Challenge

Project on Concrete Mix Design for various grades of Concrete

NNitin Raibole10 Aug 2021

AIM- Concrete Mix Design for M50 grade concrete without Fly Ash:-

PROCEDURE:-

I) Stipulations for Proportioning:-

a) Grade designation= M50.

b) Type of cement= OPC 43 Grade conforming to IS 8112.

c) Maximum Nominal size of aggregate= 20mm.

d) Minimum cement Content= 360kg/m^3(from table 5:IS 456-2000).

e) Maximum W/C ratio= 0.40(from table 5:IS:456-2000).

f) Workability= 50 mm (Slump value for pumpable concrete).

g) Exposure Condition= Extreme(for RCC).

h) Method of concrete placing= Pumping.

i) Degree of supervision= Good.

j) Type of aggregate= Crushed Angular aggregate.

k) Chemical Admixture type= Superplasticizer.

II) Test data for Materials:-

a) Cement used= OPC grade conforming to IS:8112.

b) Specific Gravity of Cement= 3.15

c) Specific Gravity of Coarse aggregate and Fine Aggregate= 2.74.

d) Water Absorption of Coarse aggregate= 0.5% and Fine Aggregate= 1.0%

e) Seive Analysis of Coarse aggregate(Conforming to table 2 IS 383) and Fine aggregate(Conforming Grading zone

1, table 4, IS383).

III) Target strength for Mix Proportioning:-

F'ck=Fck+1.65*S= 50+1.65*5= 58.25 N/mm^2

Where, F'ck = Target Average Compressive Strength at 28 days.

Fck = Characteristics Compressive Strength at 28 days.

S = Standard Deviation= 5 N/mm^2(from table 1 of IS:10262-2009).

IV) Selection of Water cement ratio:-

From table 5: IS:456-2000 for Extreme Exposure, Maximum W/C ratio= 0.40.

Based on Experience, adopted W/C ratio= 0.40.

Therefore 0.40=0.40, Hence OK.

V) Selection of Water Content:-

From table no.2 IS:10262-2009, Maximum water content for 20mm aggregate=186 litre(for 25mm to 50mm

slump range).

Estimated Water content for 50mm slump=186 litres.

As Superplasticizer is used, the water content can be reduced up to 20% and above.

Based on trials water content reduction of 29% is achieved with Plasticizer.

Hence the arrived water content= 186*0.71=132.06 litres.

VI) Calculation of cement content:-

-W/C ratio=0.40, 132.06/cement= 0.4, Therefore, Cement= 330 kg/m^3.

-From table 5:IS:456-2000, Minimum cement content for Extreme condition= 360 kg/m^3.

Therefore, 330 kg/m^3 < 360 kg/m^3, Hence OK.

VII) Proportion of volume of Coarse aggregate and Fine aggregate Content:-

-From table 3:IS:10262-2009,Volume of coarse aggregate corresponding to 20mm size aggregate and fine

aggregate(Zone 1) for W/C ratio= 0.6.

-In present case W/C ratio= 0.40.

-Therefore the volume of Coarse aggregate needs to be increased to decrease the Fine aggregate content.

-As W/C ratio is lower by 0.10, the proportion of volume of Coarse aggregate is increased by 0.02 (at rate -/+ 0.01

for every +/- 0.05 change in W/C ratio).

-Therefore corrected volume of Coarse aggregate for W/C ratio 0.40=0.62.

(Note: If Coarse aggregate is not angular type, then also volume required to be incresed suitably, based on experience)

-For pumpable concrete these values reduced by 10%,

Therefore, Volume of coarse aggregate= 0.62*0.9= 0.56.

Volume of Fine aggregate= 1-0.56= 0.44.

VIII) Mix Calculation:-

The Mix calculation per unit volume of concrete shall follows-

a) Volume of concrete= 1 m^3.

b) Volume of Cement= Mass of cement/Specific gravity of cement * 1/1000

= 360/3.15 * 1/1000

= 0.1142 m^3

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

= 132/1 * 1/1000

= 0.132 m^3.

d) Volume of chemical Admixture= Mass/specific gravity * 1/1000

= 7.6/1.145 * 1/1000

= 0.006 m^3.

e) Volume of aggregate (FA and CA)= [a-(b+c+d)]

= 1-(0.1142+0.132+0.006)

= 0.7478 m^3.

f) Mass of coarse aggregate(CA) = e*volume of CA*specific gravity of CA*1000

= 0.7478*0.56*2.74*1000

= 1147.43 kg/m^3.

g) Mass of Fine aggregate(FA) = e*volume of FA*specific gravity of FA*1000

= 0.7478*0.44*2.74*1000

= 901.55 kg/m^3.

IX) Mix proportion for trial (1):-

Cement= 360 kg/m^3

Water= 132 kg/m^3

Fine Aggregate= 901.55 kg/m^3

Coarse Aggregate= 1147.43 kg/m^3

Chemical Admixture= 7 kg/m^3

W/C ratio= 0.4

Trial Mix Ratio= 1:2.50:3.19

X) The slump shall be measured and water content and dosage of admixture shall be adjusted for achieving the required

slump on trial. The mix proportion shall be reworked for actual water content and checked for Durability requiredment.

XI) Two more trial having variation of 10% of W/C ratio in clause X shall be carried out and a graph between 3 W/C ratio

and corresponding strength shall be plotted to work out mix proportions for the given target strength for field.

However, Durability shall be met.

AIM- Concrete Mix Design for M35 grade of concrete using with Fly Ash as part of replacement of OPC:-

PROCEDURE:-

I) Stipulations for Proportioning:-

a) Grade designation= M35.

b) Type of cement= OPC 43 Grade conforming to IS 8112.

c) Maximum Nominal size of aggregate= 20mm.

d) Minimum cement Content= 340 kg/m^3(from table 5:IS 456-2000).

e) Maximum W/C ratio= 0.45(from table 5:IS:456-2000).

f) Workability= 100mm (Slump value for pumpable concrete).

g) Exposure Condition= Very Severe(for RCC).

h) Method of concrete placing= Pumping.

i) Degree of supervision= Good.

j) Type of aggregate= Crushed Angular aggregate.

k) Chemical Admixture type= Superplasticizer(IS-9103)

l) Type of Mineral Admixture= Fly Ash(IS-3812 part 1)

m) Maximum Cement Content= 450 kg/m^3

II) Test data for Materials:-

a) Cement used= OPC 43 grade conforming to IS:8112.

b) Specific Gravity of Cement= 3.15

c) Specific Gravity of Coarse aggregate and Fine Aggregate= 2.74.

d) Water Absorption of Coarse aggregate= 0.5% and Fine Aggregate= 1.0%

e) Seive Analysis of Coarse aggregate(Conforming to table 2 IS 383) and Fine aggregate(Conforming Grading zone

1, table 4, IS383).

f) Fly Ash= Conforming IS-3812 (Part 1)

g) Specific Gravity of Fly Ash= 2.2

III) Target strength for Mix Proportioning:-

F'ck=Fck+1.65*S= 35+1.65*5= 43.25 N/mm^2

Where, F'ck = Target Average Compressive Strength at 28 days.

Fck = Characteristics Compressive Strength at 28 days.

S = Standard Deviation= 5 N/mm^2(from table 1 of IS:10262-2009).

IV) Selection of Water cement ratio:-

From table 5: IS:456-2000 for Very Severe Exposure, Maximum W/C ratio= 0.45.

Based on Experience, adopted W/C ratio= 0.40.

Therefore 0.40<0.45, Hence OK.

V) Selection of Water Content:-

From table no.2 IS:10262-2009, Maximum water content for 20mm aggregate=186 litre(for 25mm to 50mm

slump range).

Estimated Water content for 50mm slump=186+0.06*186

=197 litres.

As Superplasticizer is used, the water content can be reduced up to 30% and above.

Based on trials water content reduction of 29% is achieved with Plasticizer.

Hence the arrived water content= 197*0.71=140 litres.

VI) Calculation of cement content:-

-W/C ratio=0.40,

-Cementitious Material(Cement+Fly Ash) contnet= 140/0.4,

Therefore, Cement= 350 kg/m^3.

-From table 5:IS:456-2000, Minimum cement content for Extreme condition= 360 kg/m^3.

Therefore, 350 kg/m^3 > 340 kg/m^3, Hence OK.

To Proportion a Mix containing Fly Ash the following steps are:-

a) The percentage of Fly Ash needs to be decided based on project requiredment and quality of materials.

b) In some cases increase in cementitious material can be warranted. Increase in Cementitious Material content and its

percentage may be based on Experience and Trial(This example is with increase of 10% Cementitious Material

conctent).

Cementitious Materials content= 350+0.1*350= 385 kg/m^3.

Water Content= 140 kg/m^3.

W/C ratio= 140/385= 0.364.

Fly Ash@ 30% total cementitious material content= 385*0.3= 115 kg/m^3.

Cement(OPC)= 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

VII) Proportion of volume of Coarse aggregate and Fine aggregate Content:-

-From table 3:IS:10262-2009,Volume of coarse aggregate corresponding to 20mm size aggregate and fine

aggregate(Zone 1) for W/C ratio= 0.6.

-In present case W/C ratio= 0.40.

-Therefore the volume of Coarse aggregate needs to be increased to decrease the Fine aggregate content.

-As W/C ratio is lower by 0.10, the proportion of volume of Coarse aggregate is increased by 0.02 (at rate -/+ 0.01

for every +/- 0.05 change in W/C ratio).

-Therefore corrected volume of Coarse aggregate for W/C ratio 0.40=0.62.

(Note: If Coarse aggregate is not angular type, then also volume of Coarse aggregate may be required to be incresed

suitably, based on experience)

-For pumpable concrete these values reduced by 10%,

Therefore, Volume of coarse aggregate= 0.62*0.9= 0.56.

Volume of Fine aggregate= 1-0.56= 0.44.

VIII) Mix Calculation:-

The Mix calculation per unit volume of concrete shall follows-

a) Volume of concrete= 1 m^3.

b) Volume of Cement= Mass of cement/Specific gravity of cement * 1/1000

= 270/3.15 * 1/1000

= 0.086 m^3

c) Volume of Fly Ash= Mass of Fly Ash/Specific gravity of Fly Ash * 1/1000

= 115/2.2 *1/1000

= 0.052 m^3

d) Volume of Water= Mass of water/specific gravity of water * 1/1000

= 140/1 * 1/1000

= 0.140 m^3.

e) Volume of chemical Admixture= Mass/specific gravity * 1/1000

= 7.6/1.145 * 1/1000

= 0.006 m^3.

f) Volume of aggregate (FA and CA)= [a-(b+c+d+e)]

= 1-(0.086+0.052+0.140+0.006)

= 0.716 m^3.

g) Mass of coarse aggregate(CA) = e*volume of CA*specific gravity of CA*1000

= 0.716*0.56*2.74*1000

= 1098 kg/m^3.

h) Mass of Fine aggregate(FA) = e*volume of FA*specific gravity of FA*1000

= 0.716*0.44*2.74*1000

= 863 kg/m^3.

IX) Mix proportion for trial (1):-

Cement= 270 kg/m^3

Water= 140 kg/m^3

Fine Aggregate= 863 kg/m^3

Coarse Aggregate= 1098 kg/m^3

Chemical Admixture= 7 kg/m^3

W/C ratio= 0.34(Lower value from W/C ratio Graph 1,2-IS:10262-2009, Table 5-IS:456-2000)

Trial Mix Ratio= 1:2.24:2.85