Project on Concrete Mix Design for various grades of Concrete

A.) The calculation for the concrete mix design for M35 grade concrete with flyash are explained below :

I.) AIM :

To determine the concrete mix design for M35 grade concrete with flyash .

II.) PROCEDURES FOR CONCRETE MIX PROPORTIONS :

1. Stipulations for proportioning :

a) Grade designation : M35

b) Type of cement : OPC 43 grade conforming to IS 8112

c) Type of mineral admixture : Fly ash conforming to IS 3812 (Part 1)

d) Maximum nominal size of aggregate : 20 mm

e) Minimum cement content : 320 kg/m^3 (From Table 5 of IS 456: 2000 - Exposure Condition)

f) Maximum water-cement ratio : 0.45 (From table 5 of IS 456: 2000 - Exposure condition)

g) Workability : 100 mm (Slump value for pumpable concrete)

h) Exposure condition : Severe (for reinforced concrete)

i) Method of concrete placing : pumping

j) Degree of supervision : Good

k) Type of aggregate : crushed angular aggregate

l) Maximum cement content : 450 kg/m^3

m) Chemical admixture type : Superplasticizer

2. Test data for materials :

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

b) Specific gravity of cement : 3.15

c) Fly ash : Conforming to IS 3812 (Part 1)

d) Specific gravity of flyash : 2.2

e) Chemical admixture : Superplasticizer conforming to IS 9103

f) Specific Gravity of :

• Coarse aggregate : 2.74
• Fine aggregate : 2.74

d)Water absoption:

• Coarse aggregate : 0.5%
• Fine aggregate : 1.0%

e) Free surface moisture :

• Coarse aggregate : Nil
• Fine aggregate : Nil

d) Sieve Analysis :

• Coarse aggregate : Conforming to table 2 of IS 383
• Fine aggregate : Conforming to grading zone I of Table 4 of IS 383

3. Target strength for mix proportioning :

f'ck = fck + 1.65 S

Where,

f'ck = Target average compressive strength at 28 days

fck = Characteristic compressive strength at 28 days

S = Standard deviation

From table 1 of IS 10262: 2009, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 35+1.65 x 5 = 43.25 N/mm^2

4. Selection of water-cement ratio :

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

• In experience w/c ratio = 0.40
• Hence 0.40 < 0.45, Hence OK.

5. select of water content:

• From table 2 of IS 10262 : 2009, maximum water content for 20mm aggregate = 186 liter ( for 25 to 50 mm slump range)
• Estimated water content for 100mm slump = 186 + 6/100 x 186

= 197 litre

• As superplasticizer is used, the water content can be reduced up to 30 %
• Based on trials water content reduction oof 29 % is achieved with plasticizer.
• Hence the arrived water content = 197 x 0.71 = 140 liters.

6. calculation of cement content :

• 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.

a) The percentage of flyash needs to be decided based on project required 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 content )

• Cementitious material content = 350 x 1.10 = 385 kg/m^3
• Water conntent = 140 kg/ m^3
• So, water-cement ratio = 140/385 = 0.364
• Fly ash @ 30 % total cementitious material content = 385 x 30% = 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

7. Proportion of volume of coarse aggregate and Fine aggregate:

• From Table 3 of IS 10262 : 2009, colume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone I) for water-cement a ratio = 0.6
• In the present case the water cement ratio is 0.40
• Therefore, the volume of coarse aggregate needs to be increased the fine aggregate content.
• As water-cement ratio is lower by 0.10 the proportion of volume of coarse aggregate is increased by 0.02 .
• (at the rate of -/+ 0.01 for every +/- 0.05 change in water-cement ratio)
• Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62

(Note: If coarse aggregate is not of angular type , then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

• For pumpable concrete these values are reduced by 10%
• Therefore, volume of coarse aggregate = 0.62 x 0.9 = 0.56
• Volume of fine aggregate content = 1 - 0.56 = 0.44

8. Mix Calcualtions :

The calcualtion per unit volume of concrete shall be as follows :

a) Volume of concrete = 1m^3

b) Volume of cement = Mass of cement / specific gravity of cement x 1/100

= 270 / 3.15 x 1 / 1000

= 0.086 m^3

c) Volume of Fly ash = Mass of fly ash / specific gravity of fly ash x 1/ 1000

= 115/ 2.2 x 1 / 1000

= 0.052 m^3

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

= 140 / 1 x 1/ 1000

= 0.140 m^3

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

= 7.6 / 1.145 x 1/1000

= 0.006 m^3

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

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

= 0.716 m^3

g) Mass of coarse aggregate = f x voume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.716 x 0.56 x 2.74 x 1000

= 1098 kg/m^3

h) Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.716 x 0.44 x 2.74 x 1000

= 863 kg/ m^3

9. Mix proportions for trial number 1 :

• Cement = 270 kg/m^3
• Fly ash = 115 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
• Water-cement ratio = 0.364

III.) RESULT :

Mix ratio = 1: 2.24 : 2.85

B.) The Calculations for the concrete mix design for M50 grade concrete without flyash are explained below:

I.) AIM :

To determine the concrete mix design for M50 grade concrete without fly ash.

II.) PROCEDURES FOR CONCRETE MIX PROPORTIONS:

1. 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 : 320kg/m^3 (From table-5 of IS 456: 2000 - Exposure condition)

e) Maximum water-cement ratio : 0.45 (From table-5 of IS 456: 2000 - Exposure condition)

f) workability : 150mm to 200mm (Slump value for termie concrete)

g) Exposure condition : Severe (for reinforced concrete)

h) Method of concrete placing : Termie

i) Degree of supervision: very good

j) Type of aggregate : Crushed angular aggregate

k) maximum cement content: 450kg/m^3

l) chemical admixture type: Superplasticizer

2. Test data for materials :

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

b) Specific gravity of cement : 3.15

c) chemical admixture: superplasticizer conforming to IS 9103

d)specific gravity of:

• Coarse aggregate : 2.74
• Fine aggregate: 2.74

e) Water absorption:

• Coarse aggregate : 0.5%
• Fine aggregate: 1.0%

f) Free surface moisture:

• Coarse aggregate: NIL
• Fine aggregate: NIL

d) Sieve analysis:

• Coarse aggregate : Conforming to table-2 of IS 383
• Fine aggregate: Conforming to grading zone I of table 4 of IS 383

3. Target mean strength for Mix proportion :

f'ck = fck + 1.65 S

where,

• f'ck = Target average compressive strength at 28 days
• fck = Charateristic compressive strength at 28 days
• S = Standard deviation

From table 1 of IS 10262: 2009, standard deviation, S = 5.0 N/mm^2

Therefore, Target strength (f'ck) = 50 + 1.65 x 5 = 58.25 N/mm^2.

4. Selection of water-cement ratio :

• From table 5 of IS 456: 2000 for severe exposure, maximum water-cement ratio = 0.45
• In experience w/c ratio = 0.40
• Hence 0.40 < 0.45, Hence OK.

5. Selection of water content :

From the table-2 of IS 10262:2009, maximum water content for 20mm aggregate = 186 liters (for 25 mm to 50 mm slump range)

• Estimated water content for 150 mm slump = 186 + 12/100 x 186 = 208 liters.
• 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 = 208 x 0.71 = 147 liters.

6. Calculation of cement content :

• Water -cement ratio = 0.40
• Cement content = 147/0.40 = 367 kg/m^3.
• From table 5 of IS 456 minimum cement content for severe exposure condition = 320 kg/m^3.
• 367 kg/m^3 > 320 kg/m^3, Hence OK.

7. Proportion of volume of coarse aggregate and fine aggregate content :

From table-3 of IS 102626: 2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone I) for water-cement ratio = 0.6

• In this case the water-cement ratio is 0.40
• Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As water-cement ratio is lower by 0.10, the proportion of 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, corrected w/c ratio for volume of the coarse aggregate = 0.62
• For termie concrete the values are reduced by 10%
• Therefore, volume of coarse aggregate = 0.62 x 0.9 = 0.56
• Volume of fine aggregate content = 1 - 0.56 = 0.44

8. Mix calculations :

a) Volume of concrete = 1m^3

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

= 367/3.15 x 1/1000

= 0.116 m^3

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

= 147/1 x 1/1000

= 0.147 m^3

d) Volume of chemical admixture = Mass of chemical admixture/ Specific gravity of chemical admixture x 1/1000

= 7.6/1.145 x 1/1000

= 0.006 m^3

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

= (1-(0.116+0.147+0.006))

= 0.731 m^3

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

=0.731 x 0.56 x 2.74 x1000

= 1121 kg/m^3

g) Mass of fine aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

=0.731 x 0.44 x 2.74 x1000

= 881 kg/m^3

9. Mix proportions :

• Cement = 367 kg/m^3
• Water = 147 kg/m^3
• Chemical admixture = 7 kg/m^3
• Fine aggregate = 881 kg/m^3
• coarse aggregate = 1121 kg/m^3
• Water-cement ratio = 0.40

III.) RESULT :

Mix ratio = 1: 2.4: 3.05