Project on Concrete Mix Design for various grades of Concrete

AIM:

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

INTRODUCTION:

• Concrete is a complex material and has the right mix of constituents of concrete which if not done properly and it will have adverse effect on the properties of concrete.
• Concrete mix design is a systematic process of choosing economical relative proportion of various ingredients from available material that gives the concete of desired workability.
• The process of selecting suitable ingredients for producing concrete of required strength durability and workability as economical as possible is known as concrete mix design.
• The compressive strength of the concrete depends on the quality and quantity of cement, water and aggregate.It also depends on the mixing, batching, placing, compaction and curing.

OBJECTIVE:

• The objective of this project is to produce a mix design for M35 grade concrete containing fly ash and M50 grade concrete. The mix will be prepared as per IS method. Concrete mix proportioning guidelines from IS 10262:2009 and recommended guide lines from IS 10262:1982 are used to determine the mix design calculations.

PROCEDURE:

STEPS TO BE FOLLOWED IN MIX DESIGN CALCULATION:

• STIPULATION FOR PROPORTIONING
• TEST DATA FOR MATERIALS

• TARGET MEAN STRENGTH FOR MIX PROPORTIONING

• SELECTION OF WATER CEMENT RATIO
• SELECTION OF WATER CONTENT
• CALCULATION OF CEMENT CONTENT

• PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
• MIX CALCULATIONS

• MIX PROPORTIONS FOR TRIAL NUMBER

PART 1: TO CALCULATE THE CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH:

STIPULATION FOR PROPORTIONING:

1. Grade of designation – M35
2. Type of cement – OPC 43 Grade.
3. Type of mineral admixture – flyash (conforming to IS3812 – Part 1)
4. Maximum nominal size of aggregate – 20mm
5. Minimum cement content – 340 kg/m^3 (Table 5, IS456:2000 based on exposure condition)
6. Maximum water cement ratio – 0.45 (Table 5, IS456:2000 based on exposure condition)
7. Workability – 100mm (slump value for pumbable concrete)
8. Exposure condition – Very severe.
9. Method of concrete placing – Pumbing
10. Degree of supervision – Good
11. Maximum cement content – 450 kg/m^3 ( as per IS456:2000, Clause 8.2.4.2)
12. Chemical admixture type – Super plasticizer

TEST DATA FOR MATERIALS:

1. Cement used – OPC 43 grade (conforming to IS8112)
2. Specific gravity of cement – 3.15
3. Fly ash – Conforming to IS3812- part 1
4. Specific gravity of fly ash – 2.2
5. Chemical admixture – Superplasticizer conforming to IS9103
6. Specific gravity of coarse aggregate – 2.74
7. Specific gravity of fine aggregate – 2.74
8. Water absorption percentage of coarse aggregate – 0.5%
9. Water absorption percentage of fine aggregate – 1.0%
10. Free moisture content of coarse aggregate – Nil
11. Free moisture content of fine aggregate – Nil
12. Sieve analysis value for coarse aggregate – Based on IS383- Table 2
13. Sieve analysis value for fine aggregate - Based on IS383- Table 4

TARGET MEAN STRENGTH FOR MIX PROPORTIONING:

f^’_ck= f_ck + 1.65 * S

Where,

• f^’_ck – Target average compressive strength of 28days
• f_ck – Characteristic compressive strength at 28 days
• S – Standard deviation.

From Table 1 of IS10262:2009,

The standard deviation (S) = 5 N/mm^2

Target strength = 35+1.65*5

f^’_ck = 43.25 N/mm^2.

SELECTION OF WATER CEMENT RATIO:

• From Table 5 of IS456:2000 for very severe exposure maximum water cement ratio = 0.45.
• Based on experience the adopted water cement ratio is = 0.40
• 40 < 0.45, HENCE OK.
  
  

SELECTION OF WATER CONTENT:

• From table 2 of IS10262:2009 maximum water content for 20mm aggregate

= 186 litre (for 25mm to 50mm slump range and for every 25mm to 50mm slump range 3% of water content should be added )

• Estimated water content for 100mm slump = 186 + (6/100) * 186

= 197 litre.

• As superplasticizer is used the water content can be reduced upto 30%.
• Based on trails water content reduction of 29% is achieved with plasticizer.
• Hence the arrived water content = 197 * 0.71

= 140 litre.

CALCULATION OF CEMENT CONTENT:

• Water cement ratio = 0.4
• Cementitious material (cement+flyash) content = 140/0.4 = 350 Kg/m^3
• From table 5 of IS456:2000 the minimum cement content for very severe exposure condition is = 340 Kg/m^3
• 350 kg/m^3 > 340 Kg/m^3. HENCE OK.
• Now to proportion a mix containing flyash the flowing steps are suggested:
• The percentage of flyash needs to be decided based on project requirement and quality of materials.
• In some cases increase in cementitious material can be warrented. Increase in cementitious material content and its percentage may be based on experience and trial (this example is with 10% cementitious material content)
• Cementitious material content = 350 * 1.10

= 385 Kg/m^3

• Water content = 140 Kg/m^3
• Water cement ratio = 140/385 = 0.364
• Flyash @ 30% total cementitious material content = 385 * 30%

= 115 Kg/m^3

• Cement (OPC) = 385 – 115

= 270 Kg/m^3

• Saving of cement while using flyash = 350 – 270

= 80 Kg/m^3

• Flyash being utilized = 115 Kg/m^3.
  
  

PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

• Therefore from Table 3 of IS10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate ZONE – I for water cement ratio of 5 = 0.6.
• But in the present case the water cement ratio is 40.
• Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As water cement ratio is lower by 0.10 the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio)
• For pumpable concrete these values are reduced by 10% .
• Therefore volume of coarse aggregate = 0.62 * 0.9 = 0.56
• Volume of fine aggregate content = 1- 0.56 = 0.44.
  
  

MIX CALCULATIONS:

The mix calculation per unit volume of concrete shall be as follows.

1. Volume of concrete = 1 m^3
2. Volume of cement = (mass of cement / specific gravity of cement) *
   (1/1000)

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

= 0.086 m^3

2. Volume of flyash = (mass of flyash/specific gravity of flyash) * (1/1000)
   = (115/2.2) * (1/1000)
   = 0.052 m^3
3. Volume of water = (mass of water / specific gravity of water) * (1/1000)
   = (140/1) * (1/1000)
   = 0.140 m^3
4. Volume of chemical admixture = (mass of chemical admixture / specific gravity of admixture) * (1/1000)
   = (7.6/1.145) * (1/1000)
   = 006 m^3
5. Volume of aggregate (coarse aggregate and fine aggregate)
   = (a-(b+c+d+e))
   = (1-(0.086+0.052+0.140+0.006))
   =716 m^3
6. Mass of coarse aggregate = f * volume of coarse aggregate * specific gravity of coarse aggregate*1000
   = 0.716 * 0.56 * 2.74 * 1000
   = 1098 kg/m^3
7. Mass of fine aggregate = f * volume of fine aggregate * specific gravity of fine aggregate * 1000
   = 0.716 * 0.44 * 2.74 * 1000
   = 863 Kg/m^3
   
   

MIX PROPORTIONS FOR TRIAL NUMBER:

1. Cement – 270 kg/m³
2. Fly ash – 115 kg/m³
3. Water – 140 kg/m^3
4. Fine aggregate – 863 kg/m³
5. Coarse aggregate – 1098 kg/m³
6. Chemical admixture – 6 kg/m³
7. Water cement ratio – 0.364

Trial mix ratio – 1 : 2.24 : 2.85

1. The 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
2. 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.

PART 2: TO CALCULATE THE CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLY ASH:

STIPULATION FOR PROPORTIONING:

1. Grade of designation – M50
2. Type of cement – OPC 43 Grade.
3. Maximum nominal size of aggregate – 20mm
4. Minimum cement content – 340 kg/m³ (Table 5, IS456:2000 based on exposure condition)
5. Maximum water cement ratio – 0.45 (Table 5, IS456:2000 based on exposure condition)
6. Workability – 100mm (slump value for pumbable concrete)
7. Exposure condition – Very severe.
8. Method of concrete placing – Pumbing
9. Degree of supervision – Good
10. Maximum cement content – 450 kg/m^3 ( as per IS456:2000, Clause 8.2.4.2)
11. Chemical admixture type – Super plasticizer.
    
    

TEST DATA FOR MATERIALS:

1. Cement used – OPC 43 grade (conforming to IS8112)
2. Specific gravity of cement – 3.15
3. Chemical admixture – Superplasticizer conforming to IS9103
4. Specific gravity of coarse aggregate – 2.74
5. Specific gravity of fine aggregate – 2.74
6. Water absorption percentage of coarse aggregate – 0.5%
7. Water absorption percentage of fine aggregate – 1.0%
8. Free moisture content of coarse aggregate – Nil
9. Free moisture content of fine aggregate – Nil
10. Sieve analysis value for coarse aggregate – Based on IS383- Table 2
11. Sieve analysis value for fine aggregate - Based on IS383- Table 4
    
    
    

TARGET MEAN STRENGTH FOR MIX PROPORTIONING:

f^’_ck= f_ck + 1.65 * S

Where,

• f^’_ck – Target average compressive strength of 28days
• f_ck – Characteristic compressive strength at 28 days
• S – Standard deviation.

From Table 1 of IS10262:2009,

The standard deviation (S) = 5 N/mm²

Target strength = 50+1.65*5

f^’_ck= 58.25 N/mm².

SELECTION OF WATER CEMENT RATIO:

• From Table 5 of IS456:2000 for very severe exposure maximum water cement ratio = 0.45.
• Based on experience the adopted water cement ratio is = 0.35
• 35 < 0.45, HENCE OK.
  
  

SELECTION OF WATER CONTENT:

• From table 2 of IS10262:2009 maximum water content for 20mm aggregate

= 186 litre (for 25mm to 50mm slump range and for every 25mm to 50mm slump range 3% of water content should be added )

• Estimated water content for 100mm slump = 186 + (6/100) * 186

= 197 litre.

• As superplasticizer is used the water content can be reduced upto 30%.
• Based on trails water content reduction of 29% is achieved with plasticizer.
• Hence the arrived water content = 197 * 0.71

= 140 litre.

CALCULATION OF CEMENT CONTENT:

• Water cement ratio = 0.35
• Cementitious material (cement+flyash) content = 140/0.35 = 400 Kg/m³
• From table 5 of IS456:2000 the minimum cement content for very severe exposure condition is = 340 Kg/m³
• 400 kg/m³ > 340 Kg/m³. HENCE OK.
  
  

PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

• Therefore from Table 3 of IS10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate ZONE – I for water cement ratio of 5 = 0.6.
• But in the present case the water cement ratio is 35.
• Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As water cement ratio is lower by 0.10 the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio)
• For pumpable concrete these values are reduced by 10% .
• Therefore volume of coarse aggregate = 0.63 * 0.9 = 0.567
• Volume of fine aggregate content = 1- 0.567 = 0.433.
  
  

MIX CALCULATIONS:

The mix calculation per unit volume of concrete shall be as follows.

1. Volume of concrete = 1 m³
2. Volume of cement = (mass of cement / specific gravity of cement) *
   (1/1000)

= (400 / 3.15) * (1/1000)

= 0.1269 m³

1. Volume of water = (mass of water / specific gravity of water) * (1/1000)
   = (140/1) * (1/1000)
   = 0.140 m³
2. Volume of chemical admixture = (mass of chemical admixture / specific gravity of admixture) * (1/1000)
   = (8/1.145) * (1/1000)
   = 0069 m³
3. Volume of aggregate (coarse aggregate and fine aggregate)
   = (a-(b+c+d+e))
   = (1-(0.1269+0.140+0.0069))
   =7262 m³
4. Mass of coarse aggregate = e * volume of coarse aggregate * specific gravity of coarse aggregate*1000
   = 0.7262 * 0.567 * 2.74 * 1000
   = 1128 kg/m³
5. Mass of fine aggregate = e * volume of fine aggregate * specific gravity of fine aggregate * 1000
   = 0.7262 * 0.433 * 2.74 * 1000
   = 862 Kg/m³
   
   

MIX PROPORTIONS FOR TRIAL NUMBER:

• Cement – 400 kg/m³
• Water – 140 kg/m³
• Fine aggregate – 862 kg/m³
• Coarse aggregate – 1128 kg/m³
• Chemical admixture– 8 kg/m³
• Water cement ratio – 0.35

Trial mix ratio – 1 : 2.155 : 2.82

1. The 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
2. 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.

RESULTS:

Part 1

• In this mix design for M35 grade concrete is successfully calculated with 30% of flyash is used as a replacement for cement in this mix.
• It gives better result and hence satisfy the mix design IS code norms.
• Via this test the water cement ratio is 0.364 and the mix ratio for this M35 grade concrete with flyash is 1 : 2.24 : 2.85

Part 2

• In this mix design for M50 grade concrete is successfully calculated by using Is codes.
• It gives better result and hence satisfy the mix design IS code norms.
• Via this test the water cement ratio is 0.35 and the mix ratio for this M50 grade concrete with flyash is 1 : 2.155 : 2.82.

APPENDIX

1. Physical characteristics of different OPC cement
   
2. Table – 5 Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregate of 20 mm Nominal Maximum Size IS: 456-2000
   
3. Table 2 of IS 383: Grade size distribution for different nominal sizes of coarse aggregate
   
4. Table 4 of IS 383: Grading of fine aggregate
   
5. Table I of IS 10262:2009: Assumed standard deviations
   
6. Table 2 of IS 10262:2009: maximum water content for 20 mm aggregate