A Proposed Technology Evaluation Program for Warm-Mix Asphalt (2012) / Chapter Skim
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NAtioNAl CooperAtive HigHwAy reseArCH progrAm Responsible Program Officer: Edward T Harrigan July 2012 C O N T E N T S Introduction, 1 Research Objective, 1 Study Approach, 2 Literature Summary, 2 Survey Results, 3 Questionnaire for WMA Producers, 3 Questionnaire for State Transportation Agencies and Local Public Agencies, 5 Scoping Interviews of Accelerated Pavement Test Facilities, 10 Work Plan and Commentary for a Proposed WMA Technology Evaluation Program, 10 Definition of WMA, 10 Cost Supportable by WMA Manufacturers, 10 Proposed Work Plan and Commentary, 11 References, 25 A PROPOSEd TEChNOLOgy EvALuATION PROgRAM fOR WARM MIx ASPhALT This digest summarizes key findings from the project final report for NCHRP Project 20-07, Task 311, "Development of a Warm Mix Asphalt Technology Evaluation Program," conducted by Villanova University, Villanova, Pennsylvania, under the direction of the principal investigator, Dr.
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2WMA manufacturers and accelerated pavement test facilities to further help shape the product in Task 3. Based on the results of Tasks 1 and 2, a proposed work plan to evaluate WMA technologies by sponsoring organizations such as AASHTO NTPEP was prepared in Task 3.
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3that WMA appears to be more susceptible to stripping and coating issues; however, such moisture damage has not been evident in the field (Epps Martin et al.
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4a large portion of the fuel consumed at an asphalt plant is used in heating the binder, aggregate, and mix during mix production, 53% of the manufacturers were able to quantifiably measure their energy usage. Eighty percent of respondents reported having compared the energy used for HMA to the energy used for WMA.
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5also partner with NAPA or state APA activities. A few respondents actually develop a product-based QC plan (11%)
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6WMA technology. Numerous state DOTs hosted WMA demonstrations to determine whether WMA should be allowed for state-funded paving projects.
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7was reported as the third most frequently used. These findings imply that most agencies, including local agencies, apply state-level specifications for WMA projects.
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8Six organizations were unsure as to the exact cause of difficulty reaching compaction targets, while a few indicated it had been a function of mixture design and the plant mix produced. Some additional comments suggested that difficulty in reaching target density was due to a lack of experience or the learning curve associated with constructing a new technology.
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9varied. Some respondents have never been approached, others were approached as often as monthly (11% of respondents)
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10 respondents cited monitoring of rutting, moisture damage, and fatigue cracking. Agencies reported that it was difficult to estimate a cost for monitored, full-scale WMA field sections subjected to live traffic and typical construction conditions, since these were placed in conjunction with HMA projects.
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11 program would be the cost to complete APT for field performance. All of the WMA manufacturers who responded to the survey indicated that they would be willing to pay between $10,000 and $25,000 to have their product evaluated in a national program like AASHTO NTPEP.
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12 Chemically-processed warm mix asphalt -- Asphalt mixing process which includes technologies that use a combination of emulsification agents, surfactants, polymers, and additives to improve coating, mixture workability, and compaction, as well as adhesion promoters. The chemical additive package is used either in the form of emulsion or added to bitumen in mix production process and then mixed with hot aggregate.
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13 COMMENTARy: In addition, a requirement for plant-mixed, quality control laboratory- compacted (PMQLC) specimens may cause challenges in that the majority of contractors do not have the capability of compacting tall gyratory specimens.
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14 Control Manager. These evaluations shall be performed at 6-month intervals unless the technician does not routinely perform the test.
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15 additive package is used either in the form of emulsion or added to asphalt binder in the mix production process and then mixed with hot aggregate.
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16 Binder Testing. The continuous performance grade of original WMA binder and extracted WMA binder shall be determined to ascertain the impact of WMA additive or process on binder stiffness.
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17 Mixture Volumetric Testing. Reheat bulk mixture sampled during production from ambient temperature for 2.5 hours at the WMA compaction temperature.
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18 Compactability. Determine the number of gyrations to 92 percent relative density in accordance with section 8.3 of the draft appendix to AASHTO R 35 (Bonaquist 2011)
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19 Rutting. Specified tests shall be performed to evaluate the test mixture's propensity to rut.
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20 AASHTO T 340 shall also be conducted on bulk mixture laboratory-compacted samples and extracted core conditions using the Asphalt Pavement Analyzer (APA) to evaluate rutting.
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21 Summary of Laboratory Tests Tables 1 through 4 provide a summary of the laboratory tests for binder, aggregates, mixture volumetrics, and mixture performance. Products may be tested either as supplied (neat)
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22 Accelerated Pavement Testing. Two pavement locations will be selected at an APT facility.
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23 • 205-mm (8-inch) stabilized granular aggregate base, suitable for rutting and fatigue cracking testing applications.
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24 If the manufacturer is absent during the scheduled construction, or fails to carry out its responsibilities during the scheduled production and paving of the WMA and HMA sections, all costs associated with labor, materials and equipment, preparation of the test site, and any potential repairs of the paving site will be charged to the manufacturer. If an alternate date can be arranged it will be the manufacturer's responsibility to furnish traffic control (if necessary)
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25 tion; 3 in the wheelpath at 3, 6, and 12 months; and 3 between the wheelpaths at 3, 6, and 12 months. • Level of compactive effort during placement of test section.
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26 Engineering Properties, Emissions, and Field Performance of Warm Mix Asphalt Technologies. Volume 1: Literature Review.
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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP)
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