Tài liệu Airfield and highway pavements 2017 airfield pavement technology and safety

d from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all right Airfield and Highway Pavements 2017 Airfield Pavement Technology and Safety Selected Papers from the Proceedings of the International Conference on Highway Pavements and Airfield Technology 2017 Edited by Imad L. Al-Qadi, Ph.D., P.E. Hasan Ozer, Ph.D. Eileen M. Vélez-Vega, P.E. Scott Murrell, P.E. Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. AIRFIELD AND HIGHWAY PAVEMENTS 2017 AIRFIELD PAVEMENT TECHNOLOGY AND SAFETY PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON HIGHWAY PAVEMENTS AND AIRFIELD TECHNOLOGY 2017 August 27–30, 2017 Philadelphia, Pennsylvania SPONSORED BY The Transportation & Development Institute of the American Society of Civil Engineers EDITED BY Imad L. Al-Qadi, Ph.D., P.E. Hasan Ozer, Ph.D. Eileen M. Vélez-Vega, P.E. Scott Murrell, P.E. Published by the American Society of Civil Engineers Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Published by American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4382 www.asce.org/publications | ascelibrary.org Any statements expressed in these materials are those of the individual authors and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process, or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. The materials are for general information only and do not represent a standard of ASCE, nor are they intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. 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Errata: Errata, if any, can be found at https://doi.org/10.1061/9780784480953 Copyright © 2017 by the American Society of Civil Engineers. All Rights Reserved. ISBN 978-0-7844-8095-3 (PDF) Manufactured in the United States of America. Airfield and Highway Pavements 2017 iii Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Preface An ever-growing number of highway and airport agencies, companies, organizations, institutes, and governing bodies are embracing principles of sustainability in managing their activities and conducting business. Overarching goals emphasize key environmental, social, economic, and safety factors in the decision-making process for every pavement project. Therefore, the theme of the conference was chosen as “Sustainable Pavements and Safe Airports.” It is dedicated to the state-ofthe-art and state-of-practice areas durability, cost-effective, and sustainable airfield and highway pavements. In addition, recent advancements and technologies to ensure safe and efficient airport operations are included. This international conference provides a chance to interact and exchange information with worldwide leaders in the fields of highway and airport pavements, as well as airport safety technologies. This conference brought together researchers in transportation and airport safety technologies, designers, project/construction managers, academics, and contractors from around the world to discuss design, implementation, construction, rehabilitation alternatives, and instrumentation and sensing. The proceedings of 2017 International Conference on Highway Pavements and Airfield Technology have been organized in four (4) publications as follows: Airfield and Highway Pavements 2017: Design, Construction, Evaluation, and Management of Pavements This volume includes papers in the areas of mechanistic-empirical design methods and advanced modeling techniques for design of conventional and permeable pavements, construction specifications and quality, accelerated pavement testing, pavement condition evaluation, and network level management of pavements. Airfield and Highway Pavements 2017: Testing and Characterization of Bound and Unbound Pavement Materials This volume includes papers in the areas of laboratory and field characterization of asphalt binders, asphalt mixtures, base/subgrade materials, and recent advances in concrete pavement technology. This volume also features papers for the use of recycled materials, in-place recycling techniques and unbound layer stabilization methods. Airfield and Highway Pavements 2017: Pavement Innovation and Sustainability This volume is dedicated to the papers featuring most recent technologies used for structural health monitoring of highway pavements, intelligent compaction, and innovative technologies used in the design and construction of highway pavements. The volume also includes papers in the area of sustainability assessment using life-cycle assessment of highway and airfield pavements and climate change impacts and preparation for pavement infrastructure. © ASCE Airfield and Highway Pavements 2017 Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Airfield and Highway Pavements 2017: Airfield Pavement Technology and Safety This volume is dedicated to recent advances in the area of airfield pavement design technology and specifications, modeling of airfield pavements, use of accelerated loading systems for airfield pavements, and airfield pavement condition evaluation and asset management. The papers in these proceedings are the result of peer reviews by a scientific committee of more than 90 international pavement and airport technology experts, with three to five reviewers per paper. Recent research was presented in the technical podium and poster sessions including the results from current Federal Aviation Administration (FAA) airport design, specifications, and safety technologies; design and construction of highway pavements; pavement materials characterization and modeling; pavement management systems; and innovative technologies and sustainability. The plenary sessions featured the Francis Turner Lecture by Dr. Robert Lytton and the Carl Monismith Lecture by Dr. David Anderson. In addition, two technical tours were offered: Philadelphia International Airport and the Center for Research and Education in Advanced Transportation Engineering Systems (CREATEs) Lab of the Henry M. Rowan College of Engineering at Rowan University. Three workshops were presented prior to the conference: hands-on FAA’s FAARFIELD software, design and construction of permeable pavements, and environmental product declarations. The editors would like to thank the members of the scientific committee who volunteered their time to review the submitted papers and offered constructive critiques to the authors. We are also grateful for the work of the steering committee members in planning and organizing the conference: Katie Chou, Jeffrey Gagnon, John Harvey, Brian McKeehan, Shiraz Tayabji, and Geoffrey Rowe; as well as the local organizing committee chaired by Geoffrey Rowe and members including James A. McKelvey, Timothy Ward, Ahmed Faheem, and Yusuf Mehta for their help with the technical tours. Finally, we would like to especially thank the ASCE T&DI staff who helped put the conference together: Muhammad Amer, Mark Gable, Drew Caracciolo, and Deborah Denney. Imad L. Al-Qadi, Ph.D., P.E., Dist. M.ASCE, University of Illinois at Urbana-Champaign Hasan Ozer, Ph.D., M.ASCE, University of Illinois at Urbana-Champaign Eileen M. Vélez-Vega, P.E., M.ASCE, Kimley-Horn Puerto Rico, LLC Scott D. Murrell, P.E., M.ASCE, Applied Research Associates © ASCE iv Airfield and Highway Pavements 2017 v Contents Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Airport Design Specification and Materials Towards a Performance-Based Airport Asphalt Specification .............................. 1 Greg White Incorporation of Reliability into Airport Pavement Design Using Backcalculated Pavement Layer Moduli ................................................................ 15 Richard Ji, Zilong Wang, and Nassim Sabahfar Providing a Durable Airfield Concrete Specification at Kansas City International .............................................................................................................. 27 Christopher S. Decker, Jason Fuehne, and Gary L. Mitchell Advanced Statistical Learning and Prediction of Complex Runway Incursion .................................................................................................................... 38 I. Song, I. Cho, T. Tessitore, T. Gurcsik, and H. Ceylan Advanced Modeling and Analysis of Airfield Pavements Alternative Approaches to Determining Robust ANN Based Models for Predicting Critical Airport Rigid Pavement Responses........................................ 51 Orhan Kaya, Adel Rezaei-Tarahomi, Kasthurirangan Gopalakrishnan, Halil Ceylan, Sunghwan Kim, and David R. Brill Investigation of Deformation Trends Observed in Pavement Test Section Unbound Aggregate Layers Due to Heavy Aircraft Loading with Wander ....... 61 Priyanka Sarker and Erol Tutumluer Modeling Interface Debonding between Asphalt Layers under Dynamic Aircraft Loading ....................................................................................... 71 Seyed-Farzan Kazemi, Adam J. T. Hand, Elie Y. Hajj, Peter E. Sebaaly, and Raj V. Siddharthan Airfield Pavement Design Evaluation of Airfield Pavements Using FAARFIELD ........................................ 82 Andreas Loizos, Angeliki Armeni, and Christina Plati © ASCE Airfield and Highway Pavements 2017 Advances in FAA Pavement Thickness Design Software: FAARFIELD 1.41 ..................................................................................................... 92 D. R. Brill and I. Kawa Case Studies of Airfield Construction Projects Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. A Case Study: Keel Section Reconstruction of Runway 08L-26R the 29 Day Wonder at Hartsfield-Jackson Atlanta International Airport .............. 103 Vissu Dokka, Roy Keck, Quintin B. Watkins, Norma Click, and Subash Kuchikulla Airfield Pavement Accelerated Loading Testing Sensitivity Analysis of Rut Depth to Longitudinal Measurement Location in Accelerated Pavement Testing with a Heavy Vehicle Simulator-Airfield................................................................................................... 115 T. A. Parsons, H. Kazmee, and N. Garg Concrete Pavement Overload Test at the FAA’s National Airport Pavement Test Facility ........................................................................................... 127 H. Yin and D. R. Brill Behavior of P-401 HMA Surface in Accelerated Pavement Testing at High Temperatures and Tire Pressures ............................................................... 152 Navneet Garg, Hasan Kazmee, and Russell Knieriem Review of a Procedure for Calibrating Unbound Layer Rutting Model in Flexible Airfield Pavements Using Accelerated Pavement Testing Data .......... 163 Rongzong Wu, John Harvey, Qi Ren, Navneet Garg, and Davis Jones Airfield Pavement Monitoring, Evaluation, and Nondestructive Testing A Comparison of Subgrade Improvement Methods ........................................... 173 Tim Ward, Ania Taylor, and Joe Grubbs Rutting Performance of Cold-Applied Asphalt Repair Materials for Airfield Pavements.................................................................................................. 185 John F. Rushing, Ben C. Cox, and Webster C. Floyd Construction, Instrumentation, and Performance of a Double Sized Slab Designed for Airport Runways .............................................................................. 196 M. T. McNerney, J. Kim, and E. P. Bescher Evaluation of HWD Backcalculation Tools and Methodologies Using FAA National Airport Pavement Test Facility’s Data ................................................. 207 A. Ashtiani, H. Shirazi, S. Murrell, and R. Speir © ASCE vi Airfield and Highway Pavements 2017 Evaluation of Flexible Pavement Using HWD and PSPA at National Airport Pavement and Materials Research Center (NAPMRC) ....................... 218 Qiang Li and Navneet Garg Airfield Pavement Asset Management Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Characterization of Pavement Condition Index Deterioration Curve Shape for USAF Airfield Pavements..................................................................... 230 T. A. Parsons and B. A. Pullen Airfield and Highway Sustainability Practices and Assessment Airfield Pavement Life Cycle Assessment Framework and Guidelines ............ 241 A. A. Butt, D. Reger, J. T. Harvey, and N. Garg © ASCE vii Airfield and Highway Pavements 2017 1 Towards a Performance-Based Airport Asphalt Specification Greg White, Ph.D.1 1 Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Adjunct Associate Professor, Univ. of the Sunshine Coast, Sippy Downs, Queensland, Australia. E-mail: [email protected] Abstract Prescriptive or recipe-based specification of asphalt surface mixture design, production and construction is normal within the airport industry. However, reports of distress in generally compliant airport asphalt has eroded confidence in this traditional approach. As a result, there is increased interest in performance-based airport asphalt specification. This aims to allow innovation for risk reduction and to make asphalt producers more contractually responsible for the performance of their airport asphalt surfaces. Where performance-indicative test methods are available for the evaluation of airport asphalt performance requirements, performance-based testing is appropriate. However, where no such performance test exists, the traditional prescriptive requirements must be retained. A combination of prescriptive and performance-based specification requirements is appropriate. Future work is expected to focus on developing additional performance-indicative test methods where they do not currently exist. Introduction Since the 1950s, a prescriptive or recipe-based approach has generally been adopted for the specification and design of airport asphalt surfaces (White 2016f). The prescriptive specification is usually based on the Marshall-design method adapted for airport surfaces by the US Army Corps of Engineers (the Corps) in the 1940s and 1950s (White 1985). Many airports and aviation authorities retain the basis of the Corps methods in current airport asphalt design, specification and construction practice (White 2016f). Importantly, grooves are generally sawn transversely in runway surfaces to promote aircraft skid resistance (Zuzelo 2014). As a consequence, the traditional airport surface asphalt is often described as ‘grooved, dense graded, Marshall-asphalt’. Although grooved Marshallasphalt is common for airport surfacing, some jurisdictions prefer alternate asphalt mixtures, which are discussed later. Generally, airport pavements are resurfaced when the condition of the asphalt presents an unacceptable risk to safe aircraft operations. Many airports traditionally planned on resurfacing flexible airport pavements on a fifteen-year cycle. Some of these airports have now reduced that expectation to resurfacing every ten years. Concerningly, a number of airports have also experienced surface distress requiring partial or full resurfacing within six years of surface construction (White & Embleton 2015; White 2016f). This has resulted in reduced confidence in the traditional prescriptive airport asphalt specification to provide reliable surface performance under modern aircraft loadings. The reduction of confidence in the traditional prescriptive specification has prompted interest in a performance-based approach to airport asphalt specification. The aim is to allow asphalt producers to innovate for risk reduction and to make asphalt producers contractually responsible for the performance of airport asphalt surfaces. This paper outlines the basis and approach for the implementation of a performance-based asphalt specification for airports. The focus is on Australian experience, but international issues are incorporated where appropriate. However, the issues and concepts apply to many airports around the world where a performance-based specification is of interest. © ASCE Airfield and Highway Pavements 2017 2 Background Airport surface requirements Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. As described below, the modes of distress requiring earlier than expected airport pavement resurfacing are generally linked to inadequate asphalt mixture resistance to either fracture and deformation (White 2016f). Durability is also important and includes both resistance to moisture damage (stripping) and resistance to the generation of loose stones (ravelling) that damage aircraft. Surface friction for aircraft skid resistance is also critical to aircraft safety, and asphalt surface texture is essential, particularly when grooving is not provided (Table 1). Table 1. Summary of airport asphalt performance requirements (White 2016f) Physical requirement Deformation resistance Fracture resistance Surface friction and texture Durability Protects against Groove closure Rutting Shearing/shoving Top down cracking Fatigue cracking Skid resistance Compliance requirement Pavement generated FOD Resistance to moisture damage Level of importance High Moderate High Moderate Surface deformation Asphalt surface deformation has been reported at airports. Some Australasian examples include rutting at Cairns (Australia), Perth (Australia), Kuala Lumpur (Malaysia), Doha (Qatar) and Dubai (UAE) airports (Rodway 2009). Taxiways at San Francisco (USA) airport also rutted during hot weather, under slow moving and sharp turning B747 aircraft (Monismith et al. 2000). At San Francisco it was concluded that a more viscous bitumen was required to improve the shear strength of the asphalt mixture. Surface shearing has also been reported. Mooren et al. (2014) investigated surface tearing under aircraft turning at Amsterdam airport (Netherlands). A lack of mixture cohesion at elevated temperature, due to softening of the bitumen, was found to result in inadequate shear strength in the surface. Similarly, an Australian airport was reported to experience unusual softness during summer months (Emery 2005). It was concluded that the binder had a high temperature susceptibility although a reduction in softness was observed after three years. A similar case of surface tenderness was reported at another Australian airport, also linked to bitumen (White 2014). Moreover, Newark airport, in New Jersey (USA) experienced similar asphalt shearing in the heavy aircraft braking zone associated with aircraft landings (Bognacki et al. 2007). Groove closure is one of the most commonly reported airport asphalt surface distresses, particularly in hot countries like Australia (Rodway 2016). Groove closure most commonly occurs where aircraft move slowly and in a direction parallel to the alignment of the grooves, such as entering a runway from a perpendicular taxiway (White & Rodway 2014). Groove closure has been reported at numerous airports in Australia, usually occurring within the first three years and most often during extended periods of unusually hot weather (Emery 2005). The two ends (approximately 800 m long each) of the main runway at Brisbane airport (Australia) were resurfaced in 2013. Grooving was performed over the full length and width of the new asphalt six weeks following construction. During a week of unusually hot weather in the following summer, significant groove closure was observed, particularly at the intersection of the dominant departure taxiway and the main runway (White & Rodway 2014). Melbourne and Perth airports (Australia) also experienced significant groove closure in runways and taxiways (White 2016f). Groove closure was reported at the new Hong Kong airport despite trafficking being delayed for 12 months after its construction (White & Rodway 2014). Similarly, the runway at the new airport at Delhi (India) was intended to be grooved following its construction in 2008. In order to confirm that the grooves would not close, a test section of grooving was constructed across the runway and © ASCE Airfield and Highway Pavements 2017 trafficked by a heavy pneumatic tyred roller. The grooves closed, even under the relatively low roller load. As a result, grooving was deferred until a similar test confirmed the ability for the asphalt to resistant groove closure. However, as at March 2014 the surface remained un-grooved (White & Rodway 2014). Surface fracture Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Conventional fatigue cracking is not generally an issue for airport pavements (Rodway 2016). This reflects the relatively low number of load repetitions and the relatively high stiffness of the pavement structure compared to roads. However, top down cracking, resulting from high shear and tensile stresses at the surface of the pavement is now a recognised distress mode for all pavement types (Collop & Roque 2004). Australian airports have experienced significant top down cracking, likely associated with chemical hardening of acid modified bitumen (White 2016e). In one severe case, loose material was generated from interconnected surface cracks and required surface full replacement after just five years. Factors affecting airport surface distress The increase in observed airport asphalt distress indicates a reduction in the factor of safety associated with the traditional prescriptive airport asphalt specification. Natural variability of materials, environment and construction combine to increase the risk of surface distress. The reduced factor of safety reflects increased shear stresses imparted by modern aircraft, in combination with less stress-resistant asphalt mixtures (White 2016b). Particularly since WWII, aircraft wheel loads and tyre pressures have increased significantly (Roginski 2007; Fabre et al. 2009). This trend is expected to continue in the future as aircraft manufacturers strive for ever greater fuel efficiency (Rodway 2016). The result is higher shear stresses in asphalt surface layers, even when wheel spacings have been increased to protect the subgrade. Importantly, the international airport pavement strength rating system, known as ACNPCN, protects the pavement against subgrade rutting, but does not protect against the increased risk of surface distress associated with modern aircraft (White 2016d). Asphalt resistance to stress is greatly influenced by mastic and binder properties so these are critical to airport asphalt performance (Emery 2005). There is a perception that bitumen quality has reduced over the last thirty years. Evidence indicates that crude oil quality has generally reduced and has become more variable, oil refining processes have become more efficient and bitumen is extended by the addition of materials that were previously considered waste (White 2016a). Changes in bitumen supply and production have anecdotally been linked to a number of airport asphalt surface distresses, including early life shearing, premature ageing and early life top-down cracking (White & Embleton 2015). Selecting and specifying bitumen for the production of asphalt is now the most uncertain part of airport surface asphalt design (Rodway 2016). Marshall-designed asphalt The Marshall asphalt mixture design method was developed in 1939 by Bruce Marshall for the Mississippi Highways Department (White 1985). During the 1940s and 1950s, it was adapted and evolved for military aircraft loads. Many countries, including Australia, predominantly retain Marshall-designed asphalt for airport surfacing. The primary basis of the Marshall design method include (White 1985): • A densely graded aggregate skeleton with 15% voids in the mineral aggregate. • Filling the voids in the mineral aggregate with bituminous binder to retain a 4% air voids content. • Marshall Stability and Marshall Flow values are determined over a range of binder contents and an optimal binder content selected. Aggregate grading, bitumen content, compacted density, Marshall Flow and Marshall Stability are the primary design criteria and quality assurance parameters. To improve durability, the bitumen content is higher than that used for road mixes. This results in deformation resistance of Marshall- © ASCE 3 Airfield and Highway Pavements 2017 designed asphalt for aircraft pavements being highly influenced by the engineering properties of the bitumen (Emery 2005), reflecting the high reliance on the bituminous mastic to bind the coarse aggregate particles together. In practice, Marshall-designed dense graded airport asphalt mixtures contain 5.4-5.8% bitumen by mass and 4-6% fine (passing 75 µm sieve) aggregate by volume. The result is around 14% (by volume) of airport asphalt being the mastic. This is a relatively high proportion compared to road and highway asphalt mixtures. Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Alternate asphalt mixtures Grooving of dense graded Marshall-designed airport asphalt is costly and introduces the risk of groove closure. Due to the high reliance of airport asphalt on the deformation resistance of the mastic, groove closure is likely the most difficult mode of airport asphalt distress to avoid in hot climates. Due to the risk of groove closure a range of alternative airport asphalt surfaces have been considered. These alternative mixtures aim to provide adequate surface texture and skid resistance, without necessitating grooving of the surface (White 2016f). Open Graded Friction Course (OGFC), also referred to as popcorn mix or porous asphalt, has a low portion of fine aggregate to create an open grading (TRB 2000). The benefit of OGFC for improved aircraft skid resistance on runways was first recognised in the 1970s (Jones 1973; White 1976). The UK utilised OGFC extensively for runway surfacing for over 40 years (EAPA 2003). However, dense graded asphalt is still utilised in parking aprons and slow moving taxiways where OGFC is less suitable. Experimental surface sections in the touch down zone of the runway at Johannesburg airport (South Africa) included OGFC (Joubert et al. 2004). Australia also used OGFC, as early as 1973, to improve skid resistance prior to grooving becoming economically competitive (White & Rodway 2014). Stone Mastic Asphalt (SMA) was developed in Germany in the 1970s for resistance to damage from studded snow tyres. Associated durability and resistance to shearing benefits were quickly recognised (Nunn 1994). SMA has been used as an airport runway surface in parts of Europe for many years. For example, SMA, along with dense graded asphalt, is a normal runway surface in Denmark, Germany and Norway (EAPA 2003). Campbell (1999) also reported SMA on European airports in Austria, Switzerland and the Czech Republic. The main runway at Brussels airport (Belgium) was surfaced with SMA with good performance. Further, SMA was selected for the surfacing of the King Shaka airport runway, near Durban (South Africa) based on higher deformation resistance than other mixtures and to avoid grooving (Hofsink & Barnard 2004). Asia has followed Europe and China is the leader in SMA for runway surfacing (NCAT 2009). SMA, either 13 mm of 16 mm maximum aggregate size, is now a normal runway surface mixture in China, with over 35 runways surfaced with SMA commencing with Beijing airport in 1996 (Xin 2013; Xin 2015). In northern America, SMA has been successfully used for surfacing at least two runways in Mexico in 2004 and 2005 (NCAT 2009) and Indianapolis airport (USA) surfaced a significant taxiway with SMA in 2005 (NCAT 2009). However, runways in the USA remain primarily surfaced with grooved dense graded asphalt (Zuzelo 2014) or are rigid pavements. Beton Bitumeux Aeronautique (BBA) is one of a range of high modulus asphalt mixtures developed in France since the 1980s (Austroads 2013). When a gap graded and 14 mm sized mixture is selected, the surface texture is generally 1.2-1.3 mm immediately following construction and grooving of the surface is avoided (Hakim et al. 2014). BBA has been used as a standard airport surfacing for French runways for more than 30 years (Widyatmoko et al. 2011). Since 2006, seven runways in the UK have been surfaced with a BBA product. Of these, three comprised the ungrooved, gap graded 14 mm version (Widyatmoko et al. 2013). The importance of binder The contribution of the bituminous binder to asphalt performance is significant (Motamed & Bahia 2011). Otherwise identical asphalt mixtures with different bitumen types, or even two sources of nominally identical bitumen, can respond differently due to differences in chemical and rheological composition (Harnsberger et al. 2011; White 2016c). Asphalt binder performance is also complicated by the process of bitumen ageing. Bitumen hardening with age results from chemical ageing, steric © ASCE 4 Airfield and Highway Pavements 2017 Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. hardening, oxidation and loss of volatiles (Airey 2003; Wu et al. 2007; Bianchetto et al. 2007). Ageing is often measured in terms of change in viscosity and a hardening of bitumen during asphalt production may only be around 30% of the hardening expected over the life of the asphalt (Crawford 1986). It follows that bitumen properties change over the life of a pavement surface and this affects surface performance. Qiu et al. (2013) stated that the mastic is the ‘real’ binder in asphalt. Tashman et al. (2005) supported this by stating that the micro-constituents govern the behaviour of the overall mix. It follows that testing mastic provides greater insight into asphalt performance than testing bitumen (Elnasri et al. 2013). Despite agreement regarding the importance of mastic, less is known about mastic properties than the properties of binders (Liao et al. 2013). Faheem & Bahia (2010) explained that mastics of seemingly similar constituents can behave differently. This can only be explained by physio-chemical interaction between the bitumen and mineral elements. Such interactions cannot be assessed by considering the bitumen and mineral components separately. It is expected that future performance-indicative characterisation of asphalt constituents will focus more on mastic. Performance-based asphalt In the USA, a number of Departments of Transport developed nine-year warranty provisions for asphalt surfacing works (Diefenderfer et al. 2006). The aim was to extend pavement life by making the contractor more responsible for the performance of the asphalt. However, other agencies have avoided the performance warranty approach, citing concerns regarding reduced competition and increased project delivery cost (Cui et al. 2004). In contrast to this concern, Krebs et al. (2001) found that warranted highways were 30% smoother and 14% less expensive than un-warranted works of comparable age. Importantly, the reduced costs were associated only with projects that were appropriately selected for warranted delivery. Where circumstances were not suited to warranty provisions, the cost was higher than for the comparable un-warranted works (Krebs et al. 2001). More recently, the Netherlands road authority has delivered the majority of highway projects using either design and construct or design, construct and maintain contracts. Initially a five or ten year-warranty was required, but this was recently increased to twenty or twenty-five years, with the addition of long term maintenance responsibility (Moenielel & de Vries 2016). The warranty extension has reportedly increased innovation, reduced cost and improved pavement quality. More focussed on the asphalt surface, increased traffic loading and volumes prompted the Superpave project in the USA. A number of tests, intended to be indicative of asphalt mixture field performance were developed, including durability, fatigue, brittle fracture, dynamic modulus and creep/flow (Ero-Phillips 2016). These tests substantially replaced the traditional Marshall and Hveem mixture design parameters and provided a pathway to performance-based asphalt mixture specification (Ero-Phillips 2016). Despite these efforts, only 11 of the 50 State Departments of Transport of the USA have implemented moisture damage evaluation at the mixture design stage (Kim et al. 2015). It was also reported that only four States perform wheel tracking as part of the asphalt mixture specification. All other States of the USA continue to reply upon volumetric properties for asphalt mixture design. This emphasises the general reluctance to discard the traditional prescriptive approach in favour of performance-indicative testing for mixture design. For example, the state of Louisiana developed performance-based asphalt mixture design properties. Key parameters included deformation resistance by laboratory wheel tracking, intermediate temperature cracking (fatigue) and low temperature fracture (Kim et al. 2015). However, it was recommended that these parameters be added to the existing volumetric-based specification, rather than replacing it. Summary of background Overall, airport surface distress is similar to that for road and highway asphalt with deformation resistance and fracture resistance the primary requirements. However, asphalt fracture is not commonly a problem for airport asphalt surfaces but skid resistance and durability against loose aggregate generation are important for safe aircraft operation. Marshall-design of airport asphalt surfaces empirically provides a balance between these requirements, but the factor of safety associated with the prescriptive specification has reduced. Increased aircraft-induced stress, © ASCE 5 Airfield and Highway Pavements 2017 combined with more variable bitumen properties, present a challenge for Marshall-asphalt performance. This has resulted in some airports adopting alternate asphalt mixtures, primarily aimed at avoiding the need to groove the surface for aircraft skid resistance. Interest in more performancebased specifications has also increased. Prescription versus Outcome Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. As described above, the traditional approach to airport asphalt specification is prescriptive. Although a ‘mixture design’ is performed by the asphalt producer, the process is focused on verifying that the locally available materials are capable of producing a mixture that complies with the specification, and determining the associated constituent proportions. The constituent material requirements, bitumen type/grade, target aggregate grading, air voids and bitumen content are all prescribed. Further, the measured mixture properties, Marshall Flow and Marshall Stability, are only empirically linked to similar mixtures with historically adequate performance (Rushing et al. 2012). The asphalt producer is primarily responsible for compliance with the specification. This includes controlling the constituent materials, the production, construction and finishing of the asphalt surface. If all specified requirements are achieved, the intention is that the asphalt producer is not responsible for the resulting performance of the asphalt. The traditional approach is ‘prescriptive-compliance’ reflecting the compliance-based nature of the prescriptive specification. A purely performance-based approach contrasts with the traditional approach. The asphalt producer is advised of the aircraft using the pavement, details of the underlying pavement structure and the local environment factors impacting the performance of the surface. Performance expectations and limits are set and defined. The asphalt producer designs the asphalt mixture to meet all these requirements and warrants the adequate performance of the asphalt mixture for the specified life of the surface, typically 10-12 years. Warranted performance also requires the asphalt producer to periodically inspect and maintain the pavement surface. Any time during the warranty period that the asphalt condition falls below the defined expectations, the asphalt producer is responsible for undertaking corrective action or, in an extreme case, removal and replacement of part or all of the surface. This approach focusses on the outcome and is ‘performance-outcome’ in nature. Aside from the aircraft loading, pavement details and environmental factors, the client only specifies the throughlife performance expectations and warranty period. The asphalt producer must be allowed to adopt any mixture type, design method and constituent ingredients. Further, the production and construction equipment and methods must also be determined by the asphalt producer. A balance between these two approaches is achieved by a ‘performance-compliance’ approach. A combination of performance-indicative and prescriptive properties is required to achieve surface performance expectations (Table 1). The prescriptive requirements must be limited to properties not able to be directly measured by available performance tests. For example, the durability (aggregate breakdown) of asphalt is empirically linked to coarse and fine aggregate properties. However, no established asphalt mixture test is accepted as being indicative of asphalt durability due to aggregate breakdown. It follows that aggregate properties must be prescriptively specified. However, other asphalt performance requirements, such as deformation resistance and fracture resistance, can be directly measured in the laboratory with performance-indicative tests during the mixture design. The asphalt producer must still have an understanding of the aircraft and environment. However, the responsibilities of the asphalt producer are a balance between compliance with the minimum prescriptive requirements and compliance with the parameters indicative of field performance. The asphalt producer must have more flexibility regarding constituent material selection, volumetric composition and importantly the type/grade of bitumen. In return, a warranted performance guarantee is required. However, the warranty does not need to extend to the full asphalt surface life expectancy, which is typically 10-15 years. For example, the constituent material requirements partly address asphalt durability. It follows that the performance guarantee need only cover the period during which the distress modes assessed by performance-indicative laboratory measurement are expected to become evident. Those distresses generally relate to deformation resistance and fracture resistance, which usually become evident within three years of construction. A warranted performance guarantee of five years is reasonable. © ASCE 6 Airfield and Highway Pavements 2017 7 Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Table 2 summarises the significant differences between the three approaches to asphalt specification. The traditional ‘prescriptive-compliance’ approach requires a reliable empirical link between the prescriptive recipe and adequate field performance. Recently reported distress indicates the historical empiricism no longer exists for modern aircraft and the available constituent material supplies. The ‘performance-outcome’ approach represents a revolutionary change. Significant development of performance expectations and measurement tools is required. Further, this approach requires airport owners to trust the asphalt producer. This is not appropriate when consequential losses associated with surface failures are significant compared to the cost of the work. For example, asphalt surface distress associated with loose stones or aircraft skid resistance have potentially significant consequential losses if aircraft are damaged. Furthermore, the cost to airlines and airports of disruptions to aircraft operations when failed surfaces are being repaired is prohibitive. Adopting a performance-outcome approach is too great a change to immediately implement. However, the traditional prescriptive-compliance approach is no longer reliable. Therefore, the performancecompliance approach is recommended and provides a transitionary step towards the performanceoutcome approach, which may be considered in the future. Table 2. Summary of specification approaches Element General basis Prescriptive-Compliance Follow the recipe with the locally available materials Specification Approach Performance-Compliance Meet performance-indicating test targets and minimum prescription Performance-Outcome Do what is necessary to ensure field performance No Yes Yes Limited Designer Designer Moderate Asphalt producer Designer Total Asphalt producer Asphalt producer Defects liability only Medium term Expected life of surface No Optional Yes Mixture design considered ‘design’ Contractor flexibility Binder selection by Aggregate quality by Warranted performance guarantee Aircraft and environment specified Basis of a Performance-based Specification A performance-compliance specification is proposed, focused on laboratory testing with tangible links to airport asphalt surface field performance. Performance requirements not measurable in the laboratory, such as raw ingredient durability and aircraft skid resistance, necessitate the retention of the current prescriptive parameters. Constituent Materials Important constituent materials for airport asphalt performance include coarse and fine aggregate, bitumen and added filler (White 2016f). The traditional prescriptive specification controls the characteristics and production tolerances of all constituents. Aggregates are routinely characterised by a combination of the consensus (angularity, size and shape) and source properties (abrasion resistance, strength, deleterious material content and chemical composition) (Bessa et al. 2012). Consensus properties such as shape and angularity of the aggregate particles are important for asphalt mixture resistance to deformation (Holleran et al. 2008; Shen & Yu 2011). However, source properties, such as abrasion resistance, strength and deleterious material content are established indicators of aggregate durability and resistance to breakdown over time. It follows that aggregate source property specification is appropriate for a performance-compliance specification. However, consensus property specification is less appropriate because mixture testing for deformation resistance will evaluate the suitability of the aggregate angularity, shape grading and size. Mixture testing also indicates if the aggregate properties adversely impact mixture workability during construction. Bitumen type and grade also contributes significantly to deformation resistance, including rutting, shearing and groove closure. Bitumen type and grade also contribute to fracture resistance. © ASCE Airfield and Highway Pavements 2017 Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Existing performance-indicative test methods evaluate these important mixture properties. However, ageing of bitumen and the associated impact on fracture resistance and ravelling, is not well evaluated by asphalt testing at the mixture design stage. Rather, specification of accelerated binder ageing limits is recommended. In summary, the traditional aggregate source properties must still be prescribed in a performance-compliance specification for airport asphalt. These properties directly contribute to asphalt durability by controlling aggregate breakdown and deleterious mineral inclusion. Consensus properties also contribute to asphalt performance. However, testing of the asphalt mixture is more appropriate under a performance-compliance specification. Similarly, the contribution of binder type/grade to asphalt performance can be measured by performance-indicative testing, but the susceptibility of the bitumen to age hardening must be prescriptively limited at the constituent level. Mixture design Mixture design encompasses the selection of the type/grade of bitumen, selection of the aggregate sources, selection of added fillers or other additives, as well as overall grading and volumetric portions of the various constituents. These parameters significantly affect the performance of airport asphalt mixtures. However, the critical links between mixture properties, aircraft skid resistance (surface texture) and durability (ravelling) are empirical. Airport asphalt skid resistance evaluation is most commonly undertaken on runway surfaces using continuous friction measuring devices rather than by laboratory testing. (Yager 2014). Skid resistance testing is primarily intended for pavement management and the scheduling of rubber contamination removal in the aircraft landing zone (White & Rodway 2014). Furthermore, wet weather aircraft skid resistance is dominated by macro-texture, rather than micro-texture, which is reflected in the 1 mm minimum surface texture recommended internationally and mandated in some countries. The continued achievement of either 1 mm surface texture, or surface grooving, is critical for the performance-compliance specification of airport asphalt surfaces. However, the balance between surface texture and surface durability (ravelling resistance) is also empirical. The aggregate grading and bitumen content significantly impact the surface texture. Increased surface texture is possible with open graded, gap graded and other aggregate grading options. However, surface ravelling risk is also affected. For example, open graded mixtures are favoured for improved surface drainage (TRB 2000) but are prone to early life ravelling and usually have a lower surface life expectancy (Cooley et al. 2000). Some jurisdictions have developed laboratory ravelling resistance evaluations, such as the Cantabro losses test (Bianchetto et al. 2007). However, this requires specific testing equipment that is not widely available. To avoid impacting the empirical balance between surface durability and aircraft skid resistance, asphalt mixture type, aggregate grading and mixture volumetrics must be retained consistent with common practice in the particular jurisdiction. For example, in Australia, dense graded and grooved asphalt must be retained. Alternate mixture types, such as OGFC or SMA, must be considered separately to the development of a performance-based airport asphalt specification. Other mixture design parameters are readily evaluated by laboratory testing of the asphalt mixture. The primary tests and properties indicative of asphalt performance in the field are summarised in Table 3. For example, an asphalt producer must consider hydrated lime and liquid anti-stripping agent for improving resistance to asphalt moisture damage. Different materials are better suited to different sources of aggregate (Kennedy & Ping 1991). As long as the moisture damage resistance of the asphalt mixture exceeds the limit indicative of acceptable performance in the field, the asphalt producer must be allowed to select the most appropriate solution for the circumstances. As described above, the primary distresses observed in airport asphalt surfaces are groove closure and surface shearing or shoving, resulting from bitumen creep or viscous flow during hot weather (White 2016f). It follows that significant technological advancement has focussed on reducing bitumen and asphalt creep and viscous flow potential. Although asphalt surface fatigue has usually not been a significant issue for airport pavements (Rodway 2016) asphalt fracture resistance must be considered to ensure that the balance between deformation resistance and fracture resistance remains appropriate. © ASCE 8 Airfield and Highway Pavements 2017 9 Table 3. Summary of airport asphalt test methods Physical requirement Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Deformation resistance Prescriptive Test Methods Marshall Stability Marshall Flow Fracture resistance Not traditionally tested Durability Not traditionally tested Performance Test Methods Wheel tracking Flow Number/Flow Time Two/Four point bending beam Repeated load indirect tension Cantabro losses (ravelling) TSR (moisture damage) In summary, the balance between surface durability (ravelling) and aircraft skid resistance (surface texture) is significantly affected by the aggregate grading and volumetrics. Prescribed retention of well performing mixture type and volumetrics requirements is therefore appropriate. The remaining performance requirements are more appropriately evaluated by established laboratory test methods, indicative of deformation resistance, fracture resistance and moisture damage resistance. Additional testing indicative of other asphalt performance requirements, such as the Cantabro losses for ravelling resistance, is expected to be introduced in the future. Asphalt Production Testing of asphalt mixtures for properties indicative of field performance is viable at the mixture design stage. However, the performance-indicative testing equipment and methods are not viable for production compliance testing, particularly in regional and remote areas. For example, in Australia, the equipment required to perform asphalt wheel tracking is not available outside the six capital cities. That leaves around 80% of asphalt surfaced Australian runways without reasonable access to wheel tracking devices for production testing. It follows that an alternate approach is required for asphalt production compliance. During the mixture design process, expected asphalt field performance is evaluated by test methods indicative of asphalt surface performance. Parallel testing of volumetric and Marshall parameters provides a mixture-specific relationship between volumetric/Marshall properties and performance parameters. Further, asphalt volumetrics and Marshall properties are established production compliance parameters. The associated testing is rapidly performed and the equipment is readily transportable to regional and remote locations. It follows that asphalt volumetric and Marshall properties provide an appropriate basis for asphalt production compliance testing. Further, to recognise the variable nature of constituent materials and asphalt mixture properties, production tolerances, applied to the mixture design values, are also required. A typical airport runway resurfacing project has a duration of between one and six months. During that time, constituent material properties and sources may change. For example, the coarse aggregate may be produced from a different face within the source quarry or a new importation shipment of bitumen may change the feedstock for modified bitumen production. Many examples of airport surface distress have been related to changes in constituent material sources after the mixture design process (White 2015; White 2016c). The mixture-specific link between volumetric properties and performance-indicative properties relies on consistent constituent materials. It follows that a performance-based asphalt specification, reliant upon volumetric properties for production compliance, must include a trigger to reconsider the mixture design when any constituent material source changes. In summary, performance-indicative properties are appropriate for mixture design but not for daily production compliance testing. Rather, volumetric and Marshall properties are more appropriate for asphalt production compliance, taking into account reasonable production tolerances. The volumetric and Marshall property tests are also established within industry and the equipment is readily available and transportable. Once established by the mixture design process, the mixturespecific link between performance properties and volumetrics must be maintained by consistent constituent material sources and properties. © ASCE Airfield and Highway Pavements 2017 10 Asphalt Construction Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Producing asphalt that is uniform and consistent with a performance-based mixture design is only part of the challenge. The construction of the surface is equally important for adequate airport asphalt surface performance. The traditional prescriptive-compliance approach specifies the number, capacity, type and operation of the cold planing machines, pavers, rollers and other construction equipment. The temperature and methods for handling the materials are also prescriptively specified. An outcome-focussed approach to construction is more appropriate for a performance-compliance specification. The key requirements for the construction of airport asphalt surfaces include preparation of the existing surface, asphalt density, asphalt thickness, tightness of the paving joints, tightness of the surface, level and smoothness. Some of these factors are readily assessed by outcome-focussed testing. However, others require specialist equipment or processes, as summarised in Table 4 and discussed further below. Table 4. Summary of asphalt construction evaluation Construction requirement Can impact Surface preparation Bond to underlying pavement Asphalt density Excess air voids Asphalt thickness Ride quality and pavement strength Paving joint tightness Joint opening and ravelling Surface tightness Ravelling Surface level Ride quality Surface smoothness Ride quality Leading to De-bonding and slippage Rutting by asphalt densification. Uneven surface and structural pavement failure Loose stones on surface and moisture ingress Loose stones on surface Unacceptable unevenness Unacceptable unevenness Evaluation method(s) or Strategy Mandating cold planing, cleaning and tack coat Density testing Physical measurement and survey data Visual inspection Mandating pneumatic rollers and visual inspection Survey data Measuring straight edge deviation and Boeing bump index Density of placed asphalt is assessed by determining the density of recovered cores. Backfilling of the core holes represents a weakness in the surface and avoiding coring is advantageous if an alternate method of evaluation is available. Nuclear density gauges are economically available as a non-destructive alternate to coring. However, the relationship between density determined by physical testing of cores and by nuclear gauges is mixture-specific (NATA 2013). Therefore, some airports have continued to cut up to 16 cores from the asphalt placed in each work period for the purpose of density testing. However, a construction trial provides the opportunity to evaluate the surface by both methods and perform mixture-specific calibrations of the nuclear gauge results. The nuclear gauge can then be utilised for compliance testing throughout the project, as long as the mixture design does not change. Surface smoothness is traditionally evaluated by deviation under a straight edge and comparison of the design surface level to the actual finished surface level at every point on the design grid. The Boeing Bump Index, developed by the FAA, provides a more rational approach to evaluating the impact of surface smoothness on aircraft operation (Roginski 2012). The Boeing Bump Index determines the criticality of bumps of all lengths from 0.5 m to 60 m at intervals along the runway as close as 0.25 m (FAA 2009). However, bump lengths longer than 10 m likely reflect geometric design and are beyond the control of the asphalt producer. It follows that surface construction smoothness must be limited to bump lengths less than 10 m, which better reflect construction quality, with longer wavelength bumps controlled by overall geometric design levels. Assessment of the condition of the surface and the paving joints is subjective and difficult to specify in a quantitative manner. Consequently, comparison to an established and agreed acceptable standard is required. An asphalt production and construction trial is essential to verify the production, paving, rolling and finishing processes proposed by the asphalt producer. An acceptable surface finish of the asphalt and the paving joints must also be agreed. The trial area can then be utilised during the project to assess the quality of the work performed in each work period. © ASCE Airfield and Highway Pavements 2017 In summary, factors affecting surface layer bond, density and shape must be controlled during the construction of airport asphalt surfaces. Some factors, such as asphalt density, thickness and smoothness, can be controlled by physical measurements. Other factors, such as the surface finish, require comparison to an acceptable standard developed during the construction trial. Further, some factors must be addressed by mandating particular equipment or processes in the performancecompliance specification. Examples include preparation of the existing surface by cold planing, cleaning and tack coating. Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. Related issues A performance-based specification for airport asphalt requires a number of associated procurement and contractual provisions. These provisions are documented outside of the specification itself, but are critical to its implementation. Tendering requirements Airport surfacing work is generally more demanding than road and highway surfacing. This reflects the common requirement to perform the work during short night-time work periods, the requirement to return the pavement to an operational condition at the end of each work period and a low tolerance of defects in airport pavement surfaces. It follows that value-for-money and risk minimisation constitute a significant portion of airport surfacing tender evaluation. However, where a performancebased asphalt specification is adopted, the asphalt mixture, work methods and quality assurance processes must also form part of the tender evaluation. Tenderers required to design the asphalt mixture as part of the tender process appropriately expect a reasonable probability of a return on that investment. An expression of interest, with two to four organisations selected to tender, is recommended to reasonably limit the number of tenderers required to make such investment. Further, the time required to prepare the mixture design and the associated performance-based testing is significant. It is therefore essential that a minimum eightweek tender period be provided. In return, the tenderers must be required to include details relating to the asphalt mixture, production and construction in their submissions. Contractual requirements The works contract must be consistent with the performance-based approach to asphalt specification. Specifically, the contract must recognise the design of the asphalt mixture as a ‘design activity by the contractor’, with associated professional liability requirements, even within a construct-only contract. Further, the contract must include appropriate warranty provisions. An asphalt producer warranting the performance of an airport asphalt surface reasonably requires the surface to be appropriately maintained. As a minimum, maintenance must include an annual inspection and preventative maintenance treatments. Otherwise, a crack appearing in year two is likely to result in significant moisture damage and distress in the future. It is unreasonable to hold the asphalt producer responsible for distress that is a direct consequence of a lack of routine or preventive maintenance undertaken by the airport. The asphalt producer must be involved in the annual pavement surface condition inspection. It is also recommended that the contractor perform the agreed maintenance regime where reasonable and practicable. Warranty provisions A critical requirement of the performance-based asphalt specification is a warranted performance guarantee by the asphalt producer. The warranty must define the expected level of performance, detail a protocol for performance measurement, establish liability if the surface fails to perform, and state the duration of the warranty. Dispute resolution mechanisms are also required. Defining the performance requirements and methods of measurement is challenging. Critical modes of distress must be stated and quantities of distress that trigger the warranty must be defined. A periodic performance evaluation and distress measurement protocol must also be outlined. © ASCE 11 Airfield and Highway Pavements 2017 Importantly, the warranty cannot be open ended. A material change in use, such as regular use by substantially more damaging aircraft that results in surface distress must not trigger the warranty. It would also be unreasonable for the warranty to be triggered by distress attributable to the underlying pavement or to a natural disaster. Summary and Conclusions Downloaded from ascelibrary.org by RMIT UNIVERSITY LIBRARY on 01/04/19. Copyright ASCE. For personal use only; all rights reserved. The performance-based specification of airport asphalt provides an opportunity to introduce riskreducing innovation for better performing airport pavement surfaces. In return for increased flexibility to innovate, the asphalt producer provides a warranted performance guarantee. Airport managers are better protected against the cost of correcting early-life distress and can expect better performing pavements. A performance-compliance approach is recommended with a combination of performance-indicative mixture design requirements, as well as prescriptive constituent properties for long term durability. The link between volumetrics, aircraft skid resistance and surface durability must also be prescriptively retained. Importantly, the specification itself is only one element of the procurement system. The tender and contract documentation must be consistent with the performance-based approach to airport asphalt surface specification. Further work is required to develop or implement test methods indicative of the performance requirements that are not currently available. Examples include interface bond to the underlying pavement, aircraft skid resistance and asphalt durability (ravelling). This will allow alternate asphalt mixtures, with different grading and volumetric properties, to be considered on a performance-basis and incorporated into performance-based airport asphalt specifications in the future. References Airey, GD 2003, ‘State of the art report on ageing test methods for bituminous pavement materials’, International Journal of Pavement Engineering, vol. 4, no. 3, pp. 165-176. Austroads 2013, EME Technology Transfer for Australia: An Explorative Study, AP-T249-13, Austroads Project Number TT1353, Sydney, New South Wales, Australia, October. Bessa, IS, Castelo Branco, VTF & Soares, JB 2012, ‘Evaluation of different digital image processing software for aggregates and hot mix asphalt characterizations’, Construction and Building Materials, vol. 37, pp. 370-378. Bianchetto, H, Miró, R, Pérez-Jiménez, F & Martínez, AH 2007, ‘Effect of calcareous fillers on bituminous mix aging’, Transport Research Record: Journal of the Transportation Research Board, no. 1998, pp. 140148. Bognacki, CJ, Frisvold, A & Bennert, T 2007, ‘Investigation into asphalt pavement slippage failures on Runway 04R-22L Newark International Airport’, Proceedings 2007 FAA Worldwide Airport Technology Transfer Conference, Galloway, New Jersey, USA, 16-18 April, Federal Aviation Administration. Campbell, C 1999, The Use of Stone Mastic Asphalt on Aircraft Pavements, Submitted in fulfillment of the requirements for SEN713 Research/Professional Practice Projects, School of Engineering and Technology, Deakin University, Geelong, Victoria, Australia, December. Collop, AC & Roque, R 2004, ‘Report on the prediction of surface-initiated longitudinal wheel path cracking in asphalt pavements’, Road Materials and Pavement Design, vol. 5, no. 4, pp. 409-434. Cooley, Al, Brown, Er & Watson, DE 2000, Evaluation of OGFC containing Cellulose Fibers, NCAT Report 00-05, National Centre for Asphalt Technology, December. Crawford, C 1986, Tender Mixes, Report QIP 108, National Asphalt Pavement Association, Maryland, USA. Cui, Q, Bayraktar, ME Hastak, M & Minkarah, I 2004, ‘Use of warranties on highway projects’, Journal of Management in Engineering, vol. 20, no. 3, pp. 118-124. Diefenderfer, BK & Bryant, JW 2006, ‘Development of a pavement warranty contract and performance specification for hot-mix asphalt resurfacing project’, 2006 Airfield and Highway Pavements Specialty Conference, Atlanta, Georgia, USA, 1-3 May. EAPA 2003, Airfield use of Asphalt, European Asphalt Pavement Association, May, viewed 25 November 2013, . Elnasri, M, Airey, G & Thom, N 2013, ‘Experimental investigation of bitumen mastics under shear creep and creep-recovery testing’, Proceedings T&DI Airfield and Highway Pavement Speciality Conference, Los Angeles, California, USA, 9-12 June, American Society of Civil Engineers, pp. 921-932. Emery, S 2005, ‘Asphalt on Australian airports’, Proceedings AAPA Pavements Industry Conference, Surfers Paradise, Queensland, Australia, 18-21 September, Australian Asphalt Pavements Association. © ASCE 12