Project on Concrete Mix Design for various grades of Concrete

Project on Concrete Mix Design for various grade of Concrete

AIM

I am performing the project on Concrete Mix Design for M35 grade of concrete with fly ash & M50 grade of concrete without fly ash.

INTRODUCTION

Concrete is a composite building material made by mixing cement, aggregate and water in define proportion are cured and then hardened to form a mass like substance. Concrete is a blender material that binds the materials together and cement in composition with aggregate acts as a strong building material. All these ingredients modify the properties of fresh as well as hardened concrete. Concrete mix design is carried out to choose the ingredients in desired proportion. In concrete mix the main ingredients are:

• Cement and water when mixed from a paste that coats the aggregate and sand in the mix. The paste hardens and bind the aggregate and sand.
• Water reacts with cement and provide workability with the concrete. The amount of water with the amount of cement is called as water/cement ratio. The lower the W/C ratio stronger the concrete.
• Sand is used as fine aggregate and crushed stones as coarse aggregate.

MATERIALS

1. Cement
2. Fine aggregate
3. Coarse aggregate
4. Water
5. Admixture (superplasticizers)
6. Fly ash

DATA PROVIDED FOR M35 GRADE OF CONCRETE WITH FLY ASH

1. Stipulations for proportioning
2. Grade designation : M35
3. Type of cement : OPC 43 grade conforming to IS 8112
4. Type of mineral admixture : Fly ash conforming to IS 3812 (part 1)
5. Maximum nominal size of aggregate : 20 mm
6. Minimum cement content : 340 kg/mm^3 (from Table 5 of IS 456:200-Exposure condition)
7. Maximum w/c ratio : 0.45 (from Table 5 of IS 456:2000-Exposure condition)
8. Workability : 100 mm (slump value for pumpable concrete)
9. Exposure condition : Very sever (for reinforced concrete)
10. Method of concrete placing : Pumping
11. Type of aggregate : Crushed angular aggregate
12. Maximum cement content : 450 kg/m^3
13. Chemical admixture type : superplasticizer
14. Test data for material:
15. Cement used : OPC 43 grade conforming to IS 8112
16. Specific gravity of cement : 3.15
17. Fly ash : conforming to IS 3812 (part 1)
18. Specific gravity of fly ash : 2.2
19. Chemical admixture : superplasticizer conforming to IS 9103
20. Specific gravity of:

• Coarse aggregate : 2.74
• Fine aggregate : 2.74

1. Water absorption:

• Coarse aggregate : 0.5%
• Fine aggregate : 1.0%

1. Free surface moisture:

• Coarse aggregate : Nil
• Fine aggregate : Nil

1. Sieve Analysis:

• Coarse aggregate :

• Fine aggregate : conforming to grading zone l Table 4 of IS 383
• Target strength for Mix proportioning:

f’ck = fck + 1.65 S

where, f’ck = Target average compressive strength at 28 days

fck = Characteristic compressive strength at 28 days

S = Standard deviation

From Table 1 of IS 10262:2009, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 35+1.65x5 = 43.25 N/mm^2

1. Selection of water-cement ratio:

From Table 5 of IS 456:2000 for very sever exposure, maximum water-cement ratio = 0.45

Based on experience, adopt water-cement ratio as 0.45

0.40 < 0.45, Hence O.K

1. Selection of water content

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 mm to 50 mm slump range)

Estimated water content for 100 mm slump = 186 + 6/100*186

= 197 litre

As superplasticizer is used, the water content can be reduced up to 30%

Based on trials water content reduction of 29% is achieved with plasticizer.

Hence the arrived water content = 197 x 0.71 = 140 litre

1. Calculation of cement content:

Water-cement ratio = 0.4

Cementitious material( cement + fly ash)content = 140/0.4 = 350 kg/m^3

From Table 5 IS 456 minimum cement content for ‘very severe’ exposure condition = 340 kg/m^3

349.95 kg/m^3 > 340 kg/m^3, Hence OK

Now, to proportion a mix containing fly ash the following steps are suggested:

1. The percentage of fly ash needs to be decided based on project requirement and quality of materials.
2. In some case increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial ( This is with increase of 10% cementitious 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% total cementitious material content = 385 x 30% = 115 kg/m^3

Cement (OPC) = 385-115 =270 kg/m^3

Saving of cement while using fly ash = 350-270 = 80 kg/m^3 and

Fly ash being utilized = 115 kg/m^3

• Proportion of volume of coarse of aggregate and fine aggregate content:

From Table 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone l) for water-cement ratio of 0.5 = 0.6

In the present case the water cement ratio is 0.40

• Therefor, 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 05 change in water-cement ratio)

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62

(Note: if coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.62*0.9 = 0.56

Volume of fine aggregate content = 1 – 0.56 = 0.44

• Mix calculation:

The mix calculation per unit volume of concrete shall be as follows:

1. Volume of concrete = 1 m^3
2. Volume of cement = (mass of cement)/(specific gravity of cement ) x 1/100

= 270/3.15 x 1/1000

= 0.086 m^

1. Volume of fly ash = (mass of fly ash)/(specific gravity of fly ash) x 1/1000

= 115/2.2 x 1/1000

= 0.052 m^3

1. Volume of water = (mass of water)/(specific gravity of water) x 1/1000

= 140/1 x 1/1000

= 0.140 m^3

1. Volume of chemical admixture = (mass of chemical admixture)/(specific gravity of admixture) x 1/1000

= 7.6/1.145 x 1/1000

= 0.006 m^3

1. Volume of aggregate (FA & CA) = (a-(b + c + d + e))

= (1-(0.086+0.052+0.140+0.006))

= 0.716 m^3

1. Mass of coarse aggregate = f x volume of coarse aggregate x specific

gravity of coarse aggregate x 1000

= 0.716 x 0.56 x 2.74 x 1000

= 1098 kg/m^3

1. Mass of fine aggregate = f x volume of fine aggregate x specific gravity

of fine aggregate x 1000

= 0.716 x 0.44 x 2.74 x 1000

= 863 kg/m^3

1. Mix proportion for Trial Number 1:

Cement = 270 kg/m^3

Fly ash = 115 kg/m^3

Water = 140 kg/m^3

Fine aggregate = 863 kg/m^3

Coarse aggregate = 1098 kg/m^3

Chemical admixture = 7 kg/m^3

Water-cement ratio = 0.364

Trial Mix Ratio = 1:2.24:2:85

1. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
2. Two more trials having variation of 10% of water-cement ratio in clause X shall be plotted to work out the mix proportions for the given target for field trials. However, durability shall be met.

REFRENCE CODE BOOK

• IS 8112
• IS 3812
• IS 456:2000
• IS 9103
• IS 383
• IS 10262:2009

DATA PROVIDED FOR M50 GRADE OF CONCRETE WITHOUT FLY ASH

1. Stipulations for proportioning
2. Grade designation : M50
3. Type of cement : OPC 53 grade conforming to IS 122669-1987
4. Type of mineral admixture : Fly ash conforming to IS 3812 (part 1)
5. Maximum nominal size of aggregate : 20 mm
6. Minimum cement content : 320 kg/mm^3 (from Table 5 of IS 456:200-Exposure condition)
7. Maximum w/c ratio : 0.45 (from Table 5 of IS 456:2000-Exposure condition)
8. Workability : 100 mm (slump value for pumpable concrete)
9. Exposure condition : Sever (for reinforced concrete)
10. Method of concrete placing : Pumping
11. Type of aggregate : Crushed angular aggregate
12. Maximum cement content : 450 kg/m^3
13. Chemical admixture type : superplasticizer
14. Test data for material:
15. Cement used : OPC 43 grade conforming to IS 8112
16. Specific gravity of cement : 3.15
17. Fly ash : conforming to IS 3812 (part 1)
18. Specific gravity of fly ash : 2.2
19. Chemical admixture : superplasticizer conforming to IS 9103
20. Specific gravity of:

• Coarse aggregate : 2.74
• Fine aggregate : 2.64

1. Water absorption:

• Coarse aggregate : 0.5%
• Fine aggregate : 1.0%

1. Free surface moisture:

• Coarse aggregate : Nil
• Fine aggregate : Nil

1. Sieve Analysis:

• Coarse aggregate :

• Fine aggregate : conforming to grading zone l Table 4 of IS 383
• Target strength for Mix proportioning:

f’ck = fck + 1.65 S

where, f’ck = Target average compressive strength at 28 days

fck = Characteristic compressive strength at 28 days

S = Standard deviation

From Table 1 of IS 10262:2009, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 50+1.65x5 = 58.25 N/mm^2

1. Selection of water-cement ratio:

From Table 5 of IS 456:2000 for very sever exposure, maximum water-cement ratio = 0.45

Based on experience, adopt water-cement ratio as 0.44

0.44 < 0.45, Hence O.K

1. Selection of water content

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 mm to 50 mm slump range)

Estimated water content for 100 mm slump = 186 + (6/100)*186

= 197 litre

As superplasticizer is used, the water content can be reduced up to 20%

Based on trials water content reduction of 20% is achieved with plasticizer.

Hence the arrived water content = 197 x 0.8 = 158 litre

1. Calculation of cement content:

Water-cement ratio = 0.44

Cementitious material( cement + fly ash)content = 158/0.44 = 359 kg/m^3

From Table 5 IS 456 minimum cement content for ‘severe’ exposure condition = 320 kg/m^3

359 kg/m^3 > 320 kg/m^3, Hence OK

Now, to proportion a mix containing fly ash the following steps are suggested:

1. The percentage of fly ash needs to be decided based on project requirement and quality of materials.
2. In some case increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial ( This is with increase of 10% cementitious material content )

• Proportion of volume of coarse of aggregate and fine aggregate content:

From Table 3 of IS 10262:2009, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone l) for water-cement ratio of 0.5 = 0.6

In the present case the water cement ratio is 0.40

• Therefor, 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 05 change in water-cement ratio)

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.63

(Note: if coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.63*0.9 = 0.56

Volume of fine aggregate content = 1 – 0.76 = 0.43

• Mix calculation:

The mix calculation per unit volume of concrete shall be as follows:

1. Volume of concrete = 1 m^3
2. Volume of cement =(mass of cement)/(specific gravity of cement ) x 1/100

= 359/3.15 x 1/1000

= 0.114 m^

1. Volume of fly ash = (mass of fly ash)/(specific gravity of fly ash) x 1/1000

= 115/2.2 x 1/1000

= 0.052 m^3

1. Volume of water = (mass of water)/(specific gravity of water) x 1/1000

= 158/1 x 1/1000

= 0.158 m^3

1. Volume of chemical admixture = (mass of chemical admixture)/(specific gravity of admixture) x 1/1000

= 7.6/1.145 x 1/1000

= 0.006 m^3

1. Volume of aggregate (FA & CA) = (a-(b + c + d + e))

= (1-(0.114+0.058+0.140+0.006))

= 0.722 m^3

1. Mass of coarse aggregate = f x volume of coarse aggregate x specific

gravity of coarse aggregate x 1000

= 0.722 x 0.56 x 2.64 x 1000

= 1123 kg/m^3

1. Mass of fine aggregate = f x volume of fine aggregate x specific gravity

of fine aggregate x 1000

= 0.722 x 0.43 x 2.64 x 1000

= 821 kg/m^3

1. Mix proportion for Trial Number 1:

Cement = 359 kg/m^3

Fly ash = 115 kg/m^3

Water = 158 kg/m^3

Fine aggregate = 821 kg/m^3

Coarse aggregate = 1123kg/m^3

Chemical admixture = 7.18 kg/m^3

Water-cement ratio = 0.44

Trial Mix Ratio = 1:2.28:3.12

1. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
2. Two more trials having variation of 10% of water-cement ratio in clause X shall be plotted to work out the mix proportions for the given target for field trials. However, durability shall be met.

REFRENCE CODE BOOK

• IS 8112
• IS 3812
• IS 456:2000
• IS 9103
• IS 383
• IS 10262:2009
• IS BIS 12269-1987

RESULTS

By performing this project we have gained the design mix for M35 concrete with fly ash & M50 concrete without fly ash.

1. Trial mix ratio for M35 grade concrete with fly ash 1:2.24:2.85
2. Trial mix ratio for M50 grade concrete without fly ash 1:2.56:3.26

CONCLUSION

I would like to conclude my project by stating that every design mix varies depending on the aggregate present, the state of aggregate and many other factors. Using this mix ratio perform experiments to find if the concrete meets the target mean strength, this design mix if no alter few values and calculator new design mix till the target mean strength is reached.