The values at optimum asphalt content shown in part 6 shows that the stability

The values at optimum asphalt content shown in part 6

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The values at optimum asphalt content shown in part 6, shows that the stability and voids in mineral aggregate (VMA) achieve the specifications, while the air voids and flow didn’t achieve the specifications due to the errors of the experiment. The errors in this experiment can be summarized as the following: 1) The major source of errors is due to the deficient number of blows, which give higher voids than it should be. 2) Mistakes in preparing the aggregate samples. 3) The using of a typical values of aggregate specific gravity and water content. 4) Errors in devices, which include the balance, the stability testing machine. 5) Errors in calculation, especially because of using different unit systems. Conclusion: 1) The Marshall method is a method used in mix design of asphalt concrete pavement, to find the optimum asphalt content. 2) The Marshall method is very long, and has a very large source of errors, so more cares must be taken. 3
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3) It is very important in any paving project to know the optimum asphalt content which gives the best properties, by any method of design. 4) If some of the results do not match the specification, some of the materials properties must be changed and the design must be made again to achieve the specifications. 5) Never take a lab in the summer. References: 1) ASTM, D 1559 – 76 (year 76), pages (437 – 446). 2) MS – 2, chapter 3, pages (17 – 32), chapter 6, pages (67 – 80). Tables: Test Results: Groupe# Unit Weight (Kg/Cm3) Adj. Stability Flow Air Void VMA I 2.161 971.9 22 8.972 21.526 II 2.161 469.4 18 11.579 19.84 III 2.146 769.6 20 10.88 21.230 IV 2.194 689.7 50 11.603 17.76 Aggregate Size Distribution. Sieve size Passing weight specification limits (%) Passing middle point (%) Retained (%) % in between Weight in between Cumulative weight 100 100 0 5 60 60 ¾˝ 90 – 100 95 5 14.5 174 234 ½˝ 71 – 90 80.5 19.5 12.5 150 384 ⅜˝ 56 – 80 68 32 22.5 270 654 #4 35 – 56 45.5 54.5 15 180 834 4
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#8 23 – 38 30.5 69.5 10.5 126 960 #16 13 – 27 20 80 9 108 1068 #50 5 – 17 11 89 2 24 1092 #100 4 – 14 9 91 4 48 1140 #200 2 – 8 5 95 5 60 1200 Pan 0 0 100 check 100% 1200 Table 5–2: Asphalt Content. Group No. Asphalt % by total weight Weight of asphalt, (g) 1 4.5 50 2 5 63 3 5.5 77 4 6 90 Appendix Sample of calculation, Sieve #4: Passing weight specification limits = 35 – 56 % Passing middle point = (upper limit + lower limit) / 2 = (56 + 35) / 2 = 45.5 % Retained percent = 100 – passing middle point = 100 – 45.5 = 54.5 % Percent in between = retained #8 – retained #4 = 69.5 – 54.5 = 15 % Weight in between = percent in between * total weight of aggregate = 15 % * 1200 = 180 g Cumulative weight = previous weight + weight in between = 654 + 180 = 834 Sample of calculation, group # 1: Assume weight of asphalt = x Then x / (1200 + x) = 4% x = 50 gm Calculations: Part 1: 1) Column 3 = % of asphalt by weight of total mix for each group. 2) Column 4 = weight of the mix specimen in air, in grams. 5
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3) Column 5 = weight of the mix specimen in water, in grams. 4) Column 6 = weight of the mix specimen in saturated surface dry condition, in grams. 5) Column 7 = bulk volume, in cm 3 = weight of mix specimen in saturated surface dry conditions – weight of the mix specimen in water. 6) Column 8 = bulk specific gravity of compact mix = weight of the mix specimen in air / bulk volume.
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  • Winter '16
  • Madrid Metro, Metropolitana di Napoli, Bruce Marshall

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