Project on Concrete Mix Design for various grades of Concrete

Q1.Calculate the concrete mix design for M35 grade of concrete with fly ash &M50 grade concrete without fly ash.

Ans: Mix design for M35 grade of concrete with fly ash.

Aim: Mix design for M35 grade of concrete with fly ash.

Procedure:

Step1: stipulations for concrete design mix.

• Grade designation : M35.
• Type of cement : OPC 43 grade confirming to IS 8112.
• Type of mineral admixture: Fly ash confirming to IS 3812(Part 1).
• Maximum nominal size of aggregate: 20 mm.
• Minimum cement content: 320 kg/m^3(Table 5 of IS 456:2000-exposure condition).
• Workability : 100mm (slump value for pumpable concrete).
• Exposure condition: Severe(for reinforced concrete).
• Method of concrete placing: Pumping
• Degree of supervision: Good.
• Type of aggregate : Crushed angular aggregates.
• Maximum cement content: 450 kg/m^3.
• Chemical admixture type : Super plasticizer.

Step 2:Test data for materials.

• Cement used : OPC 43 grade conforming IS 8112.
• Specific gravity of cement: 3.15
• Fly ash : Confirming to IS 3812(part1).
• Cpecifi gravity of fly ash: 2.2.
• Chemical admixture: Super plasticizer confirming to IS 9103.
• Specific gravity of coarse aggregate: 2.74.
• Specific gravity of fine aggregate: 2.74.
• Water absorption of coarse aggregate: 0.5%.
• Water absorption of fine aggregate: 1.0%.
• Free surface moisture of coarse aggregate : Nill.
• Free surface moisture of fine aggregate : Nill.
• Sieve analysis coarse aggregate: Confirming to Table 2 IS 383.
• Sieve analysis fine aggregate: Confirmini to grading zone second of Table 4 of IS 383.

Step 3: Target strength for mix proportioning.

f'ck=fck+1.65s

Where,

• f'ck=Target compressive strength at 28 days.
• fck=Characteristics compressive strength at 28 days .
• s=Standard deviation(from table of IS 10262:2009,standard deviation,s=5n/mm^2.

f'ck=35+1.65*5

f'ck=43.25n/mm^2.

Step4:Selection of watr-cement ratio.

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

Based on experience,adopted water-cement ratio is 0.44

0.44<0.45,hence O.K

Adopted w/c ratio=0.44

Step 5: Selection of Water Content

From Table 2 of IS 10262:2009,maximum water content for 20 mmaggregate=186 litre(for 25 mm to 50mm slump range)

Clause 4.2 suggests increasing of 3% of water content for every extra 25 mm slump from 50 mm slump.so a 6% is to added to it .

Estimated water content foe 100mm slump=186+(6/100)*186

=197 litre.

As Super Palsticizer is used,the water content can bereduced up to 20% and above.

Based on trials with Super Plasticizer water content reduction of 20% has been achieved.

Hence,the arrived water content=197*0.8=158 litre.

=158 litre.

Water required 158 litre.

Step 6:Calculation of cement content and fly ash required.

Adopted w/c ratio=0.44

Cement Content=Water content/water -cement ratio.

=158/0.44=359 kg.

Total Cementitious (cement +fly ash)requirement.

The cementitious content has to be increased in order to attain good worakability andstrengt.the increment required is determined on the basis of experience and research , here we are increasing cementitious content by 10%.

Final cementitious content=359*1.10=395 kg.

From table 5 of IS 456,minimum cement content for severe exposure conditions =320kg.

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

New water -cement ratio=158/395 =0.4

Fly ash content is taken as 30% of the total cementitious content.

= 395*0.3 =118.5 kg/m^3

Cement required =395-118=277 kg/m^3

Cement quantity saved due =350-277=73kg/m^3

to fly ash additio.

cementitious material,cement and fly ash required is,395kg/m^3,277kg/m^3 and 118kg/m^3 the new water -cement ratio is 0.4 respectively.

Step 7:Volume of Coarse Aggregate and Fine Aggregate Content.

From table 3 of (IS 10262:2009)volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone second) for water-cement ratio of 0.50 is.

In the present case water -cement ratio is 0.44 .

Therefore ,volume of coarse aggregate is required to be increased to decrease the fine aggregate content.as the water-cement ratio is lower by 0.06.the proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of-/+0.001 for every+/- 0.05 change in water-cement ratio.)

Therefore,corrected proportion of volume of coasre aggregate =0.632

For the water -cement ratio of 0.44

For pumpable concrete thses values are reduced by 10%.

Therefore,volume of coarse aggregate =0.632*0.9=0.568

Volume of fine aggregate content =1-568 =0.431

Volume of fine aggregate and coarse aggregate is 0.431 and 0.568 .

Step 8: Mix Calculations.

The mix calculation as 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)]*1/1000

=[277/3.15]*1/1000

= 0.087m^3

c)Volume of Fly ash =[Mass of Fly ash/specific gravity of fly ash]*1/1000

=[118/2.2]*1/1000

=0.053 m^3

d)Volume of Water =[Mass of Water/Specific Gravity of Water]*1/1000

=[158/1]*1/1000

=0.158 m^3

e)Volume of Chemical admixture =[Mass of Admixture/Specific gravity of admixture]1/1000

=[7.6/1.145]*1/1000

=0.006m^3

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

=[1-(0.087+0.053+0.158+0.006)]

=0.696 m^3

g)Mass of coarse aggregate =Volume of all * Volume of *Specific gravity *1000

aggregate coarse coarse

aggregate aggregate

=0.696*0.568*2.74*1000

=1077kg/m^3

h)Mass of fine aggregate =Volume of all * Volume of * Specific gravity *1000

aggregate fine aggregate fine aggregate

=0.696*0.431*2.74*1000

=822kg/m^3

Step 9: Mix Proportions.

Cement =277kg/m^3

Fly ash =118 kg/m^3

Water =158 kg/m^3=158l/m^3

Fine Aggregate =822kg/m^3

Coarse Aggregate =1077kg/m^3

Chemical Admixture =7.18 kg/m^3

Water -Cement Ratio =0.4

(lowest w/c ratio is selected)

Mix Proportion by =1:2.08:2.72

Step10:

The slump shall be measured,the water content and dosage of admixture shall be adjusted fo achivieving the required slump on trial the mix proportion shall be reworked for the actual water content and checked for durability requirements.

Step11:

Two more trials having variation of 10% of water-cement ratio shall be carried out anda graph between three water-cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target for field trials.

Q2.To calculate the concrete mix design for M50 grade concrete without fly ash.

Ans:

Aim: M50 grade concrete without fly ash.

Procedure:

Step1: Stipulations for Concrete Design Mix.

Grade Designation = M50

Type of Cement =OPC 53 grade confirminig to IS BIS 12269-1987

Maximum nominal size of =20mm

aggregate.

Minimum cement content =320 kg/m^3(table 5 of IS 456:2000-exposure conditio)

Maximum water cement ratio =0.45(table 5 of IS 456:2000 exposure condition)

Workability =100mm(slump value for pumpable concrete)

Exposure condition =severe (for reinforced concrete)

Method of concrete placing =pumping

Degree of supervision =good

Type of aggregate = crushed angular aggregates

Maximum cement content =450kg/m^3

Chemical admixture type =super plasticizer.

Step2: Test Data for Materials.

Cement used = OPC 53 grade conforming IS 12269-1987

Specific gravity of cement =3.15

Chemical admixture =super plasticizer conforming to IS 9103.

Specific gravity of coarse aggregate =2.74

Specific gravity of fine aggregate =2.64

Water absorption of coarse aggregate =0.5%

Water absorption of fine aggregate =1.0%

Free surface moisture of coarse =Nill

aggregate.

Free surface moisture of fine aggregate =Nill

Sieve analysis coarse aggregate =Conforming to table 2 of IS 383

Sieve analysis fine aggregate =Conforming to grading zone second of table 4 of IS383

Step 3:Target strength for mix proportioning.

f'ck=fck+1.65s

Where,

f'ck=target average compressive strength at 28 day

fck=characteristic compressive strength at 28 days ,

s = standard deviation (from table 10262:2009,standard deviation,s=5 N/mm^2)

f'ck =50+1.65*5

f'ck =58.25 N/mm^2

Step 4: Selection of Water -Cement Ratio.

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

Based on experience,adopted water-cement ratio is 0.44

0.44 < 0.45, hence ok

Adopted w/c ratio=0.44

Step5: Selection of Water Content.

From table 2 of IS 10262:2009,maximum water content for 20 mm aggregate=186 litre.

(for 25mm to 50mm slump range )

Clause 4.2 suggests incresing of 3%of water content for extra 25mm slump from 50mm slumps.so a 6% is to be added to it.

Estimated water content for 100mm slump =186+(6/100)*186

=197 litre.

Based on super plasticizer water content reduction of 20% has been achieved,

Hence the arrived water content =197*0.8=158 litre.

Water required =158 litre.

Step6:Calculation of Cement required.

Adopted water /cement ratio =0.44

Cement content =water/water-cement ratio

=158/0.44=359 kg/m^3.

From table 5 of IS 456-2000,maximum cement content for 'severe'exposure conditions.

=320kg/m^3.

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

Cement required is 359kg/m^3.

Step 7: Volume of coarse aggregate & fine aggregate content.

From tble 3 of( IS 10262:2009) volume of coarse aggregate to 20 mm size aggregate and fine aggregate (zone second).

For water-cement ratio of 0.50 is.

In the present case water-cement ratio is 0.44.

Therefore,volume of coarse aggregate is required to be increased to decrease the fine aggregate content as water cement ratio is lower by 0.06.

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 proportion of coarse aggregate =0.632.

For the water-cement ratio =0.44.

For Pumpable concrete thses values should reduced up to 10%.

Volume of coarse aggregate =0.632*0.9=0.568

Volume of fine aggregate =1-0.576 =0.431

Volume of fine aggregate and coarse aggregate is 0.431 &0.568 respectively.

Step 8: Mix Calculations.

The Mix calculations per unit volume of concrete shall be as followes,

a) Volume of Concrete =1m^3

b)Volume of Cement =[Mass of cement/specific gravity of cement]*1/1000

=[359/3.15]*1/1000

=0.114m^3

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

=[158/1]*1/1000

=0.158m^3

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

admixture

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

=[1-(0.114+0.158+0.006)]

=0.722m^3

f)Mass of coarse aggregate =Volume of all *Volume of*Specific gravity*1000

in aggregate coarse coarse

aggregate aggregate

=0.722*0.568*2.74*1000

=1123kg/m^3

g)Mass of fine aggregate =Volume of all in*Volume of *Specific gravity*1000

aggregate fine fine aggrgate

aggregate

=0.722*0.431*2.64*1000

=821kg/m^3

Step 9: Mix Proportions

Cement = 359 kg/m^3

Water =158 litre

Fine aggregate =831 kg/m^3

Coarse aggregate =1123 kg/m^3

Chemical admixture =7.18 kg/m^3

Water-cement ratio =0.44

Mix Proportion by Weight =1:2.28:3.12

Step 10:

The slump shall be measured,the water content and dosage of admixture shall be adjusted for achieving the required slump on trial the mix proportion shall be reworked for the actual water content and checked for durability requirements.

Step11:

Two more trials having variation of 10% of water-cement ratio shall be carried out and a graph between three water-cement ratios and corresponding strength shall be plotted to work out the mix proportion for the given target for field trials.