A Proposed Technology Evaluation Program for Warm-Mix Asphalt (2012)

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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. Leslie McCarthy. The project final report was prepared by Dr. McCarthy, Dr. Seri Park, and Mr. David Mensching. Research Results Digest 374 INTROduCTION Warm mix asphalt (WMA) has been gaining acceptance across the United States and Canada in recent years. A large number of state departments of transpor- tation (DOTs) have hosted WMA dem- onstrations to determine if WMA should be allowed for state-funded paving proj- ects. These demonstrations have shown that WMA is constructible and can reduce fuel usage and emissions associated with hot mix asphalt (HMA) production. How- ever, many of these demonstrations were conducted with only one or two WMA technologies. Now there are over 25 com- mercially available WMA technologies in the United States. Most states do not approve a WMA technology for use on state-maintained roads without a well- documented demonstration project. The WMA technology suppliers that were not part of these early demonstration projects often are required to organize a demonstra- tion on their own to gain approval for state paving projects. A standard evaluation program for con- struction of WMA demonstration projects, including a process for laboratory evalu- ation of WMA mixtures, can encourage collection of reliable data sufficient for state agencies to approve a WMA tech- nology. The American Association of State Highway and Transportation Offi- cials (AASHTO) National Transportation Product Evaluation Program (NTPEP) suc- cessfully conducts over $1M in engineer- ing materials evaluation testing per year. NTPEP represents a centralized system of testing, evaluation, and data reporting of engineering materials for the state DOTs. A prospective NTPEP process for evalua- tion of WMA technologies might consist of a combination of laboratory, plant, and field testing. NTPEP “one-time approval” of a product is indicative of its complying with key performance properties; however, each transportation agency could still fol- low its own process for accepting a NTPEP- compliant WMA technology. RESEARCh OBJECTIvE The primary objective of NCHRP Project 20-07, Task 311, was to define a WMA technology evaluation program that would be compatible with a central- ized system of testing, evaluation, and data reporting of engineering materials for the state DOTs, such as the AASHTO NTPEP.

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 spon- soring organizations such as AASHTO NTPEP was prepared in Task 3. The work plan was focused on evaluating WMA technologies through both labo- ratory testing and field demonstration sections. The program was developed to be compatible with, and suitable for adoption by, NTPEP. A project final re- port summarizing the results, findings, and conclu- sions of Tasks 1 through 3 was prepared in Task 4. LITERATuRE SuMMARy The numerous research reports, technical articles, presentations, and WMA manufacturer communi- cations reviewed consistently cited measurement of WMA’s resistance to rutting and moisture suscepti- bility as a critical element. Numerous research proj- ects in the United States and abroad stressed the im- portance of conducting laboratory tests that would define a WMA mixture’s propensity to rut, crack, or strip in the presence of water. Other important prop- erties cited were mixture stiffness, workability, and compactability. Many of the research projects fol- lowed the evaluation of potential impacts to WMA performance in a manner similar to those defined in NCHRP Projects 9-47 and 9-47A (Anderson et al. 2008; Kvasnak et al. 2009): • Rutting: reduced aging of the binder could in- crease rutting potential; • Fatigue life: reduced aging of the binder may increase mixture fatigue capacity; • Mixture stiffness: reduced aging of the binder may reduce the mixture stiffness; • Moisture susceptibility: incomplete drying of the aggregate could increase moisture sensi- tivity of the mixture; and • Low-temperature cracking: certain WMA additives may increase the potential for low- temperature damage, based on the results of binder tests. At the same time, the reduced aging of the binder could reduce the potential for low-temperature cracking. The fact that WMA has been reported as hav- ing lower stiffness than traditional HMA provides the potential to incorporate more recycled asphalt pavement (RAP) in WMA. Laboratory tests showed STudy APPROACh The objective of NCHRP Project 20-07, Task 311, was accomplished in four tasks: 1. Evaluate current state of practice in WMA, 2. Survey state DOTs on WMA use, 3. Prepare framework for WMA evaluation, and 4. Submit final report. In Task 1, current practices reported in the litera- ture by state DOTs, Federal Highway Administra- tion (FHWA), academia, and industry for evaluat- ing WMA technologies were reviewed. The review included (1) relevant results from NCHRP Projects 9-43, 9-47, and 9-47A; (2) the test frameworks and guidelines available from the WMA Technical Working Group at http://www.warmmixasphalt. com/Default.aspx; (3) National Asphalt Paving As- sociation (NAPA) Publication QIP-125, “Warm- Mix Asphalt: Best Practices”; and (4) comparable AASHTO practices such as (a) R 15, Asphalt Additives and Modifiers, (b) R 26, Certifying Sup- pliers of Performance-Graded Asphalt Binders, (c) R 34, Evaluating Deicing Chemicals, and (d) R 31, Evaluation of Protective Coating Systems for Struc- tural Steel. In Task 2 the state DOTs, industry, and local agencies were surveyed to determine the types of information these stakeholders would require to make an informed decision about using a new WMA technology. A response rate of 94% was achieved for the DOT survey. The survey was submitted through the AASHTO Subcommittee on Materials/NTPEP Committee with an NCHRP transmittal letter. The survey was distributed via the online software, SurveyMonkey®. In order to en- courage a more comprehensive stakeholder dataset, the asphalt industry in each of the states (i.e., state Asphalt Pavement Association) was also invited to participate in the survey in an effort to collect supplemental information and possibly capture a view of the use of WMA at the private industry level. Since there are a number of local agencies in the United States who have aggressively pursued implementation of WMA, feedback from at least five of these local agencies was solicited. Follow- up interviews were conducted via phone or email to gather more detailed information from agencies that have been using more advanced techniques for evaluating WMA technologies in their state. This task ultimately included additional surveys of both

3that WMA appears to be more susceptible to strip- ping and coating issues; however, such moisture damage has not been evident in the field (Epps Martin et al. 2011). Fuel savings was also reported as a by-product of using WMA in lieu of traditionally produced HMA. However, it should be noted that fuel savings can be offset by the cost of the WMA additives, estimated at $2 to $4 per ton of WMA produced (Anderson et al. 2008). It should also be noted that since 2008, fuel costs have risen significantly, enhancing the cost benefit of WMA use. In April 2011, Northeast Asphalt User-Producer Group (NEAUPG) established a definition for WMA and criteria for qualification of WMA technologies. The definition adopted by NEAUPG was originally established by the New York State DOT as the following: Warm Mix Asphalt (WMA) technologies gener- ally allow a reduction in the temperature at which asphalt mixes are produced and placed, thus help- ing the environment and worker health and safety. WMA technologies can also be used as a compac- tion aid extending the paving season in colder cli- mates when produced at normal temperatures at which the hot mix asphalt mixes are produced. The issue of writing a specification for WMA alone was raised, and NEAUPG members agreed that writing such a specification would not be efficient. Rather, it was agreed that a process like that of AASHTO NTPEP or New York State DOT (NYSDOT) should be adopted by NEAUPG. NYSDOT has a qualification process to vet vari- ous WMA technologies and contractors. Once a technology is approved by NYSDOT, it is added to an approved products list. A contractor can then elect to use that approved technology in a paving project. The WMA qualification process may include labo- ratory testing of materials with the Hamburg rutting test (AASHTO T 324), APA rutting test (AASHTO T 340), and the dynamic modulus test (AASHTO T 342, AASHTO TP 79). As a result of the April 2011 meeting, the northeastern state DOTs plan to adopt NYSDOT’s qualification process until AASHTO provides an NTPEP evaluation program for WMA. SuRvEy RESuLTS The results of the following three surveys were analyzed as part of this research project: a ques- tionnaire for WMA producers; a questionnaire for state departments of transportation and local transportation agencies; and scoping interviews of Accelerated Pavement Test (APT) facilities. These results were used to define the WMA tech- nology evaluation program presented in the fol- lowing section. Questionnaire for WMA Producers The questionnaire for WMA producers solicited feedback from the WMA industry on what aspects should be addressed in the future potential develop- ment of a WMA technology evaluation program. The questionnaire was distributed to the 22 tech- nology contacts listed in the Warm-Mix Asphalt: Best Practices 2nd Edition (Prowell et al. 2011) and a response rate of approximately 50% was obtained from these WMA producers, manufacturers, and contractors who construct with WMA. Approximately 70 percent of manufacturers responded they were familiar with the AASHTO NTPEP process. Many respondents did not provide feedback regarding what aspects of an AASHTO NTPEP evaluation program they would recommend. However, the respondents who did provide feedback suggested the comparison of performance between HMA and WMA, moisture susceptibility tests, and rutting potential tests as being key elements. All man- ufacturers agreed they would be willing to partici- pate in a compliance testing and evaluation process such as NTPEP. Many manufacturers are already working in several states and they see this potential evaluation process as a clear advantage. Seventy percent of the manufacturers indicated a willingness to spend $10,000 to participate in a program such as NTPEP compliant, while 30 percent would be will- ing to spend $25,000. Energy and Emissions A few questions were aimed at providing infor- mation as to the methods for emissions reductions and energy savings. Manufacturers were asked if they used a quantifiable method for measuring emissions. Sixty percent of manufacturers measure emissions at the plant and 10 percent also measure emissions dur- ing construction. Forty percent answered they do not have a quantifiable measure for emissions. Manufacturers were also asked if they had a quantifiable method to measure the amount of energy expended to produce and construct their product. Fig- ure 1 illustrates the responses to this question. Since

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 manufactur- ers were able to quantifiably measure their energy usage. Eighty percent of respondents reported hav- ing compared the energy used for HMA to the energy used for WMA. Some manufacturers calculated energy usage by analyzing the time it took to pro- duce the WMA mix. There are circumstances in which asphalt mix may also require on-site reheat- ing during construction. As a result, approximately 18% of manufacturer respondents indicated that they also measured fuel usage factors during construction. Only 6% reported measuring energy usage in terms of the time it took to transport the mix. WMA Production and Quality Control Testing The survey also asked how manufacturers of the various technologies ensure quality during produc- tion and construction of their products (Figures 2 and 3). All of the WMA manufacturers and contrac- tors offer some type of training by their company to ensure successful production of their product; some also partner with NAPA or state APA activities related to WMA. Other efforts include overseeing plant modifications for use of their product, issu- ing a product specification, and developing a quality control (QC) plan for the plant. Only 8% of respon- dents mentioned sponsoring a control mix. The majority of manufacturers (39%) ensure pavement contractors are capable or outfitted to con- struct WMA by offering contractor-specific training, as shown in Figure 3. In addition, 17% of respondents figure 1. Methods used by WMA manufacturers for measuring energy savings. Fuel usage at plant 53% N one of the above 6% Fuel usage by material transport 0% Fuel usage by pavers, rollers, site equip 0% Time to produce WMA mix 17% Time to transport mix 6% Time to construct and compact pavement 18% figure 2. Methods used by WMA manufacturers for ensuring quality during production. On-site training by your company 38% Plant certification process (one time only) 0% Periodic certification every "x" years 0% Partner with NAPA or State APA activities 12% Oversee plant modification 15% Develop product based QC plan for plant 8% Control mix sponsored by your company 8% Product specifications to follow8% Off-site or web-training by your company11%

5also partner with NAPA or state APA activities. A few respondents actually develop a product-based QC plan (11%), sponsor an onsite (17%) or off-site control section (5%), or both. Two of the respondents developed a construction specification collaboratively with a transportation agency. Seventy percent of manufacturers require or rec- ommend running a full suite of commonly used labo- ratory tests to measure the physical properties of the WMA mix prior to construction. Manufacturers were asked to comment on what type of QC was important to successful implementation of their product. Some suggested that the same QC system currently in place for HMA be used. Other feedback cited proper installation and calibration of plant equipment was important as well as the use of best practices. Factors Affecting WMA The manufacturers were queried as to which types of field conditions may affect their products. Field conditions listed included the following: snow plows and studded tires; wet versus dry climate; freeze versus no-freeze climate; long haul distances; use of material transfer vehicle (MTV) versus no mix re-agitation; and heavy truck traffic (greater than 20% trucks). The results are shown in Figure 4. When asked which mixture variations signifi- cantly alter the base condition performance of their products, half the respondents answered their prod- uct would not be affected. However, the factors that were mentioned as potentially requiring more atten- tion included those shown in Figure 5. Questionnaire for State Transportation Agencies and Local Public Agencies The state DOT and local agency questionnaire gathered information on approaches used by agen- cies to make an informed decision about any new figure 3. Methods used by WMA manufacturers for ensuring quality in construction. Partner with NAPA or State APA activities 17% Construction contractor training by your company 39% Construction specifications joint with DOT 11% Control section sponsored by your company on site 17% De vel op pro duc t- bas ed QC pla n for lay dow n 11 % Control section sponsored by your company off site 5% Contractor qualification process (one time only) 0% Presence of snow plows or studded tires 7% Wet vs. Dry Climate 6% Freeze vs. No freeze climate 6% Longhaul distances 6% Use of MTV vs. No agitation 6% Heavy truck traffic (>20%) 6% Other 13% Not affected by any listed condition 50% figure 4. Field conditions assessed as potentially affecting WMA performance.

6WMA technology. Numerous state DOTs hosted WMA demonstrations to determine whether WMA should be allowed for state-funded paving projects. Taken together, these demonstrations have estab- lished that WMA is constructible and can reduce fuel usage and emissions associated with hot mix asphalt (HMA) production. The majority of these demonstrations were conducted with one or two WMA technologies; a small number involved three. A number of local public agencies have also used, or are imminently planning to use, WMA for paving projects in their jurisdictions. Data from the survey were analyzed to identify how agencies are handling the use of WMA and whether they are finding suc- cess in doing so. The response rates for this survey were excellent, with 94% of state DOTs (including the District of Columbia, Puerto Rico, and FHWA Federal Lands); 130% of local public agencies (more replied than the number initially invited); and 16% of state asphalt pavement associations (APAs) providing input on what they see as items necessary to make informed decisions regarding implementation of WMA specifi- cations. A total of 99 organizations responded to this questionnaire (53 DOT respondents, 6 state APAs, and 40 local agencies, including City of Oshawa in Canada). Figure 6 identifies the locations of the sur- vey respondents. The survey first asked respondents about their WMA project experience to date. Approximately 65% (64 responses) have built WMA projects to date, 4% have designed but not yet built WMA projects, and 31% have not yet designed or built any WMA projects. When asked about their current specifications for constructing WMA pavements, the respondents’ top two approaches were use of either a state agency WMA specification or a state agency HMA specification followed at lower temperatures. The use of as-is state agency HMA specifications figure 5. Mixture modifications ranked as potentially affecting WMA performance. Anti-strip agents or lime 0% Recycled shingles 8% Asphalt rubber 7% High percentage (>30%) recycled asphalt pavement 7% Stone matrix asphalt gradation 7% High polymer modification (TLA, SBS) 7% Porous or permeable gradation 7% Other 7% Not affected by any modifications 50% figure 6. Distribution of NCHRP Project 20-07, Task 311, survey respondent locations.

7was reported as the third most frequently used. These findings imply that most agencies, including local agencies, apply state-level specifications for WMA projects. When determining factors for mix design (e.g., mixing and compaction temperatures, mix- ture conditioning temperature, etc.), survey results showed that most agencies used the recommenda- tions of the WMA manufacturer. Respondents were asked with which WMA technologies (chemically- processed, organic-additive, and foaming-processed/ water-based) they have the most experience to date, in order to assess general application trends. Results showed that foaming-processed or water-based WMA technologies are the most frequently used by the majority of transportation agencies. WMA Pavement Damage Ninety-two (92%) percent of organizations re- ported having observed no damage since WMA pavements had been placed and exposed to traffic. However, since detailed information on the traffic exposure period was not captured, any firm conclu- sions regarding the WMA pavement performance would be premature. Two agencies observed mois- ture damage and three agencies observed reflective cracking damage in field WMA sections. Another phenomenon reported by one agency was a sheen observed on several projects after construction and construction-related raveling. Although the sample size was not significant enough to develop any fur- ther correlation between reported damage types and geographical location, it is interesting to note that all organizations who reported field damage are located in the Long-Term Pavement Performance (LTPP) freeze zone, which includes the United States north of about latitude 37° except for portions of California and the Pacific coasts of Washington and Oregon. The two organizations that reported evidence of moisture damage in WMA sections are located in LTPP Wet-Freeze zones (roughly the states in the Northeast, Middle Atlantic, and Midwest). Subsequent phone interviews were conducted to obtain more detailed information on the observed field damage. All the interviewees indicated that the damage observed in their WMA pavement sections was comparable to that found in similar HMA sec- tions or in the adjacent HMA control section. The main exception to this finding was with construction- related issues which the agencies could not conclu- sively attribute to the WMA additive or process as the primary cause of failure. In a few cases, agen- cies echoed concerns about the future of WMA in their respective regions due to the issues reported. However, a key finding of this survey is the lack of low-temperature cracking in the WMA sections and the impression that the damage in WMA sections is not reported as being more severe than that seen in HMA pavements when cracking does occurs. Control Section and Post-Compaction Monitoring The majority of agencies reported the use of HMA control sections; 4 organizations used a WMA control section; 17 did not use any control section. Methods used to test or document any noticeable differences between the control and WMA sections were also obtained. Most agencies performed volu- metric testing and visual inspection. One agency paved a 3-mile stretch of two-lane rural highway with HMA and WMA side-by-side for testing and documentation. One organization stated that before a WMA technology could be approved, the contrac- tor was asked to provide a WMA control section to demonstrate that the application can meet all con- struction specifications. For WMA post-compaction monitoring, the most widely used method involves taking pavement cores. The nuclear density gauge and visual distress survey were reported as the next most frequently followed methods. The Pavement Quality Indicator (PQI) non-nuclear gauge was also mentioned as being used by one organization. WMA Mix Variation and Core Extraction Recycled asphalt pavement (RAP) was the most commonly used WMA mix additive reported in the survey, with 83% of respondents using RAP. Polymer modifiers and anti-stripping agents were the next widely used, respectively. Only one orga- nization used recycled ceramics or glass and Trini- dad Lake asphalt (TLA) as mix design additives. Most of the organizations reported that they extract WMA cores at the time of construction and post- final compaction. It should also be noted that about 12% of respondents stated that they do not extract WMA cores. The number of cores collected ranged from 5 to 40, depending on the organization and project size. Field Compaction Targets Approximately 45% of organizations reported no difficulty with contractors reaching field compac- tion targets during completion of WMA projects.

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 addi- tional comments suggested that difficulty in reach- ing target density was due to a lack of experience or the learning curve associated with constructing a new technology. Decision Making for Use of WMA In order to capture the factors that would influ- ence agencies when deciding when to use WMA, many questions associated with decision making were asked. Because there were a number of agen- cies who had not yet built WMA in their jurisdictions, responses in the following sections are split into two categories: (1) responses from organizations with WMA project experience, and (2) responses from organizations without WMA project experience. For both categories, agencies were asked which element they would monitor if there were no constraints on cost, staff resources, and time. It is interesting to note that regardless of whether the respondent has had actual WMA project implementation experi- ence, most answers exhibited similar patterns. For example, the ability of the mix to resist rutting, fol- lowed by its ability to resist cracking and moisture damage, ranked as the most important elements to monitor for all respondents. This suggests that most agencies would like to generate a performance- related standard, such as through specifications, for actual production and construction of WMA. A few respondents alluded that there should be no require- ment of additional testing for WMA as compared to HMA, with the exception of emissions testing. The major factor that helped agencies decide whether to select WMA in lieu of HMA was reported to be the contractor’s option or election to pave with WMA. This finding is aligned with the group of respondents who have already implemented WMA projects. Two main elements of the “other” category were budget and traffic conditions and respondents considered those main factors to guide their deci- sion for selecting WMA. One DOT cited that haul distance was considered a major decision factor. No correlation was observed between an agency’s geo- graphical location and its decision to select WMA for paving sections. The top two factors ranked as needing to be overcome for full-scale implementation of WMA were: (1) contractors’ experience with WMA, and (2) lack of detailed WMA specifications. The two factors were observed to be related in that as an organization develops a standard set of specifica- tions for WMA implementation, reliance on the contractors’ experience may decrease. Therefore, the development of a standard process and specifi- cations for WMA implementation were reported to be important. Other difficult factors to overcome were reported to be: cost of building WMA; lack of detailed information on various WMA technolo- gies; lack of documented observations of long-term performance; and, especially, lack of education and training of employees involved with design and construction of WMA. WMA performance was also evaluated by sur- veying the importance of different WMA material properties. The level of importance ranged from Very Important (value of 4) to Not Important (value of 1). Based on level of importance, in situ density and air void properties were reported to be the main factors in determining WMA performance. In addi- tion, binder content, mixture tensile strength, and mixture compactability had average values higher than 3. Lesser values were assigned to moisture susceptibility, long-term raveling, and permanent deformation. One organization pointed out that the need for proper design, placement, compaction, and mix performance is common to WMA, HMA, or any other asphalt mix system. When asked which pavement distress would be most critical in WMA pavements, the majority of respondents cited rutting or moisture damage. Long- term durability of a WMA technology as compared to an HMA technology, and the amount of moisture retained in the mix, were also reported as items which were important to monitoring pavement distresses. WMA Paving Season and Interaction with WMA Producers and Contractors As expected, summer was the predominant sea- son in which WMA projects were constructed. Fall and spring were ranked as the next two seasons in which the majority of WMA projects had been paved. Forty-four (44) percent of respondents indi- cated that WMA did not enable them to pave outside their normal paving period, but 15% of organizations replied that they were able extend their paving sea- son by using WMA instead of HMA. The frequency with which respondents were approached by new WMA producers or contrac- tors wanting to pave with a new WMA technology

9varied. Some respondents have never been ap- proached, others were approached as often as monthly (11% of respondents); every 3 months (11% of respondents); or every 6 months (19% of respondents). One organization indicated that WMA producers often approach it to incorporate new WMA technologies but that contractors rarely request to use WMA. Another organization men- tioned that it has been approached at the end of a normal paving season to switch from the specified HMA to a WMA application. Certification Process Among respondents currently implementing WMA projects, 21% have a WMA technology cer- tification process or qualification program. Organi- zations that have some type of WMA certification process or qualification program were then asked about future implementation of WMA projects. Seventy-seven percent indicated that certification of WMA technologies in future projects would streamline project delivery. Potential Use of AASHTO NTPEP as a WMA Technology Evaluation Program About 40% of respondents were familiar with AASHTO NTPEP while 32% of respondents were not. The majority of respondents unfamiliar with NTPEP were local agencies. The majority of those familiar with AASHTO NTPEP were already par- ticipating in it. Respondents were asked their level of willing- ness to use WMA technologies if NTPEP were to develop a WMA technology evaluation program. Ninety-two (92%) percent of organizations stated that they would be somewhat or very likely to use the results if NTPEP developed a WMA technol- ogy evaluation program. Some DOTs indicated they would require NTPEP evaluation and compliance, while others stated their usage of NTPEP would depend on how the WMA technology evaluation program is formulated. Of the 45 agencies who answered, 33% would require mandatory use of the NTPEP process, while 66% stated that NTPEP pro- cess would be optional. When asked about issues related to the impor- tance of a standard process on which to base WMA production decisions, the majority of respondents that it is very important and only 4% of respondents stated that a standard process would not be important at all. These results imply that a need exists for WMA production to be held to a standard process, accom- panied by potential specification development. WMA Material Sampling Respondents were asked about the frequency with which they collect WMA materials, such as the binder from a supplier, sampling from aggre- gate and RAP stockpiles, loose bulk mixture, and the WMA additive. Agencies routinely collect sam- ples of loose mix at the plant or at the paver (57% of respondents); binder at the supplier or plant (44% of respondents); aggregate stockpiles at the plant (38% of respondents); and RAP at the plant (31% of re- spondents). However, the WMA additive was rarely sampled at the plant, and 48% of respondents indi- cated that no WMA additive sampling is done. Sam- pling of RAP at the plant varied between “routinely collected” and “no sampling is done.” Interestingly, the results indicated that only a small percentage of organizations performed sampling on WMA dem- onstration projects. Conditioning Methods for WMA Samples When asked about the application of conditioning methods to WMA samples, 44% responding reported that no conditioning method was currently being used. Among those who did employ sample conditioning methods, the most frequently reported was 2 hours at the compaction temperature. The next most fre- quently used conditioning method was reheating to compaction temperature. As reheating of WMA specimens can have a criti- cal effect on their measured performance, respondents were asked when they believe that the reheating of WMA specimens should be allowed. The majority reported that reheating of specimens is allowed for Independent Assurance and Acceptance. For dispute resolution testing and quality assurance, some agen- cies (greater than 20%) allowed reheating of WMA specimens, but 19% responded that they did not per- mit reheating of mix in any situation. Supplemental comments provided by respondents varied signifi- cantly regarding the topic of reheating WMA speci- mens. For example, one organization stated that it fol- lows the same reheating process as done for HMA; whereas others reported that reheating is allowed only for research purposes, or for the correction of discrep- ancies related to end-of-load segregation issues, or for determining asphalt content.

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 con- ditions, since these were placed in conjunction with HMA projects. The respondents indicated that break- ing out the actual cost for the HMA alone would have been difficult. However, one agency did provide a rough estimate of $150,000 for conducting the full- scale field evaluation. One local public agency conducted a field eval- uation of HMA and WMA by constructing WMA test sections adjacent to new HMA sections. Both pavement sections received virtually the same mon- itoring; i.e., ARAN, visual inspection, and PASER. Distresses monitored included smoothness, crack- ing, and rutting. Both sections were exposed to live traffic. There were no special warranty or accep- tance criteria involved in either section. WORK PLAN ANd COMMENTARy fOR A PROPOSEd WMA TEChNOLOgy EvALuATION PROgRAM This section presents a proposed work plan for a WMA technology evaluation program, with associ- ated commentary. definition of WMA Based on the information gathered via the lit- erature review, survey responses, and subsequent detailed interviews with manufacturers and state DOTs, the majority of the asphalt industry defines WMA as a material essentially having the same basic mixture volumetrics and performance proper- ties as HMA. The major differences between HMA and WMA were reported to be how the mixture is produced and whether modification is accom- plished through the use of additives or an alternate production process at the plant. This feedback from industry was key to establishing the proposed work plan for the WMA technology evaluation program described herein. Cost Supportable by WMA Manufacturers Based on the survey results, the main challenge to implementation of a WMA technology evaluation Sixty-three percent of respondents do not follow any standard process for reheating WMA specimens. For those who do follow a standard reheating process, 62% consider the time and temperature of reheating as a necessary part of the evaluation procedure. Scoping Interviews of Accelerated Pavement Test facilities Scoping interviews were conducted to solicit key information from staff of Accelerated Pavement Testing (APT) facilities since their use was consid- ered to be a critical element of any WMA technology evaluation program measuring field performance. The interviews gathered general cost information on both full-scale field control test sections and APT control sections. Interviews were conducted with five APT facilities, one DOT, and one local agency. The average cost of installing a typical test sec- tion in an APT facility was reported to be approxi- mately $200,000. Additional in-house costs, such as personnel, indirect costs, and equipment monitor- ing, were not included in this estimate. The range of reported costs for an APT experiment and test sec- tion varied from $20,000 to $400,000. The length of test sections constructed was generally reported to be approximately 200 ft. However, one facility con- structs 550-foot sections. All facilities constructed sections that were at least 50 ft beyond the intended monitoring length; i.e., for a 550-ft section, the moni- tored length was 500 ft, and for a 250-ft section, the monitored length was 200 ft. The number of lanes per APT facility varied from 2 to 12. One facility split up its lanes into 44-ft sections to enable more varied types of testing. Most of the facilities reported that duplicate sections are not routinely installed. Fifty percent of respondents reported their facili- ties conducted test cycles in less than 1 year. The other 50% of respondents indicated an average cycle time of 3 to 5 years. One facility could control temperature from 10 to 70°C. Another facility reported it was ca- pable of maintaining temperature at 50 to 52°C. The rest of the respondents used ambient temperature at their facilities. Reported load levels ranged from 10 to 20 kips. Half of the facilities reported that super- single loading is used, while the other facilities use dual and dual tandem loads. Most facilities employ a unidirectional load with wander and one facility in- corporated a live traffic section of interstate highway. When asked what aspects of a WMA technology evaluation program they consider important, most

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. There were several reasons for this relatively low level of funding. Many of the WMA manufacturers who have been active in the United States and Canada over the past 10 years have already sponsored a sub- stantial number of demonstration pavement sec- tions in multiple states or provinces. Because of this past investment, they are not willing to invest an additional significant amount for evaluation and certification. However, the manufacturers were in- terested in modestly investing to participate in a national program. In addition, they indicated that as new modifications or products are integrated into their systems, there are benefits to being evalu- ated through an ongoing third-party program (such as AASHTO NTPEP). A few manufacturers also indicated that such a program would be a major benefit to others who have not yet made significant investments toward sponsoring individual state DOT pavement sections. Thus, the cost of intensive testing necessary for rigorously evaluating a potential WMA addi- tive or process (in particular in the field with APT) is far greater than the amount that manufacturers indicated that they could support. These findings were instrumental in shaping the details of the proposed laboratory and field testing presented below. Results of the survey of six APT facilities throughout the United States estimated that for an APT facility with multiple cells, based on an av- erage cost of $200,000 and multiple small (e.g., 50 ft by 14 ft) test sections, a number of manufac- turers’ products could be installed and tested si- multaneously during a 1-year evaluation cycle. In this case, it may be feasible that each WMA sec- tion could cost $5,000 to $10,000. However, each manufacturer would be asked to sponsor one WMA and one HMA control test section, resulting in an approximate cost of $10,000 to $20,000 per manu- facturer for APT field testing in one location. The field test data would be captured and analyzed by a designated independent laboratory or test facility. The field testing cost might conceivably fit into the $10,000 to $25,000 range reported as reasonable by the WMA manufacturers; however, this amount excludes the cost of laboratory testing, installation, material transport, sampling equipment, etc. More- over, if the testing were required to be done in two different climatic locations (wet-freeze and wet-no freeze), then the estimated costs would double, at a minimum. Proposed Work Plan and Commentary Summary This work plan is furnished for the benefit of (1) manufacturers interested in participating in a WMA technology evaluation program and (2) state and local agencies that are interested in re- viewing and utilizing the data generated through such a product evaluation. The testing format has been established to provide test results which can be used to assess the performance of material addi- tives or processes for WMA applied to traditional hot mix asphalt production. This work plan defines the evaluation proce- dures for material additives and processes for WMA that could potentially serve as a proposed standard testing protocol for a WMA technology evaluation program (such as through AASHTO NTPEP). The testing facility may be any public or private laboratory appropriately equipped and capable of performing the required evaluations. Evaluation reports will provide performance data but will not indicate that the technology passed or failed spe- cific criteria. Terminology COMMENTARy: Terms provided here are de- rived from those provided in AASHTO specifica- tions and NCHRP Report 691 (Bonaquist 2011). Accelerated pavement testing (APT)—The controlled application of a prototype wheel load- ing, at or above the appropriate legal load limit to a prototype or actual, layered, structural pave- ment system to determine pavement response and performance under a controlled, accelerated accu- mulation of damage in a compressed time period. Air voids (Va)—The total volume of small pockets of air between the coated aggregate par- ticles throughout a compacted paving mixture, expressed as a percent of the bulk volume of the compacted paving mixture.

12 Chemically-processed warm mix asphalt— Asphalt mixing process which includes technolo- gies that use a combination of emulsification agents, surfactants, polymers, and additives to improve coat- ing, 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. Creep—The time-dependent portion of strain that results from stress. Creep compliance—The time-dependent strain divided by the applied stress. Dynamic modulus—|E*|—the absolute value of the complex modulus calculated by dividing the peak-to-peak stress by the peak-to-peak strain for a material subjected to a sinusoidal loading. Dynamic modulus master curve—A compos- ite curve constructed at a reference temperature by shifting dynamic modulus data from various tem- peratures along the log frequency axis. Flow number—FN, the number of load cycles corresponding to the minimum rate of change of permanent axial strain during a repeated load test. Foaming-processed warm mix asphalt— Asphalt mixing process which includes processes that introduce small amounts of water to hot asphalt, either via a foaming nozzle, damp aggregate, or a mineral additive such as zeolite. Organic-additive warm mix asphalt— Asphalt mixing process which includes technolo- gies that use organic or wax additives to achieve the temperature reduction by reducing viscosity of binder. Tensile strength—The strength shown by a spec- imen subjected to tension. Voids in the mineral aggregate (VMA)—The volume of the intergranular void space between the aggregate particles of a compacted paving mix- ture that includes air voids and the effective binder content, expressed as a percent of the total volume of the specimen. Voids filled with asphalt (VFA)—The per- centage of the VMA filled with binder (the effective binder volume divided by the VMA). Warm mix asphalt (WMA)—Warm mix asphalt refers to asphalt concrete mixtures that are produced at temperatures approximately 28°C (50°F) or more cooler than typically used in the production of hot mix asphalt. The goal with warm mix asphalt is to produce mixtures with similar strength, durability, and performance characteris- tics as HMA using substantially reduced produc- tion temperatures. Manufacturer Participation COMMENTARy: One item addressed as part of the DOT, industry, and manufacturer surveys was the type of specimens (both conditioned and manufactured) to be used in the work plan. The majority of survey respondents indicated that they allow reheating of specimens but do not have a standard procedure for doing so. The survey also queried agencies as to the im- portance of including various types of plant- produced specimens. The response was that plant-mixed laboratory-compacted (PMLC) and plant-mixed field-compacted (PMFC) spec- imens were ranked of almost equal importance for inclusion in a WMA technology evaluation program. For this reason, the mixture perfor- mance tests proposed are to be done on both bulk mixture plant samples and cores extracted from the in-place pavement mat, and do not in- clude laboratory-mixed, laboratory-compacted (LMLC) specimens. Manufacturers of material additives and pro- cesses for WMA who elect to participate in the pro- gram must submit a completed application form. For the purposes of this testing program, products intended for vertical or any non-highway applica- tions will not be evaluated. The manufacturer shall supply sufficient quan- tities of each product to perform the required test- ing. The testing facility determines what constitutes “sufficient quantities” for laboratory testing and installation. The manufacturer shall supply bulk mixture samples of WMA (commonly referred to as plant-mixed, laboratory-compacted [PMLC] specimens), preferably compacted immediately after sampling to eliminate the need for mixture reheating (commonly referred to as plant-mixed, quality control laboratory-compacted [PMQLC] specimens). The manufacturer shall also supply cores extracted from the testing facility test pave- ment (commonly referred to as plant-mixed, field- compacted [PMFC] specimens). The test materials shall be labeled with sample numbers traceable to the WMA produced.

13 COMMENTARy: In addition, a requirement for plant-mixed, quality control laboratory- compacted (PMQLC) specimens may cause challenges in that the majority of contrac- tors do not have the capability of compact- ing tall gyratory specimens. Moreover, there has been significant evidence that reheating plant samples above the field compaction tem- perature can alter the true properties of an asphalt mixture. For these reasons, the following two options regarding PMQLC specimens should be con- sidered: (1) allow manufacturers to choose as part of their submittal whether they will allow reheating of their product and, therefore, place the responsibility of defining specimen type (PMLC versus PMQLC) on the manufacturers; or (2) establish a maximum reheating tempera- ture as part of the laboratory testing framework regardless of whether specimens are manufac- tured as PMLC or PMQLC. 6. Verify that the facility is in conformance with applicable federal and state occupational safety and health regulations. 7. Verify that it performs all testing in confor- mance with the requirements of the speci- fied individual test methods. Accreditation through the AASHTO Accreditation Program is the preferable verification. However, ac- creditation through other nationally recog- nized programs such as the National Volun- tary Laboratory Accreditation Program or the International Organization for Standardiza- tion (ISO) Technical Committee 176 (TC 176, Quality Management and Quality Assurance) ISO 9000 and TC 261 (Additive Manufactur- ing) may be considered. Candidate facilities that wish to be designated as an authorized test facility shall meet the following Personnel requirements: 1. Provide an organizational chart that iden- tifies the names and positions of manage- ment personnel and each person that will be involved in or associated with testing and the review of test reports. A laboratory Qual- ity Control Manager shall be designated for review of all Standard Operating Procedures and proficiency evaluations of technicians as described herein. 2. Provide resumes or credentials for all per- sons identified in the organizational chart. The responsible persons supervising the lab- oratory and the staff performing the testing shall have levels of formal education appro- priate for their duties. Quality Control. The laboratory shall identify pro- cedures used to ensure that all testing is conducted at an acceptable quality level. The QC process shall be based upon statistically supported conclusions. The conclusions shall verify that the laboratory is capable of producing reproducible and repeatable test results. The preferred technique for comparative conclusions is to obtain results based on tests per- formed on identical samples by other laboratories that are statistically evaluated for their comparative similarity. The comparative testing must be per- formed using the testing procedures required by the WMA technology evaluation program. Testing proficiencies of all technicians shall be evaluated and documented by the laboratory Quality Testing Facility Criteria Candidate facilities that wish to be designated as an authorized test facility shall meet the following Facilities requirements: 1. Provide documentation to demonstrate experi- ence in performing testing of asphalt materials and mixtures. 2. Verify that the facility has the equipment, facilities, and capability to perform the required testing procedures contained in this work plan by providing a list of equipment that it uses for testing asphalt materials and mixtures. 3. State its policies regarding qualifications and training of its staff to ensure high quality per- formance. This shall include performance reviews of testing proficiency and Standard Operating Procedures for each testing pro- cedure as detailed in the Quality Assurance portion of this document. 4. State the administrative procedures in place to ensure a high quality of comparative test- ing results. 5. Demonstrate the ability to complete all labo- ratory testing of the WMA materials within 3 months of the date that samples are received.

14 Control Manager. These evaluations shall be per- formed at 6-month intervals unless the technician does not routinely perform the test. In this case, proficiency of the technician shall be evaluated and documented prior to testing of products for this program. Testing Capability. The testing facility shall be com- prised of a single entity or a combination of no more than three entities. When more than one facility is used, a single lead facility shall be responsible for the coordination and oversight of all testing and reporting and for the compilation of the final report. The lead facility is re- sponsible for identifying the tests that will be subcon- tracted and for determining that each of the facilities is properly accredited and operates under a rigorous QC plan. Subcontracted facilities cannot be changed with- out the approval of the sponsoring organization(s). The field testing shall be at an appropriate testing facility as designated by sponsoring organization(s). Tests and Test Methods The standard tests and methods are detailed later in this work plan. Test Report The primary testing facility is responsible for entering data generated in its facility into an online database (or other appropriate storage medium) and reviewing any data generated at subcontracted fa- cilities that is entered in the database. All information noted in the Test Report Section of this work plan shall be included in the test report. Product Submission Guidelines Once the manufacturer is notified that its WMA technology system has been accepted for evaluation, the test facility will request that the manufacturer submit clearly marked samples of the product. Once the laboratory testing has been started or the field installation process is complete, no direct written or verbal correspondence between the manufacturer and the testing laboratory is permitted. Any implica- tion of interference from the manufacturer during the testing will be cause for the evaluation to cease. Testing Fees Testing fees are assessed to cover all costs asso- ciated with laboratory testing, material installation, field evaluation, administrative costs, and report generation and distribution. Laboratories will be reimbursed for testing per- formed if a system is withdrawn after testing has begun. If the manufacturer elects to withdraw ini- tial samples after testing begins and resubmit prod- ucts, the manufacturer will be charged additionally for all costs incurred by the laboratory during the initial testing. Policy for Withdrawing Materials from the WMA Technology Evaluation Program A written request to withdraw the material from the evaluation cycle must be received at least 5 busi- ness days before scheduled sampling is to occur. If sampling has occurred, a handling fee of 10 percent of the testing fee will be charged in addition to any laboratory test costs that may have been incurred for evaluation. Testing and Reporting Requirements The laboratory and field evaluation procedures consist primarily of AASHTO and, if necessary because of the lack of a comparable AASHTO method, ASTM tests. It should be noted that this evaluation program is intended for structural asphalt mixtures; thus, bituminous seals, coatings, pres- ervation, or other experimental materials are not included as part of this work plan. Results of the laboratory and field evaluations will be entered directly into an online database or other appropriate storage medium. A timeline for product evaluations is shown in Figure 7. Material Criteria The program will accept three types of additive or process submittal: 1. Foaming-processed warm mix asphalt in- cludes processes that introduce small amounts of water to hot asphalt binder, either via a foaming nozzle, damp aggregate, or through an additive such as zeolite. 2. Chemically-processed warm mix asphalt includes technologies that use a combina- tion of emulsification agents, surfactants, polymers, and additives to improve coating, mixture workability, and compaction, as well as adhesion promoters. The chemical

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. 3. Organic-Additive warm mix asphalt includes technologies that use organic or wax additives to achieve temperature reduction by reducing binder viscosity. 4. In order to be classified as WMA, the mixture must be produced at a plant temperature less than or equal to 132°C (270°F) which is ap- proximately 28°C (50°F) lower than current HMA production temperatures. Material submittals may be limited per manu- facturer per year. A generic material composition description and Material Safety Data Sheet (MSDS) must accompany the submittal for classification and worker safety purposes. WMA material additives and processes may be required to be resubmitted and tested (in the labora- tory only) at a specified interval of time. A signed certification from the manufacturer will be required with the re-submittal stating that the formulation has not changed since the original submission. Once a manufacturer has submitted a product and a sample ID has been assigned, the manufac- turer and product name will remain unchanged throughout the reporting cycle. Laboratory Tests Laboratory Testing to Be Performed. Standard tests should be used to evaluate WMA material additives and processes. There are also provisional, non-standard AASHTO procedures which can assist in ensuring materials are tested to best eval- uate their quality. Both bulk mixture sampled dur- ing production and cores extracted from pavement test sections will be evaluated in the laboratory. Any testing of bulk mixture sampled during pro- duction must be conducted after 5 days but before 30 days after specimen fabrication. An exception to the 30-day rule can be made only if specimens are vacuum-sealed and stored at constant temperature and humidity. Details Duration(Months) -3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Stage 1 Submission Administration Testing Cycle is Posted 0 Submissions Are Due 0 Assignment Letters 1 Stage 2 Product Sampling Coordination Sampling 1 1 2 Stage 3 Product Application Coordination Field Installation 1 2 Installation 1 1 1 2 Stage 4 Product Testing Lab Testing 3 1 2 3 Field Evaluation 12 1 2 3 4 5 6 7 8 9 10 11 12 Stage 5 Product Reporting Lab Testing Results 1 1 Field Evaluation Results 5 1 2 3 4 5 Stage 6 Manual Review Lab Testing Review 1 1 Field Evaluation Review 1 1 Stage 7 Report/Data Release Lab Report Release 0 Field Evaluation Release 0 Warm Mix Asphalt Material Additives and Processes Time Line (months) COMMENTARy: It is proposed that all accelerated field testing of trial WMA sections be conducted within 12 months. This recommendation is based on the survey feedback from a number of APT facilities that indicated that a full-scale pavement experiment is typically completed within a 1-year timeframe. In the rows that compose Stage 5 Product Reporting, both laboratory and field testing is indicated at 3, 6, and 12 months (after installation) to address cores which are extracted commentary from the APT pavement lift and taken into the laboratory for testing. figure 7. Timeline for WMA technology evaluation program.

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. A dynamic shear rheometer (DSR) suitable for testing stiff asphalt binders shall be used. Tests shall be run on original and extracted WMA binder both before and after aging in the pressure aged vessel (PAV). The same process shall then be completed on rolling thin-film oven (RTFO)-aged binder for short-term aging performance. Asphalt binder extraction shall be performed using AASHTO T 164 Method A or ASTM D5404. The use of trichloroethylene (TCE) solvent is not permitted for extraction. One 1-gallon sealed bucket of asphalt binder should be sampled from the plant. COMMENTARy: The recommendation for types of samples and the associated testing time- frame is based on the guidelines established in NCHRP Research Results Digest 370 (Baker et al. 2012). Since the testing facilities may have up to 3 months to complete testing of the manu- facturer’s materials, adherence to the recom- mended time frame between fabrication and testing of the samples is encouraged. The exclusion of TCE as an extraction solvent is founded on research presented by the Fed- eral Highway Administration that showed TCE hardens the extracted binder. The use of 85/15 toluene/ethanol is recommended instead (Baker et al. 2012). COMMENTARy: The recommendation for one 1-gallon sealed bucket of binder comes from Minnesota DOT Report MN/RC 2007-43 (Marasteneau and Zofka 2007) that desig- nates quantities required for state DOT field sampling sites. COMMENTARy: The FHWA WMA Technical Working Group had considered the use of the multiple stress creep recovery (MSCR) test on asphalt binders to gauge their potential for fa- tigue and thermal cracking, following the ap- proach presented by Wen et al. (2010). The work plan proposed herein does not include the MSCR test due to time and budget constraints, as well as questions about the test’s precision and bias; however, it should be noted that this test may prove to be more accurate than the current AASHTO methods in gauging the po- tential for fatigue and thermal cracking. COMMENTARy: The section on binder testing is based on findings by Bonaquist (2011). These are also in line with a portion of the binder test- ing required in NCHRP Research Results Digest 370 (Baker et al. 2012). Additional testing information included herein is based on both user-producer group (NEAUPG) and DOT protocols for binder testing with and without WMA additives. It should be noted that the full sweep of accep- tance testing should be considered in cases where new additives (e.g., rubber, recycled shingles, anti-stripping agent, a new polymer modifica- tion, etc.) have been combined with a WMA technology. In addition, when processes are used that introduce foam into the binder as it enters the plant, sampling binder at the plant may be preferable. However, it may not be pos- sible to safely sample foamed binder at the plant, depending on how the plant is configured. Aggregate Testing. Contractor QC data shall be submitted from aggregate tests conducted prior to production of the test mixtures by the manufacturer. Data must be furnished for the following aggregate properties: gradation, bulk specific gravity, absorp- tion, stockpile moisture content, coarse aggregate angularity, fine aggregate uncompacted voids, flat and elongated, and sand equivalent. For gradation properties, AASHTO T 27 will be employed, while bulk specific gravity and absorption will be obtained through AASHTO T 84 and T 85 procedures.

17 Mixture Volumetric Testing. Reheat bulk mixture sampled during production from ambient tempera- ture for 2.5 hours at the WMA compaction tem- perature. Conduct mix design verification with test data from specimens produced by contractor or state DOT laboratory and with 150-mm (6-inch) diame- ter and 115-mm (4.5-inch) high Superpave gyratory specimens at the design number of gyrations (Ndesign). Conduct in-place density and thickness tests on cores extracted from the WMA test section to compare with properties tested on bulk mixture samples. Mixture Performance Testing. Standard laboratory tests shall be used to evaluate the performance of WMA. All laboratory test specimens shall be pre- pared from bulk mixture sampled during production of the test materials (PMLC) and cores extracted from the paved surface (PMFC). The manufacturer will have the option of providing PMLC or plant- mixed QC laboratory-compacted (PMQLC) material for mixture testing. Preferably, the contractor produc- ing mix for the evaluation shall have a Superpave gyratory compactor equipped to compact tall speci- mens in its QC laboratory. COMMENTARy: The mixture volumetric test- ing required as part of the proposed work plan is limited since the main intent is not mix acceptance. Testing is limited to comparison of the bulk mixture properties with those of the extracted cores. For this reason, the primary tests proposed include Gmm, compaction to Ndesign, air voids, and Gmb. These tests agree with the suite of tests and specimen conditioning recom- mended by Baker et al. (2012). COMMENTARy: Laboratory-mixed laboratory- compacted (LMLC) specimens will not be tested. Therefore, the aggregates used in the manufac- turer’s mix design are not the focus of the evalu- ation, as long as highly absorptive aggregates or those with a history of stripping are not used. The provision of the aggregate property data (e.g., stockpile moisture content, coarse aggre- gate angularity, fine aggregate uncompacted voids, flat and elongated, and sand equivalent) is critical to tracking mixture performance. The proposed suite of tests to be conducted by the testing facilities does not include aggre- gate testing. State DOTs using the results of the evaluation should still rely on their own indi- vidual quality verification or quality acceptance procedures in practice. The laboratory aggregate tests proposed herein are based on those listed by Baker et al. (2012). Only three of the tests shall be conducted by the testing facility (AASHTO T 27, T 84, and T 85), which can be compared to contractor QC labo- ratory data; all other test results shall be provided by contractor data. COMMENTARy: The recommendation for sealed metal buckets totaling to 660 lb of loose asphalt mixture to be sampled from multiple points in the truck bed at the plant comes from the sampling practice employed by the FHWA Mobile Asphalt Mixture Testing Laboratory. The recommendation for 6-inch outside diam- eter cores, extracted to include all asphalt layers down to the interface with the aggregate base, was based on the Minnesota DOT field sam- pling program (Marasteneau and Zofka 2007), which designates quantities required for sam- pling state DOT field sites. The report lists min- imum original material quantities based on different types of laboratory tests and sample geometry requirements. COMMENTARy: As stated previously, two op- tions regarding PMQLC specimens may be con- sidered: (1) allow the manufacturers to choose, as part of their submittal, whether they will allow reheating of their product and therefore, place the responsibility of defining specimen type (PMLC versus PMQLC) on the manufacturer; Sealed metal buckets totaling 660 lb of loose asphalt mix should be sampled from multiple points in the truck bed at the production site or plant. One- hundred fifty (150)-mm (6-inch) outside diameter cores should be extracted to include all asphalt layers down to the interface with the aggregate base.

18 Compactability. Determine the number of gyra- tions to 92 percent relative density in accordance with section 8.3 of the draft appendix to AASHTO R 35 (Bonaquist 2011) with the following modifi- cations: maximum increase in gyrations of 25% at 30°C (54°F) below the planned field compaction temperature, and at the planned field compaction temperature. or (2) establish a maximum reheating tempera- ture as part of the laboratory testing framework regardless of whether specimens are manufac- tured as PMLC or PMQLC. If the contractor participating with the manufac- turer as part of the evaluation has the capability of compacting tall specimens, it is recommended that plant-mixed QC laboratory-compacted (PMQLC) samples be a suitable alternative to the PMLC specimens as long as no reheating (or reheating within specified limits) is applied to the mixture sampled. A major component of carrying out this step successfully is to ensure that the contractor selected to produce WMA for the evaluation has a Superpave gyratory com- pactor (SGC) equipped to compact tall samples. COMMENTARy: Conditioning of bulk mix- ture test specimens is in accordance with the procedure provided in Baker et al. (2012) and AASHTO T 312. The target air void level of 7% ± 1% for compacting bulk mixture test specimens is chosen to represent a typical air void content based on agency construction specifications and the average air void level after rolling. The dynamic modulus testing is conducted in accor- dance with AASHTO TP 79 and PP 61. The dynamic modulus may be used as input to a structural design analysis program such as DARWin-ME to estimate pavement rutting and fatigue cracking levels over the expected ser- vice life. If DARWin-ME is not available for use, the spreadsheet program AMPT_QA_Program (Jeong 2010), which uses pre-solved solutions of the MEPDG to permit estimation of rutting and fatigue cracking, uses the dynamic modu- lus as input. The survey responses did not indicate a strong concern with fatigue cracking and most respon- dents likened the fatigue performance of WMA to be similar to that of HMA. However, a few respondents did report having observed trans- verse reflective cracking in WMA field sections that were placed over jointed Portland cement concrete (JPCP) or over HMA pavement layers. In Minnesota, reflective cracking is being reported in WMA over JPCP and WMA over HMA sections. However, the cracking was not as severe as seen in similar HMA sections. In Cass County, MI, reflective cracking was noted on a WMA over HMA section. The county indicated that the trans- verse cracks observed in the WMA section were no more severe than those in the HMA con- trol section. In Oregon, reflective cracking was observed in a section where a cement-treated base in poor condition was underlying the WMA. There were no cracking problems in similarly located HMA sections, but the substructure characteristics were different. For the reasons discussed above, the stiffness properties of WMA would be of interest, albeit with measurements made with the Asphalt Mix Performance Tester (AMPT) at the reduced set of test conditions (temperature and frequency) called for in AASHTO TP 79 compared to the COMMENTARy: Compactability was consid- ered an element of interest as per the survey responses and the discussion presented in Sec- tion 8.3 of the draft appendix to AASHTO R35 (Bonaquist 2011). Although compactability testing is more akin to mixture design testing, its inclusion is recommended as it would pro- vide a data point to fall back upon if premature field damage occurs during the subsequent field testing phase. Dynamic Modulus. Bulk mixture test specimens shall be conditioned 2 hours at the WMA compac- tion temperature, followed by 16 hours at 60°C (140°F), and an additional 2 hours at the WMA compaction temperature. A target air void level of 7% ± 1% shall be used for compacting bulk mixture test specimens. AASHTO TP 79 and PP 61 shall be followed to determine the dynamic modulus of the mixture.

19 Rutting. Specified tests shall be performed to eval- uate the test mixture’s propensity to rut. Testing shall be done on both loose bulk mixture from the plant and extracted cores from the test facility’s field section. Air void tolerance for test specimens and specimen size shall be in accordance with AASHTO TP 79. Specimens shall be conditioned for 2 hours at the WMA compaction temperature, followed by 16 hours at 60°C (140°F), and an additional 2 hours at the WMA compaction temperature. Repeated load (triaxial confined) testing shall be done on bulk mixture sampled during production in accordance with the procedure in AASHTO TP 79 for measuring flow number (FN) with the Asphalt Mixture Performance Tester (AMPT). The repeated axial load applied shall be 483 kPa (70 psi); a con- fining pressure of 69 kPa (10 psi) shall be used. AASHTO T 324 shall be conducted on bulk mixture laboratory-compacted samples and extracted core specimens at standard conditions and 50°C (122°F) under water. Top and bottom of cores shall be sawed in accordance with AASHTO PP 60, followed by measurement of bulk specific grav- ity (AASHTO T 166 or T 275) and calculation of air voids of each specimen (AASHTO T 269). For comparison, laboratory-compacted samples shall full set required by AASHTO T 342. Justification for the reduced set of test conditions was pre- sented by Bonaquist and Christensen (2005), who found that the reduced data set produces comparable results at less than half the cost of necessary test equipment ($50,000 compared to $125,000) and could be performed in a single day, requiring only 13.5 hours to complete. The testing conditions specified in AASHTO TP 79 include: • Frequencies of 10, 1, 0.1, and 0.01 Hz • Temperatures of 4°, 20°, and 35°, 40° or 45°C (determined by the asphalt binder performance grade) COMMENTARy: In the near future, AASHTO may consider revising the Flow Number section of AASHTO TP 79 to include the latest develop- ments in the evaluation of rutting presented in NCHRP Report 719 (Von Quintus et al. 2012). Guidance presented in the report on preparing and testing the bulk mixture PMLC specimens (e.g., target air void level, number of specimens, load conditions, test procedure) to measure plastic deformation is followed in the Rutting section of this work plan. A method presented in the report for recovering cores from the in-place HMA mat is also proposed for use here as is the concept of using an equivalent test tempera- ture option for testing bulk mixture sampled during production. The report suggests that the analysis use “one test temperature that is defined as the equivalent temperature that will result in the same level of rutting at the end of the design period with the rutting predicted using temperatures defined for that climate and structure.” COMMENTARy: Use of the Indirect Tension (IDT) Method to calculate the dynamic mod- ulus of asphalt concrete from PMFC samples (Kim et al. 2004) was seriously considered. The practical benefit of extracting core samples (38 to 50 mm) from the field test section for the IDT test could be a more accurate measure of in situ dynamic modulus. The proposed work plan does not include this test due to limits on the time available to complete the labora- tory testing and lack of IDT equipment at many laboratories. COMMENTARy: In the case of the WMA tech- nology evaluation program, the climate would be that of the location of the APT facility and the structure would be that built into the field sec- tion at the accelerated pavement testing facility. The procedure presented in Von Quintus et al. (2012) to determine equivalent test temperature offers two methods. The advantage of using this method to determine the flow number is the reduced number of specimens (down to three) required for testing and its applicability to plant produced specimens, both of which may result in time and cost savings.

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. Six (6) cylindrical speci- mens, 150-mm (6-inch) in diameter and 75 ± 2-mm (3.0 ± 0.1-inch) tall, are required to be tested at the high performance-grade temperature of the asphalt binder to evaluate rutting susceptibility of the mixture. Air voids shall be determined through the measure- ment of the bulk specific gravity (AASHTO T 166) after sawing. For test result verification purposes, laboratory-compacted specimens shall be compacted to a common air void content. Durability. Bulk mixture test specimens shall be compacted to 150-mm (6-inch) diameter and 62-mm (2.5-inch) height for analysis with AASHTO T 283. The amount and type of anti-strip additive included in the test mixture shall be recorded and the pro- posed appendix to AASHTO R 35 (Bonaquist 2011) shall be followed for evaluation of moisture sensi- tivity using AASHTO T 283. Specimens shall be conditioned 16 hours at 60°C (140°F) followed by 2.5 hours at the compaction temperature. One freeze/ thaw cycle shall be included in the test sequence. AASHTO T 283 and T 324 tests shall be run on both specimens prepared from bulk mixture sampled dur- ing production and those extracted from the pave- ment mat at the APT facility. COMMENTARy: The proposed laboratory test- ing work plan includes Hamburg rut testing of both bulk plant mixture samples compacted in the lab (PMLC) and cores extracted from the pavement (PMFC). COMMENTARy: The proposed laboratory test- ing framework includes APA rut testing of both bulk plant mixture samples compacted in the lab (PMLC) and cores extracted from the pave- ment (PMFC). This recommendation is based on NJ DOT and NEAUPG WMA protocols; in addition, the APA is a commonly utilized pro- cedure for rut testing reported among DOT survey respondents. The FHWA WMA Techni- cal Working Group also recommends the use of the APA test for rutting resistance of PMLC WMA specimens. COMMENTARy: Although a moderate number of DOT and industry survey respondents indi- cated that low-temperature (thermal) cracking COMMENTARy: The majority of DOT and industry survey respondents cited concern with durability issues in WMA pavements. In par- ticular, the survey indicated that respondents would be a concern for WMA performance, none of the respondents reported having ob- served thermal cracking in WMA field sections. Interviews with responding agencies who re- ported observing transverse cracks in their WMA (and HMA control) sections traced the damage back to non-temperature related causes such as construction issues or reflective cracking propa- gating up from joints or cracks in the under- lying layer. Therefore, the WMA technology evaluation program does not include laboratory evalu- ation of low-temperature properties of WMA mixtures. This recommendation allows stream- lining the laboratory testing portion of the pro- gram to include only low-temperature binder performance tests. The reasons for not requir- ing low-temperature mixture testing include: lack of low-temperature damage reported as observed in actual field WMA pavement sec- tions; costs of conducting low-temperature mix- ture testing (considering amount of funds man- ufacturers willing to pay); and time required to conduct low-temperature mixture testing (12-month evaluation period proposed). be compacted to a common air void content for verification purposes. Low-Temperature Cracking. Testing to determine the test mixture’s propensity to low-temperature crack- ing is not included in the work plan for the WMA technology evaluation program.

21 Summary of Laboratory Tests Tables 1 through 4 provide a summary of the laboratory tests for binder, aggregates, mixture vol- umetrics, and mixture performance. Products may be tested either as supplied (neat) or modified with a maximum amount of 15% recy- cled asphalt pavement (RAP) allowed according to the manufacturer’s written instructions. However, the same mix design used in the field installation must be used in the laboratory testing. believed WMA might be more susceptible to moisture damage than traditionally produced HMA. However, the existence of moisture damage (stripping) in WMA field sections was only reported as having been observed by one agency (Taylor County, WI) to date. The specimen conditioning and testing process for preparing moisture sensitivity test (AASHTO T 324 and T 283) samples is proposed to follow the consensus in NCHRP Research Results Digest 370 (Baker et al. 2012). COMMENTARy: Section 4.1.6 of NCHRP Re- port 691 (Bonaquist 2011) described the issue of WMA processes that include anti-strip addi- tives, and their resultant effect on tensile strength ratio in AASHTO T 283 test results. This infor- mation was the basis of the requirements in this proposed work plan for recording the amount and type of anti-strip additive included in the test mixture, and following the draft appendix to AASHTO R 35 for evaluation of moisture sen- sitivity using AASHTO T 283. COMMENTARy: The DOT and industry survey found that an overwhelming majority of respon- dents are adding RAP to their WMA mixes. For this reason, it is proposed that the WMA technol- ogy evaluation work plan allow candidate WMA material additives and processes to be tested as either part of a neat mixture or a mixture modified with a maximum amount of 15% Table 1 Summary of laboratory tests: binder. Test Specification Performance grade of original binder AASHTO R 28, R 29, and T 240 Performance grade of extracted binder AASHTO R 26, R 28, R 29, and T 240 or AASHTO T 164 with Rotovap recovery Performance grade of base binder AASHTO R 28, R 29, and T 240 Table 2 Summary of laboratory tests: aggregates. Test Specification Gradation AASHTO T 27 Bulk specific gravity and absorption AASHTO T 84 and T 85 Flat and elongated or AIMS method ASTM D 4791 or use state or contractor data Sand equivalent AASHTO T 176 or use state or contractor data Stockpile moisture content AASHTO T 255 or use state or contractor data Coarse aggregate angularity AASHTO T 335 or use state or contractor data Fine aggregate uncompacted voids AASHTO T 304 or use state or contractor data Geologic type Use state or contractor data Soundness AASHTO T 104 or use state or contractor data LA abrasion or Micro Deval test AASHTO T 96 or T 327, or use state or contractor data RAP. The decision whether to include RAP in the laboratory and field tested mixtures should lie with the manufacturer. Review of some other DOT-proposed WMA specifications included: (a) PR DOT allows 20% maximum RAP content; and (b) NJ DOT allows up to 35% maximum recycled products (RAP, recycled asphalt shingles, and crushed recycled container glass) for intermediate and base as- phalt lifts. It should be noted that the NEAUPG WMA Qualification Process requires test results for WMA, and a corresponding HMA control mixture, designed without RAP.

22 Accelerated Pavement Testing. Two pavement loca- tions will be selected at an APT facility. Sites should generally meet the following criteria: • 102-mm (4-inch) WMA surface lift, excluding overlays or interlayers. Table 4 Summary of laboratory tests: mixture performance. Test Specification Mixture design verification with 150-mm diameter AASHTO T 320 Rutting AASHTO TP 79, T 324, and T 340 Dynamic modulus AASHTO TP 79 and PP 61 Compactability AASHTO R35 draft appendix section 8.3 Durability AASHTO T 283 and T 324 observe whether failures are due to a deficiency of the WMA system itself. Isolating the asphalt layer’s performance characteristics from those of the entire pavement system should be consid- ered. A conventional pavement structure is pro- posed with 4 inches of asphalt mix, 8 inches sta- bilized granular base, and a subgrade prepared to optimum water content and maximum dry unit weight. This pavement configuration and conditions are suggested based on the findings in NCHRP Report 719 (Von Quintus et al. 2012). Preparation of subgrade conditions may dictate the timing of construction at the APT facility. COMMENTARy: The recommendation for a 4-inch conventional surface lift is based on the discussion provided in NCHRP Report 719 (Von Quintus et al. 2012) on site features and layer properties. The report notes that maximum rut depths were slightly greater for thin HMA layers than in thick (8 inches or thicker) lifts. COMMENTARy: The WMA technology evalu- ation program suggests field performance test- ing in both a freeze and no-freeze environment. However, requiring accelerated pavement test- ing to be done in both a no-freeze and freeze cli- mate will substantially increase the total cost of the field evaluation (i.e., double the cost of APT testing by having two separate experiments in two different sites being conducted simultane- ously). Ultimately, a decision on climate should be based on consideration of whether the plant process or binder grade has the greater effect on WMA performance. Field Performance Tests COMMENTARy: The pavement structure and supporting layer material properties of the test sections should be designed (to the greatest ex- tent possible) to isolate the WMA lift and limit damage in the section to that occurring in the WMA surface layer. COMMENTARy: Use of an APT facility in lieu of a field site serves the purpose of isolating the per- formance of an asphalt mixture processed with (1) a system to produce warm mix or (2) a warm mix additive, and allows the opportunity to • Wet, no-freeze climate and wet, freeze climate. Table 3 Summary of laboratory tests: mixture volumetrics. Test Specification Theoretical maximum specific gravity and density of HMA AASHTO T 209 Preparing and determining density of HMA specimens by means of superpave gyratory compactor AASHTO R35 and T 312 Practice for superpave volumetric design for HMA AASHTO R35 Laboratory confirmation of extracted core density AASHTO T 166 or T 275 Laboratory confirmation of extracted core thickness ASTM D 3549

23 • 205-mm (8-inch) stabilized granular aggregate base, suitable for rutting and fatigue cracking testing applications. • Field test areas will be 200 feet long by 12 to 14 feet wide. COMMENTARy: This requirement is based on the discussion of calibration and validation for unbound layers discussed in NCHRP Report 719 (Von Quintus et al. 2012). The report indicated that sections with highest measured rut depths were a result of subgrade soils with higher moisture contents and lower densities. Thus, the testing facility should prepare the subgrade soil to isolate the effects of rutting to the WMA lift only. COMMENTARy: This recommendation is based on dimensions of test sections reported from the brief survey of APT facilities in the United States. The minimum test section length was consistently reported to be 200 feet. It is rec- ommended that the manufacturer be allowed to stipulate the required test section length as part of its initial submittal. In addition, it is rec- ommended that the manufacturer be required to produce, present, and place the WMA (and control HMA) mixtures in the selected test sections. COMMENTARy: The DOT and industry survey respondents overwhelmingly agreed that an HMA control section must be used as part of any WMA field testing framework. The HMA control section can provide direct comparison to isolate the effects of the material additive or process used to transform the same HMA material into WMA. COMMENTARy: This recommendation is con- sistent with the average load level reported in the survey of U.S. APT facilities. COMMENTARy: This requirement is based on review of the forensic investigations of field pavements described in Von Quintus et al. (2012), where it was found that asphalt treated base layers exhibited much greater rut depths than sections without asphalt stabilized base. Likewise, the report also documented high lev- els of rutting in untreated aggregate base lifts that were susceptible to moisture due to peri- ods of heavy rainfall during construction. A careful review of the type and amount of sta- bilization proposed for the base lift, dependent on the location and climate of the APT facility, is mandatory. A suitable granular base may be used to allow for rutting and fatigue cracking evaluation in the WMA lift without the risk of inducing reflective cracking (especially when using a cement treated base). Three survey respondents (Cass County, Michi- gan; Oregon DOT; and Minnesota DOT) noted the presence of reflective cracking in WMA field observations. Therefore, the field sections should not be placed over badly cracked or badly jointed HMA, or jointed concrete pave- ment, in order to eliminate the presence of joints that cause reflective cracking. • Subgrade conditioned to optimal water con- tent and maximum dry unit weight. • Equivalent HMA control section adjacent to the WMA section. The HMA control pave- ment shall have the same dimensions, com- paction target, aggregate source, mix design (excepting any elements of the WMA process or additives), structure, and number of traffic load applications. • Load level of 44 kN (10 kips) on a single axle. • Testing conducted at ambient temperature of the APT facility locations.

24 If the manufacturer is absent during the sched- uled construction, or fails to carry out its responsi- bilities 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 con- trol (if necessary), prepare the pavement underlying layers, and provide for the construction and place- ment of both the HMA control section and the pave- ment section with WMA manufactured using its product or process. Field Observations. Testing will commence upon completion of the installation and continue for 1 year. Field observations will be made during installation; at 3 months; 6 months (interim); and 12 months (final). Accelerated loading will be applied in equal frequencies and cycles to both the HMA and WMA test sections over a 12-month period. Installation. The manufacturer will supply all labor and equipment to completely install the properly sampled and produced WMA mixture. The facil- ity will provide site preparation and preparation of the subgrade and stabilized base layers. Paving of the WMA and HMA surfaces will be the manu- facturer’s responsibility. At the time of installation the manufacturer will provide written instructions to the paving contractor for the proper installation of the material. COMMENTARy: This recommendation is based on the results of the APT survey which reported that the majority of accelerated pavement test- ing facilities conducts performance testing at the ambient temperature of their facilities. COMMENTARy: The testing facility shall de- velop the supporting structure of the APT section including preparation of the base and subgrade layers. COMMENTARy: It is recommended that the field evaluation be conducted only at APT facili- ties that do not include real-time traffic, unless the facility will receive sufficient loading to guar- antee failure within the timeframe specified in the evaluation program. It is additionally recom- COMMENTARy: Challenges to successful im- plementation of full-scale field-section testing are (1) the time required to observe the perfor- mance of actual field sections and (2) the cost of potential maintenance and protection of traffic. In order to completely characterize the perfor- mance of WMA produced with any particular process or additive, a field section would re- quire monitoring for many years (e.g., upwards of 5 years) in order to capture distresses either visually or through the use of nondestructive testing (NDT). Manufacturers indicated in the survey that they would support reporting of key results within 2 years of application, but pref- erably sooner. Although indications of damage generation may be potentially captured sooner through the use of instrumented field sections (fitted with strain gauges, etc.), the instrumen- tation required would cost significantly more than what the manufacturers can support. Thus, Traffic control and installation scheduling will be arranged by the manufacturer, if deemed necessary by the nature of the APT facility. The manufacturer’s representative will certify that the WMA mixture pro- duced is constructed in accordance with the construc- tion specifications identified for use and to the manu- facturer’s satisfaction. If the representative indicates that the installation using its product was unsatisfac- tory, notification to the testing facility must be made in writing, within 1 week of the installation. Upon notification, the manufacturer’s installation may be dropped from further testing without a refund of fees. If no written notification is received within the first week, the installation will be accepted and included in the field testing. mended that the construction specifications of the state in which the testing facility resides be used during construction of the APT section.

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. Field performance test results shall be compiled into an electronic report by the testing facility. COMMENTARy: The following field monitor- ing data types to be collected are based on in- formation from field projects in various states and other related research projects. The field data types proposed for collection are based on those reported with the following quali- ties: most frequently used; lower in cost; and most widely available. In addition, the work plan may be amended to include field moni- toring tools that will capture key elements of WMA such as amount of fuel savings and ease of compactability. COMMENTARy: Since some WMA additives have been promoted as reducing the level of compactive effort, the possibility of measuring that characteristic during construction of the field trial pavement sections should be consid- ered. One potential tool for capturing this ele- ment is to use Intelligent Compaction to docu- ment the number of passes required to achieve the desired mat density. COMMENTARy: This paragraph may be de- leted if a decision is made to only use APT facili- ties that do not include real-time traffic. the use of field sections to evaluate the WMA technologies does not appear feasible. It is proposed that all accelerated field testing of trial WMA sections be conducted within 12 months. Another reason for this recommen- dation, in addition to those previously men- tioned, stems from the APT survey in which fifty percent (50%) of respondents reported that their facilities typically conduct test cycles in less than 1 year. That report shall include, as a minimum, the following field performance monitoring data: • Rut depth profile at construction using pro- filograph. • ASTM E965 sand patch test for moisture sus- ceptibility of the compacted mat. • Visual distress survey using LTPP manual to capture percentages of fatigue cracking, low- temperature cracking, and other distress types. • Ground penetrating radar (GPR) or seismic analysis surface wave (SASW) equipment at construction. • Falling weight deflectometer (FWD) to pre- dict cracking potential and in situ stiffness. • Bond strength between layers by taking three (3) cores at construction (West et al. 2005). • In-place thickness and density by extracting cores at the following frequencies: 9 at installa- During the field evaluation, if a product fails to the extent that it becomes a safety issue for the travelling public (if installed on an APT facility that includes real-time traffic), as determined by the test- ing facility, the manufacturer will be charged for the actual cost incurred by the DOT to repair the pavement section. This charge will include all labor, materials, maintenance, and protection of traffic (MPT) set-up and equipment costs. REfERENCES Anderson, R., G. Baumgardner, R. May, and G. Reinke. (2008). Unpublished Phase I Interim Report for NCHRP Project 9-47: Engineering Properties, Emissions, and Field Performance of Warm Mix Asphalt Technologies. Transportation Research Board, National Research Council, Washington, DC. Available on request to NCHRP. Baker, T., M. Corrigan, J. Bukowski, J. Epps, D. Newcomb, and E. Harrigan. (2012). NCHRP Re- search Results Digest 370: Guidelines for Project Selection and Materials Sampling, Conditioning, and Testing in WMA Research Projects. Trans- portation Research Board, National Academies, Washington, DC.

26 Engineering Properties, Emissions, and Field Per- formance of Warm Mix Asphalt Technologies. Vol- ume 1: Literature Review. Transportation Research Board, National Academies, Washington, DC. Available on request to NCHRP. Marasteneau, M., and A. Zofka. (2007). Report MN/RC 2007-43: Investigation of Low-Temperature Crack- ing in Asphalt Pavements—A Transportation Pooled Fund Study. Minnesota Department of Transporta- tion, St. Paul, MN. Prowell, B., G. Hurley, and B. Frank. 2011. NAPA QIP 125: Warm-Mix Asphalt: Best Practices: 2nd Edition. National Asphalt Pavement Associa- tion, Lanham, MD. Von Quintus, H., J. Mallela, R. Bonaquist, C. Schwartz, and R. Carvalho. 2012. NCHRP Report 719: Cali- bration of Rutting Models for Structural and Mix Design. Transportation Research Board, National Academies, Washington, DC. Wen, H., S., Shen, Z. Ma, J. Wang. (2010). Modeling the Effects of Temperature and Loading Rate on Fatigue Property of Asphalt Binder. Journal of Testing and Evaluation 38:6, 6 pp. West, R.C., J. Zhang, and J. Moore. (2005). NCAT Re- port 05-08: Evaluation of Bond Strength Between Pavement Layers. National Center for Asphalt Tech- nology, Auburn University, Auburn, AL. Bonaquist, R. (2011). NCHRP Report 691: Mix Design Practices for Warm Mix Asphalt. Transportation Research Board, National Academies, Washing- ton, DC. Bonaquist R. and D. Christensen. (2005). Practical Pro- cedure for Developing Dynamic Modulus Master Curves for Pavement Structural Design. Transpor- tation Research Record 1929:208–217, National Academies, Washington, DC. Epps Martin, A., E. Arambula, C. Estakhri, et al. (2011). Unpublished Phase I Interim Report for NCHRP Proj- ect 9-49: Performance of WMA Technologies: Stage I—Moisture Susceptibility. Transportation Research Board, National Academies, Washington, DC. Jeong, M. (2010). Manual of Practice: HMA Quality Assurance Spreadsheet Program Using Measured Values of E* and D. Excerpt of Ph.D. Disserta- tion, Arizona State University, Tempe, AZ. Avail- able at http://onlinepubs.trb.org/onlinepubs/nchrp/ docs/NCHRP09-22_AMPT_QA_SoftwareManual OfPractice.pdf. Accessed March 20, 2012. Kim, Y.R., Y. Seo, et al. (2004). Dynamic Modu- lus Testing of Asphalt Concrete in Indirect Ten- sion Mode. Transportation Research Record 1891: 163-173, National Academies, Washington, DC. Kvasnak, A., B. Prowell, et al. (2009). Unpublished Phase I Interim Report NCHRP Project 9-47A:

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