 1000)
= (160 / 1) x (1 / 1000)
= 0.16 m3
e. Volume of Superplasticizer = (Mass of superplasticizer / specific gravity of admixture) x (1 / 1000)
= (2.35 / 1.12) x (1 / 1000)
= 0.002 m3
f. Volume of all aggregate = 1 - (b+c+d+e)
= 1 - (0.087+0.041+0.160+0.002)
= 0.71 m3
g. Mass of coarse aggregate = Volume of all aggregate x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.71 x 0.567 x 2.74 x 1000
= 1103.04 kg
h. Mass of fine aggregate = Volume of all aggregate x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.71 x 0.433 x 2.74 x 1000
= 842.36 kg
Step-9) Concrete Mix Proportions -
- Cement = 275 kg/m3
- Fly ash = 118 kg/m3
- Fine aggregate = 842.36 kg/m3
- Coarse aggregate = 1103.04 kg/m3
- Water = 160 L
- Super plasticizer = 2 kg/m3
- W/C ratio = 0.45
To find the design mix ratio divide the calculated value of all materials by the weight of cement.
RESULT - Thus the Mix Ratio of M35 Grade concrete by weight is,
Cement : Flyash: F.A : C.A : Water = 1 : 0.43 : 3.06 : 4.01 : 0.58
2) Concrete mix design for M50 grade concrete -
AIM - To determine the concrete mix proportions of M50 grade concrete by Indian Standards recommended.
REFERENCE -
- IS 10262-2009 - Concrete Mix Proportioning - Guidelines (First Revision )
- IS 456-2000 - Plain and Reinforced Concrete - Code of Practice (Fourth Revision)
INTRODUCTION -
- The process of selecting suitable ingredients of concrete and determining their relative amounts with the objective of producing a concrete of the required, strength, durability, and workability as economically as possible, is termed the concrete mix design.
- The proportioning of ingredient of concrete is governed by the required performance of concrete in two states, the plastic and the hardened states. If the plastic concrete is not workable, it cannot be properly placed and compacted. The property of workability, therefore, becomes of vital importance.
- The compressive strength of hardened concrete which is generally considered to be an index of its other properties, depends upon many factors, e.g. quality and quantity of cement, water and aggregates; batching and mixing; placing, compaction and curing.
- The cost of concrete is made up of the cost of materials, plant and labour. The variations in the cost of materials arise from the fact that the cement is several times costly than the aggregate, thus the aim is to produceas lean a mix as possible.
Requirements of concrete mix design-
- The requirements which form the basis of selection and proportioning of mix ingredients are the minimum compressive strength required from structural consideration.
- The adequate workability necessary for full compaction with the compacting equipment available.
- Maximum water-cement ratio and/or maximum cement content to give adequate durability for the particular site conditions.
- Maximum cement content to avoid shrinkage cracking due to temperature cycle in mass concrete.
PROCEDURE -
Step-1) Data Required -
| 1 | Grade Designation | : M 50 |
| 2 | Type of Cement | : OPC 53 Grade |
| 3 | Max. nominal size of aggregate | : 20 mm |
| 4 | Min. cement content | : 360 kg/m3 |
| 5 | Max. cement content | : 450 kg/m3 |
| 6 | Max. Water-Cement ratio | : 0.35 |
| 7 | Workability | : 100 mm |
| 8 | Exposure Condition | : Extreme |
| 9 | Method of Placing | : Pumping |
| 10 | Type of aggregate | : Crushed Angular aggregate |
| 11 | Type of Chemical admixture | : Superplasticizer |
Step-2) Test Data of Material -
| 1 | Specific Gravity of Cement | : 3.15 |
| Specific Gravity of Coarse Aggregate | : 2.74 | |
| Specific Gravity of fine aggregate | : 2.56 | |
| Water absorption of Coarse Aggregate | : 0.50% | |
| Water absorption of fine Aggregate | : 1.00% | |
| Sieve analysis fine aggregates confirming | : zone-II |
Step-3) Calculate F(Target) -
f(target)= fck +1.65 x s
Where, f(target) = Targeted average strength at 28 days
fck = Characteristic compressive strength at 28 days
s = standard deviation
F(target) = 50 + 1.65 x 5.0 = 58.25 N/mm2
F(target) = 58.25 N/mm2
Step-4) Selection of W/C ratio -
as per IS 456:2000 Table - 5 , the maximum W/C ratio = 0.45
take W/C ratio = 0.35
Step-5) Selection of Water content -
From IS 456:2000 Table -2,
maximum water content = 186 lit. for 20mm aggregate (For 25 - 50 mm slump range)
Estimated Water content for 100 mm slump = 186 + (6/100) x 186 = 197.16 litres
Assume 25 % water content is reduced due to superplasticizer.
Water Content = 197.16 - (25% of 197.16) = 147.87 ~ 150 litres.
Therefore, Water content = 150 litres
Step-6) Calculation of Cement Content -
W/C ratio = 0.35
Cement Content = 150/0.35 = 428.57~ 430 kg/m3
Cement Content = 430 kg/m3
As per IS 456:200 table-5, minimum cement content for extreme exposure is 360 kg/m3.
430 kg/m3 > 360 kg/m3, hence ok.
Calculation of Super Plasticizers @ 2.0% to the mass of cement content = = 430*(2/100) = 8.3 kg/m3
Cement Content = 430 kg/m3
Superplasticizer content = 8.3 kg/m3
Step-7) Calculation of Aggregate content -
From IS 10262:2009, table-3, the volume of coarse aggregate corresponding to 20 mm and fine aggregate zone-II for W/C ratio of 0.50 = 0.62
As the W/C ratio is lowered by 0.05, the proportion of volume of coarse aggregate is increased by 0.01
Corrected volume of coarse aggregate for W/C ratio 0.35 = 0.65
For pumpable concrete, these values lowered by 10%.
Therefore Volume of coarse aggregate = 0.65 x 0.9 = 0.567
Volume of coarse aggregate = 0.585
Volume of fine aggregate = 1-0.567 = 0.415
Volume of fine aggregate = 0.415
Step-8) Mix Calculations -
a. Volume of Concrete = 1 cu.m
b. Volume of Cement = (Mass of Cement / specific gravity of cement) x (1/1000)
= (430 / 3.15) x (1 / 1000)
= 0.137 m3
c. Volume of Water = (Mass of water / specific gravity of water) x (1 / 1000)
= (150 / 1) x (1 / 1000)
= 0.150 m3
d. Volume of Superplasticizer = (Mass of superplasticizer / specific gravity of admixture) x (1 / 1000)
= (8.3 / 1.145) x (1 / 1000)
= 0.007 m3
e. Volume of all aggregate = 1 - (b+c+d)
= 1 - (0.137+0.150+0.007)
= 0.706 m3
f. Mass of coarse aggregate = Volume of all aggregate x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.706 x 0.585 x 2.74 x 1000
= 1113.65 kg
g. Mass of fine aggregate = Volume of all aggregate x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.706 x 0.415 x 2.56 x 1000
= 750.05 kg
Step-9) Concrete Mix Proportions -
- Cement = 430 kg/m3
- Fine aggregate = 750.05 kg/m3
- Coarse aggregate = 1113.65 kg/m3
- Water = 150 L
- Super plasticizer = 7 kg/m3
- W/C ratio = 0.35
To find the design mix ratio divide the calculated value of all materials by the weight of cement.
RESULT - Thus the Mix Ratio of M50 Grade concrete by weight is,
Cement : F.A : C.A : Water = 1 : 1.74 : 2.59 : 0.35.