Project on Concrete Mix Design for various grades of Concrete

CONCRETE MIX DESIGN FOR M35 GRADE WITH FLY ASH:

• Stipulation for proportioning:
• Grade designation- M35
• Type of cement-OPC 43 grade (conforming IS code 8112)
• Type of mineral admixture- fly ash
• Maximum nominal size of aggregate- 20 mm
• Minimum cement content- 320 kg/m^3 (IS 456-2019)
• Maximum free w/c ratio- 0.45(IS456-2019)
• Workability- 100 mm slump value (reinforced concrete)
• Exposure- severe (reinforced concrete)
• Method of concrete placing- pumping
• Degree of supervision- good
• Type of aggregate – crushed angular aggregate
• Maximum chemical cement content (OPC)- 450kg/m^3
• Chemical admixture type- super plasticizer
• Test data for materials:
• Cement used = OPC 43 grade
• Specific gravity of cement= 3.15
• Specific gravity of cement= 2.2
• Chemical admixture=superplasticizer
• Specific gravity of coarse aggregate=2.74
• Specific gravity of fine aggregate= 2.74
• Water absorption (CA)=0.5%
• Water absorption (FA)=1.0%
• Free moisture content=nil both CA and FA
• sieve analysis (CA)= conforming to grading zone 1 of table 4 of IS-383
• sieve analysis (FA)= table 4 of IS-383
• target strength for mix proportioning:

f’ck= fck+1.65S

where

f’ck= target average compressive strength at 28 days

fck= characteristics compressive strength at 28 days and

S= standard deviation

From table, S= 5 N/mm^2

Therefore, target strength =35+1.65(5)=43.25N/mm^2

• Water cement ratio:

Max. w/c ratio= 0.45(for severe, reinforced concrete)

Based on experience, adopt w/c ratio =0.38 assuming 0.40

0.4<0.45

Hence OK

• Selection of water content:

For 20mm aggregate, max w/c content= 186 kg/m^3( for 25-50mm)

Estimated water content for 100mm slump= 186+6%186=197litre (the water content may be increase or decrease by about 3 percent for each increase or decrease of 25mm slump)

As superplasticizer is used , the water content can be reduced 20% and above.

Based on trials, water content reduction of 29% has been achieved.

Hence, the arrived water content= 197 * 0.71=140 kg/m^3

• Calculation for weight of cement:

Estimate w/c ratio= 0.4

Cementitious material (fly ash +cement) content= 140/0.4=350kg/m^3

From table 5 of IS-456 minimum cement content for severe condition 350>320 kg/m^3

Hence OK

Thus, the proportion a mix containing fly-ash the following step

In some cases,

This example is with increase 10% cementitious material content.

Cementitious material content=350*1.10=385 kg/m^3

As water content =140

Then w/c ratio=140/385=0.4

Fly-ash @ 30% total cementitious = 30% of 385=115.5 kg/m^3

Mass of cement (OPC)=385-115=270 kg/m^3

Saving of cement while using fly-ash=350-270=80kg/m^3

• Proportion of volume of CA and FA:

From table of IS 10262-2019

Volume of CA corresponding to 20mm size aggregate and FA zone 1 for w/c ratio of 0.5=0.6

In the present case the w/c ratio is 0.38. so, assuming 0.4

Therefore, the volume of CA needs to be increased by 0.10

The proportion of volume of CA is increased by 0.02

Corrected volume of CA for w/c ratio of assumed 0.4 =0.60+0.02=0.62

For pumpable concrete these values are reduced by 10%

Therefore, volume of CA= 0.62*0.9=0.56

Volume of FA= 1-0.56=-0.44

• Mix calculation

1. Volume of concrete= 1m^3
2. Volume of cement=

mass of cement/specific gravity of cement * 1/1000=270/3.15*1/1000= 0.085m^3

3.Volume of fly-ash= 115/2.2*1/1000=0.052m^3

4.Volume of water=140/1.145*1/1000= 0.140m^3

5.Volume of chemical admixture(superplasticizer)@ 2% by mass of cementitious material= 8/1.145*1/1000=0.006m^3

6.volume of aggregate(FA&CA)= 1-(2+3+4+5)= 1-(0.085+0.052+0.140+0.006)=0.717 m^3

• mass of CA= (6)*vol. of CA*specific gravity of CA*1000= 0.717 *0.56*2.74*1000= 1110.1
• mass of FA= (6)*vol. of FA*specific gravity of FA*1000=0.717 *0.44*2.74*1000=864.41
• mix proportional for trial mix of 1m^3 of concrete

cement=270 kg/m^3

fly-ash=115 kg/m^3

water=140 kg/m^3

FA=864.41 kg/m^3

CA=1110.1 kg/m^3

Chemical admixture=8 kg/m^3

w/c ratio=0.38

trial mix ratio= 1:3.2:4.1

CONCRETE MIX DESIGN FOR M50 GRADE

• Stipulation for proportioning:
• Grade designation- M50
• Type of cement-OPC 43 grade (conforming IS code 8112)
• Type of mineral admixture- fly ash
• Maximum nominal size of aggregate- 20 mm
• Minimum cement content- 320 kg/m^3 (IS 456-2019)
• Maximum free w/c ratio- 0.45(IS456-2019)
• Workability- 100 mm slump value (reinforced concrete)
• Exposure- severe (reinforced concrete)
• Method of concrete placing- pumping
• Degree of supervision- good
• Type of aggregate – crushed angular aggregate
• Maximum chemical cement content (OPC)- 450kg/m^3
• Chemical admixture type- super plasticizer
• Test data for materials:
• Cement used = OPC 50 grade
• Specific gravity of cement= 3.15
• Specific gravity of cement= 2.2
• Chemical admixture=superplasticizer
• Specific gravity of coarse aggregate=2.74
• Specific gravity of fine aggregate= 2.74
• Water absorption (CA)=0.5%
• Water absorption (FA)=1.0%
• Free moisture content=nil both CA and FA
• sieve analysis (CA)= conforming to grading zone 1 of table 4 of IS-383
• sieve analysis (FA)= table 4 of IS-383
• target strength for mix proportioning:

f’ck= fck+1.65S

where

f’ck= target average compressive strength at 28 days

fck= characteristics compressive strength at 28 days and

S= standard deviation

From table, S= 5 N/mm^2

Therefore, target strength =50+1.65(5)=58.25N/mm^2

• Water cement ratio:

Max. w/c ratio= 0.34(for severe, reinforced concrete)

Based on experience, adopt w/c ratio =0.34 assuming 0.35

0.34<0.45

Hence OK

• Selection of water content:

For 20mm aggregate, max w/c content= 186 kg/m^3( for 25-50mm)

Estimated water content for 100mm slump= 186+6%186=197litre (the water content may be increase or decrease by about 3 percent for each increase or decrease of 25mm slump)

As superplasticizer is used , the water content can be reduced 20% and above.

Based on trials, water content reduction of 29% has been achieved.

Hence, the arrived water content= 197 * 0.71=140 kg/m^3

• Calculation for weight of cement:

Estimate w/c ratio= 0.35

Cementitious material (fly ash +cement) content= 140/0.35=say 400kg/m^3

From table 5 of IS-456 minimum cement content for severe condition 400>320 kg/m^3

Hence OK

• Proportion of volume of CA and FA:

From table of IS 10262-2019

Volume of CA corresponding to 20mm size aggregate and FA zone 1 for w/c ratio of 0.5=0.6

In the present case the w/c ratio is 0.35.

Therefore, the volume of CA needs to be increased by 0.15

The proportion of volume of CA is increased by 0.03

Corrected volume of CA for w/c ratio of assumed 0.35 =0.60+0.03=0.63

For pumpable concrete these values are reduced by 10%

Therefore, volume of CA= 0.63*0.9=0.56

Volume of FA= 1-0.56=-0.44

• Mix calculation

1. Volume of concrete= 1m^3
2. Volume of cement= mass of cement/specific gravity of cement * 1/1000=400/3.15*1/1000= 126m^3
3. Volume of water=140/1.145*1/1000= 140m^3
4. Volume of chemical admixture(superplasticizer)@ 2% by mass of cementitious material= 8/1.145*1/1000=007m^3
5. volume of aggregate(FA&CA)= 1-(2+3+4)= 1-(0.126+0.140+0.007)=727m^3

mass of CA= (5)*vol. of CA*specific gravity of CA*1000= 0.727*0.56*2.74*1000=1115.5 m^3

mass of FA= (5)*vol. of FA*specific gravity of FA*1000=0.727*0.44*2.74*1000=876.4 m^3

• mix proportional for trial mix of 1m^3 of concrete

cement=400 kg/m^3

water=140 kg/m^3

FA=876.4 kg/m^3

CA=1115.5 kg/m^3

Chemical admixture=8 kg/m^3

w/c ratio=0.35

trial mix ratio= 1:2.2:2.8