Project on Concrete Mix Design for various grades of Concrete

Step 1 - Stipulations for proportioning

Grade of designation = M35

Type of cement = OPC 43 grade

maximum nominal size of aggregate = 20mm

minimum cement content = 360kg/m^3 (from table 5 IS 456 - exposure condition)

maximum water cement ratio = 0.45 from table 5 IS456

workability = 100mm slump value

exposure condition = Extreme

Type of aggregate = crushed angular

maximum cement content = 450 kg/m^3

The values of fine aggregate should conform to zone 1 of table 4 of IS383.

Step 2 - Target mean strength of concrete,

f'ck = fck + 1.65s

where fck is characteristics compressive strength at 28 days,

s = standard deviation (IS 10262:2009,table 1)

for M35 , s = 5N/mm^2

f'ck = 43.25 N/mm^2

Step 3 - Water cement ratio

From table 5 of IS 456 2000 it can be taken depending upon the exposure condition,

Assume the weather condition is Extreme , then water cement ratio is 0.40.

From figure 1 of IS10262 -2019 the water cement ratio is 0.40.

therefore, water cement ratio is taken as 0.40

Step 4 - Selection of water content

From table 4 of IS10262-2009, the maximum water content for 25mm-50mm slump is 186Kg= 186 lit

As superplasticizer 20% reduction

Estimated water content for 100mm slump is [186*(80/100)] = 148.8 lit

Water content = 149 litres

Step 5 - Selection of cement content

It is calculated from water cement ratio

w = 149

w/c = 0.40

Cement content = w/0.33 = 149/0.40 = 372.5 Kg/m^3 = 370 Kg/m^3

From table 5 of IS456 minimum cement content for sever exposure condition is 320Kg/m^3

360 > 370 hence ok.

Increase by 10%

370 * 0.10 + 370 = 407 Kg/m^3

W = 149 kg

Water cement ratio = 149/407 = 0.366

Fly ash at 30% total cementitious material content

407 * ( 30/100 ) = 122 Kg/m^3

Cement ( OPC ) = 407 - 122 = 285 Kg/m^3

Saving of cement while using fly ash = 370 - 285 = 85 Kg/m^3

Fly ash = 122 Kg/m^3

Step 6 - Volume of coarse aggregate and fine aggregate

This can be determined from table 3 IS10262 - 2009. Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) for water cement ratio = 0.6

In our case the w/c ratio is 0.40

therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As in this case the water cement ratio is lower by 0.17, the proportion of volume of coarse aggregate is increased by 0.034 (at the rate of -/+ 0.01 for every for every +/- 0.05 change in water cement ratio.

Therefore corrected volume of coarse aggregate for the water cement ratio of 0.40 = 0.63

For pumpable concrete these values are reduced by 10%

therefore volume of coarse aggregate = 0.62

volume of fine aggregate content = 1-0.62 = 0.38

Step 7- Mix calculations,

Volume of concrete = 1 m^3

Volume of cement = 285/3.15*1/1000 = 0.090 m^3

Volume of fly ash = 122/2.2*1/1000 =0.055 m^3

Volume of water = 149/1 * 1/1000 = 0.149 m^3

Volume of chemical admixture = 7.6/1.145*1/1000 = 0.006m^3

Volume of aggregate = 1 - ( 0.090 + 0.055 + 0.006 ) = 0.7 m^3

Mass of coarse aggregate = 0.72 * 0.62 * 2.74 * 1000 = 1189.16 Kg/m^3

Mass of fine aggregate = 0.7 * 0.38 * 2.74 * 1000 = 728 Kg/m^3

Step 8- mix proportion

Cement = 285 Kg/m^3

Fly ash = 122 Kg/m^3

Water = 149 kg

Fine aggregate = 728 Kg/m^3

Coaarse aggregate = 1189 kg/m^3

Chemical admixture = 7.6 Kg/m^3

Water cement ratio = 0.366

Total mix ratio = 285 : 728 : 1189 = 1 : 2.55 : 4.77

RESULTS AND CONCLUSION :

Cement = 285 Kg/m^3

Fly ash = 122 Kg/m^3

Water = 149 kg

Fine aggregate = 728 Kg/m^3

Coaarse aggregate = 1189 kg/m^3

Chemical admixture = 7.6 Kg/m^3

Water cement ratio = 0.366

Total mix ratio = 285 : 728 : 1189 = 1 : 2.55 : 4.77

• This trial mix ratio should match the workability, durability, minimum strength of M35 grade concrete

Step 1 - Stipulations for proportioning

Grade of designation = M50

Type of cement = OPC 43 grade

maximum nominal size of aggregate = 20mm

minimum cement content = 320 kg/m^3 (from table 5 IS 456 - exposure condition)

maximum water cement ratio = 0.45 from table 5 IS456

workability = 100mm slump value

exposure condition = severe

Type of aggregate = crushed angular

maximum cement content = 450 kg/m^3

The values of fine aggregate should conform to zone 1 of table 4 of IS383.

Step 2 - Target mean strength of concrete,

f'ck = fck + 1.65s

where fck is characteristics compressive strength at 28 days,

s = standard deviation (IS 10262:2009,table 1)

for M50, s = 5N/mm^2

f'ck = 58.25 N/mm^2

Step 3 - water cement ratio

From table 5 of IS 456 2000 it can be taken depending upon the exposure condition,

Assume the weather condition is severe, then water cement ratio is 0.45.

From figure 1 of IS10262 -2019 the water cement ratio is 0.33.

therefore, water cement ratio is taken as 0.33

Step 4 - selection of water content

From table 4 of IS10262-2009, the maximum water content for 25mm-50mm slump is 186Kg= 186 lit

Estimated water content for 100mm slump is 186 + 6/100*186 = 197lit

As superplasticizer is used, the water content can be reduced upto 30% and above.

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

Hence arrived water content is 197*0.71 = 140 lit

Step 5- selection of cement content

It is calculated from water cement ratio

w = 140

w/c = 0.33

Cement content = w/0.33 = 140/0.33 = 424 Kg/m^3

From table 5 of IS456 minimum cement content for sever exposure condition is 320Kg/m^3

424>320 hence ok.

Step 6 - volume of coarse aggregate and fine aggregate

This can be determined from table 3 IS10262 - 2009. Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) for water cement ratio = 0.6

In our case the w/c ratio is 0.33

therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As in this case the water cement ratio is lower by 0.17, the proportion of volume of coarse aggregate is increased by 0.034 (at the rate of -/+ 0.01 for every for every +/- 0.05 change in water cement ratio.

Therefore corrected volume of coarse aggregate for the water cement ratio of 0.33 = 0.63

For pumpable concrete these values are reduced by 10%

therefore volume of coarse aggregate = 0.63*0.9 = 0.57

volume of fine aggregate content = 1-0.56 = 0.43

Step 7- Mix calculations,

a)volume of concrete = 1 m^3

b)volume of cement = mass of cement/specific gravity of cement * 1/1000

= 424/3.15*1/1000 = 0.134 m^3

c) volume of water = mass of water/specific gravity of water * 1/1000

= 140/1 * 1/1000 = 0.140 m^3

d) volume of chemical admixture = mass of chemical admixture/sp gravity * 1/1000

= 7.6/1.145*1/1000 = 0.006m^3

e) volume of aggregate = (a-(b+c+d))

= 1-(0.134+0.140+0.006) = 0.72

g) mass of coarse aggregate = 0.72 * 0.57*2.74*1000 = 1124.5 Kg/m^3

h) mass of fine aggregate = 0.72 * 0.43* 2.74 * 1000 = 848.3 Kg/m^3

Step 8- mix proportion

cement = 424 Kg/m^3

fine aggregate = 848.3 Kg/m^3

coaarse aggregate = 1124.5 kg/m^3

total mix ratio = 1:2:2.65

RESULTS AND CONCLUSION :

Water = 140 kg/m^3

Cement = 424 Kg/m^3

Fine aggregate = 848.3 Kg/m^3

Coaarse aggregate = 1124.5 kg/m^3

Chemical admixture = 7.6 kg/m^3

Total mix ratio = 424 : 848.3 : 1124.5 = 1 :2 :2.65

• This trial mix ratio should match the workability, durability, minimum strength of M50 grade concrete
• If it does not satisfy the above criteria two or more trials for increase of 10% should be done