Project on Concrete Mix Design for various grades of Concrete

1)

Aim: To calculate Concrete Mix Design for M35 grade concrete with fly ash

Procedure:

Grade designation: M35
Type of cement: OPC 43 grade
Type of miniral admixture : Fly ash
Maximum nominal size of aggregate: 20mm
Maximum free water content ratio : 0.45
Exposure type: Moderate
Minimum cement content: 320 kg/m^3
Workability: 100mm slump
Degree of supervision : Good
Method of concrete placing: pumping
Type of aggregate: Crushed angular
Maximum cement content: 450 kg/m^3
Chemical admixture : Nil
Water absorbtion for Coarse aggregate : 0.5 percent
Water absorbtion for Fine aggregate : 1 percent
Free (surface) moisture - nil
Specific gravity of cement: 3.15
Specific gravity of fine aggregate: 2.74
Specific gravity of coarse aggregate: 2.74
Coarse and fine aggregate: Grade 1

• Target strength strength for mix proportioning :
  f'ck = fck + 1.65s
  s = 5 (From table 1 of IS 10262 2009)
  f'ck = 35 + 1.65 x 5 = 43.25 N/mm^2

• Selection of water-cement ratio
  From table 5 of IS456 2000 for moderate exposure,
  maximum water cement = 0.5
  Based on experience, adopt water cement ratio as 0.40
  0.40 < 0.5 Hence OK

• Selection of water content :
  From table 2 of IS 10262 : 2009
  maximum water content for 20mm aggregate = 186 L
  Estimated water content for 100mm slump = 186 + 6/100 x 186 = 197.16 L
  As superplasticizer is used,the water content can be reduced upto 29%,
  197.16 x 0.71 = 139.98 L

• Selection of cement content :

water cement ratio - 0.4
Cementious material (cement and fly ash) content = 139.98/0.4 = 349.95 kg/m^3

From table 5 of IS456 2000 Minimum cement for severe exposure condition = 300 kg/m^3

349.95Kg/m^3>300Kg/m^3.

Now to proportion a mix containing fly ash the following steps are suggested :
a) The percentage of fly ash needs to be decided based on project requirement and quality of materials
b) In some case increase in cementitious material can be warranted
Cementitious material content = 349.95 x 1.10 = 384.94 kg/m^3

• Water content = 140 kg/m^3
  So, water cemeent ratio = 140/384.94 = 0.363
  Fly ash @ 30% total cementitious = 384.94 x 30% = 115.6 kg/m^3
  material content = 115.6 kg/m^3Cement (opc) = 384.94 - 115.6 = 269.34 kg/m^3

Saving of cement while using fly ash = 384.94 - 269.34 = 115.6 kg/m^3
Fly ash being utilized = 115.6 kg/m^3
Proportion of volume of Coarse aggregate and fine aggregate content : from table 3 of Is10262
Volume of Coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone 1) water cement = 0.6
In the present case the water cement ratio is 0.4
Volume of coarse aggregate = 0.62 x 0.9 = 0.56
Volume of fine aggregate = 1 - 0.56 = 0.44

• Mix calculation :
  a) Volume of concrete = 1m^3
  b) Volume of cement = (Mass of cement/specific gravity)x(1/1000)
  349.95/3.15 x 1/1000 = 0.11 m^3
  c) Volume of fly ash = (mass of fly ash/specific gravity of fly ash) x (1/1000)
  115.6/1 x 1/1000 = 0.115 m^3
  d) Volume of water = (Mass of water/specific gravity)x(1/1000)
  140/1 x 1/1000 = 0.14
  e) Volume of aggregate (fine aggregarte and coarse aggregate) = a - (b+c+d)
  [1 - (0.111 + 0.115 + 0.14)]
  = 0.634 m^3

Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
0.634 x 0.56 x 2.74 x 1000 = 942.8 kg
Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000
0.634 x 0.44 x 2.74 x 1000 = 764.3 kg

Result

Mix proportion :
Cement = 384 kg/m^3
Fly ash = 115.6 kg/m^3
Water content = 140 kg/m^3
Fine aggregate = 764.3 kg/m^3
Coarse aggregate = 942.8 kg/m^3
Water cement ratio = 0.4

2)

Aim: To calculate Concrete Mix Design for M50 grade concrete without fly ash

Procedure:

Data required :
Grade designation : M50 grade
Type of cement : OPC 53 grade
Maximum nominal size of aggregate: 20mm
Exposure type: Moderate
Minimum cement content: 320 kg/m^3
Workability: 50mm slump
Method of concrete placing: pumping
Type of aggregate: Crushed angular
Maximum cement content: 450 kg/m^3
Chemical admixture : Super plasticizer
Specific gravity of cement: 3.15
Specific gravity of fine aggregate: 2.56
Specific gravity of coarse aggregate: 2.74

• Target strength:
  f'ck = fck + 1.65s
  s = 5 (From table 1 of IS 10262 2009)
  f'ck = 50 + (1.65 x 5) = 58.25 N/mm^2

• Selection of water cement ratio:
  For severe exposure condition maximum w/c = 0.45 (From table 5 IS 456:2000), 0.4<0.45

• Selection of water content:
  Maximum water content = 186lit
  Super plasticizer reduces 29% of water content.
  New water content = (71/100)*186 = 134.19

• Calculating cement content:
  Water/cement = 0.4
  cement = 134.19/0.4 = 335.47 > 320kg/m^3 Hence OK
  Cement content = 335 kg/m^3

• Proportioning of volume of coarse and fine aggregate:
  Volume of coarse aggregate for w/c 0.4 = 0.62 x 0.9 =0.56
  Volume of fine aggregate = 1 - 0.56 = 0.44

• Volume of coarse aggregate = 0.56
  Volume of fine aggregate = 0.44

• Mix calculations:

a. Volume of concrete = 1m^3

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

335/3.15 x 1/1000 = 0.106 m^3

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

134.19/1 x 1/1000 = 0.134 m^3

d. Super plasticizer is upto 2% of mass of total cementitious content

6.7/1.15 x 1/1000 = 0.006 m^3

e. Volume of aggregate = a - (b+c+d) = 1-(0.106+0.134+0.0060 = 0.754 m^3

f. Mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate

0.754 x 0.56 x 2.73 x 1000 = 1152kg

g. Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate

0.754 x 0.44 x 2.61 x 1000 = 866kg

Result:

Mix proportion :

Cement = 335

Fine aggregate = 866

Coarse aggregate = 1152