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Project on Concrete Mix Design for various grades of Concrete

JJeya Kannan R S12 Feb 2023

@. The calculation of M35 grade concrete with fly ash .

ans;

1. Stipulations for proportioning;

  1. Grade designation : M35
  2. Type of cement : OPC 43 grade conforming to IS 8112
  3. Type of mineral admixture : Fly ash conforming to IS 3812 part1
  4. Maximum naminal size of aggregate : 20mm
  5. Maximum water-cement ratio : 0.45
  6. minimum cement contant : 340 kg / m^3
  7. Maximum cement content : 450 kg/m^3
  8. workability : 100mm ( slump value of pumpable concrete)
  9. Exposure condition : very severe ( for RCC)
  10. Method of concrete placing : pumping
  11. Degree of supervision : Good
  12. Type of agggregate : Crushed angular aggregate.
  13. Chemical admixture type : superplasticizer.

2. Test data for materials ;

  1. Specific gravity of cement : 3.15
  2. Specific gravity of fly ash : 2.2
  3. Specific gravity of coarse aggregates : 2.74
  4. Specific gravity of fine aggregates : 2.65
  5. Specific gravity of admixture : 1.14
  6. chemical admixture type : Super Plasticizer conforming to IS 9103

3. Defermation of Target strength;

F'ck = fck + 1.65 S

  • F'ck= the target mean compressive strength at 28 days,
  • fck = the characteristic compressive strength at 28 days,
  • S = the standard deviation

As per the table I of IS: 10262-2009 , standard deviation, S = 5.0 N/mm^2

Therefore, target strength = 35 +( 1.65 x 5.0) = 43.25 N/mm^2

4. Selection of water cement ratio ;

As per the table of IS: 456-2000 (from table-5), the minimum water cement ratio = 0.45

5. Selection of water content ;

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

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

(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 20% has been achieved,
  • Hence the water content = 197-[197 x (20/100)] = 158 litres.

6. Calculation of cement content ;

  • Water-cement ratio = 0.45
  • Cement content = 158/0.45 = 351.11

from Table 5 of IS 456, minimum cement content for ‘Very Severe' exposure condition = 340 kg/m3

351 kg/m^3 > 340 kg/m^3 , hence O.K.

  • 351 kg/m^3 is a cementitious material (cement + fly ash) content.

The cementitious content has to be increased in order to attain good workability and strength. The increment required is determined on the basis of experience and research. Here we are increasing cementitious content by 10%

  • Cementitous material content = 351 + (351x10)/100 = 385.1 kg/m^3
  • Water content = 158 kg/m^3
  • water-cement ratio = 158/385.1= 0.41
  • Fly ash is 30% total cementitious material content = 385.1 x 30% = 115.53 kg/m^3
  • cement content = 385.1 - 115.53 = 269.57 kg/m^3
  • Saving of cement while using of fly ash = 351-269.57 = 81.47 kg/m^3

7. 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 II) for a water-cement ratio of 0.50 = 0.62.

In the present case, the water-cement ratio is 0.45. Therefore, the volume of coarse aggregate is required to be increased to reduce 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 0.45 = 0.63.
  • 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 = 0.63 x 0.9 = 0.567.
  • Volume of fine aggregate content =1 – 0.567 =0.433

8. Mix calculation ;

  1. Volume of concrete = 1 m^3
  2. volume of cement = ( mass of cement / Sg of cement )X(1/1000) = (269.57/3.15)X(1/1000) = 0.0856 m^3
  3. volume of fly ash = ( mass of fly ash / Sg of fly ash )X(1/1000) = (115.53/2.2)X(1/1000) = 0.053 m^3
  4. Volume of Water = ( mass of water / Sg of water )X(1/1000) = (158/1)X(1/1000) = 0.158 m^3
  5. Volume of admixture = ( mass of admixture / Sg of admixture)X(1/1000) = (7.6/1.145)X(1/1000) = 0.006 m^3
  6. Volume of all aggregate = [ a - (b+c+d+e) ] = [ 1-( 0.0856 + 0.053 + 0.158 + 0.006)] = 0.6974 m^3
  7. Mass of coarse aggregate = Volume of all agregate X volume of coarse aggregate X Sg of coarse aggregate X 1000 =( 0.697 X 0.567 X 2.74 X 1000)= 1082.84 kg/m^3
  8. Mass of fine aggregate = Volume of all agregate X volume of fine aggregate X Sg of fine aggregate X 1000 = ( 0.697 X 0.433 X 2.65 X 1000)= 799.77 kg/m^3

9. Mix proportion;

  • Cement = 270 kg/m^3
  • Fly ash = 116 kg/m^3
  • Fine aggregate = 800 kg/m^3
  • coarse aggregate = 1083 kg/m^3
  • Water content = 158 litter
  • Water cement ratio = 0.45

10. Mix ratio ;

The Mix Ratio of M35 as obtained is 1 : 2.077 : 2.81 (Cement : Fine aggregate : Coarse aggregate)

  • he slump shall be measured, the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements
  • Two more trials having variation of 10% of water-cement ratio shall be carried out and a graph between three water- cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target for field trials.

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#The concrete mix design for M50 with out fly ash.

1. Stipulations for proportioning;

  1. Grade designation : M50
  2. Type of cement : OPC 53 grade conforming to IS 8112
  3. Maximum naminal size of aggregate : 20mm
  4. Maximum water-cement ratio : 0.35
  5. minimum cement contant : 360 kg / m^3
  6. Maximum cement content : 450 kg/m^3
  7. workability : 100mm ( slump value of pumpable concrete)
  8. Exposure condition : Extreme ( for RCC)
  9. Method of concrete placing : pumping
  10. Degree of supervision : Good
  11. Type of agggregate : Crushed angular aggregate.
  12. Chemical admixture type : super plasticizer.

2. Test data for materials ;

  1. Specific gravity of cement : 3.15
  2. Specific gravity of coarse aggregates : 2.74
  3. Specific gravity of fine aggregates : 2.65
  4. Specific gravity of admixture : 1.145
  5. chemical admixture type : Super Plasticizer conforming to IS 9103

3. Defermation of Target strength;

F'ck = fck + 1.65 S

  • F'ck= the target mean compressive strength at 28 days,
  • fck = the characteristic compressive strength at 28 days,
  • S = the standard deviation

As per the table I of IS: 10262-2009 , standard deviation, S = 5.0 N/mm^2

Therefore, target strength = 50+( 1.65 x 5.0) = 58.25 N/mm^2

4. Selection of water cement ratio ;

As per the table of IS: 456-2000 (from table-5), the minimum water cement ratio = 0.35

5. Selection of water content ;

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

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

(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 27% has been achieved,
  • Hence the water content = 197-[197 x (27/100)] = 143.8 litres.

6. Calculation of cement content ;

  • Water-cement ratio = 0.35
  • Cement content = 143.8/0.35 = 410 kg/m^3

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

410 kg/m^3 > 360 kg/m^3 , hence O.K.

7. 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 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 reduce 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 0.45 = 0.63.
  • 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 = 0.585.
  • Volume of fine aggregate content =1 – 0.585 =0.415

8. Mix calculation ;

  1. Volume of concrete = 1 m^3
  2. volume of cement = ( mass of cement / Sg of cement )X(1/1000) = (410/3.15)X(1/1000) = 0.13 m^3
  3. Volume of Water = ( mass of water / Sg of water )X(1/1000) = (143.8/1)X(1/1000) = 0.1438 m^3
  4. Volume of admixture = ( mass of admixture / Sg of admixture)X(1/1000) = (8.2/1.145)X(1/1000) = 0.007 m^3
  5. Volume of all aggregate = [ a - (b+c+d) ] = [ 1-( 0.13 + 0.1438 + 0.007)] = 0.7192 m^3
  6. Mass of coarse aggregate = Volume of all agregate X volume of coarse aggregate X Sg of coarse aggregate X 1000 =( 0.7192 X 0.585 X 2.74 X 1000)= 1152.8 kg/m^3
  7. Mass of fine aggregate = Volume of all agregate X volume of fine aggregate X Sg of fine aggregate X 1000 = ( 0.7192 X 0.415 X 2.65 X 1000)= 790.9 kg/m^3

9. Mix proportion;

  • Cement = 410 kg/m^3
  • Fine aggregate = 791 kg/m^3
  • coarse aggregate = 1153 kg/m^3
  • Water content = 144 litter
  • super plasticizer = 7 kg/m^3
  • Water cement ratio = 0.35

10. Mix ratio ;

The Mix Ratio of M35 as obtained is 1 : 1.93 : 2.81 (Cement : Fine aggregate : Coarse aggregate)

  • he slump shall be measured, the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements
  • Two more trials having variation of 10% of water-cement ratio shall be carried out and a graph between three water- cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target for field trials.

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