Project on Concrete Mix Design for various grades of Concrete

1. Aim : Determination of mix proportion for M35 grade concrete with fly ash using method of design mix

The mix proportion of M35 grade concrete is designed using design mix as grade of concrete is above M30. The following are the standards are applied for designing M35 grade concrete :

• IS 456 : 2000 - Code of practise for plain and reinforced concrete
• IS 10262 : 2009 and reaffirmed 2019 - Concrete mix proportioning guidelines
• IS 383 : 1970 - Specification of coarse and fine aggregates from natural sources for concrete
• IS 8112 : 1989 - Ordinary porland cement, 43 grade specification
• IS 9103 : 1999 - Specification for admixtures for concrete

Data Required :

1. Grade of concrete : M35
2. Type of cement : OPC 43 Grade conforming to IS 8112
3. Maximum nominal size of aggregate : 20mm
4. Minimum cement content : 340 kg/m3
5. Maximum water cement ratio : 0.45
6. workability : 100mm (slump)
7. Exposure condition : Very severe ( for RCC )
8. Method of concrete placing : Pumping
9. Degree of supervision : Good
10. Type of aggregate : Crushed angular aggregate
11. Maximum cement content : 450kg/m3
12. Chemical admixture : Superplasticizer

Test data for materials :

1. Cement used : OPC 43 Grade conforming to IS 8112
2. Specific gravity of cement : 3.15
3. Fly ash : Conforming to IS 3812 Part 1
4. Specific gravity of flyash : 2.2
5. Chemical admixture : Super plasticizer conforming to IS 9103 : 1999
6. Specific gravity
   Coarse aggregate : 2.74
   Fine aggregate : 2.74
7. Water absorption
   Coarse aggregate : 0.5%
   Fine aggregate : 1%
8. Free surface moisture
   Coarse aggregate : Nil
   Fine aggregate : Nil
9. Sieve analysis for Coarse aggregate and Fine aggregate : Conforming to Table 2 and Table 4 of IS 383 : 1970

Calulation:

1. Target strength for mix proportioning
   
   In order to find the variability in the performance of given concrete mix, characteristic strength is specified in order to calculate higher target mean strength for mix design which is given in IS 10262.
   
   Target strength fck' = fck + 1.65s Where fck' = target average compressive strength at 28 days
   = 35 + 1.65 x 5 fck = Characteristi compressive strength at 28 days
   = 43.25 N/mm2 S = Standard deviation taken from table 1 IS 10262 : 2009
   
   
2. Selection of water cement ratio
   
   i) Calculation of water cement ratio using graph from IS 10262 : 2019
   
   Required water cement ratio for target strength 43.25 N/mm2 is taken from the graph of water cement ratio vs 28 day compressive strength. Curve 2 in the graph represents target strength between 43N/mm2 to 53N/mm2. Therefore taking curve 2 as a reference, the water cement ratio is plotted and it is approximately near 0.37.
   
   ii) Calculation of water cement ratio using graph from IS 4031 : 1968
   
   Required water cement ratio for target strength 43.25 N/mm2 is taken from the graph of water cement ratio vs 28 day compressive strength. Curve E in the graph represents target strength between 41.5 N/mm2 to 48 N/mm2. Therefore taking curve E as a reference, the water cement ratio is plotted and it is shows 0.45.
   
   iii) Calculation of water cement ratio using table 5 of IS 456 : 2000
   
   Maximum water cement ratio calculated according to environment exposure condition given in table 5 of IS 456 : 2000
   As given exposure condition is very severe and grade of concrte is M35, the water cement ratio is 0.45.
   
   Lowest water cement ratio is considered from above calculated water cement ratios because lower water cement ratio, higher the strength and durability.
   
   Therefore water cement ratio is taken as 0.37
   
   
3. Approximate Air content
   
   From table 3 of 10262 : 2019 approximate amount of entrapped air to be expected in normal concrete (non air entrained) is 1% for 20mm nominal maximum aggregate size.
   
   
4. Selection of water content
   
   From table 2, IS 10262 : 2009 Maximum water content for 20mm aggregate = 186 litre (25 to 50 mm slump range)
   
   Estimated water content for 100mm slump = 186+(6/100) x 186
   = 197 lit
   As super plasticizer is used, the water content can b reduced upto 20% and above. Based on trials water content reduction of 29% is achieved with plasticizer. Hence the arrived water content = 197 x 0.71 = 140 litre
   
   
5. Calculation of cement content
   
   The cement content per unit volume of concrete is calculated using quantity of water and water cement ratio
   
   Water content = 140 lit and Water cement ratio : 0.37
   
   Cement content = Water / Water cement ratio
   = 140 / 0.37
   = 378.37 kg/m3
   
   From table 5 IS 456 : 2000 minimum cement content for very severe exposure condition = 340 kg/m3
   378.37 kg/m3 > 340 kg/m3 Hence okay
   
   
6. Proportion of mix containing flyash
   
   - Percentage of flyash needs to be decided based on project requirement and quality materials.
   - In some cases increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trail.
   - In this mix design, 10% increase in cementitious material is taken.
   
   Cementitious material content = 378.37 x 1.1 = 416.2 kg/m3
   Water content = 140 kg/m3
   Water cement ratio = 140 / 416.2 = 0.336
   
   Flyash at 30% of total cementitious material = 416.2 x 30%
   = 124.86
   ~ 125 kg/m3
   
   Cement content = 416.2 - 125
   = 291.2 kg/m3
   ~ 291 kg/m3
   
   From table 5 IS 456 : 2000 minimum cement content for very severe exposure condition = 340 kg/m3
   416.2 kg/m3 > 340 kg/m3, Hence okay
   
   
7. Proportion of volume of coarse aggregate and fine aggregate content
   
   From table 3 Volume of coarse aggregate corresponding to 20mm size aggragagte and fine aggregate (Zone I) for water cement ratio of 0.5 is 0.6. But the present water cement ratio is 0.336. Therefore volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water cement ratio is lower by 0.164, the proportion of volume of coarse aggregate is increased by 0.0328 (at the rate of +/- 0.01 for every +/- 0.05 changes in water cement ratio).
   Therefore, corrected proportion of volume of coarse aggregate for water cement ratio 0.336 = 0.6 + 0.0328 = 0.6328
   
   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 by 10%
   
   Therefore, volume of coarse aggregate = 0.6328 x 0.9 = 0.56952 ~ 0.57 m3
   
   Volume of fine aggregate content = 1 - 0.57 = 0.43 m3
   
   
8. Mix calculations as per unit of volume of concrete
   
   i) Volume of concrete = 1m3
   
   ii) Volume of entrapped air in wet concrete = 0.01 m3
   
   iii) Volume of cement = (Mass of cement / Specific gravity of cement) x (1/1000)
   = (291 / 3.15) x (1/1000)
   = 0.092 m3
   
   iv) Volume of fly ash = (Mass of flyash / Specific gravity of water) x (1/1000)
   = (125 / 2.2) x (1/1000)
   = 0.056 m3
   
   v) Volume of water = (Mass of water / Specific gravity of water) x (1/1000)
   = (140 / 1) x (1/1000)
   = 0.140 m3
   
   vi) Volume of chemical admixture (1% of mass of cementitious material)
   = (Mass of chemical admixture / Specific gravity of chemical admixture) x (1/1000)
   = (4.162 / 1.145) x (1/1000)
   = 0.00363 m3
   
   vii) Volume of aggregate (Fine aggregate + coarse aggregate) = (i - ii) - (iii + iv + v + vi)
   = (1-0.01) - ( 0.092+0.056+0.140+0.00363)
   = 0.69837 m3
   
   viii) Mass of coarse aggregate
   = Volume of aggregate x Volume of coarse ggregate x specific gravity of coarse aggregate x 1000
   = 0.69837 x 0.57 x 2.74 x 1000
   = 1090.71 kg/m3
   ~ 1090.7 kg/m3
   
   ix) Mass of fine aggregate
   = Volume of aggregate x Volume of fine ggregate x specific gravity of fine aggregate x 1000
   = 0.69837 x 0.43 x 2.74 x 1000
   = 822.81 kg/m3
   ~ 822.8 kg/m3
   
   
9. Mix proportion
   
   Cement = 291 kg/m3
   Water = 140 kg/m3
   Fine aggregate = 822.8 kg/m3
   Coarse aggregate = 1090.7 kg/m3
   Chemical admixture = 4.162 kg/m3
   Water cement ratio = 0.336
   
   Mix Proportion = 1: 2.82 : 3.74

The mix proportion is calculated to satisfy conditions such as strength, durability, workability and economy by testing on
fresh concrete. In the case, if measured values are different from stipulated value, the water content or admixture
content is adjusted suitably. And more than 2 trail batch mixes gives an idea about compressive strength and
water cement ratio, from which final mix proportions are calculated.

According to IS 10262

• The slump shall be measured and water content, dosage of admixture shall be adjusted for achieving the required slump on trail. The mix proportion shall be reworked for the actual water content and checked for durability.
  
  
• Two more trails having variation of 10% water cement ratio in clause x shall be carried out and graph between water cement ratios and corresponding strengths shall be plotted to workout the mix proportions for the given target strength for field trails. However durability shall be met.

2. Aim : Determination of mix proportion for M50 grade concrete without fly ash using method of design mix

The mix proportion of M50 grade concrete is designed using design mix as grade of concrete is above M30. The following are the standards are applied for designing M50 grade concrete :

• IS 456 : 2000 - Code of practise for plain and reinforced concrete
• IS 10262 : 2009 and reaffirmed 2019 - Concrete mix proportioning guidelines
• IS 383 : 1970 - Specification of coarse and fine aggregates from natural sources for concrete
• IS 8112 : 1989 - Ordinary porland cement, 43 grade specification
• IS 9103 : 1999 - Specification for admixtures for concrete

Data Required :

1. Grade of concrete : M50
2. Type of cement : OPC 43 Grade conforming to IS 8112
3. Maximum nominal size of aggregate : 20mm
4. Minimum cement content : 340 kg/m3
5. Maximum water cement ratio : 0.45
6. workability : 100 mm (slump)
7. Exposure condition : Very severe ( for RCC )
8. Method of concrete placing : Pumping
9. Degree of supervision : Good
10. Type of aggregate : Crushed angular aggregate
11. Maximum cement content : 450 kg/m3
12. Chemical admixture : Superplasticizer

Test data for materials :

1. Specific gravity of cement ( OPC 43 Grade)
2. Chemical admixture : Super plasticizer conforming to IS 9103 : 1999
3. Specific gravity
   Coarse aggregate : 2.74
   Fine aggregate : 2.74
4. Water absorption
   Coarse aggregate : 0.5%
   Fine aggregate : 1%
5. Free surface moisture
   Coarse aggregate : Nil
   Fine aggregate : Nil
6. Sieve analysis for Coarse aggregate and Fine aggregate : Conforming to Table 2 and Table 4 of IS 383 : 1970

Calulation:

1. Target strength for mix proportioning
   
   In order to find the variability in the performance of given concrete mix, characteristic strength is specified in order to calculate higher target mean strength for mix design which is given in IS 10262.
   
   Target strength fck' = fck + 1.65s Where fck' = target average compressive strength at 28 days
   = 50 + 1.65 x 5 fck = Characteristi compressive strength at 28 days
   = 58.25 N/mm2 S = Standard deviation taken from table 1 IS 10262 : 2009
   
   
2. Selection of water cement ratio
   
   i) Calculation of water cement ratio using graph from IS 10262 : 2019
   
   Required water cement ratio for target strength 58.25 N/mm2 is taken from the graph of water cement ratio vs 28 day compressive strength. Curve 3 in the graph represents target strength between 53 N/mm2 to above. Therefore taking curve 3 as a reference, the water cement ratio is plotted and it is approximately near 0.34.
   
   ii) Calculation of water cement ratio using graph from IS 4031 : 1968
   
   Required water cement ratio for target strength 58.25 N/mm2 is taken from the graph of water cement ratio vs 28 day compressive strength. Taking curve F as a reference, the water cement ratio is plotted and it is shows approximately 0.38.
   
   iii) Calculation of water cement ratio using table 5 of IS 456 : 2000
   
   Maximum water cement ratio calculated according to environment exposure condition given in table 5 of IS 456 : 2000
   As given exposure condition is very severe and grade of concrte is M35, the water cement ratio is 0.45.
   
   Lowest water cement ratio is considered from above calculated water cement ratios because lower water cement ratio, higher the strength and durability.
   
   Therefore water cement ratio is taken as 0.34.
   
   
3. Approximate Air content
   
   From table 3 of 10262 : 2019 approximate amount of entrapped air to be expected in normal concrete (non air entrained) is 1% for 20mm nominal maximum aggregate size.
   
   
4. Selection of water content
   
   From table 2, IS 10262 : 2009 Maximum water content for 20mm aggregate = 186 litre (25 to 50 mm slump range)
   and increasing at the rate of 3% for every 25mm slump
   
   Estimated water content for 100 mm slump = 186 + (6/100) x 186
   = 197 lit
   
   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 = 197 x 0.71 = 140 litre
   
   
5. Calculation of cement content
   
   The cement content per unit volume of concrete is calculated using quantity of water and water cement ratio
   
   Water content = 140 lit and Water cement ratio : 0.34
   
   Cement content = Water / Water cement ratio
   = 140 / 0.34
   = 411.76 kg/m3
   
   From table 5 IS 456 : 2000 minimum cement content for very severe exposure condition = 340kg/m3
   411.76 kg/m3 > 340 kg/m3 Hence okay
   
   
6. Proportion of volume of coarse aggregate and fine aggregate content
   
   From table 3 Volume of coarse aggregate corresponding to 20mm size aggragagte and fine aggregate (Zone I) for water cement ratio of 0.5 is 0.6. But the present water cement ratio is 0.34. Therefore volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water cement ratio is lower by 0.16, the proportion of volume of coarse aggregate is increased by 0.032. (at the rate of +/- 0.01 for every +/- 0.05 changes in water cement ratio).
   Therefore, corrected proportion of volume of coarse aggregate for water cement ratio 0.34 = 0.6 + 0.032 = 0.632.
   
   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 by 10%
   
   Therefore, volume of coarse aggregate = 0.632 x 0.9 = 0.5688
   
   Volume of fine aggregate content = 1 - 0.5688 = 0.4312
   
   
7. Mix calculations as per unit of volume of concrete
   
   i) Volume of concrete = 1m3
   
   ii) Volume of air entrapped in wet concrete = 0.01 m3
   
   iii) Volume of cement = (Mass of cement / Specific gravity of cement) x (1/1000)
   = (411.76 / 3.15) x (1/1000)
   = 0.130 m3
   
   iv) Volume of water = (Mass of water / Specific gravity of water) x (1/1000)
   = (140/1) x (1/1000)
   = 0.140 m3
   
   v) Volume of chemical admixture (1% of mass of cementitious material)
   = (Mass of chemical admixture / Specific gravity of chemical admixture) x (1/1000)
   = (4.11 /1.145) x (1/1000)
   = 0.0035 m3
   
   vi) Volume of aggregate (Fine aggregate + coarse aggregate) = (i -ii) - (iii + iv + v)
   = (1-0.01)-(0.130+0.140+0.0035)
   = 0.7165 m3
   
   vii) Mass of coarse aggregate
   = Volume of aggregate x Volume of coarse ggregate x specific gravity of coarse aggregate x 1000
   = 0.7165 x 0.5688 x 2.74 x 1000
   = 1116.67 kg/m3
   ~ 1116.7 kg/m3
   
   viii) Mass of fine aggregate
   = Volume of aggregate x Volume of fine ggregate x specific gravity of fine aggregate x 1000
   = 0.7165 x 0.4312 x 2.74 x 1000
   = 846.53 kg/m3
   ~ 846.5 kg/m3
   
   
8. Mix proportion
   
   Cement = 411.76 kg/m3
   Water = 140 kg/m3
   Fine aggregate = 846.5 kg/m3
   Coarse aggregate = 1116.7 kg/m3
   Chemical admixture = 4.11 kg/m3
   Water cement ratio = 0.34
   
   Mix Proportion = 1: 2 : 2.71
   = Cement : Fine aggregate : Coarse aggregate
   
   
   The mix proportion is calculated to satisfy conditions such as strength, durability, workability and economy by testing on fresh concrete. In the case, if measured values are different from stipulated value, the water content or admixture
   content is adjusted suitably. And more than 2 trail batch mixes gives an idea about compressive strength and water cement ratio, from which final mix proportions are calculated.
   
   According to IS 10262
   

• The slump shall be measured and water content, dosage of admixture shall be adjusted for achieving the required slump on trail. The mix proportion shall be reworked for the actual water content and checked for durability.
  
  
• Two more trails having variation of 10% water cement ratio in clause x shall be carried out and graph between water cement ratios and corresponding strengths shall be plotted to workout the mix proportions for the given target strength for field trails. However durability shall be met.