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CEMENT CONCRETE MIX DESIGN

CEMENT CONCRETE MIX DESIGN. Prepaid by: 130670106041 130670106042.

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CEMENT CONCRETE MIX DESIGN

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  1. CEMENT CONCRETE MIX DESIGN Prepaid by: 130670106041 130670106042

  2. 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.

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

  4. 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

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

  6. Workability (Clause 7.1, IS:456-2000)

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

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

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

  10. STEPS INVOLVED IN CONCRETE MIX DESIGN • Step I:- Determine the physical properties of concrete ingredients. I. CEMENT (OPC 43 Grade)

  11. 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)

  12. 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

  13. IV. MECHANICAL PROPERTIES

  14. V. 10.0mm COARSE AGGREGATE 1. Sieve Analysis 2. Unit Weight in Kg/Cu.m a) Loose : 1427 b) Rodded : 1587

  15. VI. BLENDING OF COARSE AGGREGATE:

  16. Step II:- Compute Target Mean Compressive Strength: Fck = fck + t * S Fck = Target Mean Compressive Strength at 28 days in N/Sq.mm fck = 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

  17. Values of t

  18. Assumed Standard Deviation (Table 8, IS:456-2000)

  19. Step III:- Select the Water-Cement ratio of trial mix from experience

  20. Step IV:- Select the water content per cubic metre of concrete from table2 of I.S: 10262-2009.

  21. Approximate water content (Kg) per cubic metre of concrete (Table 32, SP:23-1982)

  22. Volume of Coarse Aggregate per Unit Volume of Total Aggregate (Table 3, IS:10262-2009)

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

  24. Step VI:- Then we find the quantities of Fine & Coarse aggregate by absolute volume method. V = (W+C/Sc+(1/p) * (fa/Sfa)) * (1/1000) - (Eq.1) and V = (W+C/Sc+(1/(1-p)) * (ca/Sca)) * (1/1000) - (Eq.2) Where V = Absolute volume of fresh concrete = 1 m3 W = Mass of Water (Kg) per m3 of concrete C = Mass of Cement (Kg) per m3 of concrete p = Percentage of fine aggregate. fa = Mass of fine aggregate ca = Mass of coarse aggregate Sc = Specific gravity of cement. Sfa = Specific gravity of fine aggregate. Sca = Specific gravity of coarse aggregate.

  25. 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.

  26. 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.

  27. 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

  28. 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.

  29. 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

  30. 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

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

  32. 28 Days Compressive Strengths of Trial Mixes

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

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

  35. Final Mix:- From the graph, for a target strength of 390 Kg/Cm2, 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

  36. 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.

  37. 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.

  38. 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

  39. TEST REPORT Concrete Mix RCC M30 with 20.0mm M.S.A.

  40. Secondary Slides:

  41. Sieve size Weight retained(g) Cumulative weight retained (g) % Cumulative weight retained (g) % Passing IS:383-1970 Specifications Zone =II • Sieve Analysis of Fine Aggregate Trail 1 Trail2 Total 10mm 0 0 0 0 0 100 100 4.75 mm 2 2 4 4 0 100 90-100 2.36 mm 6 7 13 17 2 98 75-100 1.18 mm 166 165 331 348 35 65 55-90 600 micron 118 117 235 583 58 42 35-59 300 micron 175 160 335 918 92 8 8-30 150 micron 36 42 78 996 100 0 0-10 150 micron pass 2 2 4 - - - - • Weight of sample = 500g (approx) • Observations:

  42. Sieve Size IS : 383 – 1970 Zones of Fine Aggregate % Passing for Zone I Zone II Zone III Zone IV 10.00 mm 100 100 100 100  4.75 mm 90-100 90-100 90-100 95-100  2.36 mm 60-95 75-100 85-100 95-100 1.18 mm  30-70 55-90 75-100 90-100 600 micron  15-34 35-59 60-79 80-100 300 micron 5-20 8-30 12-40 15-50 150 micron  0-10 0-10 0-10 0-15

  43. Sieve size Weight retained (Kg) Cumulative weight retained (Kg) % Cumulative weight retained (Kg) % Passing IS:383-1970 Specifications Graded Single sized 40 0.0 0.0 0 100 100 100 20 4.7 4.7 10 90 95-100 85-100 10 41.5 46.2 97 3 25-55 0-20 4.75 1.6 47.8 100 0 0-10 0-5 4.75 P 0 47.8 - - - - Sieve Analysis of Coarse Aggregate 2 20 mm aggregate : a.Minimum weight of sample = 25 Kg b.Observations :

  44. Sieve size Weight retained (Kg) Cumulative weight retained (Kg) % Cumulative weight retained (Kg) % Passing IS:383-1970 Specifications Single Sized 12.5 0.0 0.0 0 100 100 10 5.4 5.4 15 85 85-100 4.75 24.3 29.7 81 19 0-20 2.36 6.9 36.6 100 0 0-5 2.36 P 0 36.6 - - - - Sieve Analysis of Coarse Aggregate 2 10 mm aggregate : a.Minimum weight of sample = 12 Kg b.Observations :

  45. Target mean compressive strength

  46. The value of ‘S’ depends on Degree of Site control and grade of concrete as given in I.S: 456–2000 (Table.8)

  47. Step IV:-Fixation of Water Cement ratios for trial mixes.

  48. Final Mix for RCC-M25:- From the graph, for a target strength of 322 Kg/Cm2, 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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