Project on Concrete Mix Design for various grades of Concrete

THE CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH & M50 GRADE CONCRETE WITHOUT FLY ASH.

First we calculate the M35 concrete mix design with neatly explain step by step.

Concrete mix design for M35 without fly ash.

1. Grade of concrete = M35.

2. Characteristic compressive strength required in field at 28 days = 35mpa.

3.Types of exposures = Moderate.

4. Design mix target slump or workability = 150-175mm.

5. Maximum size of coarse aggregates = 20mm.

6.Maximum size of fine aggregates = Zone3.

7. Specific gravity of cement = 2.93.

8. Specific gravity of water = 1.

9. Specific gravity of admixtures = 1.121.

10. Specific gravity of coarse aggregates = 2.82.

11. Specific gravity of fine aggregates = 2.65.

{12. Water absorption of coarse aggregates = 0.86%.

13. Water absorption of fine aggregates = 1.25%.}these two are Super satuarated dry condition or saturated sulphate dry condition.

Step.1: TARGET MEAN STRENGTH OF CONCRETE.

formula: fck = fck + 1.65 X S.

Where fck = target mean compressive strength at 28 days in N/mm^2.

fck = characteristic compressive strength at 28 days in N/mma^2 = 35N/mm^2.

S = standard deviation = 5N/mm^2.

1.65 = tolerance factor. (the code is IS 456-2000).

Therefore, fck+1.65 X S

=35+1.65 X 5

=43.25N/mm^2.

Step-2: DETERMINATION OF WATER-CEMENT RATIO :

1.As per table 5 of IS 456-2000 is a moderate state.

2. The maximum cement ratio is 0.5.

3.Based on experience adopt water-cement ratio = 0.5-0.05 = 0.45

the water cement ratio is 0.45.

Step-3: DETERMINATION OF WATER CONTENT:

1.Now the target slump is 150-175mm.

2.Maximum water content for 20mm coarse aggregates = 186litres(this value is for 25 to 50mm slump range).

3.Estimated water content for 175mm slump = 186+15/100 X 186 =213.9litres.

note: as admixture is used the water content can be reduced by 15% and above. The actual water content to be used = 213.9-(15/100*213.9) = 181.82litres.

Therefore, the water content = 181.82litres.

Since, 25-30mm aggregates the slump values = 175mm=3%, 150mm=3%, 125mm=3%, 100mm=3%, 75mm=3% these are all percentages add to get the admixture water content is 15%.

Step-4: CALCULATION OF CEMENT CONTENT:

As per table 5 of IS 456-2000, for moderate exposure minimum.

Minimum cement = 300kg/m^3.

water cement ratio = 0.45.

water used = 181.82 litres.

Therefore, cement content = Water content/water cement ratio=181.82/0.45= 404kg/m^3 (this is the greater than the 300kg/m^3)hence it is ok.

Therefore, The cement content = 404kg/m^3.

Step-5: CALCULATION OF VOLUME OF COARSE & FINE AGGREGATES:

Volume of coarse aggregates corressponding to 20mm size and fine aggregates is zone3 for water cement ratio of 0.5 = 0.64 (IS 10262-2009).

Now,

Actual cement ratio = 0.45, it is led by 0.5-0.45=0.05.

The coarse aggregates is increased at the rate of 0.01 for every decrease in water cement ratio of 0.05.

so,for decrease of every 0.05 water cement ratio = Coarse aggregates led by 0.01.

so, for decrease of every 0.05 water cement ratio = Coarse aggreagates led by = 0.01/0.05.

so,for decrease of every 0.05 water cement ratio = coarse aggreagates led by = 0.01/0.05 X 0.05 = 0.01.

for decrease of every 0.05 water cement ratio = 0.01.

corrected proportional of volume of Coarse aggregates = o.64+0.01 = 0.65.
Since,it is an angular aggreagates and concrete is to be pumped the coarse aggreagates can be reduced by 10%.

Therefore, By reducing 10% we get = 0.65-10/1000.65 = 0.585.

Volume of coarse aggreagates = 0.585.

Volume of fine aggreagates = 1-0.585 = 0.415.

Step-6: DESIGN MIX CALCULATION:

a) Volume of concrete = 1m^3.

b) Volume of cement = mass of cement/specific gravity of cement X 1000

=404/2.93*1000 = 0.138m^3.

Volume of cement = 0.138m^3.

c) Volume of water = mass of water/specific gravity of water X 1000.

=181.82/1*1000 = 0.182M^3.

Volume of water = 0.182m^3.

d) Volume of admixtures = mass of admixtures/specific gravity of admixtures X 1000.

= assuming dosage of 1.2% by weight of cement materials = 1.2/100 X 404 = 4.840m^3.

mass of admixtures = 4.840m^3.

Therefore, 4.840/1.121 X 1000 = 0.004m^3.

Volume of admixtures = 0.004m^3.

e) Volume of entrapped air = 2% for 20mm Coarse aggreagates.

= 2/100 0.02m^3(2% is as IS 10262-2009).

f)Volume of all aggreagates (coarse + fine)

Volume of all agggreagates = (volume of cement + volume of water + volume of admixtures + volume of entrapped air =

1-(0.138+0.182+0.004+0.02)0.656m^3.

volume of all aggreagates = 0.656m^3.

g) Mass of Coarse aggreagates = Volume of all aggreagates X volume of proportion of coarse aggreagates X specific gravity of coarse aggreagates X 1000 = 0.656 X 0.585 X 2.82 X 1000 = 1082.2kg/m^3.

Mass of coarse aggreagates = 1082.2kg/m^3.

h) Mass of fine aggreagates = volume of all aggreagates X volume of fine aggreagates proportion X specific gravity of fine aggreagates X 1000.

= 0.656X0.415X2.65X1000 = 721.4kg/m^3.

Mass of fine aggreagates = 721.4kg/m^3.

Therefore,

cement = 404kg/m^3.

Coarse aggreagates = 1082.2kg/m^3.

Fine aggreagates = 721.4kg/m^3.

Water = 181.82kg/m^3.

Admixtures = 4.848 or 4.840 .

Water cement ratio = 0.45.

These is the M35 grade of concrete mix design .

Now,

WE DESIGN AND CALCULATE THE M50 GRADE OF CONCRETE MIX DESIGN AS PER IS CODE.

Step-1: STIPULATIONS FOR CONCRETE MIX DESIGN:

Grade Designation = M50.

Type of cement = OPC 53 grade of concrete.

Maximum Nominal Size of aggregates = 20mm.

Maximum Nominal Size of fine aggregates = Zone3.

Minimum Cement Content = 320kg/m^3.(as per IS 456-2000).

Maximum Water Cement Ratio = 0.45.

Workability = 100mm.(slump value for pumpable concrete).

Exposure condition = Severe(for reinforced concrete).

Method of concrete placing = Pumping.

Degree of supervision = Good.

Types of aggregates = Crushed angular aggregates.

Maximum Cement Content = 450kg/m^3.

Chemical Admixture type = Super Plasticizer.

Step-2: TEST DATA FOR MATERIALS:

Specific gravity of cement = 3.15.

Specific gravity of water = 1.

Specific gravity of Coarse aggregates = 2.74.

Specific gravity of Fine aggregates = 2.64.

Water absorption of Coarse aggregates = 0.5%

Water absorption of fine aggregates = 1%.

Moisture condition of Coarse aggregates = nil.

Moisture condition of fine aggregates = nil.

Step-3: TARGET STRENGTH FOR MIX PROPORTIONING:

fck = fck + 1.65 X S

= 59+1.65 X 5 = 58.25N/mm^2.

Where fck = target average compressive strength at 28 days .

fck = Characteristics compressive strength at 28 days.

S= Standard deviation = 5N/mm^2.

Therefore, The target strength for mix proportion = 58.25N/mm^2.

Step-4: SELECTION OF WATER CEMENT RATIO:

The maximum water cement ratio = 0.45.(as per IS 456-2000).

Based on experience adopted water cement ratio = 0.44.

0.44<0.45.

Adopted water cement ratio = 0.44.

Step-5: SELECTION OF WATER CONTENT:

The maximum water content for 20mm aggregates = 180litres(for 25-50mm slump range).

Increasing of 3% of water content for every extra 25mm slump from 50mm slump.

So, as 6% is to be added to it.

Estimated water content for 100mm slump.

Therefore, 186+6/100 X 186 = 197litres.

(Note: If super plasticizer is used the water content can be reduced up to 20%) .

Since, 197 X 0.8 = 158litres.

Hence, The water content or water required is 158litres.

Adopted water cement ratio = 0.44.

Cement content = Water content/Water cement ratio = 158/0.44 = 359kg/m^3.

Minimum cement content for severe = 320kg/m^3.

therefore, 359kg/m^3>320kg/m^3.

Minimum cement content = 359khg/m^3.

Step-6: VOLUME OF ALL AGGREGATES (C.A.+F.A.).

Volume of coarse aggregates corressponding to 20mm size of aggregates.

Volume of fine aggregates = Zone2.

Water cement ratio = 0.5.

The water cement ratio is less by 0.06.

The proportion volume coarse aggregates is increased by 0.02.

Change in water cement ratio = 0.5.

Corrected proportion of volume of coarse = 0.632.

the water cement ratio = 0.44.

For pumpable concrete these values should be reduced up to 10%.

Volume of coarse aggregates = 0.638 X 0.9 = 0.568.

Volume of Fine aggregates = 1-0.568 = 0.432.

Volume of all aggregates (C.A.+F.A.) = 0.568, 0.432.

Step-7: MIX CALCULATIONS FOR M50 GRADE OF CONCRETE:

The mix calculations per unit volume of concrete.

A)Volume of concrete 1m^3.

b)volume of cement = mass of cement/specific gravity of cement X 1000 = 354/3.15 X 1000 = 0.114.

c) Volume of water = mass of water/specific gravity of water = 158/1X1000 = 0.158m^3.

d) Volume of chemical admixture = mass of admixture/specific gravity of admixture X 1000 = 7.6/1.145X1000 = 0.006m^3.

e)Volume of all aggregates = (a-(b+c+d) = (1-(0.114+0.158+0.006) = 0.722m^3.

f)Mass of coarse aggregates = e X Volume of Coarse aggregates X Specific gravity of Coarse aggregates X 1000 = 0.722 X 0.568 X 2.74 X 1000 = 1123kg/m^3.

g)Mass of fine aggregates = e X Volume of fine aggregates X Specific gravity of Fine Aggregates X 1000 = 0.722 X 0.432 X 2.64 X 1000 = 823kg/m^3.

Step-8: MIX PROPORTIONS OF M50 GRADE OF CONCRETE:

Cement = 359kg/m^3.

water = 158litres/m^3.

Fine aggregates = 823kg/m^3.

Coarse aggregates = 1123kg/m^3.

Chemical admixture = 7.18kg/m^3.

Water cement ratio=0.44.

mix proportion by weight = 1:2.28:3.12.T

THESE IS THE CONCRETE MIX DESIGN FOR M35 GRADE OF CONCRETE WITH FLY ASH AND M50 GRADE OF CONCRETE WITHOUT FLY ASH FOR NEATLY EXPLAIN IN STEP BY STEP