Project on Concrete Mix Design for various grades of Concrete

1. The strength of concrete may vary depending on the quality of materials the mixing method and the construction procedure

There fore the target strength (Fck) must be greater than the required strength of the concrete

Fck=fck+1.65s

=35+1.65×5

=44.25 N /mm2

Table of IS 456 gives the standard deviation value

(S) for different grade concrete

Selection of water cement ratio:-

The maximum water cement ratio for different grade of concrete are given in table 5 IS 457

The water content ratio directly affects the strength of concrete

Maximum water cement ratio =0.45

Adapted water cement ratio @=0.45

Selection of water content =186litre

The water content above is for a slump of 25mm 50mm but according the specifications our concrete requires slump of 100mm there fore to get the desired slump. The water content must be increased IS 1026 recommonds increasing the water content by 3%to obtain additional 25mm slump ther fore to obtain an additional 25mm slump there for to obtain a slump of 50mm in addition to our concrete the water content must be increased by 6%.

Water content for 100mm slump =186+(0.06×186)

. =197.17l

So we use the superplastizer we can reduce the water content to gain the strength

% of reduction of water content = 20%

Water content requirement after superplastizer = = 198- (0.02x198)

Adapted water content = 157.73=160L

Calculation of cement and fly ash content

Adopted water cement ratio = 0.45

Total cementious

(Cement +fly ash) requirements =water content/ water cement ratio

= 160/0.45

=355.55kg

The % of increasing cementious content depend on experience and research here we have increased the cementious content by 10%

Final cementious content = 356×1.10

=391.6 kg

Minimum cement content

Require for severe exposure = 340kg Z( table 5 Is 456)

Fly ash content requirement =391.6×0.030

=117.48=118@kg

Cement content required =cementious content _ flyash

= 391.6-117.48

=274.12 kg

Course and fine aggregate

From table 3of IS 1026 :2009 volume of course aggregate corresponding to 20mm size aggregate and fine aggregate (zone1) for water cement ratio =0.6 in present case the water cement ratio is 0.4 there for the volume of course aggregate content

As the water cement ratio is lowered by 0.10 .The proportions of volume of course aggregate is increased by 0.02 at the rate of ×/-0.01 for every +/- 0.05 change in water hence the corrected value of course aggregate of the water @- cement ratio=0.64

For pumpable concrete these are reduced by10%

Volume of course aggregate =0.64×0.9=0.576

Volume of fine aggregate = 1-0.576=0.424

Mix calculation

Mix calculation per unit volume of concrete

A.volume of concrete = 1m3

B.volume of cement = mass of cement/specific gravity cement ×1/100

270/3.15× 1/ 1000= 0.086 m3

Volume of fly ash = mass of fly ash / s.g of fly ash× 1/100

118/2.2÷1/1000=0.052m3

Volume of water = mass of water/ s.g of water ÷ 1/100

160/2×1/1000=0.160

Volume of chemical admixture=mass of admixture ÷1/1000

7.6/1.14×1/100=0.006

Volume of course aggregate a-(b+c+d+e)

1-(0.086+0.052+0.140+0.006)=0.716m3

Mass of course aggregate =volume of course aggregate ×specific gravity c.a×1000

0.716×0.576×2.74×1000=1130kg/m3

Mass of fine aggregate = 0.716×0.424×2.84×1000

=831kg/m3

Cement =270kg/m2

Fly ash =118kg/m2

Fine aggregate =831@@kg/m2

Course aggregate =1140kg/m2

M50 grade concrete without fly ash :-

Target mean strength =f'ck=fck+ 1.65s

50+1.65×5= 58.25N/m3

Selection of water cement ratio

From table 5 of IS 456-2000 by exposure conditions

Here .maximum water/c ratio = 0.45

Based on experience water cement ratio =0.4

0.4<0.45

Hence ok

Selection of water cement ratio

From table of IS 2009 by 1026 of 25 mm to 50mm slump range

For 100m slump 186+6/100×186=197litr

As super plasticizers is used the water content reduction of 29% is achieved with plastisizierhen

Hence arrived water content =197×0.71=148liter

Calculation of cement content

Water cement ratio = 0.40

Cement content 140/0.40=350@kg / m3

From table for severe ecposure 320kg /m3

Mix calculation

Volume of concrete =1m3

Volume of cement =373/3.15×1/1000=0.118m3

Volume of water= 14.9/1×1/100=0.149

volume of admixtures = 7.6/1.145×1/1000=0.006

Volume of course fine aggregate=0.727m3

Mass of course aggregate 0.727x0.62x2.74x1000=1235.02 kg / m3

Mass of fine aggregate =0.727×0.38×2.74×1000

756.9kg /m3