Project on Concrete Mix Design for various grades of Concrete

1. Mix Design for M35 grade concrete with fly ash :

Assuming the all-other data requirements for the mix design of M35 Grade concrete as below,

A- 1 Stipulation of proportions:

1. Grade Designation - M35
2. Type of cement - OPC 43 Grade confirming IS 8112
3. Type of Mineral admixture - Fly ash confriming to IS 3812 (part 1)
4. Maximum nominal size of aggregate -20mm
5. minimum cement content - 320 Kg/m3
6. Maximum Water cement ratio - 0.45
7. Workability - 100mm slump
8. Exposure condition - Severe (RCC)
9. Method of concrete placing - Pumping
10. Degree of supervision - Good
11. Type of Aggregate - Crushed angular
12. Maximum cement content - 450 Kg/m3
13. Chemical admixture type - superplasticiser

A-2 Test Data of Materials:

1. Cement used – - OPC 43 Grade confirming IS 8112
2. Specific gravity of cement – 3.15
3. Specific gravity of fly ash - 2.2
4. Chemical admixture – Superplasticizer confirming IS 9103
5. Specific gravity of coarse aggregate - 2.74
6. Specific gravity of fine aggregate - 2.74
7. Specific gravity of admixture - 1.145
8. Water absorption fine aggregate – 0.5 %
9. Water absorption coarse aggregate – 1.0 %
10. Free (surface) moisture coarse aggregate – Nil
11. Free (surface) moisture Fine aggregate - Nil
12. Sieve analysis Coarse aggregate – Table 2 IS 383
13. Sieve analysis Fine aggregate – Confirming zone I of table 4 of IS 383

A-3 Target Strength for mix proportioning:

Target Mean strength f'ck = fck + 1.65 S

where, S = Standard deviation as per IS 456 - 2000 for different grade of concrete Table 8

f’ck = 35 + 1.65 x 5

f’ck = 43.25 MPa

A-4 Selection of water cement ratio:

Calculation of Water Cement ratio from Graph 28th day compressive strength Vs water cement ratio graph - 1 IS 10262 - 1982:

Assuming the WC ratio as per the Graph - 1= 0.35

Calculation of Water Cement ratio from Graph 28th day compressive strength Vs water cement ratio with respect to 28th day cement compressive strength in Graph -2 IS 10262 - 1982:

Assuming the Cement grade OPC 43 Grade of cement and 28th day compressive strength will be 43 MPa.

Assuming the WC ration as per the Graph -2 = .35

Calculation of water cement ratio as per the Weather condition as per the IS code 456 - 2000 Table - 5

For Severe weather condition the WC ratio = 0.45

Comparison and selection of Water cement ratio:

The lower value of WC ratio is recommended for design mix from below,

0.35, 0.376, 0.45

Hence WC Ratio based on experience will take = 0.35

From Table 5 of IS 456, maximum water content ratio = 0.45

0.40 < 0.45, Hence OK.

A-5 Selection of water content:

Water content as per the IS 10262 - 2009 Table - 2 for 25 mm to 50 mm slump = 186 L

For increase every 25 mm slump add 3 %

Water content = 186 + (0.06 * 186 ) = 197.16 L says 197 L

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

Based on the trails with superplasticizer water content reduction of 29% has been achieved. Hence the arrived water content = 197 X 0.71 = 140

A-6 Calculation of cement and Fly ash content:

Water cement ratio = 0.35

Water content = 140 kg

Cementious (Cement + Fly ash) content = 140/0.35 = 400 Kg/m3

From Table 5 of IS 456, minimum cement content for severe exposure condition = 320 kg/cum

400kg/m3 > 320 Kg/m3 Hence OK.

Now, to proportion a mix containing fly ash the following steps are suggested:

• Decide the percentage of fly ash to be used based on the project requirments and quantity of the materials
• In certain sitiations increase in cementitious materials content may warrented. the decesion on the increase in cementitious material content and its percentage may be based on the experience and trail.

Hence 10% Increase the cementitiouse content based on experience,

Cementitiouse material content = 400 x 1.10 = 440 Kg/m3

Water content = 140

So, Watercement ratio = 140/440 = 0.318

Fly ash @ 30% on the cementitiou material content = 440 x 30% = 132 Kg/m3

Cement content = 440 - 132 = 308 Kg/m3

Saving of cement while using fly ash = 400 - 308 = 92 Kg/m3 ,

Utilization of fly ash = 132 Kg/m3

A-7 Proportion of volume of coarse aggregate and fine aggregate content as per IS 10262 - 2009:

Assume nominal and maximum size of aggregate = 20 mm

Water cement ratio = 0.35

shape of aggregate = angular

from table 3 volume of coarse aggregate per unit volume of total aggregate for different zones of fine aggregate is 0.5 = .60

In the present case water-cement ratio is 0.35. Therefore. volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.15. 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 this value should be reduced by 10 percent.

therefore, volume of coarse aggregate = 0.62 x 0.9 = 0.57

Volume of fine aggregate content = 1 - 0.57 = 0.43

A-8 Mix Calculations:

a) Volume of concrete = 1 m3

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

= 308/3.15 x 1/1000

= 0.098 m3

c) Volume of Fly ash = Mass of fly ash / Specific gravity of fly ash * 1/1000

= 132/2.2 x 1/1000

= 0.060 m3

d) Volume of water = Mass of water / specific gravity of water * 1/1000

= 140/1 x 1/1000

= 0.140 m3

e) Volume of chemical admixture (superplasticiser) (@ 2 percent by mass of cementitious material) = Mass of chemical admixture / Specific gravity of chemical admixture * 1/1000

= 8.8/1.145 x 1/1000

= 0.008 m3

f) Volume of all in aggregate = (a - (b+C+d+e))

= (1 –(0.098+0.060+0.140+0.008))

= 0.694 m3

g) Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.694 x 0.57 x 2.74 x 1000

= 1084 kg

h) Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.694 x 0.43 x 2.74 x 1000

= 818 Kg

Proportion = Cement: Fine aggregate: Coarse of aggregate.

Mix Proportions for trail mix number -1

Cement = 308 kg/m3

Fly ash = 132 kg/m3

Water = 140 kg/m3

Fine aggregate = 818 kg/m3

Coarse aggregate = 1084 kg/m3

Chemical admixture = 8.8 Kg/m3

Water cement ratio = 0.318

Remaks:

A-9 The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall be reworked for the actual water content and checked for durability requirements.

A-10Two more trials having variation of ±1O percent of water-cement ratio in A-9 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.

2. Design Mix for M50 Grade Concrete

Assuming the all-other data requirements for the mix design of M50 Grade concrete as below,

A- 1 Stipulation of proportions:

1. Grade Designation - M50
2. Type of cement - OPC 53 Grade confirming IS 12269 : 1987
3. Type of Mineral admixture - Fly ash confriming to IS 3812 (part 1)
4. Maximum nominal size of aggregate -20mm
5. minimum cement content - 320 Kg/m3
6. Maximum Water cement ratio - 0.45
7. Workability - 75mm slump
8. Exposure condition - Severe (RCC)
9. Method of concrete placing - Pumping
10. Degree of supervision - Good
11. Type of Aggregate - Crushed angular
12. Maximum cement content - 450 Kg/m3
13. Chemical admixture type - superplasticiser

A-2 Test Data of Materials:

1. Cement used – - OPC 43 Grade confirming IS 8112
2. Specific gravity of cement – 3.15
3. Chemical admixture – Superplasticizer confirming IS 9103
4. Specific gravity of coarse aggregate - 2.74
5. Specific gravity of fine aggregate - 2.74
6. Specific gravity of admixture - 1.145
7. Water absorption fine aggregate – 0.5 %
8. Water absorption coarse aggregate – 1.0 %
9. Free (surface) moisture coarse aggregate – Nil
10. Free (surface) moisture Fine aggregate - Nil
11. Sieve analysis Coarse aggregate – Table 2 IS 383
12. Sieve analysis Fine aggregate – Confirming zone I of table 4 of IS 383

A-3 Target Strength for mix proportioning:

Target Mean strength f'ck = fck + 1.65 S

where, S = Standard deviation as per IS 456 - 2000 for different grade of concrete Table 8

f’ck = 50 + 1.65 x 5

f’ck = 58.25 MPa

A-4 Selection of water cement ratio:

Calculation of Water Cement ratio from Graph 28th day compressive strength Vs water cement ratio graph - 1 IS 10262 - 1982:

Assuming the WC ratio as per the Graph - 1= 0.30

Calculation of Water Cement ratio from Graph 28th day compressive strength Vs water cement ratio with respect to 28th day cement compressive strength in Graph -2 IS 10262 - 1982:

Assuming the Cement grade OPC 53 Grade of cement and 28th day compressive strength will be 53 MPa.

Assuming the WC ration as per the Graph -2 = .33

Calculation of water cement ratio as per the Weather condition as per the IS code 456 - 2000 Table - 5

For Severe weather condition the WC ratio = 0.45

Comparison and selection of Water cement ratio:

The lower value of WC ratio is recommended for design mix from below,

0.30, 0.32, 0.45

Hence WC Ratio based on experience will take = 0.30

From Table 5 of IS 456, maximum water content ratio = 0.45

0.30 < 0.45, Hence OK.

A-5 Selection of water content:

Water content as per the IS 10262 - 2009 Table - 2 for 25 mm to 50 mm slump = 186 L

For increase every 25 mm slump add 3 %

Water content = 186 + (0.03 * 186 ) = 197.16 L says 191 L

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

Based on the trails with superplasticizer water content reduction of 29% has been achieved. Hence the arrived water content = 192 X 0.71 = 135

A-6 Calculation of cement content:

Water cement ratio = 0.30

Water content = 135 kg

Cement content = 140/0.30 = 450 Kg/m3

From Table 5 of IS 456, minimum cement content for severe exposure condition = 320 kg/cum

450kg/m3 > 320 Kg/m3 Hence OK.

A-7 Proportion of volume of coarse aggregate and fine aggregate content as per IS 10262 - 2009:

Assume nominal and maximum size of aggregate = 20 mm

Water cement ratio = 0.30

shape of aggregate = angular

from table 3 volume of coarse aggregate per unit volume of total aggregate for different zones of fine aggregate is 0.5 = .60

In the present case water-cement ratio is 0.30. Therefore. volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.2. the proportion of volume of coarse aggregate is increased by 0.04 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).

for pumpable concrete this value should be reduced by 10 percent.

therefore, volume of coarse aggregate = 0.64 x 0.9 = 0.576

Volume of fine aggregate content = 1 - 0.57 = 0.424

A-8 Mix Calculations:

a) Volume of concrete = 1 m3

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

= 450/3.15 x 1/1000

= 0.142 m3

c) Volume of water = Mass of water / specific gravity of water * 1/1000

= 135/1 x 1/1000

= 0.135 m3

d) Volume of chemical admixture (superplasticiser) (@ 2 percent by mass of cementitious material) = Mass of chemical admixture / Specific gravity of chemical admixture * 1/1000

= 9/1.145 x 1/1000

= 0.007 m3

e) Volume of all in aggregate = (a - (b+C+d))

= (1 –(0.142+0.135+0.007))

= 0.716 m3

f) Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.716 x 0.576 x 2.74 x 1000

= 1130 kg

g) Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.716 x 0.424 x 2.74 x 1000

= 832 Kg

Proportion = Cement: Fine aggregate: Coarse of aggregate.

Mix Proportions for trail mix number -1

Cement = 450 kg/m3

Water = 135 kg/m3

Fine aggregate = 832 kg/m3

Coarse aggregate = 1130 kg/m3

Chemical admixture = 9.0 Kg/m3

Water cement ratio = 0.30

Remaks:

A-9 The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall be reworked for the actual water content and checked for durability requirements.

A-10Two more trials having variation of ±1O percent of water-cement ratio in A-9 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.