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Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction (2017)

Chapter: APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing

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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Page 135
Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
Page 135
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
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Page 138
Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
Page 138
Page 139
Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
×
Page 139
Page 140
Suggested Citation:"APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing." National Academies of Sciences, Engineering, and Medicine. 2017. Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. Washington, DC: The National Academies Press. doi: 10.17226/24959.
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122 APPENDIX Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing

123 Standard Method of Test for Long‐Term Conditioning of Hot Mix Asphalt  (HMA) for Performance Testing  AASHTO Designation: TP xxx-xx 1 SCOPE  1.1 This standard practice describes a procedure for the long‐term conditioning  of uncompacted hot mix asphalt (HMA) for performance testing to simulate  the aging that occurs over the service life of a pavement. The procedure for  long‐term conditioning in performance testing is preceded by a procedure  for short‐term conditioning in mixture mechanical property testing in  AASHTO R 30.  1.2 This standard may involve hazardous material, operations, and equipment.  This standard does not purport to address all safety problems associated  with its use. It is the responsibility of the user of this procedure to establish  appropriate safety and health practices and to determine the applicability of  regulatory limitations prior to use.  2 REFERENCED DOCUMENTS  2.1 AASHTO Standards:   PP 3, Preparing Hot Mix Asphalt (HMA) Specimens by Means of the Rolling Wheel Compactor  PP 60, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC)  R 30, Mixture Conditioning of Hot Mix Asphalt (HMA)  T 312, Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor  T 316, Viscosity Determination of Asphalt Binder using Rotational Viscometer 2.2 Other Document:   Draft Final Report for NCHRP Report 9-54, Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction, October 1, 2017.

124 3 TERMINOLOGY  3.1 Definitions:  3.1.1 Enhanced Integrated Climatic Model (EICM) – A one‐dimensional coupled heat  and moisture flow model that can be used to determine pavement temperature  at any depth of interest.  4 SUMMARY OF Practice  4.1 A mixture of binder and aggregate is conditioned in a forced‐draft oven at  95°C after prior short‐term conditioning for mixture mechanical property  testing according to R 30. The duration of conditioning at 95°C is selected  to reflect the time, climate, and pavement depth for a given pavement  location in the United States using the climatic aging index (CAI). The long‐ term conditioned loose mixture samples are prepared for maximum  specific gravity (Gmm) testing and then compacted for subsequent  performance testing.  5 SIGNIFICANCE AND USE  5.1 The long‐term performance of HMA can be predicted more accurately by  using conditioned test samples rather than unconditioned samples. The  long‐term mixture conditioning in the performance testing procedure is  designed to simulate the aging that the mixture will undergo in service.  6 APPARATUS  6.1 Oven: A forced‐draft oven, thermostatically‐controlled with horizontal air  flow, and capable of maintaining any desired temperature setting from  room temperature to 176°C within ± 3°C.  6.2 Thermometers: Thermometers having a range from 50°C to 260°C and  readable to 1°C.  6.3 Miscellaneous: A metal pan for heating aggregate, a shallow metal pan for  the short‐term conditioning of uncompacted HMA, a 1‐inch tall metal pan  for the long‐term conditioning of uncompacted HMA, a metal spatula or  spoon, timer, and gloves for handling hot equipment. 

125 7 HAZARDS  7.1 This standard involves the handling of HMA that can cause severe burns if it  contacts skin. Follow safety precautions to avoid burns.   8 LONG‐TERM MIXTURE CONDITIONING PROCEDURE  8.1 The long‐term conditioning for performance testing applies to laboratory‐ prepared loose mixtures that have been subjected to short‐term  conditioning as part of the mixture mechanical property testing procedure  described in R 30.  8.2 Determine the required long‐term conditioning duration that reflects the  desired field aging in terms of age, climate, and depth using Equation 1.  1 exp( / ) / 24 N oven a i i t DA E RT    (1) where  toven = required oven aging duration at 95°C to reflect field aging (days); CAI = climatic aging index; D = depth correction factor; A = frequency (pre-exponential) factor; Ea = activation energy; R = universal gas constant, or ideal gas constant; Ti = pavement temperature obtained from the EICM at the depth of interest at the hour of interest, i (Kelvin);   Table 1 lists the values of D, A, and Ea.  Table 1 — Climatic Aging Index Fitting Coefficients Pavement Layer Depth CorrectionFactor (D) Pre-exponential Factor (A) Activation Energy (Ea) Surface Layer (6 mm) 1.0000 1.40962 13.3121 20-mm Depth 0.4565 1.40962 13.3121 Deeper Layers (below 20 mm) 0.2967 1.40962 13.3121 8.2.1 Break down any large chunks of asphalt mixtures in the short-term aged loose mixture sample, taking care to avoid fracturing the aggregate, so that the clusters of the fine aggregate portion are not larger than the nominal maximum aggregate size (NMAS). This step needs to be performed shortly after short-term aging to ensure that the asphalt mixture is sufficiently soft to be separated into pans for

126 oven aging. If an HMA sample is not sufficiently soft to be separated manually, then place it in a pan and warm it in an oven until it can be separated as described. 8.2.2 Apportion the short‐term aged loose mixture into several pans such that each pan  has a relatively thin layer of loose mix, approximately equal to the mixture NMAS.  8.2.3 Place the pans that contain mixture in a forced‐draft oven at 95°C ± 3°C for the  duration determined by Equation (1). Place the pans on different shelves so that  the pans are arranged vertically within the oven as much as possible. Ensure that  adjacent pans do not overlap.   8.2.4 Rotate the pans to different shelves at four evenly‐spaced time intervals during  the long‐term conditioning period so that each pan has similar exposure to heat  and air flow at different locations within the oven.   8.2.5 After long‐term conditioning, remove the conditioned mixtures from the oven  and mix all of the mixtures together in order to obtain a uniform mixture.  8.2.6 Allow the mixture to cool to room temperature. The long‐term conditioned loose  mixture sample is now ready for compaction or subsequent testing as required.  8.3 Preparing Specimens from Loose HMA  8.3.1 Specimens Compacted Using the Superpave Gyratory Compactor  8.3.1.1 Compact the specimens in accordance with PP 60. Cool the test specimens at  room temperature for 16 ± 1 hour.  Note 4. Extrude the specimen from the compaction mold after cooling for 2 to 3 hours. Note 5. Specimen cooling usually is scheduled as an overnight step. Cooling may be accelerated by placing the specimen in front of a fan. 8.3.2 Specimens Compacted Using the Rolling Wheel Compactor  8.3.2.1 Compact the specimens in accordance with PP 3.  8.3.2.2 Cool the test specimens at room temperature for 16 ± 1 hour.  8.3.2.3 Remove the slab from the mold, and saw or core the required specimens from the  slab.  9 REPORT  9.1 Report the binder grade, binder content (to nearest 0.1 percent), and the  aggregate type and gradation, if applicable. 

127 9.2 Report the following long‐term conditioning information for the  performance testing conditions, if applicable:  9.2.1 Long‐term mixture conditioning temperature in laboratory (nearest 1°C);  9.2.2 Long‐term mixture conditioning duration in laboratory (nearest 5 min); and  9.2.3 Laboratory compaction temperature (nearest 1°C).  10 Keywords  10.1 Conditioning; hot mix asphalt; long‐term conditioning.  APPENDICES (Nonmandatory Information) X1. LABORATORY AGING DURATION MAPS X1.1. The CAI values for various locations in the United States were calculated, as described in Section 9, using hourly pavement temperature history data obtained from the EICM to provide an overview of the proposed laboratory aging durations for various climates, field aging durations, and depths. X1.2. The CAI values and measured durations that are needed to match field aging correlate linearly in a one-to-one relationship. Thus, the CAI values represent the required duration at 95°C that is needed to match the field aging for a given pavement temperature history and depth. X1.3. Laboratory aging durations were calculated for three field ages: 4 years, 8 years, and 16 years. For each field age, the laboratory aging durations were determined at three depths: 6 mm, 20 mm, and 50 mm, and rounded to the nearest day. X1.4. Figure X1.1 shows the CAI-determined loose mixture aging durations at 95°C that are required to match 4, 8, and 16 years of field aging at a depth of 6 mm. Figure X1.1 demonstrates that climate has a significant effect on the required laboratory aging duration that is required to match a given field age.

128 (b) (a)

Figure X pavemen field agin X1.5. X1.6. 1.1-Require t surface fo g. Figure that ar compa Figure requir indica affect A dep layer a structu d oven agin r (a) 4 year X1.2 show e required t rison betwe X1.2 demo ed to match ting that the oxidation le th of 20 mm sphalt mixt re than nea g duration s of field ag s the CAI-d o match 4, 8 en the labor nstrates tha the field agi temperature vels. represents ures becaus rer the surfa 129 at 95°C to ing, (b) 8 y etermined lo , and 16 yea atory aging t significant ng at a dept gradient an a reasonable e it better re ce and avoid match leve ears of field ose mixture rs of field a durations pr ly shorter la h of 20 mm d diffusion depth for th flects bulk b s the effect l of field ag aging, and aging durat ging at a dep esented in F boratory agi compared t in pavemen e evaluatio ehavior with of ultraviol ing 6 mm b (c) 16 year ions at 95°C th of 20 mm igure X1.1 ng duration o 6 mm, ts significan n of surface in a pavem et oxidation (c) elow s of . A and s are tly ent .

130 (b) (a)

Figure X below pa years of X1.7. X1.8. 1.2-Require vement sur field aging. Figure that ar The re simula indica surfac in a fe pavem term o Based resear mm, b evalua depth layers d oven agin face for (a) X1.3 show e required t sults demon te aging at ting the pres e of the pav w cold north ent surface ven conditi on the resu chers conclu ut does not tion of asph of 50 mm c . g duration 4 years of s the CAI-d o match 4, 8 strate that c a depth of 5 ence of a si ements. In F ern states in in these col oning to mim lts presented ded that lon change appr alt mixtures ould be usef 131 at 95°C to field aging, etermined lo , and 16 yea onsiderably 0 mm comp gnificant ox igure X1.3, dicates that d regions are ic field con in the draft g-term agin eciably belo that have b ul for evalua match leve (b) 8 years ose mixture rs of field a shorter agin ared to depth idation grad the required long-term a not signifi ditions. NCHRP Pr g does take w that dept een prepare ting interm l of field ag of field agin aging durat ging at a dep g durations s of 20 mm ient with de aging dura ging at 50 m cant enough oject 9-54 r place below h. Conseque d to match f ediate and b ing 20 mm g, and (c) ions at 95°C th of 50 mm are required and 6 mm, pth near the tion of zero m below th to require l eport, the a depth of ntly, the ield aging at ase asphalt (c) 16 . to thus days e ong- 50 a

132 (b) (a)

Figure X below pa years of 1.3-Require vement sur field aging. d oven agin face for (a) g duration 4 years of 133 at 95°C to field aging, match leve (b) 8 years l of field ag of field agin ing 50 mm g, and (c) (c) 16

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TRB’s National Cooperative Highway Research Program has released a pre-publication, non-edited Report 871: Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. The report presents a proposed standard method for long-term laboratory aging of asphalt mixtures for performance testing. The method is intended for consideration as a replacement for the method in AASHTO R 30, “Mixture Conditioning of Hot Mix Asphalt (HMA),” which was the most commonly used method for aging asphalt materials for performance testing for input to prediction models for the past 25 years. The method improves on R 30 in that the laboratory aging time is specifically determined by the climate at the project location.

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