Concrete Mix Design IS 10262:2009A K GUPTA EXECUTIVE ENGINEER (TRAINING)14/02/2017

IntroductionConcrete Mix Design means, determination of the proportion of the concrete ingredients i.e. Cement, Water, Fine Aggregate, Coarse Aggregate which would produce concrete possessing specified properties such as workability, strength and durability with maximum overall economy.

Types of Concrete MixesNominal Mixes These mixes are of fixed cement-aggregate ratio. These offer simplicity and under normal circumstances.Have a margin of strength above that specified.

Standard Mixes The minimum compressive strength has been included by IS-456:2000 in many specifications. These mixes are termed standard mixes.E.g.: M10, M15, M20, etc.

3. Designed Mixes -In these mixes the performance of the concrete is specified by the designer but the mix proportions are determined by the producer of concrete, except that the minimum cement content can be laid down.

Methods of Concrete Mix DesignAmerican Concrete Institute Method (ACI Method)Road Note Number 4 MethodDOE MethodIndian Standard Method (IS Method)

Mix Design (IS 10262 - 2009)DATA REQUIRED

Step1 Target Mean Strength

Standard DeviationNumber of test results of samples taken from site-30Standard deviation for each batch if significant changes in concrete batchesStandard deviation to be brought upto date.

Asuumed Standard Deviation

Assumptions in Standard deviation

Selection of Mix Proportion Clause 4.1

Selection of Water cement ratioFor the same water cement ratio ,the compressive strength may differ according to different cement, supplementary cemetitious materials, aggregate size, grading, shape and surface texure.Preliminary w/c may be selected from established relationship between w/c ratio and compressive strength.Alternatively w/c ratio may be selected from table 5 of IS: 456 for respective exposure condition.

Selection of w/c ratio

Workability (Clause 7.1, IS:456-2000)

Degree of Site Control(Table 8, IS:456-2000)

Type of Exposure (Table 3, IS:456-2000)

Step2 Selection of water/cement ratio

Step2 Selection of water/cement ratio

But from table 5, IS-456:2000

Step2 Selection of water/cement ratioConsidering moderate exposure, Max w/c = 0.5 Hence w/c = 0.38w/c = 0.38

4.2 Selection of Water contentWater content is influenced by..Aggregate sizeShapeTextureWorkabilityw/c ratioOther supplementary cementitious materialAdmixtureEnvironment conditions

4.2 Selection of Water content

Selection of water contentWater content in table -2 is forAngular coarse aggregate , - 10 kg for sub angular aggregate-20 kg for gravel with some crushed particles.-25kg for rounded gravelSlump-25to 50mm, increase by 3 % for every additional slump of 25mm.

Water content for admixtures-5 to -10% for water reducing admixtures -20% for superplasticisers.

Water reducersAt constant workability

The reduction in mixing water is expected to be of the order of 5% to 15%.Naturally increases the strength.At constant w/c ratio

Increased workability.Slump of 30mm to 150 mm.

Water reducersThin walls of water retaining structures with high percentage of steel reinforcementDeep beams, column and beam junctionsTremie concretingPumping of concreteHot weather concretingConcrete to be conveyed for considerable distance and in ready mixed concrete industries

Super PlasticisersSuperplasticizers constitute a relatively new category and improved version of plasticizer, the use of which was developed in Japan and Germany during 1960 and 1970 respectively. They are chemically different from normal plasticisers.Classification of Superplasticizers:Sulphonated malanie-formaldehyde condensates (SMF)Sulphonated naphthalene-formaldehyde condensates (SNF)Modified lignosulphonates (MLS)Other types

SuperplasticisersPermits reduction of water content about 30% without reducing the workabilityIt is possible to use w/c ratio as low as 0.25 or even lower and yet to make flowing concrete to obtain strength of order 120 Mpa or more.Production of high strength and high performance concreteProduction of flowing, self levelling, self compacting concrete

Step3 Selection Of Water Content.

From table 2, IS-10262:2009

(For 20mm nominal max. size of aggregate & 25 to 50mm slump) Max WC = 186 kg/m3 # Correction for slump in water content (according to clause 4.2, IS:10262) Slump = 100 mm Correct WC for 100 mm slump = 186 + 6% = 197.16 kg 197 kg of water per m3 of concrete

4.3 Calculation of cementitious Material contentCalculate cementitious material from the water cement ratio and the quantity of water per cum(water content)Check it from durability requirement .Select higher value The maximum as per IS 456

Step4 Calculation Of Cement Content

Other Cementitious materialsFly ashBlast Furnace SlagSilica FumeNano Silica fumeRice Husk ashMetakaolineSurkhi

4.4 Estimation of coarse aggregate proportion

Coarse aggregate proportions Table -3 is for water cement ratio of 0.5, proportion may be suitably adjusted for other water cement ratio.(@-or+.01 for every change in water cement ratio of .05)For given workability ,the volume of coarse aggregate depends upon its nominal max size and grading zone of fine aggregate. Reduce the estimated CA content by 10% if pumping is to be done. It should be consistent with IS 456 and meet project specifications.

4.5Combination of Different Coarse Aggregate Fractions

4.6 Estimation of Fine aggregate Proportion Find out the absolute volume of cementitious material, water and chemical admixture by dividing their masses by their respective specific gravity and multiplying by 1/1000.Subtract the result of summation above from unit volume. Find volume of total aggregatesDivide coarse and fine aggregate fractions by volume as per clause 4.4.Find CA and FA by multiplying their volumes with respective specific gravities and multyplying by 1000.

Step 5: Selection of Proposition of Volume of Coarse Aggregate

From table 3,(IS-10262:2009) for zone IIIrd of F.A. Maximum size of aggregate = 20 mm. Vol. of CA per unit vol. of total aggregate = 0.64# For 0.1 decrease in w/c & increase in CA by 0.02 Applying correction of 0.024 Vol. of CA = 0.64 + 0.024 =0.664m3 Total aggregate = 1 CA = 0.664m3 FA = 0.336m3

Quantities by volumeCement518.42/(3.15*1000)=.165 cumWater ----197/(1*1000)=.197cumAggregates -----1-(.165+.197)=.638 cumCA-------------.638*.664=.4236cumFA----------------.638*.336=.214 cum

Quantities by MassCement-----518.42 kgWater ----------197 kgCA--------------.4236*2.74*1000=1161.76kgFA------------.214*2.74*1000=586.36 kg

Step6 Mix Calculation Results:

Ratio Obtained1 : 1.13 : 2.24

Mass of CementWaterF.A.C.A.518.42197586.361161.7610.381.132.24

Trial MixesCheck the workability of trail mix-1. Free from segregation and bleeding .See finishing properties;If not satisfactory . Trial mix-2 with varying water and admixture keeping pre-selected value of water cement ratio.Trial mix 3 and 4 with same water content as that of mix-2 but varying water cement ratio.Find relationship between compressive strength and w/c ratio.Field trails

*

Thanks For Hearing

*