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This is the new text page Mix design.

Mix Design consider as per test result of local avialble material lie sand, chips and cement.

here is some desin mix as per zone iii

1. Mix design for M50 grade

2. Mix design for M40 grade

3. Mix desgn for M20 grade

Concrete Mix DesignIntroductionThe process of selecting suitable ingredients of concrete and determining their relative amounts with the objective ofproducing a concrete of the required, strength, durability, and workability as economically as possible, is termed theconcrete mix design. The proportioning of ingredient of concrete is governed by the required performance of concrete in 2states, namely the plastic and the hardened states. If the plastic concrete is not workable, it cannot be properly placed andcompacted. The property of workability, therefore, becomes of vital importance.

The compressive strength of hardened concrete which is generally considered to be an index of its other properties,depends upon many factors, e.g. quality and quantity of cement, water and aggregates; batching and mixing; placing,compaction and curing. The cost of concrete is made up of the cost of materials, plant and labour. The variations in thecost of materials arise from the fact that the cement is several times costly than the aggregate, thus the aim is to produceas lean a mix as possible. From technical point of view the rich mixes may lead to high shrinkage and cracking in thestructural concrete, and to evolution of high heat of hydration in mass concrete which may cause cracking.

The actual cost of concrete is related to the cost of materials required for producing a minimum mean strength calledcharacteristic strength that is specified by the designer of the structure. This depends on the quality control measures,but there is no doubt that the quality control adds to the cost of concrete. The extent of quality control is often an economiccompromise, and depends on the size and type of job. The cost of labour depends on the workability of mix, e.g., aconcrete mix of inadequate workability may result in a high cost of labour to obtain a degree of compaction with availableequipment.

Requirements of concrete mix design

The requirements which form the basis of selection and proportioning of mix ingredients are :

a ) The minimum compressive strength required from structural consideration

b) The adequate workability necessary for full compaction with the compacting equipment available.

c) Maximum water­cement ratio and/or maximum cement content to give adequate durability for the particular siteconditions

d) Maximum cement content to avoid shrinkage cracking due to temperature cycle in mass concrete.

Types of Mixes1. Nominal Mixes

In the past the specifications for concrete prescribed the proportions of cement, fine and coarse aggregates.These mixes of fixed cement­aggregate ratio which ensures adequate strength are termed nominal mixes. Theseoffer simplicity and under normal circumstances, have a margin of strength above that specified. However, due tothe variability of mix ingredients the nominal concrete for a given workability varies widely in strength.

2. Standard mixes

The nominal mixes of fixed cement­aggregate ratio (by volume) vary widely in strength and may result in under­ or over­rich mixes. For this reason, the minimum compressive strength has been included in many specifications. These mixes aretermed standard mixes.

IS 456­2000 has designated the concrete mixes into a number of grades as M10, M15, M20, M25, M30, M35 and M40. Inthis designation the letter M refers to the mix and the number to the specified 28 day cube strength of mix in N/mm2. Themixes of grades M10, M15, M20 and M25 correspond approximately to the mix proportions (1:3:6), (1:2:4), (1:1.5:3) and(1:1:2) respectively.

3. Designed Mixes

In these mixes the performance of the concrete is specified by the designer but the mix proportions are determined by theproducer of concrete, except that the minimum cement content can be laid down. This is most rational approach to theselection of mix proportions with specific materials in mind possessing more or less unique characteristics. The approachresults in the production of concrete with the appropriate properties most economically. However, the designed mix doesnot serve as a guide since this does not guarantee the correct mix proportions for the prescribed performance.

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For the concrete with undemanding performance nominal or standard mixes (prescribed in the codes by quantities of dryingredients per cubic meter and by slump) may be used only for very small jobs, when the 28­day strength of concretedoes not exceed 30 N/mm2. No control testing is necessary reliance being placed on the masses of the ingredients.

Factors affecting the choice of mix proportions

The various factors affecting the mix design are:

1. Compressive strength

It is one of the most important properties of concrete and influences many other describable properties of the hardenedconcrete. The mean compressive strength required at a specific age, usually 28 days, determines the nominal water­cement ratio of the mix. The other factor affecting the strength of concrete at a given age and cured at a prescribedtemperature is the degree of compaction. According to Abraham’s law the strength of fully compacted concrete is inverselyproportional to the water­cement ratio.

2. Workability

The degree of workability required depends on three factors. These are the size of the section to be concreted, the amountof reinforcement, and the method of compaction to be used. For the narrow and complicated section with numerouscorners or inaccessible parts, the concrete must have a high workability so that full compaction can be achieved with areasonable amount of effort. This also applies to the embedded steel sections. The desired workability depends on thecompacting equipment available at the site.

3. Durability

The durability of concrete is its resistance to the aggressive environmental conditions. High strength concrete is generallymore durable than low strength concrete. In the situations when the high strength is not necessary but the conditions ofexposure are such that high durability is vital, the durability requirement will determine the water­cement ratio to be used.

4. Maximum nominal size of aggregate

In general, larger the maximum size of aggregate, smaller is the cement requirement for a particular water­cement ratio,because the workability of concrete increases with increase in maximum size of the aggregate. However, the compressivestrength tends to increase with the decrease in size of aggregate.

IS 456:2000 and IS 1343:1980 recommend that the nominal size of the aggregate should be as large as possible.

5. Grading and type of aggregate

The grading of aggregate influences the mix proportions for a specified workability and water­cement ratio. Coarser thegrading leaner will be mix which can be used. Very lean mix is not desirable since it does not contain enough finer materialto make the concrete cohesive.

The type of aggregate influences strongly the aggregate­cement ratio for the desired workability and stipulated watercement ratio. An important feature of a satisfactory aggregate is the uniformity of the grading which can be achieved bymixing different size fractions.

6. Quality Control

The degree of control can be estimated statistically by the variations in test results. The variation in strength results fromthe variations in the properties of the mix ingredients and lack of control of accuracy in batching, mixing, placing, curingand testing. The lower the difference between the mean and minimum strengths of the mix lower will be the cement­content required. The factor controlling this difference is termed as quality control.

Mix Proportion designationsThe common method of expressing the proportions of ingredients of a concrete mix is in the terms of parts or ratios ofcement, fine and coarse aggregates. For e.g., a concrete mix of proportions 1:2:4 means that cement, fine and coarseaggregate are in the ratio 1:2:4 or the mix contains one part of cement, two parts of fine aggregate and four parts ofcoarse aggregate. The proportions are either by volume or by mass. The water­cement ratio is usually expressed in mass

Factors to be considered for mix design

The grade designation giving the characteristic strength requirement of concrete.

The type of cement influences the rate of development of compressive strength of concrete.

Maximum nominal size of aggregates to be used in concrete may be as large as possible within the limits prescribed by IS456:2000.

The cement content is to be limited from shrinkage, cracking and creep.

The workability of concrete for satisfactory placing and compaction is related to the size and shape of section, quantity andspacing of reinforcement and technique used for transportation, placing and compaction.

Procedure1. Determine the mean target strength ft from the specified characteristic compressive strength at 28­day fck and the level of

quality control.

ft = fck + 1.65 S

where S is the standard deviation obtained from the Table of approximate contents given after the design mix.

2. Obtain the water cement ratio for the desired mean target using the emperical relationship between compressive strengthand water cement ratio so chosen is checked against the limiting water cement ratio. The water cement ratio so chosen ischecked against the limiting water cement ratio for the requirements of durability given in table and adopts the lower of thetwo values.

3. Estimate the amount of entrapped air for maximum nominal size of the aggregate from the table.

4. Select the water content, for the required workability and maximum size of aggregates (for aggregates in saturated surfacedry condition) from table.

5. Determine the percentage of fine aggregate in total aggregate by absolute volume from table for the concrete using crushedcoarse aggregate.

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6. Adjust the values of water content and percentage of sand as provided in the table for any difference in workability, watercement ratio, grading of fine aggregate and for rounded aggregate the values are given in table.

7. Calculate the cement content form the water­cement ratio and the final water content as arrived after adjustment. Check thecement against the minimum cement content from the requirements of the durability, and greater of the two values isadopted.

8. From the quantities of water and cement per unit volume of concrete and the percentage of sand already determined in steps6 and 7 above, calculate the content of coarse and fine aggregates per unit volume of concrete from the following relations:

where V = absolute volume of concrete

= gross volume (1m3) minus the volume of entrapped air

Sc = specific gravity of cement

W = Mass of water per cubic metre of concrete, kg

C = mass of cement per cubic metre of concrete, kg

p = ratio of fine aggregate to total aggregate by absolute volume

fa, Ca = total masses of fine and coarse aggregates, per cubic metre of concrete, respectively, kg, and

Sfa, Sca = specific gravities of saturated surface dry fine and coarse aggregates, respectively

9. Determine the concrete mix proportions for the first trial mix.

10. Prepare the concrete using the calculated proportions and cast three cubes of 150 mm size and test them wet after 28­days moist curing and check for the strength.

Mix Design M­50 Grade

The mix design M­50 grade (Using Admixture –Sikament) provided here is for reference purpose only.Actual site conditions vary and thus this should be adjusted as per the location and other factors.

Parameters for mix design M50

Grade Designation = M­50Type of cement = O.P.C­43 gradeBrand of cement = Vikram ( Grasim )Admixture = Sika [Sikament 170 ( H ) ]Fine Aggregate = Zone­II

Sp. GravityCement = 3.15Fine Aggregate = 2.61Coarse Aggregate (20mm) = 2.65Coarse Aggregate (10mm) = 2.66

Minimum Cement (As per contract) =400 kg / m3

Maximum water cement ratio (As per contract) = 0.45

Mix Calculation: ­

1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa

2. Selection of water cement ratio:­Assume water cement ratio = 0.35

3. Calculation of water: ­Approximate water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table No. 5 , IS :10262 ). As plasticizer is proposed we can reduce water content by 20%.

Now water content = 180 X 0.8 = 144 kg /m3

4. Calculation of cement content:­Water cement ratio = 0.35Water content per cum of concrete = 144 kgCement content = 144/0.35 = 411.4 kg / m3

Say cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3 )Hence O.K.

5. Calculation for C.A. & F.A.: [ Formula's can be seen in earlier posts]­

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Volume of concrete = 1 m3

Volume of cement = 412 / ( 3.15 X 1000 ) = 0.1308 m3

Volume of water = 144 / ( 1 X 1000 ) = 0.1440 m3

Volume of Admixture = 4.994 / (1.145 X 1000 ) = 0.0043 m3

Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 +0.0043 = 0.2791 m3

Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m3

Volume of F.A. = 0.7209 X 0.33 = 0.2379 m3 (Assuming 33% by volume of total aggregate )

Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m3

Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919 kg/ m3

Say weight of F.A. = 621 kg/ m3

Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365 kg/ m3

Say weight of C.A. = 1284 kg/ m3

Considering 20 mm: 10mm = 0.55: 0.4520mm = 706 kg .10mm = 578 kg .Hence Mix details per m3

Increasing cement, water, admixture by 2.5% for this trial

Cement = 412 X 1.025 = 422 kgWater = 144 X 1.025 = 147.6 kgFine aggregate = 621 kgCoarse aggregate 20 mm = 706 kgCoarse aggregate 10 mm = 578 kgAdmixture = 1.2 % by weight of cement = 5.064 kg.

Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043

Observation: ­A. Mix was cohesive and homogeneous.B. Slump = 120 mmC. No. of cube casted = 9 Nos.7 days average compressive strength = 52.07 MPa.28 days average compressive strength = 62.52 MPa which is greater than 58.25MPaHence the mix accepted.

We are thankful to Er Sujieet Behera for this valuable information

Mix Design M­40 GradeThe mix design M­40 grade for Pier (Using Admixture – Fosroc) provided here is for reference purposeonly. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

Parameters for mix design M40

Grade Designation = M­40Type of cement = O.P.C­43 gradeBrand of cement = Vikram ( Grasim )Admixture = Fosroc ( Conplast SP 430 G8M )Fine Aggregate = Zone­IISp. Gravity Cement = 3.15Fine Aggregate = 2.61Coarse Aggregate (20mm) = 2.65Coarse Aggregate (10mm) = 2.66Minimum Cement (As per contract) = 400 kg / m3

Maximum water cement ratio (As per contract) = 0.45

Mix Calculation: ­

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1. Target Mean Strength = 40 + (5 X 1.65) = 48.25 Mpa

2. Selection of water cement ratio:­Assume water cement ratio = 0.4

3. Calculation of cement content: ­Assume cement content 400 kg / m3

(As per contract Minimum cement content 400 kg / m3)

4. Calculation of water: ­400 X 0.4 = 160 kg Which is less than 186 kg (As per Table No. 4, IS: 10262)Hence o.k.

5. Calculation for C.A. & F.A.: – As per IS : 10262 , Cl. No. 3.5.1

V = [ W + (C/Sc) + (1/p) . (fa/Sfa) ] x (1/1000)

V = [ W + (C/Sc) + 1/(1­p) . (ca/Sca) ] x (1/1000)

Where

V = absolute volume of fresh concrete, which is equal to gross volume (m3) minus the volume ofentrapped air ,

W = mass of water ( kg ) per m3 of concrete ,

C = mass of cement ( kg ) per m3 of concrete ,

Sc = specific gravity of cement,

(p) = Ratio of fine aggregate to total aggregate by absolute volume ,

(fa) , (ca) = total mass of fine aggregate and coarse aggregate (kg) per m3 ofConcrete respectively, and

Sfa , Sca = specific gravities of saturated surface dry fine aggregate and Coarse aggregate respectively.

As per Table No. 3 , IS­10262, for 20mm maximum size entrapped air is 2% .

Assume F.A. by % of volume of total aggregate = 36.5 %

0.98 = [ 160 + ( 400 / 3.15 ) + ( 1 / 0.365 ) ( Fa / 2.61 )] ( 1 /1000 )

=> Fa = 660.2 kg

Say Fa = 660 kg.

0.98 = [ 160 + ( 400 / 3.15 ) + ( 1 / 0.635 ) ( Ca / 2.655 )] ( 1 /1000 )

=> Ca = 1168.37 kg.

Say Ca = 1168 kg.

Considering 20 mm : 10mm = 0.6 : 0.4

20mm = 701 kg .10mm = 467 kg .

Hence Mix details per m3

Cement = 400 kgWater = 160 kgFine aggregate = 660 kgCoarse aggregate 20 mm = 701 kgCoarse aggregate 10 mm = 467 kgAdmixture = 0.6 % by weight of cement = 2.4 kg.Recron 3S = 900 gm

Water: cement: F.A.: C.A. = 0.4: 1: 1.65: 2.92

Observation: ­A. Mix was cohesive and homogeneous.B. Slump = 110mmC. No. of cube casted = 12 Nos.7 days average compressive strength = 51.26 MPa.28 days average compressive strength = 62.96 MPa which is greater than 48.25MPa

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Cem W/C Water Sand 20mm 10mm Admix400 0.43 172 635 619 564 1.2

1 0.43 1.6 1.547 1.36 0.003

Hence the mix is accepted.

Mix Design For M35 Grade Of ConcreteThe mix design for M35 Grade Of Concrete for pile foundations provided here is for reference purpose only. Actual siteconditions vary and thus this should be adjusted as per the location and other factors.

Grade of Concrete : M35Characteristic Strength (Fck) : 35 MpaStandard Deviation : 1.91 Mpa*Target Mean Strength : T.M.S.= Fck +1.65 x S.D.(from I.S 456­2000) = 35+ 1.65×1.91= 38.15 Mpa

Test Data For Material:Aggregate Type : CrushedSpecific Gravity Cement : 3.15Coarse Aggregate : 2.67Fine Aggregate : 2.62

Water Absorption:Coarse Aggregate : 0.5%Fine Aggregate : 1.0 %

MIX DESIGN

Take Sand content as percentage of total aggregates = 36%

Select Water Cement Ratio = 0.43 for concrete grade M35

(From Fig 2. of I.S. 10262­ 1982)

Select Water Content = 172 Kg

(From IS: 10262 for 20 mm nominal size of aggregates Maximum Water Content = 186 Kg/ M3 )

Hence, Cement Content= 172 / 0.43 = 400 Kg / M3

Formula for Mix Proportion of Fine and Coarse Aggregate:

1000(1­a0) = (Cement Content / Sp. Gr. Of Cement) + Water Content +(Fa / Sp. Gr.* Pf )

1000(1­a0) = (Cement Content / Sp. Gr. Of Cement) + Water Content +Ca / Sp. Gr.* Pc )

Where Ca = Coarse Aggregate Content

Fa = Fine Aggregate Content

Pf = Sand Content as percentage of total Aggregates

= 0.36

Pc = Coarse Aggregate Content as percentage of total Aggregates.

= 0.64

a0 = Percentage air content in concrete (As per IS :10262 for 20 mm nominal size of

aggregates air content is 2 %) = 0.02

Hence, 1000(1­0.02) = (400 /3.15) + 172 +(Fa / 2.62 x 0.36)

Fa = 642 Kg/ Cum

As the sand is of Zone II no adjustment is required for sand.

Sand Content = 642 Kg/ Cum

1000(1­0.02) = (400 /3.15) + 172 +(Ca / 2.67 x 0.64)

Hence, Ca = 1165 Kg/ Cum

From combined gradation of Coarse aggregates it has been found out that the proportion of 53:47 of 20 mm & 10 mmaggregates produces the best gradation as per IS: 383.

Hence, 20 mm Aggregates = 619 Kg

And 10 mm Aggregates = 546 Kg

To obtain slump in the range of 150­190 mm water reducing admixture brand SP430 from Fosroc with a dose of 0.3 % byweight of Cement shall be used.

Hence the Mix Proportion becomes:

Units – Kg/ M3

Cement : Sand: Coarse Aggregates = 1 : 1.6 : 2.907

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Concrete Mix Design – M 20 Grade Of Concrete

1. REQUIREMENTSa) Specified minimum strength = 20 N/Sq mm

b) Durability requirementsi) Exposure Moderateii) Minimum Cement Content = 300 Kgs/cum

c) Cement(Refer Table No. 5 of IS:456­2000)i) Make Chetak (Birla)ii) Type OPCiii) Grade 43

d) Workabilityi) compacting factor = 0.7

e) Degree of quality control Good

2. TEST DATA FOR MATERIALS SUPPLIED a) CEMENTi) Specific gravity = 3.05ii) Avg. comp. strength 7 days = 46.5 more than 33.0 OK28 days = 55.0 more than 43.0 OK

b) COARSE AGGREGATEi) 20mm GradedType Crushed stone aggregateSpecific gravity = 2.68Water absorption = 1.46Free (surface) moisture = 0

c) FINE AGGREGATE (Coarse sand)i) Type Natural (Ghaggar)Specific gravity = 2.6Water absorption = 0.5Free (surface) moisture = 1.4

3. TARGET MEAN STRENGTH (TMS)a) Statistical constant K = 1.65b) Standard deviation S = 4.6Thus, TMS = 27.59 N/Sqmm

4. SELECTION OF W/C RATIOa) As required for TMS = 0.5b) As required for ‘Moderate’ Exposure = 0.55Assume W/c ratio of 0.5

5. DETERMINATION OF WATER & SAND CONTENTFor W/C = 0.6C.F. = 0.8Max. Agg. Size of 20 mma) Water content = 186 Kg/cumb) Sand as percentage of total aggregate by absolute volume = 35 %

Thus,Net water content = 180.42 Kg/cumNet sand percentage = 33 %

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6. DETERMINATION OF CEMENT CONTENTW/c ratio = 0.5Water content = 180.42 Kg/cumThus, Cement content = 360.84 Kg/cum Adequate for moderate exposure Say 360 Kg/cum

7. DETERMINATION OF COARSE AND FINE AGGREGATE CONTENTAssume entrapped air as 2 %Thus,0.98 cum = [180.42+360/3.05 + 1/0.33*fa/2.6]/1000& 0.98 cum = [180.42+360/3.05 + 1/0.67*Ca/2.68]/1000Hence,fa = 584 Kg/cumCa = 1223.8 Kg/cum

The final mix proportions of M­20 grade of concrete become:­

Note: 1 The above recommended mix design must be verified, by actual cube tests.2 The mix design is based on the quality and grading of the materials actually supplied, by the client.Any variation in quality and gradation will result in changes in the mix design.

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