CONCRETE MIX DESIGN M30 GRADE IS-10262-2009

Concrete mix design is required to obtained target strength in building and structures. Concrete Mix design of M30 grade of concrete can be find from the example given below.

1.Design Stipulation For Proportioning

Grade Designation = M-30

Type of cement = OPC 53 grade confirming to IS-12269-1987

Exposure condition = Normal (for reinforced concrete)

Method of placing = Pumping 

Degree of supervision = Good

Maximum nominal size of aggregate = 20 mm

Maximum Cement content =540 kg/m³

Minimum Cement content = 310 kg/m³

Maximum water cement ratio = 0.45

Workability = 50-75 mm (Slump)

Type of aggregate = Crushed angular aggregate

Chemical admixture type = Superplasticiser

2. Test Data For Material

Cement used = Coromandal King OPC 53 grade

Sp. Gravity Cement = 3.15

Sp. Gravity Fine Aggregate = 2.61

Sp. Gravity Coarse Aggregate (20mm) = 2.88

Sp. Gravity Coarse Aggregate (10mm) = 2.868

Chemical admixture = Superplasticiser confirming IS 9103

Water absorption of coarser aggregate(20mm) = 0.97%

Water absorption of coarser aggregate(10mm) = 0.87%

Free surface moisture = Nil

Sp. Gravity of Combined Coarse Aggregates = 2.882

3. Target Mean Strength

Himsworth constant for 5% risk factor is 1.65. In this case standard deviation is taken from IS:456 against M 30 is 4.0.

f_target = f_ck + 1.65 x S

Target Mean Strength = 42 Mpa

Where,

S = standard deviation in N/mm² = 4 (as per table -1 of IS 10262- 2009)

4. Selection of water cement ratio

Maximum Water Cement Ratio = 0.45

Adopted Water Cement Ratio = 0.42

 

5. Selection Of Water Content

Maximum Water content (10262-table-2) = 186 ltr

Estimated Water content for 50-75 mm Slump = 160 ltr

Superplasticiser used = 0.5 % by wt. of cement

6. Cement Content Calculation

Water Cement Ratio = 0.42

Cement Content (160/0.42) = 380 kg/m³

Corrected water content = 160 ltr

Cement content =

From Table 5 of IS 456,

Minimum cement Content for mild exposure condition

= 310 kg/m³

380 kg/m³ > 300 kg/m³, hence, OK.

This value is to be checked for durability requirement from IS: 456.

In the present example against mild exposure and for the case of reinforced concrete the minimum cement content is 310 kg/m³ which is less than 380 kg/m³. Hence cement content adopted = 380 kg/m³.

As per clause 8.2.4.2 of IS : 456

Maximum cement content = 540 kg/ m3

7. Calculation of sand and coarse aggregate

From Table 3 of IS 10262- 2009,

For Nominal maximum size of aggregate = 20 mm,

Zone of fine aggregate = Zone II

And For w/c = 0.42

Vol. of C.A. as per table 3 of IS 10262 = 62%

Adopted Vol. of Coarse Aggregate = 62%

Adopted Vol. of Fine Aggregate ( 1-0.62) = 38% 

8. Estimation of the mix ingredients

Volume of Concrete in m^{3 = 1.0}

Volume of cement in m3 = 0.12

(Mass of Cement) / (Sp. Gravity of Cement)x1000

Volume of water in m3 = 0.160

^{(Mass of Water) / (Sp. Gravity of Water)x1000}

^{Volume of Admixture 0.5% in m3 = 0.00160}

^{(Mass of Admixture)/(Sp. Gravity of Admixture)x1000}

^{Volume of All in Aggregate in m3 = 0.718}

^{Serial. number. 1 – (Sr. no. 2+3+4)}

^{Volume of Coarse Aggregate in m3 = 0.445}

^{Serial. number. 5 x 0.62}

^{Volume of Fine Aggregate in m3 = 0.273}

^{Serial. number. 5 x 0.38}

^{Mix Proportions for One Cum of Concrete}

^{Mass of Cement in kg/m3 = 380}

^{Mass of Water in kg/m3 = 160}

^{Mass of Fine Aggregate in kg/m3 = 711} 

^{Mass of Coarse Aggregate in kg/m3 = 1283}

^{Mass of 20 mm in kg/m3 = 924}

^{Mass of 10 mm in kg/m3 = 359} 

^{Mass of Admixture in kg/m3 = 1.9} 

^{Water Cement Ratio =0.42}

CONCRETE MIX DESIGN M40 GRADE

WHAT IS CONCRTE MIX DESIGN ?

The process of selecting suitable ingredients of concrete and determining their relative amounts with the objective of producing a concrete of the required, strength, durability, and workability as economically as possible, is termed the concrete mix design.

POINT TO BE REMEMBER WHILE MAKING MIX DESIGN

• The grade designation giving the characteristics strength required of concrete.

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

• Maximum nominal size of aggregate to be used in concrete may be as large as possible within the limits prescribed by the IS : 456-2000.

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

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

CONCRETE MIX DESIGN-M40 GARDE EXAMPLE

1.Design Stipulation For Proportioning

Grade Designation = M-40

Type of cement = O.P.C-43 grade confarming to IS 8112

Maximum nominal size of aggregate = 20 mm

Maximum Cement content =450 kg / m³

Minimum Cement content = 320  kg / m³

Maximum water cement ratio = 0.45

Workability = 100 mm (slump)

Exposure condition = Severe (for reinforced concrete)

Method of placing = Pumping 

Degree of supervision = Good

Type of aggregate = Crushed angular aggregate

Chemical admixture type = Superplasticiser

2. Test Data For Material

Cement used = OPC 43 grade confirming IS 8112

Sp. Gravity Cement = 3.15

Sp. Gravity Fine Aggregate = 2.61

Sp. Gravity Coarse Aggregate (20mm) = 2.65

Sp. Gravity Coarse Aggregate (10mm) = 2.66

Chemical admixture = Superplasticiser confirming IS 9103

Water absorption of coarser aggregate = 0.5%

Water absorption of coarser aggregate = 1%

Free surface moisture = Nil

3. Target Mean Strength

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

Selection of water cement ratio

Assume water cement ratio = .40 - 0.45

4. Selection Of Water Content

Approximate water content for 20mm max. Size of aggregate = 180 kg /m³ (As per Table No. 2 , IS : 10262 ). As plasticizer is proposed we can reduce water content by 20%.

Now water content = 180 X 0.8 = 140kg /m³

5. Cement Content Calculation

Water cement ratio = 0.40

Water content per m³ of concrete = 144 kg

Cement content = 144/0.35 = 411.4 kg / m³

Say cement content = 412 kg / m³ (As per contract

Minimum cement content 350 kg / m³ )

Hence O.K.

6. Calculation of sand and coarse aggregate 

V = [ W + (C/S_c) + (1/p) . (f_a/S_fa) ] x (1/1000)

V = [ W + (C/S_c) + {1/(1-p)} . (ca/S_ca) ] x (1/1000)

Where

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

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

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

S_c = 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 of
Concrete respectively, and

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

As per Table No. 3 , IS-10262, 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 kg
Water = 160 kg
Fine aggregate = 660 kg
Coarse aggregate 20 mm = 701 kg
Coarse aggregate 10 mm = 467 kg
Admixture = 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

7. Observation for concrete mix design

% Strength of concrete : The strength of concrete increases with

age.

Table for strength of concrete at various age

Age	Strength per cent
1 day	16%
3 days	40%
7 days	65%
14 days	90%
28 days	99%

A. Mix was cohesive and homogeneous.

B. Slump value = 120 mm

C. No. of cube casted = 9 

7 days average compressive strength = 42.07 N/mm2

28 days average compressive strength = 52.52 N/mm2

which is greater than 48.25 N/mm2

Hence the mix accepted.

DIFFERENT METHOD OF MIX DESIGN OF CONCRETE PROCEDURE

MIX DESIGN

The procedure of selecting suitable ingredients and determine their relative proportions with the objectives of producing concrete of having certain minimum workability, strength and durability as economically as possible is known as mix design.

The various factors to be consider in specifying a concrete mix are :

• Water cement ratio

• Cement content gradation

• Consistency of the fresh concrete

METHOD OF MIX DESIGN OF CONCRETE

• Trial and error method 
• American concrete institute method.
• Maximum density of aggregate method
• Surface area of aggregate method
• Fineness modulus method
• Void cement ratio and mortar void ratio method
• Road note method

TRIAL AND ERROR METHOD

Based on the relationship between the w/c ratio and compressive strength. the design of the mix can be made by following steps :

• Select the water cement ratio to suit the requirement of the strength and durability.

• With this water cement ratio prepare trial batches with different aggregate cement ratios. From this it is possible to determine the optimum proportion and amount of the aggregate that will produce a workable mix with a minimum of the pastes content for determining the fine aggregate. It can be said that in the correct amount of sand is the minimum which will produce enough mortar to fill the spaces between the coarse aggregate and slightly more for workability. Understanding  creates hardness and over standing results in less yield. with judgement and experience one ma arrive at the proportions of fine and coarse aggregate.

• Having fixed water cement ratio, aggregate cement ratio and the amount of fine aggregate in the total aggregate content, block of concrete can be prepared in the laboratory following the standard procedure. After the required period of curing the blocks can be tested for its compressive strength.

• mix can be slightly adjusted, if necessary, by changing the w/c ratio or the aggregate cement ratio suit the actual requirement of the job.

In the trial and error method, due consideration has to be given for the moisture content of the aggregates.

AMERICAN CONCRETE INSTITUTE METHOD (ACI METHOD)

This is the common method for design of concrete mix. the following are the steps : 

• Select the water cement ratio to concrete of the required durability and strength. if water cement ratio is determine by both methods and then the lower of the two values obtained should be used. 

• Select the lowest slump from ASI table.

• The maximum size of aggregate recommended for the types of construction is selected by ASI table. Within the limit shown, the larges permissible maximum size should be employed, except as dictated by available and economy. 

• Estimate from the test data, minimum proportion of fine to coarse aggregate and the lowest water content as  that will give the required degree of workability.

• The cement content is computed by dividing the total water content by the w/c ratio.

• The bulk volume of the dry rodded coarse aggregate per unit volume of concrete for the particular maximum size of the aggregate and fineness modulus of the sand is determine.

• Determine the trial mix proportions and make adjustment if necessary for the materials and water cement ratio.

MAXIMUM DENSITY OF AGGREGATE METHOD

It is also known as fullar and thomson method of concrete mix design, the basis for proportioning the aggregate is maximum density. For this method, the studies made by fullar and thomson, in which sieve analyses were made to obtain proportions aggregate giving maximum density of concrete, were used. But this method is not in much uses now.

Maximum density of this combined aggregate can be determine is follow. In a of known volume certain proportions of any rodded mixed aggregate are filled in. Sand is taken as 0, 20, 30, 40, 50, 60 and 100% of the total weight. After each filling of the mould with the combined aggregates, weight is taken. A curve is then drawn showing the percentage of sand in the aggregate by weight v/s unit weight of the total aggregate in the mould, from this percentage of sand at which unit weight is maximum can be determined.