Project on Concrete Mix Design for various grades of Concrete

M35 with fly ash

• TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

Fck = fck+1.65s “S” from Table1-IS10262

Fck = 35+1.65×5

Fck = 43.25 N/mm2

SELECTION OF WATER-CEMENT RATIO

Maximum W/C ratio =0.45 Table 5-IS456

Adopted W/C ratio =0.45

• SELECTION OF WATER CONTENT

Maximum Water Content =186 L Table 2-IS1026

The water content above is for a slump of 25 to 50 mm. Adopting slump of 100 mm, to get the desired slump, the water content must be increased. Clause 4.2 of IS1026 recommends increasing the water content by 3% to obtain an additional 25 mm slump. Therefore, to obtain a slump of 50 mm in addition to our concrete, the water content must be increased by 6%.

Water-content for 100mm Slump =186 + (0.06*186)

=197.16 L

Adopting super plasticizer,

Percentage of Reduction in water content =20%

Water content requirement after SP =198 – (0.20*198)

=157.73

Adopted Water Content =160 L

• CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio =0.45

Total Cementitious (Cement +Fly ash) requirement = Water Content / WaterCement ratio

=160/0.45

=355.55 kg

Here we have increased the cementitious content by 10%,

Final Cementitious

Content (Cement + Fly ash) = 356*1.10 =391.6 kg

Minimum Cement Content required for ‘severe’ exposure = 340kg Table 5-IS456

Adopted Cementious content =391.6 kg > 340kg

Fly ash content requirement = 391.6 * 0.30 30% replacement

= 117.48 ~ 118 kg

Cement Content requirement = Cementious content – Fly ash

=391.6-117.48

= 274.12

Calculation of Super Plasticisers @ 0.6 percent to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg

• COARSE AND FINE AGGREGATE

Coarse Aggregate ratio = 0.62 Table3-IS10262 (For W/C =0.5)

Coarse Aggregate ratio for 0.45 w/c ratio = 0.63 (adding 0.01 for every decrease .05 and vice versa)

Final Fine Aggregate ratio = 0.37 (1-0.63) = 0.37

• MIX CALCULATIONS OF M35 GRADE CONCRETE

1. Volume of Concrete = 1 cu.m
2. Total Volume of Cement = Cement/(S.G*1000)= 275/(3.15*1000)= 0.087 cu.m
3. Total Volume of Fly ash = Flyash/(S.G*1000)= 118/(2.5*1000) = 0.041 cu.mVolume of Water =Water /(S.G*1000) = 160/(1*1000) = 0.160 cu.m
4. Volume of Superplasticizers = Superplasticizers /(S.G*1000) = 2.35/(1.12*1000) = 0.002 cu.m
5. Total Aggregates requirement = A – (B+C+D+E) =1 -(0.087 +0.041+0.160+0.002) = 0.71 cu.m
6. Coarse Aggregate (C.A) = F * C.A ratio * S.G * 1000 = 0.71*0.63 *2.74 *1000 = 1225.6 kg
7. Fine Aggregate (F.A) = F * F.A ratio * S.G * 1000 = 0.71*0.37*2.74 *1000 =719.8 kg

MATERIALS QUANTITY

1. Cement= 275 kg
2. Flyash= 118 kg
3. Fine Aggregate= 720 kg
4. Coarse Aggregate (20mm)= 1226 kg
5. WATER= 160 L
6. SuperPlasticizer= 2 L

Mix Ratio of M35 Grade concrete is Cement : Flyash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58

M50 grade concrete without Fly ash

STEP 1: TARGET STRENGTH FOR MIX PROPORTIONING

f’ck =fck + 1.65s

Where

f’ck = target average compressive strength at 28 days

fck = characteristics compressive strength at 28 days, and

s = standard deviation

From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.

50 + 1.65 x 5 = 58.25 N/mm2

Target mean strength = 58.25 N/mm2

STEP 2: SELECTION OF WATER-CEMENT RATIO

The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000 for severe exposure.

Maximum W/C ratio =0.45

Based on experience adopted water cement ratio is .44

0.44<0.45, hence ok

Adopted W/C ratio=0.44

STEP 3: SELECTION OF WATER CONTENT

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate

186 litre (for 25 to 50 mm slump range)

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

Estimated water content for 100 mm slump

186+ (6/100)*186 = 197 litre.

(Note: If Super plasticizer is used, the water content can be reduced 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 X 0.8 = 158 litre

Water required 158 litres

STEP 4: CALCULATION OF CEMENT REQUIRED

Adopted w/c Ratio = 0.44

Cement Content= 158/0.44 = 359 kg/m3

From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions = 320kg/m3

359 kg/m3 > 320 kg/m3 hence ok.

Cement required is 359 kg/m3

STEP 5: VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 = 0.62

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 -/+ 0.01 for every ± 0.05 change in water-cement ratio).

Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 = 0.632

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

volume of coarse aggregate = 0.632 x 0.9 =0.568.

Volume of fine aggregate content = 1 – 0.576 =0.431

Volume of fine aggregate and coarse aggregate is 0.431 and .568 respectively

STEP 6: MIX CALCULATIONS

The mix calculations per unit volume of concrete shall be as follows:

1. Volume of concrete = 1 m3
2. Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000

= (359/3.15) X (1/1000) =0.114m3

1. Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000

= (158/1) X (1/1000) = 0.158m3

7. Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000 = (7.6/1.145) X (1/1000) =0.006 m3
8. Volume of all in aggregate = [a-(b+c+d)]

[1-(0.114+0.158+0.006)] = 0.722m3

1. Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000 0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
2. Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

0.722x 0.431x 2.64 x 1000 = 821 kg/m3

STEP 7: MIX PROPORTIONS

Cement = 359 kg/m3

Water = 158 l/m3

Fine aggregate = 821 kg/m3

Coarse aggregate 20mm = 1123 kg/m3

Chemical admixture = 7.18kg/m3

Water-cement ratio = 0.44

Mix Proportion by weight 1:2.28:3.12