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2 CEMENT CONCRETE MIX DESIGN by K. RAMESH Research Officer, Engineering Materials Laboratory, A.P. Engineering Research Laboratories, Himayatsagar, HYDERABAD-500030.

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3 Cement Concrete 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.

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4 Methods of Concrete Mix Design I.S. Method British Method A.C.I. Method etc.

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5 These Methods are based on two basic assumptions Compressive Strength of Concrete is governed by its Water-Cement Ratio Workability of Concrete is governed by its Water Content

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6 Data required for concrete mix design 1.Grade of Concrete Eg: RCC-M30-A20 2.Slump required in mm Eg: 25 – 75 mm 3.Degree of Site Control Eg: Good 4.Type of Exposure Eg: Moderate 5.Grade of Cement Eg: OPC 43 Grade

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7 Placing ConditionsDegree of WorkabilitySlump (mm) 123 Blinding Concrete; Shallow Sections; Pavements using pavers Very LowSee 7.1.1 Mass Concrete; Lightly reinforced sections in Slabs, Beams, Walls, Columns; Floors; Hand placed Pavements; Canal lining; Strip Footings Low25-75 Heavily reinforced sections in Slabs, Beams, Walls, Columns; Slip form work; Pumped Concrete. Medium50-100 Trench fill; In-Situ Piling; Tremie ConcreteHigh100-150

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8 Good Site control having proper storage of cement; weigh batching of all materials; Controlled addition of water, regular checking of all materials, aggregate grading and moisture content; And periodical checking of workability and strength. FairSite control having deviation from the above.

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9 Sl. No. EnvironmentExposure Conditions 123 i)Mild Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal area. ii)Moderate Concrete surfaces sheltered from severe rain or freezing whilst wet. Concrete exposed to condensation and rain. Concrete continuously under water. Concrete in contact or buried under non-aggressive soil/ground water. Concrete surfaces sheltered from saturated salt air in coastal area. iii)Severe Concrete surfaces exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or severe condensation. Concrete completely immersed in sea water. Concrete exposed to coastal environment. iv)Very Severe Concrete exposed to sea water spray, corrosive fumes or severe freezing conditions whilst wet. Concrete in contact with or buried under aggressive sub-soil/ground water. v)Extreme Surface of members in tidal zone. Members in direct contact with liquid/solid aggressive chemicals.

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10 Approximate Quantity of Materials required for concrete mix design 1.Cement : 200 Kg. 2.Fine Aggregate : 240 Kg. 3.Coarse Aggregate : 180 Kg. (20 mm) 180 Kg. (10 mm)

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11 STEPS INVOLVED IN CONCRETE MIX DESIGN Step I:- Determine the physical properties of concrete ingredients. I. CEMENT (OPC 43 Grade) Sl. No. Particulars of TestResultSpecifications As per IS:8112-1976 1Standard consistency (% by weight) 25.6 2Setting Time in minutes a) Initial b) Final 95 210 30 Minimum 600 Maximum 3Compressive Strength in N/sq.mm at the age of a) 3 days b) 7 days c) 28 days 24 35 46 23 Minimum 33 Minimum 43 Minimum 4Specific Gravity3.00 5Fineness in Sq.m/Kg337225 Minimum

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12 Sieve Size% PassingSpecifications for Zone–II As per IS:383-1970 10.0 mm100 4.75 mm10090-100 2.36 mm9875-100 1.18 mm6555-90 600 micron4235-59 300 micron88-30 150 micron00-10 II.FINE AGGREGATE 1.Sieve Analysis 2.Specific Gravity:2.60 3.Unit Weight in Kg/Cu.m a)Loose:1460 b)Rodded:1580 4.Materials Finer than 75 micron:1.00 3 Max (% by weight)

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13 Sieve Size% PassingSpecifications As per IS:383-1970 GradedSingle Sized 40.00mm100 20.00mm9095-10085-100 10.00mm325-550-20 4.75mm00-100-5 III.20.0mm COARSE AGGREGATE 1.Sieve Analysis 2.Specific Gravity:2.65 3.Unit Weight in Kg/Cu.m a)Loose:1467 b)Rodded:1633

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14 Sl. No. Particulars of TestResultSpecifications As per IS: 383-1970 1Crushing Value in %2830 Maximum For wearing surfaces 45 Maximum For other concrete 2Impact Value in %2430 Maximum For wearing surfaces 45 Maximum For other concrete 3Los Angeles Abrasion Value in % 3030 Maximum For wearing surfaces 50 Maximum For other concrete IV.MECHANICAL PROPERTIES

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15 Sieve Size% PassingSpecifications As per IS:383-1970 GradedSingle Sized 12.50mm100– 10.00mm85–85-100 4.75mm19–0-20 2.36mm0–0-5 V.10.0mm COARSE AGGREGATE 1.Sieve Analysis 2.Unit Weight in Kg/Cu.m a)Loose:1427 b)Rodded:1587

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16 VI.BLENDING OF COARSE AGGREGATE: Sieve size (mm) IS:383-1970 Specifications (Graded) % Passing 20 mm10 mm60%+40%50%+50% 40100 2095-100901009495 1025-553854044 4.750-10019710

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17 Step II:-Compute Target Mean Compressive Strength: F ck =f ck + t * S F ck =Target Mean Compressive Strength at 28 days in N/Sq.mm f ck =Characteristic Compressive Strength at 28 days in N/Sq.mm S=Standard Deviation in N/Sq.mm t=A Statistic, depending on accepeted proportion of low results. = 1.65 for 1 in 20 accepted proportion of low results

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18 Values of t Accepted proportion of low results t 1 in 5, 20%0.84 1 in 10, 10%1.28 1 in 15, 6.7%1.50 1 in 20, 5%1.65 1in 40, 2.5%1.86 1 in 100, 1%2.33

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19 Assumed Standard Deviation (Table 8, IS:456-2000) Grade of Concrete Assumed Standard Deviation (N/Sq.mm) Good Site ControlFair Site Control M10, M153.54.5 M20, M254.05.0 M30, M35 M,40,M45 M50 5.06.0

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20 Step III:- Select the Water-Cement ratio of trial mix from experience S. No. Concrete Grade Minimum expected W/C 1M100.9 2M150.7 3M200.55 4M250.50 5M300.45 6M350.40 7M400.35 8M450.30

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21 Step IV:- Select the water content per cubic metre of concrete from table2 of I.S: 10262-2009. Maximum size of Aggregate (mm) Water Content per cubic metre of concrete (Kg) 10208 20186 40165

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22 Approximate water content (Kg) per cubic metre of concrete (Table 32, SP:23-1982) Slump (mm) Maximum Size of Aggregate (mm) 102040 30-50205185160 80-100225200175 150-180240210185

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23 Volume of Coarse Aggregate per Unit Volume of Total Aggregate (Table 3, IS:10262-2009) Maximum Size of Aggregate (mm) Volume of Coarse Aggregate per Unit Volume of Total Aggregate Zone IVZone IIIZone IIZone I 100.500.480.460.44 200.660.640.620.60 400.750.730.710.69

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25 Step V:- Compute the quantity of cement as follows. Water Cement = ------------- W/C Ratio = 185 / 0.45 = 411 Kg.

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26 Step VI:- Then we find the quantities of Fine & Coarse aggregate by absolute volume method. V = (W+C/S c +(1/p) * (fa/S fa )) * (1/1000) - (Eq.1) and V = (W+C/S c +(1/(1-p)) * (ca/S ca )) * (1/1000) - (Eq.2) Where V = Absolute volume of fresh concrete = 1 m 3 W = Mass of Water (Kg) per m 3 of concrete C = Mass of Cement (Kg) per m 3 of concrete p = Percentage of fine aggregate. fa = Mass of fine aggregate ca = Mass of coarse aggregate S c = Specific gravity of cement. S fa = Specific gravity of fine aggregate. S ca = Specific gravity of coarse aggregate.

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27 Substituting the values in Eq(1), we get 1000 = 185 + 411/3.0 + (1/0.36) * fa /2.6) = 185 + 137 + fa/0.936 = 322 + fa/0.936 fa = (1000 – 322) * 0.936 = 678 * 0.936 = 635 Kg.

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28 Substituting the values in Eq(2), we get 1000 = 185 + 411/3.0 + (1/0.64) * ca /2.65) = 185 + 137 + ca/1.696 = 322 + ca/1.696 ca = (1000 – 322) * 1.696 = 678 * 1.696 = 1150 Kg.

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29 So the mix proportion works out to be W : C : fa : ca = 185 : 411 : 635 : 1150 = 0.45 : 1 : 1.55 : 2.80 This mix will be considered as Trial Mix No.2

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30 Step VII:- Make slump trials to find out the actual weight of water to get required slump. Make corrections to the water content & %FA, if required. Step VIII:- Compute 2 more trial mixes with W/C ratios as 0.40 & 0.50, taking %FA as 34% and 38% respectively.

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31 Trial Mix No. 1:- Cement = 185 / 0.4 = 462.5 Kg. Substituting the values in Eq(1), we get 1000 = 185 + 462.5/3.0 + (1/0.34) * fa /2.6) fa = 584 Kg. Substituting the values in Eq(2), we get 1000 = 185 + 462.5/3.0 + (1/0.66) * ca /2.65) ca = 1156 Kg. So the mix proportion works out to be W : C : fa : ca = 185 : 462.5 : 584 : 1156 = 0.4 : 1 : 1.26 : 2.50

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32 Trial Mix No. 3:- Cement = 185 / 0.5 = 370 Kg. Substituting the values in Eq(1), we get 1000 = 185 + 370/3.0 + (1/0.38) * fa /2.6) fa = 683 Kg. Substituting the values in Eq(2), we get 1000 = 185 + 370/3.0 + (1/0.62) * ca /2.65) ca = 1136 Kg. So the mix proportion works out to be W : C : fa : ca = 185 : 370 : 683 : 1136 = 0.5 : 1 : 1.85 : 3.07

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33 Step IX:- Cast atleast 3 cubes for each trial mix. Step X:- Test the cubes for compressive strength at 28 days.

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34 28 Days Compressive Strengths of Trial Mixes W/C Ratio C/W Ratio Compressive Strength (Kg/Cm 2 ) 0.402.50457 0.452.22420 0.502.00360

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35 Step XI:- Draw a graph between compressive strength Vs C/W Ratio.

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37 Step XII:- From the graph, find the W/C ratio for the required target mean compressive strength. Step XIII:- C alculate the mix proportions corresponding to the W/C ratio, obtained from the graph.

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38 Final Mix:- From the graph, for a target strength of 390 Kg/Cm 2, W/C ratio = 0.47 Cement = 185 / 0.47 = 394 Kg. Substituting the values in Eq(1), we get 1000 = 185 + 394/3.0 + (1/0.38) * fa /2.6) fa = 675 Kg. Substituting the values in Eq(2), we get 1000 = 185 + 394/3.0 + (1/0.62) * ca /2.65) ca = 1123 Kg. So the mix proportion works out to be W : C : fa : ca = 185 : 394 : 675 : 1123 = 0.47 : 1 : 1.71 : 2.85

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39 Step XIV:- Check the cement content & W/C ratio against the limiting values given in Table-5 of I.S: 456-2000 for given type of exposure & type of Concrete.

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40 Table-5 Minimum Cement content Maximum Water-Cement ratio and Minimum Grade of Concrete for different exposures with normal weight of aggregate of 20mm nominal maximum size. Sl. No. Exposure Plain ConcreteReinforced Concrete Minimum Cement Content kg/m 3 Maximum Free Water Cement Ratio Minimum Grade of Concrete Minimum Cement Content kg/m 3 Maximum Free Water Cement Ratio Minimum Grade of Concrete i)Mild2200.60-3000.55M20 ii)Moderate2400.60M153000.50M25 iii)Severe2500.50M203200.45M30 iv)Very Severe 2600.45M203400.45M35 v)Extreme2800.40M253600.40M40

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41 From the table 5 of IS: 456–2000, the minimum Cement content & W/C ratio, For moderate, for RCC are 300Kgs. & 0.5 The Cement content = 394Kgs. > 300Kgs. Hence Ok The W/C Ratio = 0.47 < 0.5 Hence Ok

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42 TEST REPORT Concrete Mix RCC M30 with 20.0mm M.S.A. Sl. No. ParticularsResult 1Characteristic Compressive strength in N/Sq.mm 30 2Maximum size of Aggregate in mm20.0 3Type of ExposureModerate 4Type of Site controlGood 5Target Average Compressive Strength in N/Sq.mm 38.2 6Workability in terms of Slump in mm25-75 7Mode of CompactionVibration 8Mix Partiuclars: a.Water-Cement Ratio b.Materials per cubic metre of concrete in Kg. i)Water ii)Cement (OPC 43 Grade) iii)Fine Aggregate iv)Coarse Aggregate c.Mix Portion by weight 0.47 185 394 675 1123 1:1.71:2.85

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43 Secondary Slides:

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44 Sieve Analysis of Fine Aggregate Weight of sample = 500g (approx) Observations: Sieve size Weight retained(g) Cumulative weight retained (g) % Cumulative weight retained (g) % Passing IS:383-1970 Specifications Zone =II Trail 1Trail2Total 10 mm00000100 4.75 mm2244010090-100 2.36 mm67131729875-100 1.18 mm166165331348356555-90 600 micron118117235583584235-59 300 micron1751603359189288-30 150 micron36427899610000-10 150 micron pass224----

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45 Zones of Fine Aggregate Sieve Size IS : 383 – 1970 % Passing for Zone IZone IIZone IIIZone IV 10.00 mm100 4.75 mm90-100 95-100 2.36 mm60-9575-10085-10095-100 1.18 mm 30-7055-9075-10090-100 600 micron 15-3435-5960-7980-100 300 micron 5-208-3012-4015-50 150 micron 0-10 0-15

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46 Sieve Analysis of Coarse Aggregate 2 20 mm aggregate : a. Minimum weight of sample = 25 Kg b. Observations : Sieve size Weight retained (Kg) Cumulative weight retained (Kg) % Cumulative weight retained (Kg) % Passing IS:383-1970 Specifications Graded Single sized 400.0 0100 204.7 109095-10085-100 1041.5 46.2 97325-550-20 4.751.647.810000-100-5 4.75 P047.8----

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47 Sieve Analysis of Coarse Aggregate 2 10 mm aggregate : a. Minimum weight of sample = 12 Kg b. Observations : Sieve size Weight retained (Kg) Cumulative weight retained (Kg) % Cumulative weight retained (Kg) % Passing IS:383-1970 Specifications Single Sized 12.50.0 0100 105.4 158585-100 4.7524.3 29.7 81190-20 2.366.936.610000-5 2.36 P036.6----

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48 N = 20 Avg = 30Avg = 35 27,30,30,32,35, 27,33,34,29,28, 30,28,31,32,26, 34,33,25,27,29 28, 32,35,38,40, 34,35,35,36,39, 33,32,32,34,37, 32,35,38,39,36 Total = 600Total = 700 Target mean compressive strength

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49 The value of ‘S’ depends on Degree of Site control and grade of concrete as given in I.S: 456–2000 (Table.8) Sl. No. Concrete Grade GoodFair S1.65XS F ck S1.65XS F ck N/mm 2 Kg/cm 2 N/mm 2 Kg/cm 2 1M103.55815.81614.57.417.4178 2M153.55820.82124.57.422.4229 3M204.06.626.62715.08.328.3288 4M254.06.631.63225.08.333.3339 5M305.08.338.33906.09.939.9407 6M355.08.343.34416.09.944.9458

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50 Step IV:-Fixation of Water Cement ratios for trial mixes. Sl. No. Required Grades Trial W/C 1M20, M15, M100.55, 0.6, 0.9 2M25, M20, M150.5, 0.6, 0.7

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51 Final Mix for RCC-M25:- From the graph, for a target strength of 322 Kg/Cm 2, W/C ratio = 0.57 which is > 0.5, So, limit W/C ratio to 0.5 only. Cement = 185 / 0.5 = 370 Kg. Substituting the values in Eq(1), we get 1000 = 185 + 370/3.0 + (1/0.38) * fa /2.6) fa = 683 Kg. Substituting the values in Eq(2), we get 1000 = 185 + 370/3.0 + (1/0.62) * ca /2.65) ca = 1136 Kg. So the mix proportion works out to be W : C : fa : ca = 185 : 370 : 683 : 1136 = 0.50 : 1 : 1.85 : 3.07

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52 Specific Gravity of Cement [ IS : 4031 – 1988]: Specific gravity of cement (S c ) (W2 - W1) = ---------------------------- x 0.79 (W4 - W1) - (W3 - W2) Where, W1 = Weight of specific gravity bottle in g W2 = Weight of specific gravity bottle with about half filled cement in g W3 = Weight of specific gravity bottle with about half filled cement & rest is filled with kerosene in g. W4 = Weight of specific gravity bottle completely filled with kerosene in g 0.79 = Specific Gravity of Kerosene.

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53 Specific Gravity of Fine Aggregate & Coarse Aggregate [ IS : 2386 (Part.3) - 1963]: D Specific gravity (Gs) = -------------- C – ( A – B) Where, A = Weight of Pycnometer vessel containing sample & filled with distilled water in g B = Weight of Pycnometer completely filled with distilled water only in g C = Weight of saturated surface dry sample in g D = Weight of oven dried sample in g

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