ILLUSTRATIVE EXAMPLE ON CONCRETE MIX PROPORTIONING FOR M50 GRADE CONCRETE

Hello readers of Civil Synergy! In this post, you are about to go through the mix design calculation of M 50 grade concrete following the IS: 10262-2009 code procedure.

Stipulations for Concrete Mix Design

  • Grade designation : M 50
  • Type of cement : OPC 53 grade confirming to IS 8112
  • Maximum nominal size of aggregate : 20 mm
  • Minimum cement content : 360 kg/m3
  • Maximum water-cement ratio : 0.35
  • Workability : 50-75 mm (slump)
  • Exposure condition : Extreme (for reinforced concrete)
  • Method of concrete placing : Pumping
  • Degree of supervision : Good
  • Type of aggregate : Crushed angular aggregate
  • Maximum cement content : 450 kg/m3
  • Chemical admixture type : Super Plasticizer

Test Data for Materials

The following data are collected by performing standard tests in a laboratory.

Specific gravity of cement : 3.12

Specific gravity of Coarse Aggregate : 2.74

Specific gravity of Fine Aggregate : 2.56

Procedure for Concrete Mix Design of M 50 Concrete

1. Target Strength for Mix Proportioning 

ftarget = fck + 1.65 x s

ftarget denotes the Target Average Compressive Strength at 28 days,

 fck denotes the Characteristic Compressive Strength at 28 days,

‘s’ stands for Standard Deviation 

According to the table 1 of IS: 10262-2009 ,

standard deviation, s = 5.0 N/mm2 

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

2. Selection of Water/Cement Ratio

From Table 5 of IS 456 : 2000, 

Maximum water-cement ratio = 0.35 

3. Selection of Water Content 

From Table 2 of IS 456, 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.)

Based on trials with Super plasticizer water content reduction of 27% has been achieved, Hence the arrived water content = 197 – [197 x (27/100)] = 143 litres.

4. Calculation of Cement Content

Water-cement ratio = 0.35

Cement content = 143/0.35 = 410 kg/m3 

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

410 kg/m3 > 360 kg/m3, hence, O.K.

5. Proportion of Volume of Coarse Aggregate and Fine Aggregate Content 

From Table 3 of IS 10262. 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 0.10. the proportion of the volume 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 0.35 = 0.65.

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

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

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

Volume of fine aggregate content =1 – 0.585 =0.415

6. Mix Calculations

a) Volume of concrete = 1m3

b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

= (410/3.12) X (1/1000) 

= 0.131 m3

c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)

= (143/1) X (1/1000)

= 0.143 m3

d) Volume of Superplasticizer = (Mass of Superplasticizer / Specific gravity of admixture) X (1/1000)

= (8.2/1.145) X (1/1000)

= 0.007 m3

e) Volume of all aggregate = (a – (b + c + d))

= 1 – (0.131 + 0.143+0.007)

= 0.719 m3

e) 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

f) 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

= 763.86 kg

7. Concrete Mix Proportions 

  • Cement = 410 kg/m3
  • Water = 143 kg/m3
  • Super plasticizer = 7 kg/m3
  • Fine aggregates = 763.86 kg/m3
  • Coarse aggregate = 1152.48 kg/m3
  • W/c = 0.35

To get hold of other mix design calculation read these.

Mix Design for M25 Grade Concrete.

Mix Design For M40 Grade Concrete.

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