Project on Concrete Mix Design for various grades of Concrete

AIM – To calculate the mix design of M₃₅ grade concrete with fly ash and M₅₀ grade concrete without fly ash.

Introduction – Mix design of concrete is used to provide strength, durability for the structure as per Indian standard. In India IS 12062 – 2019 for concrete mix proportion guideline

PROCEDURE

• MIX DESIGN for M₃₅

The mix proportion of M₃₀ grade concrete was designed based on the recommendation of IS 10262-2019 for the following stipulations.

Grade designation - M₃₅

Type of Cement - OPC 43

Type of mineral admixture - Fly ash

Size of Coarse Aggregate - 20mm

Water –cement ratio - 0.45

Degree of Quality Control - Good

Type of Aggregate - Crushed angular

Minimum cement content - 320 kg/m3

Exposure condition - severe (IS 456; Table 5)

Workability - 75 mm (slump)

Maximum cement content - 450Kg/m³

Chemical admixture - superplasticizer

Data of materials

Cement used - OPC 43

Specific gravity of cement - 3.15

Specific gravity of fine aggregate - 2.65

Specific gravity of coarse aggregate - 2.74

Solution:

Target mean strength for mix design:

F_ck = f_ck + 1.65s

= 35 + 1.65(5)

= 43.25 N/mm²

1. Selection of Water Cement Ratio:

From the table 5 of IS 456, maximum water-cement ratio = 0.45

Take, Water cement ratio = 0.45

1. Selection of Water Content:

Water content for 120m slump = 186 + 0.3/100x 186

= 191.58 litres

As superplasticizer is used a admixture the water content reduced to 20%. Hence the arrived water content will be 191.58 x 0.8 = 153 litre

1. Selection of Cement Content:

W/C ratio = 0.45

Cement content = 153/0.45 = 340 kg/m³ > 320Kg/m³

Hence Ok.

Calculation of cementitious material - assume 10% of material added

=340x 1.1

=375kg/m³

w/c ratio = 153/375 = 0.408

flyash 30% of total cementitious material = 375x 0.03 = 112.5kg/m³

cement = 375-112.5= 262.5 kg/m³

1. Proportion of volume of Coarse aggregate and Fine aggregate

Volume of coarse aggregate = 0.62 for 0.50(From IS 10262-2009, Table 3)

In this case w/c ratio = 0.4 lower by 0.10. So the proportion of volume of coarse aggregate is increased by 0.02(at the rate of + or – 0.01 for every +or- 0.05 change in water cement ratio). For pumped concrete there is reduction by 10%.

Hence, volume of coarse aggregate = 0.63 x 90% = 0.567

Volume of fine aggregate = 1-0.567

= 0.433

1. Mix calculation

1. a) Volume of concrete = 1m3

b)Volume of cement = Mass / specific gravity x 1/1000

=262.5/3.15 x 1/1000

= 0.083 m³

c )Volume of fly ash = 112.5/2.2 x 1/1000

= 0.051m³

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

= 153/1 x 1/1000

= 0.153 m³

Volume of chemical admixture

2% mass of cementitious material = 375x 2% =7m³

e)Volume of superplasticizer = Mass / specific gravity x 1/1000

= 7/1.145 x 1/1000

= 0.006 m3

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

=1-(0.083+0.153+0.006+0.051)

= 0.707m³

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

= 0.707x0.576x2.84x1000

= 1128.79 Kg/m³

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

= 0.707x0.424x2.64x1000

=830.56 Kg/m³

RATIOS FOR M₃₅ MIX

Cement – 262.5 Kg/m³

Fly ash – 112.5

Water -140 Kg/m³

Chemical admixture – 7 Kg/m³

Fine aggregate – 830.56 Kg/m³

Coarse aggregate – 1128.79 Kg/m³

M₃₅ = 1: 2.17: 2.95

• MIX DESIGN for M₅₀ without fly ash

The mix proportion of M₃₀ grade concrete was designed based on the recommendation of IS 10262-2019 for the following stipulations.

Grade designation - M₅₀

Type of Cement - OPC 43

Size of Coarse Aggregate - 20mm

Degree of Quality Control - Good

Type of Aggregate - Crushed angular

Minimum cement content - 320 kg/m3

Exposure condition - severe (IS 456; Table 5)

Workability - 75 mm (slump)

Maximum cement content - 450Kg/m³

Chemical admixture - superplasticizer

Data of materials

Cement used - OPC 43

Specific gravity of cement - 3.1

Specific gravity of fine aggregate - 2.6

Specific gravity of coarse aggregate - 2.6

Solution:

Target mean strength for mix design:

F_ck = f_ck + 1.65s

= 50 + 1.65(5)

= 58.25 N/mm²

1. Selection of Water Cement Ratio:

From page 4 of IS 10262 -2019, maximum water-cement ratio = 0.34 by 3 curve method

Take, Water cement ratio = 0.35

1. Selection of Water Content:

Water content for 100m slump = 186 + 3/100x 186

= 191 litres

As superplasticizer is used a admixture the water content reduced to 20%. Hence the arrived water content will be 191x0.8 = 152 litre

1. Selection of Cement Content:

W/C ratio = 0.35

Cement content = 152/0.35 = 434 kg/m³ > 320Kg/m³

Hence Ok.

1. Proportion of volume of Coarse aggregate and Fine aggregate

Volume of coarse aggregate = 0.64 for 0.50(From IS 10262-2009, Table 3)

In this case w/c ratio = 0.35 lower by 0.1. So the proportion of volume of coarse aggregate is increased by 0.02(at the rate of + or – 0.01 for every +or- 0.05 change in water cement ratio). For pumped concrete there is reduction by 10%.

Hence, volume of coarse aggregate = 0.64 x 90% = 0.576

Volume of fine aggregate = 1-0.576

= 0.424

1. Mix calculation

1. a) Volume of concrete = 1m3

b)Volume of cement = Mass / specific gravity x 1/1000

=434/3.1 x 1/1000

= 0.141 m³

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

= 152/1 x 1/1000

= 0.152 m³

d)Volume of chemical admixture

2% mass of cementitious material = 434 x 2% =8.6m³

e)Volume of superplasticizer = Mass / specific gravity x 1/1000

= 8.6/1.145 x 1/1000

= 0.007 m3

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

=1-(0.141+0.152+0.007)

= 0.7m³

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

= 0.7x0.576x2.84x1000

= 1145.79 Kg/m³

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

= 0.7x0.424x2.64x1000

=783.56 Kg/m³

RATIOS FOR M₅₀ MIX

Cement – 434 Kg/m³

Water -152 Kg/m³

Chemical admixture – 8.6 Kg/m³

Fine aggregate – 783.56 Kg/m³

Coarse aggregate – 1145.79 Kg/m³

M₅₀ = 1: 1.77: 2.59

RESULTS

• M₃₅ = 1: 2.17: 2.95
• M₅₀ = 1: 1.77: 2.59