Project on Concrete Mix Design for various grades of Concrete

CONCRETE MIX DESIGN:-

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

CASE -1:-Calculate the Concrete Mix Design for M35 grade concrete with fly ash

1. Stipulations for Mix Design Concrete

• Grade designation: M 35
• Type of cement: OPC 53 (grade confirming to IS 8112)
• Maximum nominal size of aggregate: 20 mm
• Minimum cement content : 340 kg/m3
• Maximum water-cement ratio: 0.45
• Workability: 100 mm (slump)
• Exposure condition: Severe (for reinforced concrete)
• Method of concrete placing: Pumping
• Degree of supervision: Good
• Aggregate: Crushed angular aggregate
• Maximum cement content : 450 kg/m3
• Chemical admixture type: Super Plasticizer
• Mineral Admixture type: Fly Ash Confirming to IS 3812 Part 1
• Fly Ash: 30%

2. Test Data for Materials (to be determined in the laboratory)

• The specific gravity of cement: 3.15
• The specific gravity of Coarse aggregate: is 2.74
• The specific gravity of Fine aggregate: 2.74
• The specific gravity of Fly Ash: 2.2
• The specific gravity of Super Plasticizer: 1.145
• Water absorption of Coarse Aggregate: 0.5%
• Water absorption of Fine Aggregate: 1%
• Free surface moisture of Coarse Aggregate is Null
• Free surface moisture of Fine Aggregate is Null
• Sieve Analysis of Coarse Aggregate: Confirming to table 2 of IS 2386
• Sieve Analysis of Fine Aggregate: Confirming to grading Zone 1 of table 4 of IS 2386
  3. Procedure for Concrete Mix Design of M35 Concrete

• ftarget = fck + 1.65 x s

  ‘target‘ is the Target Average Compressive Strength at 28 days,

  ‘fck’ is the Characteristic Compressive Strength at 28 days, and

  ‘s’ is the Standard Deviation

  as per table I of IS: 10262-2009, the standard deviation, s is 5.0 N/mm2

  Therefore, target strength = 35 + 1.65 x 5.0 = 43.25 N/mm2

  4. Selection of Water/Cement Ratio

  Based on experience, adopter water-cement ratio = 0.4

  From Table 5 of IS 456:2000,

  for exposure condition being severe

  Maximum water-cement ratio = 0.45

  Adopted water-cement ratio =0.4<0.45 (Hence okay)

  5. Selection of Water Content

  From Table 2 of IS 456:2000, maximum water content =186 liters (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 Superplasticizer is used, the water content can be reduced up to 20% and above.)

  Based on trials with Superplasticizer, a water content reduction of 25% can be achieved.

  Hence the arrived water content = 197-[197 x (25/100)] = 147 litres.

  6. Calculation of Cement Content and Fly Ash Content

  Water-cement ratio =0.40

  Cementitious material content (cement + fly ash) = 147/0.40 = 370 kg/m3

  From Table 5 of IS 456:2000, minimum cement content for ‘Severe’ exposure condition = 340 kg/m3

  370 kg/m3 > 340 kg/m3, (hence okay)

  To proportion a mix containing fly ash

  The percentage of fly ash needs to be decided based on project requirements and the quality of materials.

  Since flying ash is used, the amount of cementitious content (cement + fly ash) should be increased to get good performance and strength.

  An increase in cementitious material content and its percentage may be based on experience and trial, in this increasing cementitious content by 10%.

  Cementitious material content = 370 x 1.10 = 407 kg/m3

  Water content = 147 kg/m3

  Therefore, water-cement ratio = 147/407 = 0.362

  Fly ash is of 30% of total cementitious material content = 407 x 0.3 = 122 kg/m3

  Cement (OPC) = 407 - 122 =285 kg/m3

  Amount of cement saved while using fly ash = 370-285 = 85 kg/m3

  Fly ash being utilized = 122 kg/m3

  Cement being utilized = 285 kg/m3

  7. The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content

  From Table 3 of IS 10262:2009, the volume of coarse aggregate corresponds to 20 mm size aggregate and fine aggregate (Zone I) for a water-cement ratio of 0.50 =0.60.

  In the present case, the water-cement ratio is 0.40. Therefore. The coarse aggregate volume must be increased to decrease the acceptable aggregate content as the water-cement ratio is lower by 0.10. the proportion of the importance of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. The corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62.

  NOTE – In case the coarse aggregate is not angular one. Then also the volume of coarse aggregate may be required ten be increased suitably, based on experience.

  For pumpable concrete, these values should be reduced by 10 percent.

  Therefore, volume of coarse aggregate = 0.62 x 0.9 = 0.56.

  Volume of fine aggregate content =1 – 0.56 =0.44

  8. Mix Calculations
  9. a) Volume of concrete = 1m3
  10. b) Volume of cement = (Mass of Cement/Specific Gravity of Cement) X (1/1000)

  = (285/3.15) X (1/1000)

  = 0.091 m3

  1. c) Volume of fly ash = (Mass of fly ash/Specific Gravity of fly ash) X (1/1000)

  = (122/2.2) X (1/1000)

  = 0.056 m3

  1. d) Volume of water = (Mass of Water/Specific Gravity of Water) X (1/1000)

  = (147/1) X (1/1000)

  = 0.147 m3

  1. e) Volume of Superplasticizer = (Mass of Superplasticizer / Specific Gravity of Admixture) X (1/1000)

  It is taken as 2% of total cementitious material

  = (8.14/1.145) X (1/1000)

  = 0.007 m3

  1. f) Volume of all aggregate = (a-(b+c+d))

  = 1 – (0.091+0.056 + 0.147+0.007)

  = 0.70 m3

  1. g) Mass of coarse aggregate = Volume of all Aggregate X Volume of coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

  = 0.7 x 0.56 x 2.74 x 1000

  = 1074.08 kg

  1. h) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

  = 0.7 x 0.44 x 2.74 x 1000

  = 843.92 kg

  9. Concrete Mix Proportions -
  • Cement = 285 kg/m3
  • Fly Ash = 122 kg/m3
  • Water = 147 kg/m3
  • Superplasticizer = 8.14 kg/m3
  • Fine aggregates = 843.92 kg/m3
  • Coarse aggregate = 1074.08 kg/m3
  • W/c = 0.40

Final Concrete Mix Ratio for M35 grade concrete with fly ash

The mix ratio of M35 is 1: 2.07: 2.64 (Cement: Fine aggregate: Coarse aggregate).

CASE 2-Calculation of concrete mix design for M50 grade concrete without fly ash

1. Stipulations for Mix Design Concrete

• Grade designation: M50
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 400 kg/m3
• Maximum water-cement ratio : 0.35
• Workability : 75 mm (slump)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 500 kg/m3
• Chemical admixture type : Super Plasticizer

2.Test Data for Materials (to be determined in the laboratory)

• Specific gravity of cement : 3.15
• Specific gravity of Coarse aggregate : 2.74
• Specific gravity of Fine aggregate : 2.74
• Specific gravity of Super Plasticizer : 1.145
• Water absorption of Coarse Aggregate: 0.5%
• Water absorption of Fine Aggregate: 1%
• Free surface moisture of Coarse Aggregate is Null
• Free surface moisture of Fine Aggregate is Null
• Sieve Analysis of Coarse Aggregate: Confirming to table 2 of IS 2386
• Sieve Analysis of Fine Aggregate: Confirming to grading Zone 2 of table 4 of IS 2386

3. Procedure for Concrete Mix Design of M50 Concrete

ftarget = fck + 1.65 x s

‘ftarget‘ is the Target Average Compressive Strength at 28 days,

‘fck’ is the Characteristic Compressive Strength at 28 days, and

‘s’ is the Standard Deviation

as per the table I of IS: 10262-2009 , the standard deviation, s is 5.0 N/mm2

Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm2

4. Selection of Water/Cement Ratio

From experience adopting water-cement ratio =0.35

5. 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 75 mm slump =186+(3/100) x 186 =192 litres. (for every increase in 25mm slump 3% of of water content is added)

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

Based on trials with Super plasticizer, water content reduction of 25% has been achieved. Hence the arrived water content = 192-[192 x (25/100)] = 144 litres.

6. Calculation of Cement Content

Water-cement ratio =0.35

Cement content = 144/0.35 = 412 kg/m3 (> 400 kg/m3 Hence ok)

7. The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content

From Table 3 of IS 10262:2009, the volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.

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 the volume of coarse aggregate is increased by 0.03 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.40 = 0.65.

NOTE – In case the coarse aggregate is not angular one. then also the volume of coarse aggregate may be required 10 be increased suitably, based on experience.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.59.

Volume of fine aggregate content =1 – 0.59 =0.41

8. Mix Calculations
9. a) Volume of concrete = 1m3
10. b) Volume of cement = (Mass of Cement/Specific Gravity of Cement) X (1/1000)

= (412/3.15) X (1/1000)

= 0.131 m3

1. c) Volume of water = (Mass of Water/Specific Gravity of Water) X (1/1000)

= (144/1) X (1/1000)

= 0.144 m3

1. d) Volume of Superplasticizer = (Mass of Superplasticizer / Specific Gravity of Admixture) X (1/1000)

It is taken as 2% of total cementitious material

= (8.24/1.145) X (1/1000)

= 0.007 m3

1. e) Volume of all aggregate = (a-(b+c+d))

= 1 – (0.131 + 0.144+0.007)

= 0.718 m3

1. f) Mass of coarse aggregate = Volume of all Aggregate X Volume of coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.718 x 0.59x 2.74 x 1000

= 1160.72 kg

1. g) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.718 x 0.41 x 2.74 x 1000

= 806.60 kg

9. Concrete Mix Proportions

• Cement = 412 kg/m3
• Water = 144 kg/m3
• Super plasticizer = 8.24 kg/m3
• Fine aggregates = 806.60 kg/m3
• Coarse aggregate = 1160.72 kg/m3
• W/c = 0.35

Final Concrete Mix Ratio for M50 grade concrete without fly ash

The mix ratio of M45 is 1: 1.96: 2.82 (Cement : Fine aggregate: Coarse aggregate).