Project on Concrete Mix Design for various grades of Concrete

PROJECT ON CONCRETE MIX DESIGN

Aim-

To calculate concrete mix design for M35 grade concrete with fly ash and M50 grade concrete without fly ash.

Introduction-

Concrete Mix Design means determination of the proportion of the concrete ingredients i.e. Cement, Water, Fine Aggregate, Coarse Aggregate which would produce concrete possessing specified properties such as workability, strength and durability with maximum overall economy.

Advantages of mix design concrete-

• Proper proportion of components ofconcrete obtained from mix design.
• Quality of concrete mix maintained.
• Material used from concreting is of good quality and in proper proportion so saves the cost of the project.
• With the help of concrete mix design properties of good concrete are achieved such as workability, initial ad final setting time, durability, etc.

Objectives of concrete mix design-

• To achieve the designed/ desired workability in the plastic stage.
• To achieve the desired minimum strength in the hardened stage.
• To achieve the desired durability in the given environment conditions.
• To produce concrete as economically as possible.

Procedure-

CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH

1)Data-

• Grade Designation= M35
• Type of Cement= OPC 53 grade
• Type of Admixture= Fly ash
• Maximum Nominal Size of Aggregate= 20mm crushed angular aggregate
• Exposure condition= severe
• Minimum Cement Content= 340kg
• Maximum Cement Content= 450kg
• Maximum W/C ratio= 0.45
• Workability= 100mm for pumpable concrete
• Chemical Admixture= Super plasticizer

Test data-

• Specific Gravity of Cement= 3.12
• Mineral Admixture= Fly ash
• Specific Gravity of Fly ash= 2.5
• Chemical Admixture= Super plasticizers
• Specific gravity of Coarse Aggregate=2.74, Fine Aggregate= 2.74 and Admixture used= 1.12
• Fine aggregate Zone II

2)Target compressive strength

Target compressive strength=f’ck

f'ck=fck + 1.65s

From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm².

f'ck= 35+1.65x5 =43.25 N/mm²

3)Selection of water cement ratio

From Table 5 of IS456:2000, For severe and RCC structure.

Maximum permissible water-cement ratio is 0.45

4)Selection of water content

From Table 2 of IS456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Note add 3% water content for every 25mm increase in workability.

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

But as Super plasticizer is used so the water content can be reduced upto 20%.

Super plasticizer water content reduction of 20% has been achieved.

so,water content = 197-[197 x (20/100)] = 157.73 lit = 160lit

4)Calculation of cement content

Water-cement ratio =0.45

Cement content = 160/0.45 = 355.56 kg/m³

From Table 5 of IS 456, the minimum cement content for Severe exposure condition is 320 kg/m³

In our case, it is 355.56kg/m³ which is greater than 320 kg/m³, hence satisfied.

But fly ash is used partially with cement, so fly ash content used= 30% of cement content

Fly ash content requirement=355.56x0.3 =106.66kg/m³

Cement Content requirement =Cementious content – Fly ash =355.56-106.66= kg/m³

Calculation of Super Plasticizers @ 0.6 percent to the mass of cementitious content = 355.56x(0.6/100) = 2.13 kg

5)Aggregate content

From Table 3 of IS10262 , the 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= 0.45. Therefore, the volume of the coarse aggregate is required to be increased to decrease the fine aggregate content.

Note-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

But, Volume of aggregate is reduced by 10% to get the ease for transportation, placing by pumps.

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

6)Mix calculations-

Calculations are done for every 1cu.m concrete.

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)

= (249/3.12) X (1/1000)

=0.08m³

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

= (160/1) X (1/1000)

= 0.160m³

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

= (2.13/1.12) X (1/1000)

= 0.002 m³

e)Volume of fly ash= (mass of fly ash/specific gravity of fly ash)X(1/1000)

=(106.66/2.5)X1/1000)

=0.042m³

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

= 1 – (0.08 + 0.002 + 0.042)

= 0.843m³

f) Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.843 x 0.567x 2.74 x 1000

= 1309.66 kg

g) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.843 x 0.433 x 2.74 x 1000

= 1000.15 kg

7)Mix proportion

• Cement = 249 kg/m³
• Water = 160 kg/m³
• Super plasticizer = 2.13 kg/m³
• Fine aggregates = 1000.15 kg/m³
• Coarse aggregate = 1309.66 kg/m³
• W/c = 0.45
• CEMENT : FLY ASH : FA : CA
• 1 : 0.64 : 4.01 : 5.25

CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE

1)Data-

• Grade Designation= M50
• Type of Cement= OPC 53
• Maximum Nominal Size of Aggregate= 20mm
• Type of aggregate= Crushed angular aggregate
• Exposure condition= very severe
• Minimum Cement Content= 340kg
• Maximum W/C ratio= 0.45
• Workability= 100mm
• Method of placing of concrete= pumping
• Chemical Admixture= Super plasticizer

Test data-

• Cement Used= OPC 53
• Specific Gravity of Cement= 3.12
• Chemical Admixture= Super plasticizers
• Specific gravity of Coarse Aggregate=2.74, Fine Aggregate= 2.74 and Admixture used= 1.12
• Water absorption of Coarse aggregate= 0.5% and Fine aggregate= 1%
• Fine aggregate Zone II

2)Target compressive strength

Target compressive strength=f’ck

f'ck=fck + 1.65s

From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm².

f'ck= 50+1.65x5 =58.25 N/mm²

3)Selection of water cement ratio

From Table 5 of IS456:2000, For very severe and RCC structure.

Maximum permissible water-cement ratio is 0.45 & min cement content= 340kg

4)Selection of water content

From Table 2 of IS456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Note add 3% water content for every 25mm increase in workability.

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

But as Super plasticizer is used so the water content can be reduced upto 20%.

Super plasticizer water content reduction of 20% has been achieved.

so,water content = 197-[197 x (20/100)] = 157.73 lit = 160lit

4)Calculation of cement content

Water-cement ratio =0.45

Cement content = 160/0.45 = 355.56 kg/m³

From Table 5 of IS 456, the minimum cement content for very Severe exposure condition is 340 kg/m³

In our case, it is 355.56kg/m³ which is greater than 340 kg/m³, hence satisfied.

Calculation of Super Plasticizers @ 0.6 percent to the mass of cementitious content = 355.56x(0.6/100) = 2.13 kg

5)Aggregate content

From Table 3 of IS10262 , the 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= 0.45. Therefore, the volume of the coarse aggregate is required to be increased to decrease the fine aggregate content.

Note-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

But, Volume of aggregate is reduced by 10% to get the ease for transportation, placing by pumps.

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

6)Mix calculations-

Calculations are done for every 1cu.m concrete.

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)

= (355.56/3.12) X (1/1000)

=0.113m³

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

= (160/1) X (1/1000)

= 0.160m³

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

= (2.13/1.12) X (1/1000)

= 0.002 m³

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

= 1 – (0.113 + 0.002)

= 0.89m³

f) Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.89 x 0.567x 2.74 x 1000

= 1382.68 kg

g) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.89 x 0.433 x 2.74 x 1000

= 1055.91 kg

7)Mix proportion

• Cement = 355.56 kg/m³
• Water = 160 kg/m³
• Super plasticizer = 2.13 kg/m³
• Fine aggregates = 1055.91 kg/m³
• Coarse aggregate = 1382.68 kg/m³
• W/c = 0.45
• CEMENT : FA : CA
• 1 : 2.96 : 3.88

Conclusion:

Mix proportion for M35 grade concrete with fly ash is given as CEMENT : FLY ASH : FA : CA

Therefore mix proportion for M35 grade concrete with fly ash is 1 : 0.64 : 4.01 : 5.25

and

Mix proportion for M50 grade concrete is given as CEMENT : FA : CA

Therefore mix proportion for M50 grade concrete is 1 : 2.96 : 3.88