Project on Concrete Mix Design for various grades of Concrete

WATER CEMENT RATIO FOR M50 GRADE OF CONCRETE

DATA COLLECTED

• Grade Of Concrete = M50
• Exposure Condition = Moderate
• Grade Of Cement = M33
• Fck =50N/mm^2
• Std Deviation For M50 = 5N/mm^2

SOLUTION

Target mean strength ft = Fck+(1.65 s)

Ft = 50+(1.65*5)

=50+(8.25)

=58.25N/mm^2

STEP 1

28 Days of compressive strength of concrete for target mean strength

= 58.25 N/mm^2

In graph 1

Hence we assume W/C ratio =0.34

STEP 2

EXPOSURE CONDITION

In moderate condition = 0.50

Hence the lower value of above three W/C ratio = 0.34

For M50 Grade of concrete the W/C ratio =0.34

9)

1. Characteristic compressive strength required in the field at 28 days grade designation — M 50
2. Type of Cement : OPC 43 Grade confirming to IS 8112
3. Maximum Nominal size of aggregate — 20 mm
4. minimum cement content = 340kg/m^3
5. Maximum W/C ratio = 0.45 (from table 5 of IS 456:2000-very severe condition)
6. Workabiltiy required at site — 100 mm (slump)
7. Exposure condition = very severe (for reinforced concrete)
8. Method of concrete placing: pumpable concrete
9. Degree of supervision = good
10. Type of aggregate = crushed angular aggregate
11. Maximum cement content = 450 kg/m^3
12. Chemical admixture = superplazticizer

TEST DATA FOR MATERIALS

1. Cement used = opc 43 grade conforming to IS 8112
2. Specific gravity cement = 3.15
3. Chemical admixture = superplazticizer conforming to IS 9103
4. Specific gravity

• Coarse aggragate = 2.74
• Fine aggragate = 2.74

1. Water absorption

• Coarse aggragate = 0.5%
• Fine aggragate = 1.0%

1. Free surface moisture

• Coarse aggragate = nil
• Fine aggragate = nil

Target mean strength

F’ck = fck +1.65 s

F’ck = Target average compressive strength at 28 days

Fck = Characteristic compressive strength at 28 days

S = Standard deviation

= 50+1.65*5=58.25N/mm^2

From table 5 of IS 456 2000 for very severe exposure, maximum water cement ratio = 0.45

Adopted w/c ratio is 0.34

From table 2 of IS 10262;2009 maximum content for 20mm aggregate = 186 litres (for 25mm to 50mm slump range)

i.e. Estimated water content for 100 Slump = 186+(6/100) X 186 = 197 litre

Water content = 197 liters

As a superplaztizer can be reduced upto 20% and above

Based on trail water content reduction of 29% is achieved with plasticizer

Hence the arrived water content =197*0.71=140 litre

CALCULATION OF CEMENT CONTENT

W/C ratio =0.34

Cement content = 140/0.34 = 412Kg/m^3

From table 5 of IS 456 minimum cement content for severe exposure condition =320 kg/m^3

412 kg/m^3 > 340 kg/m^3, hence ok.

Proportion of volume coarse aggregate and fine aggregate content

From table 3 IS code 10262:2009 volume of coarse aggrragate corresponding to 20mm size aggregate and fine aggregate (Zone1) for W/C ratio = 0.6

In the present case the water cement ratio is 0.34

Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.68x 0.9 = 0.61

Volume of fine aggregate = 1-0.61 = 0.39

MIX CALCULATION

The mix calculation per unit volume of concrete

1. Volume of concrete = 1m³
2. Volume of cement = Mass of cement/ sg of cement*1/1000

= 412/3.15*1/1000

= 0.130m³

3 Volume of water = Mass of water/ sg of water*1/1000

= 140/1*1/1000

= 0.140 m³

4 Volume of chemical admixture = Mass of chemical admixture/sg of chemical admixture*1/1000

= 7/1.145*1/1000

=0.006m³

5 Volume of aggragte (FA &CA) = (a-(b+c+d))

= (1-(0.130+0.140+0.006))

= 0.724 m³

6 Mass of coarse aggregate = e x volume of coarse aggregate x sg of coarse aggregate x 1000

= 0.724*0.61*2.74*1000

= 1210 kg/m³

7 Mass of fine aggregate = e x volume of fine aggregate x sg x1000

= 0.724*0.39*2.74*1000

= 774kg/m³

MIX PROPORTION FOR TRAIL NUMBER 1

CEMENT = 412 kg/m³

WATER = 140 kg/m³

FINE AGGREGATE = 774 kg/m³

COARSE AGGREAGTE = 1210 kg/m³

CHEMICAL ADMIXTURE = 7 kg/m³

W/C RATIO = 0.34

TRAIL MIX RATIO = 1 : 1.87 : 2.93

2)

1. Characteristic compressive strength required in the field at 28 days grade designation — M 35
2. Type of Cement : OPC 43 Grade confirming to IS 8112
3. Type of mineral admixtutre= fly ash conforming to IS 3812 (part1)
4. Maximum Nominal size of aggregate — 20 mm
5. minimum cement content = 320kg/m^3
6. Maximum W/C ratio = 0.45 (from table 5 of IS 456:2000-severe condition)
7. Workabiltiy required at site — 100 mm (slump)
8. Exposure condition = severe (for reinforced concrete)
9. Method of concrete placing: pumpable concrete
10. Degree of supervision = good
11. Type of aggregate = crushed angular aggregate
12. Maximum cement content = 450 kg/m^3
13. Chemical admixture = superplazticizer

TEST DATA FOR MATERIALS

1. Cement used = opc 43 grade conforming to IS 8112
2. Specific gravity cement = 3.15
3. Chemical admixture = superplazticizer conforming to IS 9103
4. Specific gravity

• Coarse aggragate = 2.74
• Fine aggragate = 2.74

1. Water absorption

• Coarse aggragate = 0.5%
• Fine aggragate = 1.0%

1. Free surface moisture

• Coarse aggragate = nil
• Fine aggragate = nil

Target mean strength

F’ck = fck +1.65 s

F’ck = Target average compressive strength at 28 days

Fck = Characteristic compressive strength at 28 days

S = Standard deviation

= 35+1.65*5=43.25N/mm^2

From table 5 of IS 456 2000 for severe exposure, maximum water cement ratio = 0.45

Adopted w/c ratio is 0.40

From table 2 of IS 10262;2009 maximum content for 20mm aggregate = 186 litres (for 25mm to 50mm slump range)

i.e. Estimated water content for 100 Slump = 186+(6/100) X 186 = 197 litre

Water content = 197 liters

As a superplaztizer can be reduced upto 30% and above

Based on trail water content reduction of 29% is achieved with plasticizer

Hence the arrived water content =197*0.71=140 litre

CALCULATION OF CEMENT CONTENT

W/C ratio =0.4

Cement content = 140/0.4 = 350Kg/m^3

From table 5 of IS 456 minimum cement content for severe exposure condition =320 kg/m^3

350 kg/m^3 > 320 kg/m^3, hence ok.

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

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

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

Water content = 140 kg/m^3

Water cement ratio = 140/385 = 0364

Fly ash 30% total cementitous = 385*30%=115 kg/m^3

Cement = 385-115 =270 kg/m^3

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

Fly ash being utilized = 115 kg/m^3

Proportion of volume coarse aggregate and fine aggregate content

From table 3 IS code 10262:2009 volume of coarse aggrragate corresponding to 20mm size aggregate and fine aggregate (Zone1) for W/C ratio = 0.6

In the present case the water cement ratio is 0.40

Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.62x 0.9 = 0.56

Volume of fine aggregate = 1-0.56 = 0.44

MIX CALCULATION

The mix calculation per unit volume of concrete

1. Volume of concrete = 1m³
2. Volume of cement = Mass of cement/ sg of cement*1/1000

= 270/3.15*1/1000

= 0.086m³

3 Volume of fly ash = Mass of fly ash/sg of fly ash/1*1000

= 115/2.2*1/1000

= 0.052 m³

4 Volume of water =Mass of water/ sg of cement*1/1000

= 140/1*1/1000

= 0.140 m³

5 Volume of chemical admixture= ass of chemical admixture/ sg of cement*1/1000

= 7/1.145*1/1000

=0.006m³

6 Volume of aggragte (FA &CA) = (a-(b+c+d))

= (1-(0.086+0.052+0.006))

= 0.716 m³

7 Mass of coarse aggregate = e x volume of coarse aggregate x sg of coarse aggregate x 1000

= 0.716*0.56*2.74*1000

= 1098 kg/m³

8 Mass of fine aggregate = e x volume of fine aggregate x sg x1000

= 0.716*0.44*2.74*1000

= 863 kg/m³

MIX PROPORTION FOR TRAIL NUMBER 1

CEMENT = 270 kg/m³

FLY ASH = 115 kg/m³

WATER = 140 kg/m³

FINE AGGREGATE = 863 kg/m³

COARSE AGGREAGTE = 1098 kg/m³

CHEMICAL ADMIXTURE = 7 kg/m³

W/C RATIO = 0.36

TRAIL MIX RATIO = 1 : 2.24 : 2.85