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Construction Technology_Concrete Mix Design_Project 1

AAlagu Natrayan7 Jan 2021

The Concrete Mix Design for M35 grade concrete with fly ash:

Step-1

Stipulations for Proportioning:

  1. Grade designation :M35
  2. Type of Cement :OPC 43grade conforming to IS8112
  3. Type of mineral admixture : Fly ash conforming to IS3821(part-1)
  4. Maximum nomnal size of aggregate :20mm
  5. Minimum cement content :320kg/mm^3
  6. Maximum water cement ratio :0.45
  7. Workability :100mm(slump
  8. Exposure condition :sever
  9. Method of concrete placing :pumping
  10. Degree of supervision :Good
  11. Types of aggregate :Crushed angular aggregate
  12. Maximum cement (opc) content :450kg/mm^3
  13. Chemical admixture type : superplasticizer

Step-2

Test Data For Materials:

  1. Cement used : OPC 43 grade conforming to IS8112
  2. Specific gravity of cement : 3.15
  3. Fly ash : 2.2
  4. Chemical admixture : Super plasticizer conforming to is1903
  5. Specific gravity of coarse aggregate : 2.74
  6. specific gravity of fine aggregate : 2.74
  7. water absorption of Coarse aggregate :0.5percent
  8. water absorption ofFine aggregate :1.0percent
  9. Free surface moisture of C.A : nil
  10. Free surface moisture of F.A : nil

Step-3

Traget Strength For Mix Proportioning:

f'ck=fck+1.65s

where,

f'ck=target average compressive strength at 28 days,

fck = characteristic compressive strength at28 days,

S= standard deviation, and
From Table 2,(IS10262:2009) standard deviation, S = 5 N/mm
Therefore,traget strength =35+1.65*5=43.45N/mm^2
Step-4
Selection of water:
From Table 5 of IS 456, maximum water-cement ratio = 0.45.
Based on experience. adopt water-cement ratio as 0.45.
0.45 = 0.45, hence, O.K.
Step-5
Selection of water content:
From Table 2, maximum water content
for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
Estimated water content for 100 mm slump= 186+6/100 X 186 = 197 litre
As supcrplas ticizcr is used. the water content ca n he reduced up 30percent.
Based on trials with superpl ast icizer wate r content reduction of 2<) percent has been achieved. Hence, the
arrived water content = 197 x 0.71 = 140 litres.
Step-6
CALCULATION OF CEMENT AND FLY ASH CONTENT:
Water-cement ratio = 0.45
Cementitious material (cement + fly ash) content =140/0.45=311kg
From Table 5 of IS 456, minimum cementcontent for 'severe' exposure conditions
311 kg/m^3 < 320 kg/m^3 hence. O.K.
Now, to proportion a mix containing fly ash the following steps are suggested:
a) Decide the percentage fly ash to be used based on project requirement and quality of materials
b) In certain situations increase in cementitious material content may be warranted, The decision on increase
in cementitious material content and its percentage may be based on experience and
NOTE - This illustrative example is with increase of 10 percent cementitious material content.
Cementitious material content
Water Content = 320 x 1.10 = 352 kg/m3
So. water-cement ratio = 140/352 kg/m3 =0.397

Fly ash @ 30% of total cementitious material content= 352 x 30% =105 kg/m3
Cement (OPC) = 352-105 =247 kg/m3
Saving ofcement while using fly ash = 320 - 247 = 73kg/m3, and
Fly ash being utilized = 105 kg/m3'
Step-7
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)
for water-cement ratio of 0.45 =0.60.
In the present case water-cement ratio is 0.45.
Therefore. volume of coarse aggregate is requ ired (0 be increasedto decrease the line aggregate content.
As the water-cement ratio is lower hy 0.10. the proportion of volume ofcoarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) ,
Therefore. corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.45 = 0.62
NOTE - In case the coarse aggregate is not angular one. then also volume: of coarse aggregate may he required to be increased
suitably. based on experience.
For pumpable concrete these values should be reduced by 10 percent.
Therefore. volume of coarse aggregate =0.62 x 0.9 =0.56.
Volume of fine aggregate content = I - 0.56 = 0.44.

Step-8

MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m3
b) Volume of cement =Mass of cement / Specific gravity ofcement *1 /1000
=247/3.15*1/1000

=0.078m3
c) Volume of fly ash =Mass of fly ash /Specific gravity of fly ash*1/1000

=105/2.2*1/1000

=0.047
d) Volume of water =Mass ofwater/specific gravity of water*1/1000
=140/1*1/1000

=0.14m3
e ) Volume of chemical admixture=Mass of admixture / Specific gravity of admixture *1/1000

(superplasticizer) @ 2.0% by mass=7/1.145*1/1000

of cementitious material) =0.007m3
f) Volume of all in aggregate = [a - (b + c + d + ej]

= 1-(0.078+ 0.047 + 0.140 + 0.007)

=0.728m3
g) Mass of coarse aggregate =f*volume of coarse aggregate *Specific gravity of coarseaggregate * 1000

=0.728*0.56*2.74*1000

= 1125kg/m3


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

= 0.728 x 0.44 x 2.74 x 1000

=884kg/m3

Step-9

MIX PROPORTIONS FOR TRIAL NUMBER 1:
Cement = 247 kg/m3
FlyAsh = 105 kg/m3
Water = 140 kg/m3
Fine aggregate = 884 kg/m3
Coarse aggregate = 1125 kg/m3
Chemical admixture = 7.7 kg/m3

The mix ratio is 1:3.57:4.55


M50 grade concrete without Fly ash:

Step-1

Stipulations for Proportioning:

  1. Grade designation :M50
  2. Type of Cement :OPC 43grade conforming to IS8112
  3. Type of mineral admixture : Fly ash conforming to IS3821(part-1)
  4. Maximum nomnal size of aggregate :20mm
  5. Minimum cement content :320kg/mm^3
  6. Maximum water cement ratio :0.45
  7. Workability :100mm(slump
  8. Exposure condition :sever
  9. Method of concrete placing :pumping
  10. Degree of supervision :Good
  11. Types of aggregate :Crushed angular aggregate
  12. Maximum cement (opc) content :450kg/mm^3
  13. Chemical admixture type : superplasticizer

Step-2

Test Data For Materials:

  1. Cement used : OPC 43 grade conforming to IS8112
  2. Specific gravity of cement : 3.15
  3. Chemical admixture : Super plasticizer conforming to is1903
  4. Specific gravity of coarse aggregate : 2.74
  5. specific gravity of fine aggregate : 2.74
  6. water absorption of Coarse aggregate :0.5percent
  7. water absorption ofFine aggregate :1.0percent
  8. Free surface moisture of C.A : nil
  9. Free surface moisture of F.A : nil

Step-3

Traget Strength For Mix Proportioning:

f'ck=fck+1.65s

where,

f'ck=target average compressive strength at 28 days,

fck = characteristic compressive strength at28 days,

S= standard deviation, and
From Table 2,(IS10262:2009) standard deviation, S = 5 N/mm
Therefore,traget strength =50+1.65*5=58.25N/mm^2
Step-4
Selection of water:
From Table 5 of IS 456, maximum water-cement ratio = 0.45.
Based on experience. adopt water-cement ratio as 0.4.
0.4 < 0.45, hence, O.K.
Step-5
Selection of water content:
From Table 2, maximum water content
for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
Estimated water content for 100 mm slump= 186+6/100 X 186 = 197 litre
As supcrplas ticizcr is used. the water content ca n he reduced up 30percent.
Based on trials with superpl ast icizer wate r content reduction of 2<) percent has been achieved. Hence, the
arrived water content = 197 x 0.71 = 140 litres.
Step-6
CALCULATION OF CEMENT CONTENT:
Water-cement ratio = 0.4
Cementitious material (cement + fly ash) content =140/0.4=350kg/m3
From Table 5 of IS 456, minimum cementcontent for 'severe' exposure conditions =320kg/m3
350 kg/m^3 > 320 kg/m^3 hence. O.K.
Step-7
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)
for water-cement ratio of 0.45 =0.60.
In the present case water-cement ratio is 0.45.
Therefore. volume of coarse aggregate is requ ired (0 be increasedto decrease the line aggregate content.
As the water-cement ratio is lower hy 0.10. the proportion of volume ofcoarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) ,
Therefore. corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.45 = 0.62
NOTE - In case the coarse aggregate is not angular one. then also volume: of coarse aggregate may he required to be increased
suitably. based on experience.
For pumpable concrete these values should be reduced by 10 percent.
Therefore. volume of coarse aggregate =0.62 x 0.9 =0.56.
Volume of fine aggregate content = I - 0.56 = 0.44.

Step-8

MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m3
b) Volume of cement =Mass of cement / Specific gravity ofcement *1 /1000
=350*3.15*1/1000

=0.111m3


c) Volume of water =Mass ofwater/specific gravity of water*1/1000
=140/1*1/1000

=0.140m3


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

(superplasticizer) @ 2.0% by mass=7/1.145*1/1000

of cementitious material) =0.006m3


e) Volume of all in aggregate = [a - (b + c + d )]

= 1-(0.111+ 0.140 + 0.006)

=0.743m3
f) Mass of coarse aggregate =f*volume of coarse aggregate *Specific gravity of coarseaggregate * 1000

=0.743*0.56*2.74*1000

= 1140kg/m3


g) Mass of fine aggregate =f x volume of fine aggregate x Specific gravity of fine aggregate*1000

= 0.728 x 0.44 x 2.74 x 1000

=896kg/m3

Step-9

MIX PROPORTIONS FOR TRIAL NUMBER 1:
Cement = 350 kg/m3
Water 140 kg/m3
Fine aggregate = 896 kg/m3
Coarse aggregate = 1140 kg/m3
Chemical admixture = 7kg/m3

Water cement ratio =0.4

The mix ratio is 1:2.56:3.25

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