Project on Concrete Mix Design for various grades of Concrete

A) CALCULATION OF CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLYASH :

Step:1 Stipulations :

a) Grade designation M35.

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

c) Type of mineral admixture : Flyash conforming to IS 3812 (PA

d) Maximum nominal size of aggegates : 20mm

e) Minimum cement content : 320kg/m^3(from table 5 of IS 456:2000- expoure condition)

f) Minimum water/cement ratio=0.45(from table 5 of IS 456:2000- expoure condition)

g) Workability : 100mm(slump value of pumpable concrete )

h) Exposure condition : severe (for rienforced concrete).

i) Method of concrete placing : pumping.

j) Degree of supervision : good

k) Type of aggregate : crushed angular aggregates

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

m) Chemical admixtures type : super plasticizers.

Step 2: Test data for meterials

a) Cement used OPC 43 grade conforming to IS 8112

b) Specific gravity of cement : 3.15

c) Flyash : Conforming to IS 3812 ( part 1 )

d) Specific gravity of flyash : 2.2

e) Chemical admixtures : super plasticisers conforming to IS 9103

f) Specific gravity of

coarse aggregate : 2.74

fine aggregate :2.74

g) Water absorption

coarse aggregate : 0.5%

fine aggregate : 1.0%

f) Free surface moisture

coarse aggregate : nill

fine aggregate : nill

g) sieve analysis

coarse aggregate=conforming to table 2 of IS 383

fine aggregate=conforming to grading zone I of table 4 of IS 383.

Step 3: Target strength for mix proportioning

f'ck=fck+1.65s

where f'ck=target average compressed strength at 28 days.

fck=characterstics compressed strength at 28 days.

s= standard deviation.

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

Therefore, target strength = 35+(1.65*5) =43.25N/mm^2

Step 4: Selection of water/cement ratio

from table 5 of IS :456-2000 for severe exposure , maximum water/cement ratio=0.44

(based on experience, adopt water/cemnt ratio as 0.40)

0.40<0.45, Hence O.K

Step 5: Selection of water content

from table 2 of IS:10262-2009, maximum water content for 20mm aggregates = 186literes( for 25-50mm slump range)

estimated water content for 100mm slump=186+6/100*186=197lit.

As super plasticizer is used, the water content can be reduced upto 30% based on trails water content reduction of 29% is achieved with plasticizer.

Hence the arrived water content=197"*0.71=140lit.

Step 6: Calulation of cement content

water/cement ratio=0.4

cementitious material (cement +flyash ) content = 140/0.4=350kg/m^3

from table 5 of IS:456 minimum cement content for severe exposure condition=320kg/m^3 amd maximum cement content for severe exposure condition=450kg/m^3

320kg/m^3<350kg/m^3<450kg/m^3 , Hemce o.k

Now, proportion a mix containing flyash the following stes are suggested :

a)The percentage of flyash needs to be decided based on project equirement and quqlity of materials

b)In some cases increase in cementitious materialcan be warranted. Increase in cementitious materialcontent and its percentage may be based on experience and trail ( this example is with increase of 10% cementitious materal content).

Cementitious material content =350*1.10=385 kg/m^3

Water content = 140 kg/m^3

So, Water-cement ratio = 140/385 = 0.365

Flyash @30% total cementitious material content = 385 *30% = 115kg/m^3

Cement (OPC) = 385-115 = 270kg/m^3

Saving of cement while using of flyash = 350-270 = 80kg/m^3 ad

Flyash being utilized = 115kg/m^3

Step 7: proportion of volume of coarse aggregate and fine aggregate content:

From table 3 of IS:10262-2009, volume of coarse aggregate corresponding to 20mm size aggregates amd fine aggregate (zone 1) fpr water/cement ratiof 0.5=0.6

In present 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 water/cement ratio)

Therefore, corrected volume of coarse aggregate for the water/cement ration 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 increased suitably , based on experience)

For pumpable concrete tthese values are reduced by 10%

Therefore volume of coarse aggregate=0.62*0.9=0.56

volume of fine aggregate content=1-0.56=0.44

Step 8: Mix calculations

The mix calculations 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.

270/3.15*1/1000=0.086m^3

c)Volume of flyash = mass of flyash/speciic gravity of flyash * 1/1000

115/2.2*1/1000=0.052m^3

d)Volume of water= mass of water/specific gravity of water*1/1000'

140/1*1/1000=0.140m^3

e)Volume of chemical admixtures=mass of chemical admixtures / specific gravity of admixtures*1/1000

where mass of chemical admixtures=2%(cementious meterial)=(350*2/100)=7

= 7/1.145*1/1000=0.006m^3

f) Volume of aggregates(FA and CA)=(a-(b+c+d))=(1-0.086+0.052+0.140+0.006))=0.716m^3

g) Mass of coarse aggregate = volume of total aggregates* volume of coarse aggregate* specific gravity of coarse aggregate*1000

=0.716*0.56*2.74*1000 = 1098kg/m^3

g) mass of fine aggregate=volume of total aggregate*volume of fine aggregate*specific gravity of fine aggregare*1000

=0.743*0.44*2.74*1000=863kg/m^3

Step 9: Mix proportion for trail no. 1

• cement =270kg/m^3
• Flyash=115kg/m^3
• water=140kg/m^3
• fine aggregate=863kg/m^3
• coarse aggregate=1098kg/m^3
• chemical admitures=7kg/m^3
• water/cement ratio=0.364

Trial mix ratio=1:2.24:2.85

Step 10: The slump shall be measured the water content and dosage of admixtures 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 requirement.

Step 11: Two or more trials having 10% of water/cement ratio in clause 10 shall be carried out and a graph between 3 water/cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target strength for field trials.Howeever, durability shall be must.

B) CALCULATION OF CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE :

Step 1: Stipulations for proportioning

a) Grade designation M50.

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

c) Maximum nominal size of aggegates 20mm

d) Minimum cement content 320kg/m^3(from table 5 of IS 456:2000-expoure condition)

e) Minimum water/cement ratio=0.45(from table 5 of IS 456:2000-expoure condition)

f) Workability 100mm(slump value of pumpable concrete )

g) Exposure condition-severe(for rienforced concrete)

h) Method of concrete placing=pumping.

i) Degree of supr vision=good

j) Type of aggregate= crushed angular aggregates

k) Maximum cement content. 450kg/m^3

l) Chemical admixtures type = super plasticizers.

Step 2:Test data for meterials

a) cement used OPC43 grade conforming to IS 8112

b) specific gravity of cement =3.15

c) chemical admixtures=super plasticisers conforming to IS 9103

d) specific gravity of

coarse aggregate=2.74

fine aggregate=2074

e) water absorption

coarse aggregate=0.5%

fine aggregate=1.0%

f) free surface moisture

coarse aggregate=nill

fine aggregate=nill

g) sieve analysis

coarse aggregate=conforming to table 2 of IS 383

fine aggregate=conforming to grading zone I of table 4 of IS 383.

Step 3: Target strength for mix proportioning

f'ck=fck+1.65s

where f'ck=target average compressed strength at 28 days.

fck=characterstics compressed strength at 28 days.

s= standard deviation.

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

Therefore, target strength = 50+(1.65*5) =58.25N/mm^2

Step 4: Selection of water/cement ratio

from table 5 of IS :456-2000 for severe exposure , maximum water/cement ratio=0.44

(based on experience, adopt water/cemnt ratio as 0.40)

0.40<0.45, Hence O.K

Step 5: Selection of water content

from table 2 of IS:10262-2009, maximum water content for 20mm aggregates = 186literes( for 25-50mm slump range)

estimated water content for 100mm slump=186+6/100*186=197lit.

As super plasticizer is used, the water content can be reduced upto 20% and above based on trails .water content reduction of 29% is acjieved with plasticizer.

Hence the arrived water content=197"*0.71=140lit.

Step 6: Calulation of cement content

water/cement ratio=0.4

cement content=140/0.4=350kg/m^3

from table 5 of IS:456 minimum cement content for severe exposure condition=320kg/m^3 amd maximum cement content for severe exposure condition=450kg/m^3

320kg/m^3<350kg/m^3<450kg/m^3 , Hemce o.k

Step 7: proportion of volume of coarse aggregate and fine aggregate content:

feo table 3 of IS:10262-2009, volume of coarse aggregate corresponding to 20mm size aggregates amd fine aggregate (zone 1) fpr water/cement ratio=0.6

in present 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 lowerr 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 ration 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 increased suitably , based on experience)

for pumpable concrete tthese values are reduced by 10%

Therefore volume of coarse aggregate=0.62*0.9=0.56

volume of fine aggregate content=1-0.56=0.44

Step 8: Mix calculations

The mix calculations 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.

350/3.15*1/1000=0.111m^3

c) volume of water= mass of water/specific gravity of water*1/1000'

140/1*1/1000=0.140m^3

d)volume of chemical admixtures=mass of chemical admixtures / specific gravity of admixtures*1/1000

where mass of chemical admixtures=2%(cementious meterial)=(350*2/100)=7

= 7/1.145*1/1000=0.006m^3

e) volume of aggregates(FA and CA)=(a-(b+c+d))=(1-0.111+0.140+0.006))+0.743m^3

f) mass of coarse aggregate=volume of total aggregates* volume of coarse aggregate* specific gravity of coarse aggregate*1000 =0.743*0.56*2.74*1000 = 1140kg/m^3

g) mass of fine aggregate=volume of total aggregate*volume of fine aggregate*specific gravity of fine aggregare*1000

=0.743*0.44*2.74*1000=896kg/m^3

Step 9: Mix proportion for trail no. 1

• cement =350kg/m^3
• water=140kg/m^3
• fine aggregate=896kg/m^3
• coarse aggregate=1140kg/m^3
• chemical admitures=7kg/m^3
• water/cement ratio=0.4

Trial mix ratio=1:2.56:3.26

Step 10: The slump shall be measured the water content and dosage of admixtures 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 requirement.

Step 11: Two or more trials having 10% of water/cement ratio in clause 10 shall be carried out and a graph between 3 water/cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target strength for field trials.Howeever, durability shall be must.