Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash

PROJECT ON CONCRETE MIX DESIGN FOR VARIOUS GRADES OF CONCRETE

Aim: To determine the mix design for M50 concrete with ordinary Portland cement consists of the following properties:

Introduction:

• Concrete mix design may be defines as the art of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible
• Basic Considerations

The following point must be considered while designing concrete mixes

• Cost
• Specifications
• Workability strength and durability

This project contains two types of concrete mix design

1. Concrete Mix design of M35

The concrete mix design of M35 is done by taking fly ash, superplasticizer and partially dry aggregates

2. Concrete Mix design of M50

The concrete mix design of M50 is done by taking superplasticizer and partially dry aggregates

IS Method of Mix Design

The Bureau of Indian Standard (IS 10262:2009 and IS 456:2000), recommended a set of procedure for design of concrete mix. The procedure is based on the research work carried out at national laboratories

1. CONCRETE MIX DESIGN OF M35
2. STIPULATIONS FOR PROPORTIONING
3. Grade : M35
4. Type of cement : OPC 53 grade conforming to IS 8112
5. Maximum size of Aggregate : 20mm
6. Minimum cement content : 340kg/m³ (From Table 5 of IS 456:2000 – Severe condition)
7. Maximum water – cement ratio : 0.45 (From Table 5 of IS 456:2000 – Severe condition)
8. Workability : 100mm (slump value for pumpable concrete
9. Exposure condition :Severe ( For Reinforced Concrete)
10. Method of concrete placing : Pumping
11. Degree of supervision : Good
12. Type of aggregate : Crushed angular aggregate
13. Maximum cement content : 450kg/m³
14. Chemical admixture type : Superplasticizer
15. Type of Mineral Admixture : Fly Ash confirming 3812 (Part -1)
16. TEST DATA FOR MATERIALS:
17. Cement used : OPC 53 grade conforming to IS 8112
18. Specific Gravity of Cement : 3.15
19. Specific Gravity of Fly Ash : 2.20
20. Chemical admixture : Superplasticizer conforming to IS 9103
21. Specific gravity of :

• Coarse aggregate : 2.74
• Fine aggregate : 2.74
• Chemical Admixture (Super Plasticizer) : 1.12

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 : Conforming to grading Zone II of Table 4 of IS 383
• Fine aggregate : : Conforming to grading Zone II of Table 4 of IS 383
• TARGET STRENGTH FOR MIX PROPORTIONING:

Target mean strength of concrete, f_t = f_ck + 1.65 S

f_t = target average compressive strength at 28 days

f_ck = Characteristic compressive strength at 28 days and

S = standard deviation

Standard deviation (s) for M35 = 5 N/mm² (Table I of IS 10262:2019)

= 35 + (1.65 x 5) = 43.25 N/mm²

1. SELECTION OF WATER – CEMENT RATIO:

From Table 5 of IS 456:2000 for severe exposure, maximum water – cement ratio = 0.45

Based on experience, adopted water-cement ratio is 0.45

0.45<0.45 (Hence it is OK)

1. SELECTION OF WATER CONTENT

From Table 2 of IS 456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197.16 litres.

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above).

Hence, the water content = 198-[198 x (20/100)] = 157.73 litres.

Adopted Water Content = 160 litres

1. CALCULATION OF CEMENT AND FLY ASH CONTENT

Water – Cement ratio = 0.45

Total Cementitious (Cement + Fly Ash) requirement = 160/0.45 =355.55 kg

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 increase depending on experience and research. Here we increased the cementitious content by 1.1%

Final Cementitious content (cement + Fly Ash) = 356 x 1.1 = 391.6 kg

Minimum Cement Content required for ‘severe’ exposure = 340 kg (IS 456:2000 – Table – 5)

Adopted Cementious Content = 391.6 kg > 340 kg

Taking the content of fly ash as 30%

Fly Ash Content Requirement = 391.6 x 0.30 = 117.48

Cement Content Requirement = Cementious Content – Fly Ash

391.6 – 117.48 = 274.12

Calculation of Superplasticizer 0.6% to the mass of cementitious content

= 391.6 x (0.6 / 100) = 2.35 kg

• PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

From Table 3 of IS 10262:2009, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone II) for water – cement ratio is 0.45 = 0.62

In the present case the water cement ratio is 0.45

Therefore, the volume of coarse aggregate for the water – cement ratio of 0.45 = 0.63

For pumpable concrete, these values should be reduced by 10%

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

Volume of fine aggregate content = 1-0.63 = 0.37

• MIX CALCULATIONS

1. Volume of concrete = 1 m³
2. Volume of cement = (Mass of cement/specific gravity of cement) x (1/1000)

= (275/3.15) x (1/1000) = 0.087m³

1. Total Volume of Fly Ash = (Mass of fly ash/specific gravity of cement) x (1/1000)

= (118/2.5) x (1/1000) = 0.041 m³

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

= (160/1) x (1/1000) = 0.160m³

1. Volume of superplasticizer = (Mass of superplasticizer/specific gravity of admixture) x (1/1000)

= (2.35/1.12) x (1/1000) = 0.002 m³

1. Mass of Coarse aggregate = Volume of all Aggregate x volume of coarse aggregate x specific Gravity of Coarse Aggregate x 1000

= 0.71 x 0.63 x 2.74 x 1000 = 1225.6 kg

1. Mass of Fine Aggregate = Volume of all Aggregate x volume of Fine aggregate x specific Gravity of Fine Aggregate x 1000

= 0.71 x 0.37 x 2.74 x 1000 = 719.8 kg

1. CONCRETE MIX PROPORTION

• Cement = 275 kg/m³
• Fly Ash = 118 kg/m³
• Water = 160kg/ m³
• Super Plasticizer = 2 kg/ m³
• Fine Aggregate = 720 kg/ m³
• Coarse aggregate = 1226 kg/ m3
• w/c = 0.35

RESULT: To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore Mix Ratio of M35 Grade Concrete by Weight is

Cement: Fly Ash: Fine Aggregate: Coarse Aggregate: Water

= 1:0.4:2.6:4.46:0.58

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. If the aggregates are dry the amount of mixing water should be increased by an amount equal to the moisture likely to be absorbed by the aggregates

2. CONCRETE MIX DESIGN OF M50
3. STIPULATIONS FOR PROPORTIONING
4. Grade designation : M50
5. Type of cement : OPC 53 grade conforming to IS 8112
6. Maximum nominal size of aggregate : 20mm
7. Minimum cement content : 360kg/m³ (from Table 5 of IS 456:2000 – Exposure condition)
8. Maximum water – cement ratio : 0.35 (From Table 5 of IS 456:2000 – Exposure condition
9. Workability : 50-75mm (slump value for pumpable concrete
10. Exposure condition : Extreme ( for reinforced concrete)
11. Method of concrete placing : Pumping
12. Degree of supervision : Good
13. Type of aggregate : Crushed angular aggregate
14. Maximum cement content : 450kg/m³
15. Chemical admixture type : Superplasticizer
16. TEST DATA FOR MATERIALS:
17. Cement used : OPC 53 grade conforming to IS 8112
18. Specific Gravity of Cement : 3.12
19. Chemical admixture : Superplasticizer conforming to IS 9103
20. Specific gravity of :

• Coarse aggregate : 2.74
• Fine aggregate : 2.56

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 : Conforming to grading Zone II of Table 4 of IS 383
• Fine aggregate : : Conforming to grading Zone II of Table 4 of IS 383
• TARGET STRENGTH FOR MIX PROPORTIONING:

Target mean strength of concrete, f_t = f_ck + 1.65 S

f_t = target average compressive strength at 28 days

f_ck = Characteristic compressive strength at 28 days and

S = standard deviation

Standard deviation (s) for M50 = 5 N/mm² (Table I of IS 10262:2019)

= 50 + (1.65 x 5) = 58.25 N/mm²

1. SELECTION OF WATER – CEMENT RATIO:

From Table 5 of IS 456:2000 for severe exposure, maximum water – cement ratio = 0.35

Based on experience, adopted water-cement ratio is 0.30

0.30<0.35 (Hence it is OK)

1. SELECTION OF WATER CONTENT

From Table 2 of IS 456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 litres.

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above).

Hence, the water content = 197-[197 x (27/100)] = 143 litres.

1. CALCULATION OF CEMENT CONTENT

Water – Cement ratio = 0.35

Cement content = 140/0.35 = 410kg/m³

From Table 5 of IS 456 minimum cement content for ‘Extreme’ exposure condition = 360kg/m³

410kg/m³ > 360kg/ m³ (Hence it is OK)

• PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

From Table 3 of IS 10262:2009, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone II) for water – cement ratio is 0.50 = 0.62

In the present case the water cement ratio is 0.35

Therefore, the volume of coarse aggregate for the water – cement ratio of 0.35 = 0.65

For pumpable concrete, these values should be reduced by 10%

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

Volume of fine aggregate content = 1-0.585 = 0.415

• MIX CALCULATIONS

1. Volume of concrete = 1 m³
2. Volume of cement = (Mass of cement/specific gravity of cement) x (1/1000)

= (410/3.12) x (1/1000) = 0.131m³

• Volume of water = (Mass of water/specific gravity of water) x (1/1000)

= (143/1) x (1/1000) = 0.143m³

• Volume of superplasticizer = (Mass of superplasticizer/specific gravity of admixture) x (1/1000)

= (8.2/1.145) x (1/1000) = 0.007 m³

• Mass of Coarse aggregate = Volume of all Aggregate x volume of coarse aggregate x specific Gravity of Coarse Aggregate x 1000

= 0.719 x 0.585 x 2.74 x 1000 = 1152.48 kg

1. Mass of Fine Aggregate = Volume of all Aggregate x volume of Fine aggregate x specific Gravity of Fine Aggregate x 1000

= 0.719 x 0.415 x 2.56 x 1000 = 763.86kg

1. CONCRETE MIX PROPORTION

• Cement = 410 kg/m³
• Water = 143kg/ m³
• Super Plasticizer = 7 kg/ m³
• Fine Aggregate = 763.86 kg/ m³
• Coarse aggregate = 1152.48 kg/ m3
• w/c = 0.35

RESULT: To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore Mix Ratio of M35 Grade Concrete by Weight is

Cement: Fine Aggregate: Coarse Aggregate: Water

= 1: 1.86: 2.81: 0.35

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. If the aggregates are dry the amount of mixing water should be increased by an amount equal to the moisture likely to be absorbed by the aggregates.

FINAL RESULTS:

From both concrete mix designs, we got to know all the concrete ingredients required to make concrete of required grade which gives desired properties as required. Concrete ingredients required for 1 cubic meter of concrete and 1 bag (50 kgs) of cement are shown in the Final Quantities Sub – section (Serial No IX)