Project on Concrete Mix Design for various grades of Concrete

PROJECT ON CONCRETE MIX DESIGN OF M35 WITH AND M50 GRADE CONCRETE

PROJECT ON CONCRETE MIX DESIGN OF M35 AND M50 GRADE CONCRETE

AIM

The aim of this project is to perform a concrete mix design of M35 grade concrete with fly ash and M50 grade concrete without fly ash.

INTRODUCTION

Concrete is a versatile and complex material. It has the right mix of constituents of concrete, which if not done properly and will have adverse effects on the properties of the concrete. To make the excellent quality of concrete, mix design can be done. It is a systematic process of choosing relative proportion of various ingredients from available material that gives the concrete of desired workability. It enables the selection of suitable ingredients for producing concrete of required strength, durability and workability as economical as possible. The compressive strength of concrete depends on the quality and quantity of cement, water and aggregates. It also depends on mixing, batching, placing, compaction and curing. The main objective of the concrete mix design is to achieve the predetermined minimum strength and durability in most economical manner.

CONCRETE MIX DESIGN OF M35 GRADE CONCRETE WITH FLY ASH

DATA FOR THE MIX DESIGN

• Grade of concrete = M35
• Grade of cement is 43
• Maximum nominal size of aggregate =20mm
• Minimum cement content =320kg/m³
• Maximum water-cement ratio =0.45
• Workability= 100 mm slump
• Exposure condition = Severe
• Method of concrete placing = Pumping
• Degree of supervision= good
• Type of aggregate = Crush angular
• Maximum cement content = 450kg/m³
• Chemical admixtures type = superplasticizers

TEST DATA FOR THE MATERIALS

• Specific gravity of cement = 3.15
• Fly ash = conforming to IS 3812 (Part 1)
• Specific gravity of fly ash = 2.2
• Specific gravity of coarse aggregate and fine aggregate=2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1.0%
• Sieve analysis of fine aggregate zone 1 (table 4, IS 383)
• Sieve analysis of coarse aggregate- table 2, IS 383

Step 1: Target mean strength

From IS 10262-2009, Table1

S=5N/mm²

f’ck = fck + 1.65S

f’ck = 35 + (1.65x5)

f’ck = 43.25 N/mm²

Step 2: Water cement ratio based on Environment exposure:

As per IS 456-2000, table-5:

w/c = 0.45,

Based on experience take 0.4

Step 3: Selection of water content: from table 2 of IS 10262:2009

Water content = 186 l (for 25mm to 50mm)

Estimated water content for a true slump of100 mm = 186 + (0.06x186) l

=197 litres

Use of superplasticizers reduces water content by 30%

After trials, w/c =29%

=197 x 0.71

= 140 litres

Step 4: Calculation of cement content

w/c = 0.4

Cement content (including fly ash) = 140/0.4

= 350kg/m³

From table 5 of IS 456,

Minimum cement content for ‘severe’ exposure condition = 320 kg/m³

350 kg/m³>320 kg/m³, Hence ok

Now, to the proportion of a mix containing fly ash, there is a 10% increase of

cementitious materials

i.e. cementitious material = 350 x 1.10

= 385 kg/m³

Water content = 140 kg/m³

Water-cement ratio = 140/385

= 0.364

Fly ash at 30% total cementitious material content = 385x 30%

= 115 kg/m³

Cement content (OPC) = 385 – 115

= 270 kg/m³

Saving of cement while using fly ash = 350 – 270

= 80 kg/m³

Fly ash being utilized = 115 kg/m³

Step 5: Volume of Aggregate (CA&FA)

From Table 3 of IS 10262:2009, the Volume of coarse aggregate corresponding to 20mm aggregate and fine aggregate zone 1, w/c = 0.6

At present, the Value of w/c =0.4

So, the volume of coarse aggregate needs to be increased to decrease in volume of water.

As the water-cement ratio is decreased by 0.10, the proportion of coarse aggregate is increased by 0.02

So, corrected volume of coarse aggregate for w/c ratio of 0.4 = 0.62

[for pumpable concrete, these values are decreased by 10%]

Volume of CA= 0.62 x 0.9

= 0.56

Volume of FA = 1 - 0.56

=0.44

Step 6: Mix calculation

a. Volume of concrete = 1m³

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

= (270/3.15) x (1/1000)

= 0.085m³

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

= (115/2.2) x (1/1000)

= 0.052m³

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

= (140/1) x (1/1000)

= 0.14m³

e. Volume of chemical admixture

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

= (7.6/1.145) x (1/1000)

= 0.006m³

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

= 1-(0.085+0.052+0.14+0.006)

= 0.717m³

g. Mass of CA = f x volume of CA x specific gravity x 1000

= 0.717 x 0.56 x 2.74 x 1000

= 1100.16 kg/m³

h. Mass of FA = f x volume of FA x specific gravity x 1000

= 0.717 x 0.44 x 2.74 x 1000

= 864.41 kg/m³

Step 7: Mix proportions

Cement = 270 kg/m³

Fly ash = 115 kg/m³

Water = 140 kg/m³

FA = 864.41 kg/m³

CA = 1100.16 kg/m³

Chemical admixtures = 7 kg/m³

Water cement ratio = 0.4

Trial mix ratio = 1:3.2:4.07

CONCRETE MIX DESIGN OF M50 GRADE CONCRETE WITHOUT FLY ASH

DATA FOR THE MIX DESIGN

• Grade of concrete = M50
• Grade of cement is 43
• Maximum nominal size of aggregate =20mm
• Minimum cement content =320kg/m³
• Maximum water-cement ratio =0.45
• Workability= 100 mm slump
• Exposure condition = Severe
• Method of concrete placing = Pumping
• Degree of supervision= good
• Type of aggregate = Crush angular
• Maximum cement content = 450kg/m³
• Chemical admixtures type = superplasticizers

TEST DATA FOR THE MATERIALS

• Specific gravity of cement = 3.15
• Fly ash = conforming to IS 3812 (Part 1)
• Specific gravity of coarse aggregate and fine aggregate=2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1.0%
• Sieve analysis of fine aggregate zone 1 (table 4, IS 383)
• Sieve analysis of coarse aggregate- table 2, IS 383

Step 1: Target mean strength

From IS 10262-2009, Table1

S=5N/mm²

f’ck = fck + 1.65S

f’ck = 50 + (1.65x5)

f’ck = 58.25 N/mm²

Step 2: Water cement ratio based on Environment exposure:

As per IS 456-2000, table-5:

w/c = 0.45,

Based on experience take 0.4

Minimum cement content = 320kg/m³

Step 3: Selection of water content: from table 2 of IS 10262:2009

Water content = 186 l (for 25mm to 50mm)

Estimated water content for a true slump of100 mm = 186 + (0.06x186) l

=197 litres

Use of superplasticizers reduces water content by 30%

After trials, w/c =29%

=197 x 0.71

= 140 litres

Step 4: Calculation of cement content

w/c = 0.4

Cement content = 140/0.4

= 350kg/m³

From table 5 of IS 456,

Minimum cement content for ‘severe’ exposure condition = 320 kg/m³

350 kg/m³>320 kg/m³, Hence ok

Step 5: Volume of Aggregate (CA&FA)

From Table 3 of IS 10262:2009, the Volume of coarse aggregate corresponding to 20mm aggregate and fine aggregate zone 1, w/c = 0.6

At present, the Value of w/c =0.4

So, the volume of coarse aggregate needs to be increased to decrease in volume of water.

As the water-cement ratio is decreased by 0.10, the proportion of coarse aggregate is increase by 0.02

So, corrected volume of coarse aggregate for w/c ratio of 0.4 = 0.62

[for pumpable concrete, these values are decreased by 10%]

Volume of CA= 0.62 x 0.9

= 0.56

Volume of FA = 1 - 0.56

=0.44

Step 6: Mix calculation

a. Volume of concrete = 1m³

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

= (350/3.15) x (1/1000)

= 0.111m³

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

= (140/1) x (1/1000)

= 0.14m³

d. Volume of chemical admixture

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

= (7.6/1.145) x (1/1000)

= 0.006m³

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

= 1-(0.111+0.14+0.006)

= 0.743m³

f. Mass of CA = f x volume of CA x specific gravity x 1000

= 0.743x 0.56 x 2.74 x 1000

= 1140kg/m³

g. Mass of FA = f x volume of FA x specific gravity x 1000

= 0.743 x 0.44 x 2.74 x 1000

= 895.76 kg/m³

Step 7: Mix proportions

Cement = 350 kg/m³

Water = 140 kg/m³

FA = 895.76 kg/m³

CA = 1140 kg/m³

Chemical admixtures = 7 kg/m³

Water cement ratio = 0.4

Trial mix ratio = 1:2.55:3.25

RESULT

From the above design mix, we got the design mix ratios for the M35 grade with fly ash and M50 grade without fly ash as follows

1. Trial mix ratio of M35 grade with fly ash = 1:3.2:4.07
2. Trial mix ratio of M50 grade = 1:2.55:3.25

CONCLUSION

By this, we can conclude the project by stating that the mix design can be done according to our requirements and with the available materials. It enables us to choose suitable ingredients for producing concrete of required strength, durability and workability as economical as possible. Using these mix ratios, we can check for the requirement and can be reworked until the requirement is met.

REFERENCES

1) IS 10262:2009 2) IS 8112

3) IS 456:2009 4) IS 3812 PART 1

5) IS 9103 6) Skill Lync course

7) IS 383