Project on Concrete Mix Design for various grades of Concrete

AIM:-

1)To calculate the Concrete Mix Design for M35 grade concrete with Fly ash

2) To calculate the Concrete Mix Design for M50 grade concrete without Fly ash.

INTRODUCTION:-

Concrete is a multipurpose and globally recognised construction material. To produce a good quality concrete the ingredients should be properly measured. Concrete is a homogeneous mixture of raw materials like cement, coarse aggregate, fine aggregate, admixtures and water. This design mix concrete is designed by the structural engineer and the mix proportions are determined by the concrete producer. Design mix is a scientific method and it is widely used for more extensive and important concrete work. M30, M35, M40 etc are Design mix concrete.

CODES CONSIDERED FOR CONCRETE MIX DESIGN:-

1. IS 10262:2009
2. IS 456:2000
3. IS 3812 (Part 1)
4. IS 8112
5. IS 383
6. IS 9103

OBJECTIVE:-

• The main objective is to produce concrete as economical as possible
• To achieve desired strength, workability & durability of concrete as per grade.

PART 1: CONCRETE MIX DESIGN FOR M35 GRADE WITH FLY ASH

A) STIPULATIONS FOR PROPORTIONING

1. Grade designation : M35
2. Type of cement : OPC 43 Grade conforming to IS 12269
3. Maximum nominal size of aggregate : 20mm
4. Minimum cement content : 340 kg/m^3 (From Table 5 of IS 456:2000- Exposure condition)
5. Maximum water-cement ratio : 0.45 (From Table 5 of IS 456:2000-Very Severe Exposure condition)
6. Workability : 100mm (slump value)
7. Exposure condition : Very Severe Exposure condition (For Reinforced Concrete)
8. Method of concrete placing : Pumping
9. Degree of supervision : Good
10. Type of aggregate : Crushed Angular Aggregates
11. Maximum cement content not including Fly ash : 450 kg/m^3
12. Chemical admixture type : Super Plasticizer

B) TEST DATA FOR MATERIALS

1. Cement used : OPC 43 Grade conforming IS 8112
2. Specific gravity of cement : 3.15
3. Fly ash : conforming to IS 3812 (Part 1)
4. Chemical admixture : SuperPlasticizer conforming to IS 9103
5. Specific gravity of

• Coarse aggregate : 2.74
• Fine aggregate : 2.74
• Fly ash : 2.2
• Chemical admixture : 1.145

6. Water absorption:

• Coarse aggregate : 0.5 %
• Fine aggregate : 1 %

7. Free (surface) moisture:

• Coarse aggregate : Nil
• Fine aggregate : Nil

8. Sieve analysis:

• Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
• Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383

C) 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
• S = Standard deviation.

From Table 1 of IS 10262:2009, Standard Deviation, S = 5 N/mm^2.

Therefore, Target Strength = 35 + 1.65 * 5 = 43.25 N/mm^2.

• Target mean strength = 43.25 N/mm^2

D) SELECTION OF WATER-CEMENT RATIO

From IS 10262:2009, Fig.1, the free w/c ratio required for the target strength of 43.25 N/mm^2 is 0.38 for OPC 43 Grade curve.

This is lower than the maximum value of 0.45 prescribed for "Very severe exposure condition" for reinforced concrete as per Table 5 of IS 456:2000.

0.38 < 0.45 Hence ok.

• Water-Cement Ratio = 0.38

E) SELECTION OF WATER CONTENT

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

Estimated water content for 100 mm slump (increasing at the rate of 3% for every 25 mm slump) = 186+ (6/186) = 197.16 litre.

As Super plasticizer is used, the water content can be reduced upto 20% and above.

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

Hence the arrived water content = 197.16 * 0.8 = 157.73 litre (Assume 158 liter)

• Water required = 158 litres

F) CALCULATION OF CEMENT CONTENT

Adopted w/c Ratio = 0.38

Cement Content = 158/0.38 = 415.79 kg/m^3

From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions= 340kg/m^3

= 415.79 kg/m^3 > 340 kg/m^3, hence ok.

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

• The percentage of fly ash needs to be decided based on project requirement and quality of materials.
• In some cases an increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial. Here, we are increasing 10 percent cementitious material content.

Cementitious material content = 415.79 * 1.10 = 457.37 kg/m^3

Water content = 158 kg/m^3

So, Water-Cementitious Ratio = 158/457.36 = 0.345

Fly ash @ 30% total cementitious material content = 457.37 * 30% = 137.211 kg/m^3

Cement (OPC) = 457.37 - 137-211 = 320.159 kg/m^3

Saving of cement while using fly ash = 415.79 - 320.159 = 95.63 kg/m^3

Fly ash to be utilized = 137.211 kg/m^3

• Cementitious material, cement and fly ash required is 457.37 kg/m^3, 320.159 kg/m^3, 137.211 kg/m^3. The new Water-Cement Ratio is 0.345.

G) PROPORTION OF VOLUME OF COARSE 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 I) for water-cement ratio of 0.5=0.6

In the present case the water-cement ratio is 0.345.

Therefore, the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.155, The proportion of volume of coarse aggregate is increased by 0.031 (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 0.345 = 0.62+0.031= 0.651.

(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 up to 10%.

Therefore, volume of coarse aggregate =0.651 * 0.9 =0.59

Volume of fine aggregate content = 1 – 0.59= 0.41.

• Volume of course and fine aggregate is 0.59 & 0.41

H) MIX CALCULATIONS

The mix calculations 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] *1000} = 320.159/{3.15 * 1000} = 0.101 m^3
3. Volume of Fly ash = [Mass of fly ash] / {[Specific Gravity of fly ash] * 1000} = 137.211/{2.2 * 1000} = 0.062 m^3
4. Volume of water = [Mass of water] / {[Specific Gravity of water] * 1000} = 158 /{1 * 1000} = 0.158 m^3
5. Volume of chemical admixture = (Mass of Chemical admixture/Specific gravity of admixture)*1/1000 = 7.6/1.145*1/1000 = 0.006 m^3
6. Volume of all in aggregate = [a-(b+c+d+e)] = [1-(0.101+0.062+0.158+0.006)] = 0.673 m^3
7. Mass of coarse aggregate= f * Volume of Coarse Aggregate* Specific Gravity of Fine Aggregate * 1000 = 0.673* 0.59 * 2.74 * 1000 = 1087.97 kg/m^3
8. Mass of fine aggregate= f * Volume of Fine Aggregate * Specific Gravity of Fine Aggregate x 1000 = 0.673* 0.41* 2.74 * 1000 = 756.05 kg/m^3

I) MIX PROPORTIONS

Cement = 320.159 kg/m^3

Fly ash = 137.211 kg/m^3

Water = 158 kg/m^3

Fine aggregate = 756.05 kg/m^3

Coarse aggregate = 1087.97 kg/m^3

Chemical admixture = 7 kg/m^3

Water-cement ratio = 0.345

RESULT:-

Trail Mix Ratio = 1 : 1.65 : 2.38

PART 2: CONCRETE MIX DESIGN FOR M50 GRADE WITHOUT FLY ASH

A) STIPULATIONS FOR PROPORTIONING

1. Grade designation : M50
2. Type of cement : OPC 53 Grade conforming to IS 12269
3. Maximum nominal size of aggregate : 20mm
4. Minimum cement content : 360 kg/m^3 (From Table 5 of IS 456:2000- Exposure condition)
5. Maximum water-cement ratio : 0.4 (From Table 5 of IS 456:2000- Exposure condition)
6. Workability : 125mm (slump value)
7. Exposure condition : Extreme Exposure condition (For Reinforced Concrete)
8. Method of concrete placing : Pumping
9. Degree of supervision : Good
10. Type of aggregate : Crushed Angular Aggregates
11. Maximum cement content not including Fly ash : 450 kg/m^3
12. Chemical admixture type : Super Plasticizer

B) TEST DATA FOR MATERIALS

1. Cement used : OPC 53 Grade conforming IS 8112
2. Specific gravity of cement : 3.15
3. Chemical admixture : SuperPlasticizer conforming to IS 9103
4. Specific gravity of

• Coarse aggregate : 2.74
• Fine aggregate : 2.74
• Chemical admixture : 1.145

6. Water absorption:

• Coarse aggregate : 0.5 %
• Fine aggregate : 1 %

7. Free (surface) moisture:

• Coarse aggregate : Nil
• Fine aggregate : Nil

8. Sieve analysis:

• Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
• Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383

C) 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
• S = Standard deviation.

From Table 1 of IS 10262:2009, Standard Deviation, S = 5 N/mm^2.

Therefore, Target Strength = 50 + 1.65 * 5 = 58.25 N/mm^2.

• Target mean strength = 58.25 N/mm^2

D) SELECTION OF WATER-CEMENT RATIO

From IS 10262:2009, Fig.1, the free w/c ratio required for the target strength of 58.25 N/mm^2 is 0.35 for OPC 53 Grade curve.

This is lower than the maximum value of 0.40 prescribed for "Extreme exposure condition" for reinforced concrete as per Table 5 of IS 456:2000.

0.35 < 0.40 Hence ok.

• Water-Cement Ratio = 0.35

E) SELECTION OF WATER CONTENT

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

Estimated water content for 125 mm slump (increasing at the rate of 3% for every 25 mm slump) = 186+ {(9/100)*186} = 202.74 litre.

As Super plasticizer is used, the water content can be reduced upto 20% and above.

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

Hence the arrived water content = 202.74 * 0.71 = 143.94 litre (Assume 144 liter)

• Water required = 144 litres

F) CALCULATION OF CEMENT CONTENT

Adopted w/c Ratio = 0.35

Cement Content = 144/0.35 = 411.43 kg/m^3

From Table 5 of IS 456, Minimum cement content for ‘Extreme’ exposure conditions= 360kg/m^3

= 411.43 kg/m^3 > 360 kg/m^3, hence ok.

• Cement required is 411.43 kg/m^3.

G) PROPORTION OF VOLUME OF COARSE 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 I) for water-cement ratio of 0.5=0.6

In the present case the water-cement ratio is 0.35.

Therefore, the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.15, The proportion of volume of coarse aggregate is increased by 0.03 (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 0.35 = 0.62+0.03= 0.65

(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 up to 10%.

Therefore, volume of coarse aggregate =0.65 * 0.9 =0.585

Volume of fine aggregate content = 1 – 0.59= 0.415.

• Volume of course and fine aggregate is 0.585 & 0.415

H) MIX CALCULATIONS

The mix calculations 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] *1000} = 411.43/{3.15 * 1000} = 0.131 m^3
3. Volume of water = [Mass of water] / {[Specific Gravity of water] * 1000} = 144 /{1 * 1000} = 0.144 m^3
4. Volume of chemical admixture = (Mass of Chemical admixture/Specific gravity of admixture)*1/1000 = 7.6/1.145*1/1000 = 0.006 m^3
5. Volume of all in aggregate = [a-(b+c+d)] = [1-(0.131+0.144+0.006)] = 0.719 m^3
6. Mass of coarse aggregate= e * Volume of Coarse Aggregate* Specific Gravity of Fine Aggregate * 1000 = 0.719* 0.585 * 2.74 * 1000 = 1152.49 kg/m^3
7. Mass of fine aggregate= e * Volume of Fine Aggregate * Specific Gravity of Fine Aggregate x 1000 = 0.719* 0.415* 2.74 * 1000 = 817.57 kg/m^3

I) MIX PROPORTIONS

Cement = 411.43 kg/m^3

Water = 144 kg/m^3

Fine aggregate = 817.57 kg/m^3

Coarse aggregate = 1152.49 kg/m^3

Chemical admixture = 7 kg/m^3

Water-cement ratio = 0.35

RESULT:-

Trail Mix Ratio = 1 : 1.99 : 2.80