Project on Concrete Mix Design for various grades of Concrete

Project on concrete mix design

1. Concrete mix design for M35 grade concrete with fly ash.

• Stipulations for proportioning
• Grade designation: M35
• Type of cement OPC 43 grade conforming to IS 8112
• Type of mineral admixture: fly ash conforming to IS 3812 (part 1)
• Exposure condition: very severe (for reinforced concrete)
• nominal size of aggregate: 20 mm
• Minimum cement content: 340 kg/m^3 (Table 5 of IS 456:2000 )
• w/c ratio : 0.45 (Table 5 IS 456:2000)
• Workability 100 mm(slump value for pumpable concrete)
• Method of concrete placing: pumping
• Degree of supervision: good
• Type of aggregate: crushed angular aggregate
• cement content: 450 kg/m^3
• Chemical admixture: Superplasticizer

• Test data for materials
• Cement used: OPC 43 Grade conforming to IS 8112
• Specific gravity of cement: 3.15
• Fly ash conforming to IS 3812 (part 1)
• Specific gravity of fly ash: 2.2
• Chemical admixture: Superplasticizer conforming to IS 9103
• Specific gravity: coarse aggregate – 2.74 and fine aggregate – 2.74
• Water absorption: coarse aggregate – 0.5% and fine aggregate – 1.0%
• Free surface moisture: NIL for both types of aggregate.
• Sieve analysis: coarse aggregate – conforming to table 2 of IS 383 and fine aggregate – conforming to grading zone 1 of table 4 of IS 383
• Target strength for mix proportioning

f’ck = fck + 1.65 S

From table 1 of IS 10262:2009, standard deviation S= 5 N/mm^2

Therefore target strength = 35 + 1.65*5

= 43.25 N/mm^2

• Selection of w/c ratio:

From table 5 of IS 456: 2000 for very severe exposure, max. w/c ratio = .45

So as per experience adopted w/c ratio = .40

• Selection of water content

From table 2 IS 10262: 2009, max. Water content for 20mm aggregate is = 186 liter (for 25mm to 50mm slump range)

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

As super plasticizer is used, the water content can be reduced to up to 20% and above based on trials water content reduction of 29 % is achieved with plasticizer.

Actual water content = 197 *.71 = 140 liter

• Calculation of cement content :

Water cement ratio = 0.40

Cementitious material (cement + fly ash) content = 140/0.40 = 350; taken as

350 kg/m^3.

From table 5 of IS 456 minimum cement content for very severe condition 340 kg/m^3

Here 350 > 340 so ok.

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

• The percentage of fly ash needs to be decided based on project requirement and quality of materials.
• In some cases increase in the cementitious material can be warranted. Increase in cement material content and its percentage may be based on experience and trials (this example is with increase of 10% cementitious material content )

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

Water content = 140 kg/m^3

w/c ratio = 140/385 = .364

Fly ash @ 30% total cementitious material content = 385*.30= 115 kg/m^3

Cement (OPC) = 385 – 115 = 270 kg/m^3

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

Fly ash utilized = 115 kg /m^3

• Proportion of volume of fine aggregate and coarse aggregate.

From table 3 IS 10262: 2009, volume of coarse aggregate corresponding to 20mm size and fine aggregate (zone 1) for water cement ratio of

0.5 =0.6

As w/c ratio is lower by 0.10, therefore the proportion of aggregate is increased by 0.02.

Therefore, corrected volume of coarse aggregate for the w/c ratio of 0.45=0.62

For pumpable concrete these value are decreased by 10%

Therefore volume of coarse aggregate =

0.62*0.9 =0.558

So volume of fine aggregate is = 1-.588 = .442

• Mix calculations

The mix calculations per unit volume of concrete be as follows:

• Volume of concrete = 1 m^3
• Volume of cement = (mass of cement/specific gravity of cement) * (1/100) = (270/3.15) * (1/1000) = 0.086 m^3
• Volume of fly ash = (mass of fly ash/specific gravity of fly ash)* (1/1000) = 115/2.2 * 1/1000 = 0.052
• Volume of water = (140/1) * (1/1000)

= 0.140 m^3

• Volume of chemical admixture = (mass of chemical admixture/specific gravity of admixture)* (1/1000)

Mass of chemical admixture = 2% of cementitious material (320* 2/100) = 6.4

6.4 /1.145 * 1/1000 = .005 m^3

• Volume of aggregate (FA & CA)= (a-(b+c+d+e))

= (1-(0.86+0.52+0.140+0.005)) =.716

• Mass of coarse aggregate = e* vol. of CA* Specific gravity of CA*1000

= .716*.558*2.74*1000 =1095 kg/m^3

• Mass of fine aggregate = e* vol. of FA* specific gravity of FA*1000

= .716*.442*2.74*1000 = 867.kg/m^3

• Mix proportions for M30 are as follows:

Cement = 350 kg/m^3

Water = 140 kg/ m^3

Fly ash = 115 kg/m^3

Fine aggregate = 867 kg/ m^3

Coarse aggregate = 1095 kg/ m^3

Chemical admixture = 6.4 kg/ m^3

Water cement ratio = 0.40

So trial mix ratio = 1 : 2.47 : 3.12

2. Concrete mix design for M50 grade concrete without fly ash.

Concrete mix design for M50 grade is as follows

• Stipulations for proportioning
• Grade designation: M50
• Type of cement OPC 43 grade conforming to IS 8112
• Exposure condition: extreme (for reinforced concrete)
• nominal size of aggregate: 20 mm
• Minimum cement content: 360 kg/m^3 (Table 5 of IS 456:2000 )
• w/c ratio : 0.40 (Table 5 IS 456:2000)
• Workability 100 mm(slump value for pumpable concrete)
• Method of concrete placing: pumping
• Degree of supervision: good
• Type of aggregate: crushed angular aggregate
• cement content: 400 kg/m^3
• Chemical admixture: Superplasticizer

• Test data for materials
• Cement used: OPC 43 Grade conforming to IS 8112
• Specific gravity of cement: 3.15
• Chemical admixture: Superplasticizer conforming to IS 9103
• Specific gravity: coarse aggregate – 2.74 and fine aggregate – 2.74
• Water absorption: coarse aggregate – 0.5% and fine aggregate – 1.0%
• Free surface moisture: NIL for both types of aggregate.
• Sieve analysis: coarse aggregate – conforming to table 2 of IS 383 and fine aggregate – conforming to grading zone 1 of table 4 of IS 383
• Target strength for mix proportioning

f’ck = fck + 1.65 S

From table 1 of IS 10262:2009, standard deviation S= 5 N/mm^2

Therefore target strength = 50 + 1.65*5

= 58.25 N/mm^2

• Selection of w/c ratio:

From table 5 of IS 456: 2000 for severe exposure, max. w/c ratio = .40

So adopted w/c ratio = .40

• Selection of water content

From table 2 IS 10262: 2009, max. Water content for 20mm aggregate is = 186 liter (for 25mm to 50mm slump range)

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

As super plasticizer is used, the water content can be reduced to up to 20% and above based on trials water content reduction of 29 % is achieved with plasticizer.

Actual water content = 197 *.71 = 140 liter

• Calculation of cement content :

Water cement ratio = 0.40

Cement content = 140/0.40 = 350; taken as

350 kg/m^3.

From table 5 of IS 456 minimum cement content for severe condition 360 kg/m^3

Here 350 < 360 so not ok.

Therefore we will take minimum cement content = 360 kg /m^3.

• Proportion of volume of fine aggregate and coarse aggregate.

From table 3 IS 10262: 2009, volume of coarse aggregate corresponding to 20mm size and fine aggregate (zone 1) for water cement ratio of

0.5 =0.6

As w/c ratio is lower by 0.10, therefore the proportion of aggregate is increased by 0.02.

Therefore, corrected volume of coarse aggregate for the w/c ratio of 0.40=0.62

For pumpable concrete these value are decreased by 10%

Therefore volume of coarse aggregate =

0.62*0.9 =0.558

So volume of fine aggregate is = 1-.558= .442

• Mix calculations

The mix calculations per unit volume of concrete be as follows:

• Volume of concrete = 1 m^3
• Volume of cement = (mass of cement/specific gravity of cement) * (1/100) = (360/3.15) * (1/1000) = .114 m^3
• Volume of water = (140/1) * (1/1000)

= 0.140 m^3

• Volume of chemical admixture = (mass of chemical admixture/specific gravity of admixture)* (1/1000)

Mass of chemical admixture = 2% of cementitious material (360* 2/100) = 7.0

7.0/1.145 * 1/1000 = .006 m^3

• Volume of aggregate (FA & CA)= (a-(b+c+d))

= (1-(0.114+0.140+0.006)) =.740

• Mass of coarse aggregate = e* vol. of CA* Specific gravity of CA*1000

= .740*.558*2.74*1000 = 1131.4 kg/m^3

• Mass of fine aggregate = e* vol. of FA* specific gravity of FA*1000

= .740*.442*2.74*1000 = 896.1 kg/m^3

• Mix proportions for M30 are as follows:

Cement = 360 kg/m^3

Water = 140 kg/ m^3

Fine aggregate = 896.1 kg/ m^3

Coarse aggregate = 1131.4 kg/ m^3

Chemical admixture = 6.4 kg/ m^3

Water cement ratio = 0.40

So trial mix ratio = 1 : 2.49 : 3.14