Project on Concrete Mix Design for various grades of Concrete

Aim: To develop the Concrete Mix Design for M35 grade concrete with fly ash and M50 grade concrete without fly ash.

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Introduction:

Concrete Mixing is the mixing of the concrete ingredients of utmost importance in order to produce good quality fresh concrete. A well-mixed concrete of desired workability and performance in both fresh and hardened states is required and the color after the mixing should be uniform.

Here, we'll be dealing with the concrete mix design for M35 grade concrete with fly ash, and in the second part, we'll be performing the same procedure for M50 grade concrete but without fly ash.

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Formulae to be kept in mind:

1. Cement content = water content / (w/c ratio)
2. Volume of cement = (Mass of cement) / (Specific Gravity of cement) * 1/1000
3. Volume of water = (Mass of water) / (Specific Gravity of water) * 1/1000
4. Volume of chemical admixture = (Mass of admixture) / (Specific Gravity of admixture) * 1/1000
5. Target mean strength, f'ck = fck + 1.65*s

Here, f'ck = targetted avg. compressive strength (28 days) ;

fck = characteristic compressive strength (28 days) ;

s = standard deviation ;

     6. Aggregate volume = [a-(b+c+d)]

     7. Mass of coarse aggregate = e * Volume of coarse aggregate * Specific gravity of fine aggregate * 1000

     8. Mass of fine aggregate = e * Volume of fine aggregate * Specific gravity of fine aggregate * 1000 

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- To develop the Concrete Mix Design for M35 grade concrete with fly ash

• Grading Information:

Grade type                                                : M35                                

Cement type                                             : OPC M43 Grade

Mineral admixture type                            : Fly Ash

Aggregate nominal size                           : 20mm

Aggregate type                                        : Crushed Angular Aggregate

Condition                                                 : Severe

Max. w/c ratio                                          : 0.45

Workability                                               : 100mm 

Max. cement content                               : 450 kg/m³

Min. cement content                                : 320 kg/m³

Chemical Admixture type                         : Superplasticizer

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• Materials test data:

Specific Gravity of Cement                     : 3.15

Specific Gravity of Fly ash                       : 2.2

Specific Gravity of coarse aggregate      : 2.74

Specific Gravity of fine aggregate          : 2.64

Water absorption (Coarse aggregate)    : 0.5%

Water absorption (Fine aggregate)        : 0.5%

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• Targetted strength of mix proportion:

f'ck = fck + 1.65*s

Here, s = 5 N/mm² (refer Table I in IS 10262:2009)

f'ck = 35 + 1.65*5

= 35 + 8.25

= 43.25 N/mm²

So, Targetted mean strength of mix proportion = 43.25 N/mm²

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• Water-Cement ratio selection:

As per IS 456:2000, the maximum w/c ratio = 0.45 (M50)

here, adopted w/c ratio = 0.44 

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• Water content required: (Refer IS 10262:2009)

From Table2, max. Water content for 20mm aggregate = 186 litre

Addition of 6% water = 186 + [(6/100)*186] = 197 litre

20% has been achieved, so

197*0.8 = 158 litre

So, Water content required = 158 litres

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• Cement calculation and required fly ash:

here, w/c ratio = 0.44

Total cement (cement + fly ash) = 158/0.44 = 359 kg/m³

Final cement content = 359 * 1.10 = 395 kg

From Table5, Min. cement content in severe condition = 320 kg

Since 320kg < 395kg>

New w/c ratio = 158/395 = 0.4

Fly Ash taken is 30% of total cement content = 395*0.3 = 118.5 kg/m³

Cement required = 395 - 118 = 277 kg/m³

Therefore, cement required in addition to fly ash = 350 - 277 = 73 kg/m³

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• Volume of coarse and fine aggregate content: (Refer IS 10262:2009)

From Table3, the volume of coarse aggregate corresponds to 20mm size for w/c ratio 0.44 

= 0.632

Since, pumpable concrete so 10% reduction, so

= 0.632 * 0.9 = 0.568

Volume of fine aggregate = 1 - 0.568 = 0.431

Therefore, the volume of coarse aggregate is 0.568, and the volume of fine aggregate is 0.431

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• Mix calculations:

Volume of concrete = 1m³

Volume of cement = (277/3.15) * (1/1000) = 0.087m³

Volume of fly ash = (118/2.2) * (1/1000) = 0.053m³

Volume of water = (158/1) * (1/1000) = 0.158m³

Volume of chemical admixture = (7.6/1.145) * (1/1000) = 0.006m³

Volume of all aggregates = [1-(0.087+0.053+0.158+0.006)] = 0.696m³

Mass of coarse aggregate = 0.696 * 0.568 * 2.74 * 1000 = 1077 kg/m³

Mass of fine aggregate = 0.696 * 0.431 * 2.74 * 1000 = 822 kg/m³

Therefore, mix proportions:

Cement = 277 kg/m³

Fly ash = 118 kg/m³

Water = 158 lit/m³

Fine Aggregate = 822 kg/m³

Coarse Aggregate = 1077 kg/m³

Chemical Admixture = 7.18 kg/m³

W/C ratio = 0.44

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• Mix Proportion = 1 : 2.08 : 2.72 

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- To develop the Concrete Mix Design for M50 grade concrete without fly ash

• Grading Information:

Grade type                                                : M50                                

Cement type                                             : OPC M53 Grade

Aggregate nominal size                           : 20mm

Aggregate type                                        : Crushed Angular Aggregate

Condition                                                 : Severe

Max. w/c ratio                                          : 0.45

Workability                                               : 100mm 

Max. cement content                               : 450 kg/m³

Min. cement content                                : 320 kg/m³

Chemical Admixture type                         : Superplasticizer

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• Materials test data:

Specific Gravity of Cement                     : 3.15

Specific Gravity of coarse aggregate      : 2.74

Specific Gravity of fine aggregate          : 2.64

Water absorption (Coarse aggregate)    : 0.5%

Water absorption (Fine aggregate)        : 1.0%

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• Targetted strength of mix proportion:

f'ck = fck + 1.65*s

Here, s = 5 N/mm² (refer Table I in IS 10262:2009)

f'ck = 50 + 1.65*5

= 50 + 8.25

= 58.25 N/mm²

So, Targetted mean strength of mix proportion = 58.25 N/mm²

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• Water-Cement ratio selection:

As per IS 456:2000, the maximum w/c ratio = 0.45 (M50)

here, adopted w/c ratio = 0.44 

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• Water content required: (Refer IS 10262:2009)

From Table2, max. Water content for 20mm aggregate = 186 litre

Addition of 6% water = 186 + [(6/100)*186] = 197 litre

20% has been achieved, so

197*0.8 = 158 litre

So, Water content required = 158 litres

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• Cement required calculation :

here, w/c ratio = 0.44

Total cement (cement + fly ash) = 158/0.44 = 359 kg/m³

From Table5, Min. cement content in severe condition = 320 kg/m³

Since 320kg/m³ < 359kg>3, so Cement content was found to be 359kg/m³

Therefore, the cement required  is 359kg/m³

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• Volume of coarse and fine aggregate content: (Refer IS 10262:2009)

From Table3, the volume of coarse aggregate corresponds to 20mm size for w/c ratio 0.44 

= 0.632

Since, pumpable concrete so 10% reduction, so

= 0.632 * 0.9 = 0.568

Volume of fine aggregate = 1 - 0.568 = 0.431

Therefore, the volume of coarse aggregate is 0.568, and the volume of fine aggregate is 0.431

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• Mix calculations:

Volume of concrete = 1m³

Volume of cement = (359/3.15) * (1/1000) = 0.114m³

Volume of water = (158/1) * (1/1000) = 0.158m³

Volume of chemical admixture = (7.6/1.145) * (1/1000) = 0.006m³

Volume of all aggregates = [1 - (0.114 + 0.053 + 0.158 + 0.006)] = 0.722m³

Mass of coarse aggregate = 0.722 * 0.568 * 2.74 * 1000 = 1123 kg/m³

Mass of fine aggregate = 0.722 * 0.431 * 2.74 * 1000 = 852 kg/m³

Therefore, mix proportions:

Cement = 359 kg/m³

Water = 158 lit/m³

Fine Aggregate = 852 kg/m³

Coarse Aggregate = 1123 kg/m³

Chemical Admixture = 7.18 kg/m³

W/C ratio = 0.44

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• Mix Proportion = 1 : 2.28 : 3.12

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Result:

The Concrete Mix Design for M35 grade concrete with fly ash is 1 : 2.08 : 2.72 

The Concrete Mix Design for M50 grade concrete without fly ash 1 : 2.28 : 3.12

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