Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories (2020) / Chapter Skim
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Pages 24-48
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24 C H A P T E R 3 A survey on practices related to fabrication of specimens for asphalt performance testing was distributed to state DOTs, Canadian provinces, and partner laboratories. A total of 80% of state DOTs, along with the District of Columbia, provided a response to the survey; no responses were received from Canadian provinces.
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State of the Practice 25 18 1 13 Conducted only in-house by agency Conducted only through consultant/university labs Conducted both in-house and through consultant/university labs Figure 3. Performance testing location reported by agencies.
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26 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories 7 9 14 13 12 26 13 23 19 17 26 7 7 4 12 18 0 5 10 15 20 25 30 APA Cantabro CTIndex DCT DTCF E*
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State of the Practice 27 1 2 8 1 2 3 1 1 1 1 1 1 1 2 1 3 0 5 10 15 20 APA Cantabro CTIndex DCT DTCF E*
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28 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories nonroutinely for research or other purposes. The uses of tests falling into the "other" category are summarized in Table 10.
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State of the Practice 29 Several agencies did report use of other compactor types (e.g., kneading compactor or Marshall hammer) but these were rare cases.
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30 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories Test Type Equipment Mix Splitter Superpave Gyratory Compactor Oven Rotary Saw Coring Drill Core Drying Device Gluing Templates Gluing Jigs Temperature Conditioning Chamber Vacuum-Bag Sealing Device APA 29% (2)
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State of the Practice 31 6 7 10 9 11 24 12 18 16 16 23 6 6 4 7 7 3 1 1 5 3 1 8 4 1 6 4 5 1 3 3 1 1 1 1 1 2 1 1 2 9 0 4 8 12 16 20 24 28 32 36 APA Cantabro CTIndex DCT DTCF E*
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32 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories Figure 15. Types of mix that agencies use in fabrication of performance test specimens by test type.
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State of the Practice 33 With respect to laboratory conditioning of asphalt mixtures during the specimen fabrication process, 37% of agency survey responses indicated no laboratory conditioning, whereas the remaining 63% of responses indicated a preference for the use of loose mix aging (Figure 17)
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34 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories 8 4 7 2 1 7 1 13 1 3 10 1 1 3 12 2 4 3 3 1 4 2 7 3 4 2 2 1 5 0 5 10 15 20 25 APA Cantabro CTIndex DCT DTCF E*
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State of the Practice 35 A detailed breakdown of the distribution between loose mix and compacted sample laboratory conditioning procedures adopted by agencies and partner laboratories is plotted in Figure 21 and Figure 22, respectively. The survey data indicated that loose-mix conditioning is more often adopted by agencies in the performance-test specimen-fabrication process than conditioning of compacted samples.
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6 6 13 10 11 10 19 14 15 22 6 6 4 12 13 3 1 1 3 3 1 5 1 8 2 3 0 5 10 15 20 25 30 35 APA Cantabro CTIndex DCT DTCF E*
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State of the Practice 37 5 4 7 1 1 6 12 1 3 7 1 1 2 10 2 2 3 2 6 1 1 3 2 3 0 5 10 15 20 APA Cantabro CTIndex DCT DTCF E*
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38 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories For survey respondents indicating that they use laboratory conditioning on compactedasphalt-mix specimens, the survey subsequently collected information on whether conditioning is conducted on bulk specimens (prior to cutting and/or coring) or on finished test specimens.
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State of the Practice 39 2 11 AASHTO R 30 Long-term Aging Protocol Other Process Figure 29. Preference of agency labs regarding protocol for long-term laboratory conditioning of compacted specimens for performance testing.
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40 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories 101 9 Target Air Void Required Target Air Void Not Required Figure 32. Distribution of agency laboratory practices regarding requirements of target air void level for performance test specimens.
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207 20 Target Air Void Required Target Air Void Not Required Figure 33. Distribution of partner laboratory practices regarding requirements of target air void level for performance test specimens.
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42 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories Figure 37. Target air void level requirements for performance test specimens as used by partner labs.
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State of the Practice 43 Figure 39. Allowable tolerances to target air void level for performance test specimens as used by partner labs.
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44 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories Test Type Number of Agencies Using the Test Between Loose-Mix Sampling and Laboratory Compaction Between Preparation of Compacted (Bulk) Specimen and Finalized Test Specimen Between Finalized TestSpecimen Fabrication and Mechanical Testing Between Repeated Mechanical Testing (if Multiple Tests Are Conducted on Same Specimens)
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From page 45... ...
State of the Practice 45 Test Type Number of Partner Labs Using the Test Between Loose Mix Sampling and Laboratory Compaction Between Preparation of Compacted (Bulk) Specimen and Finalized Test Specimen Between Finalized -TestSpecimen Fabrication and Mechanical Testing Between Repeated Mechanical Testing (if Multiple Tests Are Conducted on Same Specimens)
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46 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories 9 19 18 15 3 3 3 3 1 16 4 4 4 5 5 8 3 0 5 10 15 20 25 30 35 40 Between loose mix sampling and laboratory compaction Between preparation of compacted (bulk) specimen and finalized test specimen Between finalized test specimen fabrication and mechanical testing Between repeated mechanical testing (if multiple tests are conducted on same specimens)
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State of the Practice 47 Figure 42. Most frequent issues agencies encountered in fabricating specimens.
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48 Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories Only eight agencies reported that they are currently sponsoring or planning to sponsor research related to the fabrication of laboratory specimens for performance testing. The descriptions of research provided in the survey responses indicate that these agencies are looking at performance-engineered mixture design approaches, various testing types, and long-term aging in the laboratory.
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