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170 A Manual for Design of Hot Mix Asphalt with Commentary Example Problem 9-6. Calculating the Maximum Allowable RAP Content Given an HMA Design with a Specific New Asphalt Binder The RAP binder from Example 4 will be used in an HMA mixture. A PG 64-22 binder with excellent low temperature characteristics is available, and the pro- ducer would like to use this binder in mixtures with RAP because of limited binder storage at the plant. The RAP has a binder content of 4.4%, and the HMA mixture has a binder content of 5.2%. Determine the amount of RAP that can be used with this binder to meet the specification requirements for PG 70-22. The critical temperatures for the new binder, based on historical data provided by the supplier, are Tc(High) = 66.0 C, Tc(Int) = 19.3 C, and Tc(Low) = -17.3 C. Solution Much of the required information for this problem is the same as Example 5 and is entered in HMA Tools in the same way. The required continuous grade temper- atures for a PG 70-22 are Tc(High) = 70.0 C, Tc(Int) = 28.0 C, and Tc(Low) = -22.0 C; these values are different from those for the PG 64-22 required in the previous example and should be entered in cells C6:C8. The critical temperatures for the new binder (PG 64-22) are entered in cells C44:C45 and C47. The minimum and maximum RAP contents, as a weight percentage of the total RAP plus aggregate weight, are given in cells C64 and C65, respectively: 33.5% minimum and 38.1% maximum. For the actual mix design, a value of 35% RAP would be a good choice. Note that for RAP contents of 15% and lower, the effects of RAP on binder grading need not be considered. Therefore, if HMA Tools calcu- lates that less than 15% RAP should be used in a mix because of binder grading considerations, a value of 15% is reported in cell C64. In a similar way, RAP con- tents above 50% are discouraged because of practical difficulties in handling such a quantity of RAP in many plants, so that the highest value HMA Tools will report in cell C65 is 50%, regardless of the value calculated on the basis of binder grading. Handling RAP Materials in the Laboratory RAP materials must be handled differently than new aggregates when preparing specimens for volumetric design and performance analysis. First, the weight of the binder contained in the RAP must be accounted for during laboratory batching. Second, the RAP must be heated gently during the preparation of laboratory specimens to avoid changing the properties of the RAP binder. Recommended methods for handing RAP are discussed below. Laboratory Batching A supply of RAP for the preparation of laboratory specimens is obtained by combining the main portion of the individual samples for each stockpile and thoroughly mixing the combined material. Material for each RAP stockpile should be kept separate. Prior to batching, the RAP should be dried in an oven at 60 C (140 F) to remove field moisture. Laboratory batching is based on the weight of the aggregate, while the stockpile percentages used to produce the HMA at the hot-mix plant are based on total weight. When the HMA is composed of all new aggregates, the stockpile percentages can be used directly. However, when RAP stockpiles are used, the weight of the binder contained in the RAP must be accounted for and stockpile percentages based

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Reclaimed Asphalt Pavement 171 on the total weight of aggregate must be computed and used for laboratory batching. The required analysis was discussed earlier in the Blending and Variability section of this chapter. Example 1 illustrated the required computations. When preparing laboratory specimens, new aggregate stockpiles should be separated into the following size fractions: Passing 37.5 mm--Retained 25.0 mm Passing 25.0 mm--Retained 19.0 mm Passing 19.0 mm--Retained 12.5 mm Passing 12.5 mm--Retained 9.5 mm Passing 9.5 mm--Retained 4.75 mm Passing 4.75 mm--Retained 2.36 mm Passing 2.36 mm Because of the relatively large amount of fine material in most RAP, it is not necessary to separate the RAP into size fractions for laboratory batching. The amount of each size fraction of new aggregate needed for a laboratory batch is computed directly from the proportions based on the total weight of aggregate. The amount of each RAP stockpile needed for a laboratory batch must be increased to account for the weight of binder in the RAP using Equation 9-4: M RAPAGG M RAP = 100 (9-4) (100 - PbRAP ) where MRAP = mass of RAP required for the laboratory batch, g MRAPAGG = mass of RAP aggregate required for the laboratory batch, g PbRAP = RAP binder content, wt % The mass of binder provided by the RAP is then Pb M RAPBINDER = RAP M RAP (9-5) 100 where MRAPBINDER = mass of RAP binder in the laboratory batch, g MRAP = mass of RAP in the laboratory batch, g PbRAP = RAP binder content, wt % HMA Tools can be used to perform these and all other required calculations for determining batch weights of mix designs containing RAP. Before determining batch weights for a mix design, all of the pertinent mix design data should be entered on various worksheets, including "General," "Binders," "RAP_Binders," "Aggregates," "RAP_Aggregates," and "Trial_Batches." Other data should be entered in the worksheet "Batch." For cylindrical specimens, the diameter and height of up to three different-sized specimens are entered in cells F3:F5 and G3:G5, respectively. The numbers of specimens needed for each of these three different cylinder sizes are entered in cells I3:I5. The dimensions and number of specimens for up to two differently shaped beam-shaped specimens are entered in a similar way in cells F8:I9. If desired, an extra amount of loose mix can be entered in cell K3 (in grams)--this might be material needed for theoretical maximum specific gravity determinations. In addition to this loose mix, an extra percentage of material can be specified in cell O7. This represents a contingency, to ensure that enough material is available for the required specimens; 5 or 10% should normally be entered here. The user must also make sure to specify the trial batch number for the batch calculations in cell O1; this would be a number from 1 to 7, corresponding to the trial batch numbers in the worksheet "Trial_Batch."

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172 A Manual for Design of Hot Mix Asphalt with Commentary HMA Tools will calculate batch weights for each aggregate and RAP material, providing a complete breakdown for coarse material (retained on the 2.36-mm sieve) and three different breakdowns for fine aggregate: complete, partial (in two-sieve fractions), and with no break- down. HMA Tools also calculates the amount of new binder required--the amount of binder contributed by the RAP is automatically accounted for. The worksheet "Batch" is conveniently designed to print out a one page report that can be used to weigh out materials in the laboratory. The last example in this chapter shows how HMA Tools is used to calculate batch weights for mix designs containing RAP. Example Problem 9-7. Laboratory Batching for an HMA Mix Design Containing RAP Laboratory specimens of the mixture from Example 1 will be prepared. The aggre- gate gradations were given previously in Table 9-1. The mixture will be produced using three new aggregate stockpiles, hydrated lime, and two RAP stockpiles. The stockpiles will be combined in the following proportions: 29% of Aggregate 1, 40% of Aggregate 2, 10% of Aggregate 3, 1% lime, 10% Coarse RAP, and 10% Fine RAP. The target VMA for the mix is 16.0% and the target air void content is 4.0%. Deter- mine batch weights for making two 150-mm-diameter by 100-mm-tall cylindrical specimens with 2,000 grams of extra material for performing a theoretical maxi- mum specific gravity test. Allow 5% extra material for contingency. The fine aggre- gate fraction (passing the 2.36-mm sieve) will not be further broken down, and the RAP will not be broken down at all. Calculate weights for this trial batch. Solution The aggregate and RAP data are entered into the worksheets "Aggregates" and "RAP_Aggregates" as for Example Problem 1. In the worksheet "Batch," 1 should be entered for batch number in cell O1. Dimensions for the cylindrical specimen are entered in cells F3:G3, and 2 is entered for the number of specimens in cell I3. The amount of loose mix (2,000 g) is entered in cell K3, and 5% is entered in cell O7 for the desired amount of extra mix. After pressing shift+F9 to calculate, the batch weights appear on the lower portion of the spreadsheet. Table 9-10 sum- marizes the batch weights calculated by HMA Tools for this example. Table 9-10. Summary of batch weights for example 7. Material Total Fraction Batch wt., g Mm wt, g Aggregate 1 12.5 9.5 267 9.5 4.75 2,136 4.75 2.36 386 - 2.36 179 Aggregate 2 9.5 4.75 82 4,091 4.75 2.36 1,514 -2.36 2,495 Aggregate 3 9.5 4.75 102 1,023 4.75 2.36 389 -2.36 532 Lime 102 All 102 CRAP 1,022 All 1,022 FRAP 1,023 All 1,023 New Binder 506 All 506 Total 10,735

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Reclaimed Asphalt Pavement 173 Heating RAP Exercise care when preparing laboratory specimens with RAP to avoid changing the properties of the RAP binder. The RAP should be heated for the shortest time possible to reach the mixing temperature. Heat the RAP for no more than 2 hours in a separate oven set to 110C (230F). Higher temperatures and longer heating times have been shown to change the properties of some RAP. The new aggregates should be heated from 10 to 20 C above the mixing temperature before combining with the RAP and new binder. The mixture should be mixed, short-term aged, and compacted in the usual manner. Bibliography AASHTO Standards M 320, Standard Specification for Performance-Graded Asphalt Binder R 29, Grading or Verifying the Performance Grade of an Asphalt Binder T 2, Standard Method of Test for Sampling Aggregates T 248, Standard Method of Test for Reducing Samples of Aggregate to Testing Size T 308, Standard Method of Test for Determining the Asphalt Binder Content of Hot-Mix Asphalt (HMA) by the Ignition Method T 30, Standard Method of Test for Mechanical Analysis of Extracted Aggregates T 164, Standard Method of Test for Quantitative Extraction of Bitumen for Bituminous Paving Mixtures T 209, Standard Method of Test for Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures T 84, Standard Method of Test for Specific Gravity and Absorption of Fine Aggregate T 85, Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate T 176, Standard Method of Test for Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test T 319, Standard Method of Test for Quantitative Extraction and Recovery of Asphalt Binder from Asphalt Mixtures T 240, Standard Method of Test for Effect of Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test) T 315, Standard Method of Test for Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) T 313, Standard Method of Test for Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR) Other Standards ASTM D 5821, Standard Test Method for Determining the Percentage of Fractured Particles in Coarse Aggregate ASTM D 4791, Standard Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate Other Publications McDaniel, R., and R. M. Anderson (2001) NCHRP Report 452: Recommended Use of Reclaimed Asphalt Pavement in the Superpave Mix Design Method: Technician's Manual, TRB, National Research Council, Washington, DC, 58 pp. McDaniel, R. S., et al. (2000) NCHRP Web-Only Document 30: Recommended Use of Reclaimed Asphalt Pavement in the Superpave Mix Design Method: Contractor's Final Report, TRB, National Research Council, Washington, D.C., October, 461 pp. NAPA (2007) NAPA Quality Improvement Series 124: Designing HMA Mixtures with High RAP Content, NAPA, Lanham, MD NAPA (1996) Recycling Hot Mix Asphalt Pavement, Information Series 123, NAPA, Lanham, MD NAPA (2000) Recycling Practices for HMA, Special Report 187, NAPA, Lanham, MD, 2000. FHWA (1998) "User Guidelines for Waste and Byproduct Materials in Pavement Construction" FHWA-RD-97-148, FHWA, Washington, DC.