Project on Concrete Mix Design for various grades of Concrete

Calculate the Concrete Mix Design for M35 grade concrete with fly ash:

• Grade designation: M 35
• Type of cement: OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate: 20 mm
• Minimum cement content: 340 kg/m³
• Maximum water-cement ratio : 0.45
• Workability : 50-100 mm (slump)
• Exposure condition : Very Severe (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m³
• Chemical admixture type : Super Plasticizer
• Specific gravity of cement : 3.12
• Specific gravity of Coarse aggregate : 2.74
• Specific gravity of Fine aggregate : 2.56.

Target Strength of mix proportion:

f_target = f_ck + 1.65 x S

Table 5 of IS: 456 200

Maximum water-cement ratio = 0.45

From Table 2 of IS:456 200, maximum water content =186 liters (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 liter.

(Note: If Superplasticizer is used, the water content can be reduced up to 20% and above.)

Based on trials with Super plasticizer water content reduction of 25% has been achieved, Hence the arrived water content = 197-[197 x (25/100)] = 147 liters.

The calculation for cement content

Water-cement ratio =0.45

Cement content = 147/0.45 = 350 kg/m³

From Table 5 of IS 456, minimum cement content for ‘Very Severe‘ exposure condition = 340 kg/m³

350 kg/m³ > 340 kg/m³, hence ok.

The proportion of fine and coarse aggregates:

From Table 3 of IS 10262, volume of coarse aggregate corresponds to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 = 0.62.

In the present case, the water-cement ratio is 0.45. Therefore, the volume of coarse aggregate is required to be increased to reduce the fine aggregate content.

As the water-cement ratio is lower by 0.10, the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.45 = 0.63.

NOTE – In case the coarse aggregate is not angular one. then also the volume of coarse aggregate may be required 10 be increased suitably, based on experience.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.63 x 0.9 = 0.567.

Volume of fine aggregate content =1 – 0.567 =0.433.

Mix Calculation

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of cement/Specific Gravity of Cement) X (1/1000)

= (350/3.12) X (1/1000)

= 0.112 m³

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

= (147/1) X (1/1000)

= 0.147 m³

d) Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)

= (7/1.145) X (1/1000)

= 0.006 m³

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

= 1 – (0.112 + 0.147+0.006)

= 0.735 m³

f) Mass of coarse aggregate = Volume of all aggregate X volume of coarse aggregate X Specific gravity of coarse aggregate X 1000

= 0.735 x 0.567 x 2.74 x 1000

= 1141.88 kg

g)Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.735 x 0.433 x 2.56 x 1000

= 814.73 kg

Concrete mix proportion:

• Cement = 350 kg/m³
• Water = 147 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 814.73 kg/m³
• Coarse aggregate = 1141.88 kg/m³
• W/c = 0.45

Result : The Mix Ratio of M35 as obtained is 1 : 2.32 : 3.26 (Cement : Fine aggregate : Coarse aggregate).

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Mix design for M50 grade concrete without Fly ash:

• Grade designation : M 50
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 360 kg/m³
• Maximum water-cement ratio : 0.35
• Workability : 50-75 mm (slump)
• Exposure condition : Extreme (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m³
• Chemical admixture type : Super Plasticizer

The following data are collected by performing standard tests in a laboratory.

Specific gravity of cement : 3.12

Specific gravity of Coarse Aggregate : 2.74

Specific gravity of Fine Aggregate : 2.56.

Procedure:

Target Strength f_target = f_ck + 1.65 x s

water cement ratio - Maximum water-cement ratio = 0.35.

Cement content -

Water-cement ratio = 0.35

Cement content = 143/0.35 = 410 kg/m³

From Table 5 of IS 456, minimum cement content for ‘Extreme exposure’ condition = 360 kg/m³

410 kg/m³ > 360 kg/m³, hence, O.K.

The proportion of fine and coarse aggregates:

From Table 3 of IS 10262, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.

In the present case, the water-cement ratio is 0.35. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).

Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.

NOTE – In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.

Volume of fine aggregate content =1 – 0.585 =0.415.

Mix Calculation

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

= (410/3.12) X (1/1000)

= 0.131 m³

c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)

= (143/1) X (1/1000)

= 0.143 m³

d) Volume of Superplasticizer = (Mass of Superplasticizer / Specific gravity of admixture) X (1/1000)

= (8.2/1.145) X (1/1000)

= 0.007 m³

e) Volume of all aggregate = (a – (b + c + d))

= 1 – (0.131 + 0.143+0.007)

= 0.719 m³

e) Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.719 x 0.585 x 2.74 x 1000

= 1152.48 kg

f) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.719 x 0.415 x 2.56 x 1000

= 763.86 kg

Mix Proportion

• Cement = 410 kg/m³
• Water = 143 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 763.86 kg/m³
• Coarse aggregate = 1152.48 kg/m³
• W/c = 0.35

Result : The Mix Ratio of M50 as obtained is 1 : 1.86 : 2.81 (Cement : Fine aggregate : Coarse aggregate).