Project on Concrete Mix Design for various grades of Concrete

Aim: To calculate the concrete mix design for M35 grade concrete with fly ash.

Introduction: Concrete mix design is a process of obtaining the quantity of mix ingredients to obtain the required strength and durability of concrete. For the procedure of calculating the mix design is followed using IS 10262:2009 and also to obtain certain material content value IS 456:2000 are used.

Equation:

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

where, f'ck=target mean strength....N/mm2

           fck= compressive strength of concrete at 28 days....N/mm2

           s=standard deviation,obtain from IS 10262:2009,table1.

• Cement content=Water quantity/water-cement ratio......kg
• volume of cement=(mass of cement/specific gravity of cement)*(1/1000)......kg/m3
• volume of water=(mass of water/specific gravity of water)*(1/1000)..............kg/m3
• volume of chemical admixture=(mass of chemical admixture/specific gravity of chemical admixture)*(1/1000)............kg/m3
• volume of aggregate:(volume of concrete-(volume of cement+volume of water+volume of chemical admixture))..........m3

      where volume of concrete=1 m3

• mass of coarse aggregate=volume of aggregtae*volume of coarse aggregate*specfifc gravity of coarse aggregate*1000.......kg/m3
• mass of fine aggregate=volume of aggregtae*volume of fine aggregate*specfifc gravity of fine aggregate*1000.......kg/m3

Objectives:

The two main objective of the mix design is:

• To achieve a minimum required strength and durability of the concrete.
• To prepare the concrete in most economical way.

Procedure and Calculation:

I.stipulation for proportioning of M35 garde of concrete:

• Grade of concrete: M35
• Grade of cement: OPC 53
• Maximum nominal size of aggregate:20mm
• Type of admixture:fly ash
• From table 5 IS 456:2000- minimum cement content=340kg
• Maximum cement content as per code=450kg
• Partial relacement of cement by 30%
• Maximum water-cement ratio=0.45
• Workability= 100mm,pumpable concrete
• Chemical admixture=super plasticizer
• Exposure condition=extreme

II. data for materials:

• Specfifc garvity of cement: 3.15
• Specific gravity of fly ash: 2.9
• Specific gravity of coarse aggregate: 2.74
• Specific gravity of fine aggregate: 2.74
• Specific gravity of admixture: 1.145
• Water absorption of coarse aggregate:0.5%
• Water absorption of fine aggregate: 1%
• Fine aggregate zone II

III. Target strenngth for proportioning of M35 grade of concrete:

Target mean strength,f'ck=fck+(1.65*s)

s from table-1 of IS 10262 for M35 is 5

f'ck= 35+(1.65*5)=43.25 N/mm2

IV.Selection of water-cement ratio:

• Calculating water cement ratio using figure 1 from IS10262 - 2019.

Considering curve 1 as 28 day compressive strength is 33<43>

 For the standard deviation value of  43.25N/mm^2 the curve meets at 0.37

So we assume the water cement ratio to be 0.37  

• calculation w/c ratio from table 5 in IS456

The limited value of water cement ratio is 0.40 for extreme environmental exposure, hence we take w/c ratio as 0.40

The lower value of the above two values is adopted as w/c ratio.

Hence , 0.37 is taken as the w/c ratio.

V.SelEction of water content:

From table-2, maximum water content for 20mm sixe aggregate =186 L for 25-50mm slump 

For 100mm slump, as per clause 4.2 IS 10262 an increase of 3% of water cotent from its original value for every increase of 25mm. Hence we need to increase the value by 6%

Water content= 186+(186*0.06)=197.16L

Since here superplasticers are used, can reduce the water content by 20% and above

Based on trail, 25% is reduced

=197*0.75=147.75L

Adopted water content= 150 L

VI. Calculation of cement and fly ash content

Taken w/c ratio is 0.37

Total cementitious(cement+flyash) requirement= 150/0.37=405 kg

Since flyash is used the amount of cementitious content ca be increased by 10%

Cementitious content=405*1.1=445.5 kg

Minimum cement content required for 340kg,445.5 kg>340kg,hence ok.

Flyash content requirement=446*0.3=139kg

Cement content= 446-139=307kg

Saving of cement using flyash= 405-307=98kg

VII. Propotion of volume of coarse and fine aggregate:

For zone II w/c ratio is 0.62

Coarse aggregate ratio for 0.37 w/c ratio=0.62+0.025=0.645( adding 0.01 for every decrease in 0.05 w/c ratio and vice versa)

Since it is a pumpable concrete, volume of CA can be reduced by 10%

Therefore, volume of CA=0.645*0.90=0.58

Volume of FA=1-0.58=0.42

VIII.Mix calculation

1. Volume of concrete=1 m3
2. Volume of cement=(307/3.15)*(1/1000)=0.097 kg/m3
3. Volume of flyash=(139/2.5)*(1/1000)=0.0556 kg/m3
4. Volume of water=(150/1)*(1/1000)=0.15 kg/m3
5. Volume of superplasticizer=(7.6/1.145)*(1/1000)=0.0066....kg/m3
6. Volume of aggregate=(1-(0.097+0.0556+0.15+0.0066))=0.69 m3
7. Mass of coarse aggregate=0.69*0.58*2.74*1000=1096.5 kg/m3
8. Mass of fine aggregate=0.69*0.42*2.74*1000=794 kg/m3

Mix proportion for trail number 1

• Cement=307 kg
• Flyash=139 kg
• Water=150L
• Fine aggregate= 794 kg/m3
• Coarse aggregate=1097 kg/m3
• w/c ratio= 0.37

 Mix proportion ratio of M35 grade concrete-

cement:flyash:FA:CA= 1:0.45:2.6:3.6

IX-The slump shall be measured and 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

X- Two more trials having variation of 10% of water-cement ratio in Clause X 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 strength for field trials. However, durability shall be met. 

Aim: To calculate the concrete mix design for M50 grade concrete without fly ash. 

Introduction: Concrete mix design is a process of obtaining the quantity of mix ingredients to obtain the required strength and durability of concrete. For the procedure of calculating the mix design is followed using IS 10262:2009 and also to obtain certain material content value IS 456:2000 are used.

Equation:

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

where, f'ck=target mean strength....N/mm2

           fck= compressive strength of concrete at 28 days....N/mm2

           s=standard deviation,obtain from IS 10262:2009,table1.

• Cement content=Water quantity/water-cement ratio......kg
• volume of cement=(mass of cement/specific gravity of cement)*(1/1000)......kg/m3
• volume of water=(mass of water/specific gravity of water)*(1/1000)..............kg/m3
• volume of chemical admixture=(mass of chemical admixture/specific gravity of chemical admixture)*(1/1000)............kg/m3
• volume of aggregate:(volume of concrete-(volume of cement+volume of water+volume of chemical admixture))..........m3

      where volume of concrete=1 m3

• mass of coarse aggregate=volume of aggregtae*volume of coarse aggregate*specfifc gravity of coarse aggregate*1000.......kg/m3
• mass of fine aggregate=volume of aggregtae*volume of fine aggregate*specfifc gravity of fine aggregate*1000.......kg/m3

Objectives:

The two main objective of the mix design is:

• To achieve a minimum required strength and durability of the concrete.
• To prepare the concrete in most economical way.

Procedure and Calculation:

I.stipulation for proportioning of M35 garde of concrete:

• Grade of concrete: M50
• Grade of cement: OPC 53
• Maximum nominal size of aggregate:20mm
• From table 5 IS 456:2000- minimum cement content=360kg
• Maximum cement content as per code=450kg
• Maximum water-cement ratio=0.45
• Workability= 75mm,pumpable concrete
• Chemical admixture=super plasticizer
• Exposure condition=extreme

II. data for materials:

• Specfifc garvity of cement: 3.15
• Specific gravity of coarse aggregate: 2.74
• Specific gravity of fine aggregate: 2.74
• Specific gravity of admixture: 1.145
• Water absorption of coarse aggregate:0.5%
• Water absorption of fine aggregate: 1%
• Fine aggregate zone I

III. Target strenngth for proportioning of M35 grade of concrete:

Target mean strength,f'ck=fck+(1.65*s)

s from table-1 of IS 10262 for M50 is 5

f'ck= 50+(1.65*5)=53.25 N/mm2

IV.Selection of water-cement ratio:

• Calculating water cement ratio using figure 1 from IS10262 - 2019.

Considering curve 1 as 28 day compressive strength is 43<53>

 For the standard deviation value of  53.25N/mm^2 the curve meets at 0.33

So we assume the water cement ratio to be 0.33  

• calculation w/c ratio from table 5 in IS456

The limited value of water cement ratio is 0.40 for extreme environmental exposure, hence we take w/c ratio as 0.40

The lower value of the above two values is adopted as w/c ratio.

Hence , 0.33 is taken as the w/c ratio.

V.Selection of water content:

From table-2, maximum water content for 20mm sixe aggregate =186 L for 25-50mm slump 

For 75mm slump, as per clause 4.2 IS 10262 an increase of 3% of water cotent from its original value for every increase of 25mm. Hence we need to increase the value by 3%

Water content= 186+(186*0.03)=191.58L

Since here superplasticers are used, can reduce the water content by 20% and above

Based on trail, 29% is reduced

=192*0.71=136.32L

Adopted water content= 140 L

VI. Calculation of cement and fly ash content

Taken w/c ratio is 0.33

Water content= 140/0.33=424 kg

Minimum cement content required for 340kg,424 kg>340kg,hence ok.

VII. Propotion of volume of coarse and fine aggregate:

For zone I w/c ratio is 0.60

Coarse aggregate ratio for 0.33 w/c ratio=0.60+0.035=0.635( adding 0.01 for every decrease in 0.05 w/c ratio and vice versa)

Since it is a pumpable concrete, volume of CA can be reduced by 10%

Therefore, volume of CA=0.635*0.90=0.57

Volume of FA=1-0.57=0.43

VIII.Mix calculation

1. Volume of concrete=1 m3
2. Volume of cement=(424/3.15)*(1/1000)=0.135 kg/m3
3. Volume of water=(140/1)*(1/1000)=0.14 kg/m3
4. Volume of superplasticizer=(7.6/1.145)*(1/1000)=0.0066...kg/m3
5. Volume of aggregate=(1-(0.135+0.14+0.0066))=0.72 m3
6. Mass of coarse aggregate=0.72*0.57*2.74*1000=1125 kg/m3
7. Mass of fine aggregate=0.72*0.43*2.74*1000=848 kg/m3

Mix proportion for trail number 1

• Cement=424 kg
• Water=140L
• Fine aggregate= 848 kg/m3
• Coarse aggregate=1125 kg/m3
• w/c ratio= 0.33

 Mix proportion ratio of M50 grade concrete-

cement:FA:CA= 1:2:2.7

IX-The slump shall be measured and 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

X- Two more trials having variation of 10% of water-cement ratio in Clause X 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 strength for field trials. However, durability shall be met.