Project on Concrete Mix Design for various grades of Concrete

1.

• Mix proportion of concrete using fly ash as a part of the replacement of OPC
• The Concrete Mix Design for M35 grade concrete with fly ash

1. Stipulation for proportioning:

• a. Grade of designation: M35
  b. Type of cement: OPC 43 grade conforming to IS 8112
  c. Type of mineral admixture: Fly ash confirming to IS 3812
  d. Maximum nominal size of aggregates: 20mm
  e. Minimum cement content: 320 kg/m^3
  f. Maximum water-cement ratio: 0.45
  g. Workability:100mm slump value of pumpable concrete
  h. Exposure condition: Severe ( for reinforced concrete)
  i. Method of concrete placing: Pumping
  j. Degree of supervision: Good
  k. Type of aggregate: Crushed angular aggregate
  l. Maximum cement content : 450 kg/m^3.
  m. Chemical admixture type: Superplasticizer.

2. Test data for material:

• Cement used: OPC 43 grade confirming to IS 8112
• Specific gravity of cement: 3.15
• Fly ash: Conforming to IS 3812 part 1
• Specific gravity of fly ash: 2.2
• Chemical admixture: Superplasticizer conforming to IS 9103
• Specific gravity of Coarse aggregate: 2.74
  Fine aggregate: 2.74
• Water absorption : Coarse aggregate : 0.5%
  Fine aggregate: 1%
• Free surface moisture: Coarse aggregate: Nil
  Fine aggregate: Nil
• Sieve analysis: Conforming to table-2 of IS 383

3. Target mean strength for mix proportioning

• Target mean strength f'ck = fck +1.65s

  = 35 +1.65*5 =43.25 N/mm2

4. Selection of water content:

• Maximum water content for 20mm aggregate =186 liters ( Table 2 of IS 1026:2009) for 25mm to 50mm slump range

  For 100 mm slump ,= 186+(6/100)*186 =197 litres

  As a superplasticizer is used, the water content is reduced up to 30%

  Based on trials water content reduction of 29% is achieved with plasticizer

  Hence arrived water content = 197*0.71 = 140 litres

5. Selection of water- cement ratio:

• Maximum water-cement ratio =0.45 (for severe condition ,from table 5 of IS 456-2000)

  On experience water- cement ratio =0.4

  0.4 <0.45, Hence Ok

6. Calculation of cement content

• Water - cement ratio = 0.4
• Cementitious material ( Cement +flyash ) = 140/0.4 =350kg/m3
• In table 5 of IS 456-2000, the cement content for severe exposure =320 kg/m3
• Therefore 350kg/m3> 320kg/m3 Hence OK

To proportion the mix containing fly ash the following steps are suggested :

• a. The percentage of fly ash needs to be decided based on project requirements and quality of materials.
• b. Increases in cementitious materials can occasionally be forewarned. Based on experience and trial, cementitious material content and % may be increased. 10% more cementitious material is taken into account in this increase.
• Cementatious material content = 350*1.1 =385 Kg/m3
• Water content = 140 lts
• So, water- cement ratio = 140/385 =0.364
• Fly ash at 30% total cementatious material content = 35-30% =115 kg/m3
• Cement (OPC) =385-115 =270 kg/m3
• Saving of cement while using fly ash = 350-270=80 kg/m3
• Fly ash being utilized = 115 kg/m3

7. The proportion of the volume of coarse aggregate and fine aggregate content

• From table 3 of IS 1026:2009, the volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone 1 ) for water- cement ratio =0.6
• In the present case water-cement ratio is 0.4
• Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As the water-cement ratio is lowered by 0.1, 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 water-cement ratio)

• Hence the corrected value of coarse aggregate for the water-cement ratio = 0.64

  ( If the coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

  For pumpable concrete, these are reduced by 10 %

  Volume of coarse aggregate = 0.64*0.9 = 0.576

  Volume of fine aggregate = 1-0.576 =0.424

• 8. Mix calculation:

  Mix calculation per unit volume of concrete:

  a. Volume of concrete = 1 m^3.

  b. Volume of cement = (Mass of cement / Specific gravity of cement ) *1/1000

  = (270/3.15 )*1/1000 =0.086m3

  c. Volume of flyash = (Mass of flyash / Specific gravity of flyash )*1/1000

  = (115/2.2) *1/1000 = 0.052 m3

  d. Volume of water = ( Mass of water / Specific gravity of water)*1/1000

  = (140/1)*1/1000 =0.140m3

  e. Volume of chemical admixture = ( Mass of admixture / specific gravity of admixture)*1/1000

  =( 7.6/1.14)*1/1000 =0.006 m3

  f. Volume of aggregate ( Fine and coarse) = a- (b+c+d+e)

  = 1-(0.086+0.052+0.140+0.006) =0.716 m3

  
  g. Mass of coarse aggregate = f* Volume of coarse aggregate * Specific gravity of coarse aggregate *1000

  = 0.716*0.576*2.74*1000 =1130 kg/m3

  h. Mass of fine aggregate = f* Volume of fine aggregate* Specific gravity of fine aggreate*1000

  = 0.716*0.424*2.74*1000= 831 kg/m3

9. Mix proportion:

• Cement = 270 kg/m3

  Fly ash = 115 kg/m3

  Water = 140 kg/m3

  Fine aggregate = 831 kg/m3

  Coarse aggregate = 1130 kg/m3

  Chemical admixture = 7 kg/m3

  Water- cement ratio = 0.3

  Trial mix= 1: 2.15: 2.9

• 10. The water content and dose of the admixture must be changed for the experiment to get the appropriate slump after measuring the slump. Reworking the mix proportion for the actual water content and verifying it meets durability standards is required.

  11. To determine the mix proportions for the specified goal strength for field testing, two or more experiments with variations of 10% in the water-cement ratio in Clause 10(Step 10) must be conducted. A graph between three water-cement ratios and corresponding strengths must then be created. But durability must be fulfilled.

2. Mix design of M 50 grade concrete

1. Stipulation for proportion:

• a. Grade designation: M50

  b. Type of cement: OPC grade 43 conforming to IS 8112

  c. Maximum nominal size of aggregate: 20mm

  d. Minimum cement content: 320 kg/m3

  e. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)

  f. Workability:100mm, slump value of pumpable concrete

  g. Exposure condition: Severe ( for reinforced concrete)

  h. Method of concrete placing: Pumping

  i. Degree of supervision: Good

  j. Type of aggregate: Crushed angular aggregate

  k. Maximum cement content: 450 kg/m^3.

  l. Chemical admixture type: Superplasticizer

  2. Test data for material:
• a. Cement used: OPC 43 grade confirming to IS 8112
  b. Specific gravity of cement: 3.15
  c. Chemical admixture: Superplasticizerr conforming to IS 9103
  d. Specific gravity of Coarse aggregate: 2.74
  Fine aggregate: 2.74
  e. Water absorption: Coarse aggregate: 0.5%
  Fine aggregate: 1%
  f. Free surface moisture Coarse aggregate: Nil
  Fine aggregate: Nil
• Sieve analysis: Conforming to table-2 of IS 383

3. Find target mean strength for proportioning

• Target mean strength , f'ck =fck +1.65 s

= 50+1.65*5 =58.25

4. Selection of water content:

• Maximum water content for 20mm aggregate =186 liters ( Table 2 of IS 1026:2009) for 25mm to 50mm slump range
• For 100 mm slump ,= 186+(6/100)*186 =197 liters
• As superplasticizer is used, the water content is reduced up to 30%
• Based on trials water content reduction of 29% is achieved with plasticizer
• Hence arrived water content = 197*0.71 = 140 liters

5. Selection of water-cement ratio:

• From Table:5 of IS 456-2000, by exposure condition

  Here the severe condition is considered, Maximum water-cement ratio=0.45

  Based on experience water- cement ratio =0.4

  0.4 <0.45 ,Hence OK.

6. Selection of cement content:

• Water - cement ratio = 0.4

  Cement content = 140/0.4 =350 kg/m3

• In table 5 of IS 456-2000, the cement content for severe exposure =320 kg/m3

  350 kg/m3 > 320 kg/m3

  Hence OK.

7. The proportion of the volume of coarse aggregate and fine aggregate content:

• From table 3 of IS 1026:2009, the volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone 1 ) for water- cement ratio =0.6

  In the present case the water-cement ratio is 0.4

• In order to reduce the content of fine aggregate, the amount of coarse aggregate must be increased.

  The proportion of volume of coarse aggregate increases by 0.02 when the water-cement ratio decreases by 0.1 (at a rate of +/- 0.01 for every +/- 0.05 variation in the water-cement ratio).

  Therefore, 0.64 is the adjusted value of coarse aggregate for the water-cemnt ratio.

• According to experience, it may be necessary to increase the volume of coarse aggregate if it is not of the angular kind.

  These are 10% less for concrete that can be pumped.

• Volume of coarse aggregate = 0.64*0.9 = 0.576

  Volume of fine aggregate = 1-0.576 =0.424

8. Mix calculation:

• For a unit volume of concrete

  a. Volume of concrete = 1m3
  b. Volume of cement = ( Mass of cement / Specific gravity of cement ) *1/1000

  =(350/3.15)*1/1000 =0.111m3

  c. Volume of water = (Mass of water/ Specific gravity of water )*1/1000

  = (140/1)*1/1000 =0.140m3

  d. Volume of chemical admixture = (Mass of admixture/Specific gravity of admixture)*1/1000

  = (7.6/1.145)*1/1000 =0.006m3

  e. Volume of aggregate (fine and coarse) = a-(b+c+d)

  =1-( 0.111+0.140+0.006) =0.743m3

  f. Mass of coarse aggregate = ex Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000

  =0.743*0.576*2.74*1000= 1173 kg/m3

  g. Mass of fine aggregate =e* Volume of fine aggregate* Specific gravity of fine aggregate *1000

  = 0.743*0.424*2.74*1000 =863 kg/m3

9. Mix proportion

• Cement = 350 kg/m3
• Water = 140 kg/m^3
• Fine aggregate= 863 kg/m3
• Coarse aggregate = 1173 kg/m3
• Chemical admixture = 7 kg/m3
• Water cement ratio =0.4
  Mix ratio =1: 2.46: 3.35

10.

• The water content and dose of the admixture must be changed for the experiment to get the appropriate slump after measuring the slump. Reworking the mix proportion for the actual water content and verifying it meets durability standards is required.

11.

• A graph between three water-cement ratios and associated strengths must be created in order to determine the mix proportions for the specified goal strength for field testing after two or more experiments with variations of 10% in the water-cement ratio in Clause 10 (Step 10) have been completed. But durability must be fulfilled.