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Conference Papers & Proceedings



Download the conference program and the conference overview. Where available, links to individual conference papers and presentations are included below.


Day One


  • Marc Mastronardi, P.E., Director of Construction, Georgia Department of Transportation
  • Pete K. Rahn, Maryland Secretary of Transportation


Opening Remarks: SMA's Place Today

  • Mike Acott, President, National Asphalt Pavement Association

Paper included in Advances in the Design, Production, & Construction of SMA

Stone mastic (matrix) asphalt was first placed 50 years ago in 1968 near Kiel, Germany, while the United States implemented this premium technology 25 years ago. Despite the presence of a low bid environment, some agencies have turned to SMA as a trusted product to give them performance. As one of the individuals responsible for bringing SMA to the United States, Mike Acott explains why the industry looked to this product in the 1990s and why it is still a product truly engineered for performance today.


Panel Discussion: Why SMA?

  • Pete K. Rahn, Maryland Secretary of Transportation
  • Danny Gierhart, P.E., Senior Regional Engineer, Asphalt Institute
  • Knut Johannsen, Dr.-Ing., Head of MPA, EUROVIA Services GmbH, Germany
  • Matthew Corrigan, P.E., Asphalt Pavement Engineer, Federal Highway Administration
  • Helen Bailey, PhD, Managing Director, The Driven Company
  • J. Richard Willis, PhD, Senior Director of Pavement Engineering & Innovation, NAPA (moderator)


Implementation of SMA at the Illinois Tollway: An Overview

  • Cindy Williams, P.E., Deputy Chief of Program Implementation, Illinois Tollway


SMA: The History (presentation)

  • Horst Erdlen, Business Unit Manager, J. Rettenmaier & Söhne

Cold and long winters and the use of studded tires caused a lot of damages in the road network in Germany in the 1960s. The industry was looking for a solution how to repair these damages. A hot liquid mastic was used to fill the "mechanical ruttings" and to make the more resistant to the traffic a single size aggregates fraction was manually spread into the mastic. The repair mix showed an excellent resistance on one hand side to the damages caused by the studded tires but also to the deformations during the hot summer months caused by heavy duty traffic. Two major contractors picked-up the idea of that repair mix and industrialized it giving birth to SMA. The first section was paved on July 30, 1968 in Wilhelmshaven. A journey through 50 years of success with Stone Mastic Asphalt.


This presentation covers the further development of SMA and SMA based mixtures during the past 50 years and will show new possibilities e.g. noise reduction and structural layers. Furthermore, it will provide additional information regarding the spread of SMA around the globe will be seen with examples from Korea, Taiwan, China, the Philippines, Australia, New Zealand, Mexico, Brazil, Argentina, Israel, Turkey, and, of course, all over Europe.


SMA: Theory and Practice (presentation)

  • E. Ray Brown, PhD, P.E., Director Emeritus, National Center for Asphalt Technology (NCAT)

When it comes to asphalt pavement performance, nothing works like SMA. What is it about the design of SMA mixes that helps them achieve levels of performance beyond those of traditional mixtures? Attend this session to gain a better understanding of the theory behind SMA mix designs and how these designs provide an unparalleled level of performance in the field.


SMA in PennDOT's Long Life Pavement Program

  • Neal Fannin, P.E., Pavement Materials Engineer, PennDOT

The Pennsylvania Department of Transportation is one DOT in the US that knows SMA can be a part of its Long Life Asphalt Pavement Program. Since originally developing its SMA standards, it implemented Warm Mix SMA in 2017 and conducted performance testing to baseline and validate its premium performance. Today, PennDOT uses WMA SMA in all 11 PennDOT Engineering Districts.


Performance and Life-Cycle Cost Benefits of Stone Matrix Asphalt (presentation)

Since its introduction into the United States, stone matrix asphalt has gained great popularity among state highway agencies as a premium asphalt mix to enhance field performance and extend life expectancy of asphalt pavements and overlays. Considering that SMA is generally more expensive than the conventional Superpave dense-graded mixture, mainly due to higher asphalt contents, requirements for more durable aggregates, and inclusion of fibers as stabilizers, it remains unclear whether the higher cost of SMA can be justified by the increase in life expectancy of the mix. This presentation highlights a study undertaken to quantify the performance and life-cycle cost benefits of SMA versus those of polymer-modified Superpave dense-graded mixtures used on similar trafficked highways.


Best Practices: Plant Production (presentation)

  • Terry Roof, Assistant General Manager of Asphalt Plants, Superior Paving Corp.

While the mix design for an SMA mixture is critical, it is also important that plant operations be considered to ensure that the mixture produces replicates the design as closely as possible. This session highlights best practices for producing SMA at common asphalt plants to ensure the mixture that arrives at the job is the mixture which was designed to perform.


Best Practices: Construction (presentation)

  • Todd Mansell, Product Application Specialist, Caterpillar Paving

Efficient compaction of SMA in the field is similar in many ways to compacting other asphalt mix types; however, there are inherent challenges that can occur due to the nature of the materials in the mixture. Learn the best practices for ensuring that SMAs achieve the desired density in the field to help ensure performance. A brief comparison of field compaction approaches in North America and Europe and how they impact SMA construction is also be presented.


SMA's Evolution: Rubber Modified SMA's (presentation)

  • Kamil E. Kaloush, PhD, P.E., Professor, Arizona State University

The field performance benefits of gap-graded asphalt mixtures such as SMA have been well documented in terms of improved permanent deformation and cracking resistance. This presentation summarizes findings from several research studies conducted at Arizona State University on rubber-modified and asphalt rubber mixtures. The unique engineering properties of gap-graded asphalt rubber mixtures are discussed along with recommendation on how to use them in current pavement design practices.


Day Two

Breakout Session: Historical Perspective and Case Studies Part 1


Breakout Session: SMA Sustainability, Part 1


Breakout Session: Historical Perspectives and Case Studies, Part 2


Breakout Session: Aggregate and Innovation


Breakout Session: Historical Perspective and Case Studies Part 3


Breakout Session: Advances in SMA


Breakout Session: Laboratory Evaluations of SMA


Breakout Session: Quantifying SMA Performance


Day Three

Racetracks: SMA on the Indianapolis Motor Speedway (presentation)

  • William J. Pine, P.E., QC Director of Asphalt Technology, Heritage Construction & Materials, Heritage Research Group @ The Center

The main oval pavement structure at the Indianapolis Motor Speedway was originally constructed in 1909. Although it is commonly referred to as The Brickyard, the original pavement was an aggregate base on compacted subgrade with a sealcoat as the original racing surface. That surface failed during a series of race events on August 19, 1909 and was replaced in the fall of that same year with a layer of paving bricks, most of which still exist at the bottom of the current pavement structure. The utilization of hot-mix asphalt began on portions of the turns in 1936, but it wasn’t until 1976 before the entire track was paved at one time. The most recent rehabilitation occurred in 2004, and this presentation will inform the audience as to why SMA was chosen, what the designs looked like along with field results, how the project went and how it’s been performing today. The existing racing surface will be 14 years old this fall and has lasted longer than any full resurfacing placed to date, which is directly attributable to the use of SMA.


Airports: Introducing SMA to Australian Airfields (presentation)

  • Greg White, PhD, Director of the Airport Pavement Research Program, University of the Sunshine Coast

Paper included in Advances in the Design, Production, & Construction of SMA

SMA produced from larger sized aggregates can provide a surface texture that exceeds the 1 mm typically required by airport regulators around the world. As a result, many Australian airports are interested in SMA as an ungrooved runway surface. However, other countries, such as China and Germany, have already made significant use of SMA as an ungrooved runway surface. This paper describes the benefits and global use of SMA as an ungrooved runway surface and describes the current effort to introduce this technology to Australian airports.


Danish Experience with Low Rolling Resistance SMA: From the Lab to the Road

  • Matteo Pettinari, PhD, Specialist in Asphalt Materials and Flexible Pavements, Danish Road Directorate

While stone matrix asphalt is a mixture of choice for durability, it is also becoming the sustainable choice in Denmark. The Danish Road Directorate (DRD) has recently developed an SMA mixture designed to reduce the rolling resistance of the pavement. This, in turn, will reduce the emissions coming from vehicles and save money on fuel for the country. This presentation provides the latest information regarding the DRD and its low rolling resistance mixture.


Thin is In: Thin Stone Mastic Asphalt (presentation)

  • Martin McLaughlin, CEng MICE, Engineering and Program Manager, Transport Scotland

While many agencies worldwide use SMA for standard thickness overlays and wearing courses, few have ventured into thinner applications for these mixtures. Transport Scotland has been successfully placing SMA less than 30 mm (1.18 inches thick). This session highlights why Transport Scotland is looking at thinner SMA applications and how they plan to effectively use this tool for network management.


SMA: Wide-Open on the Autobahn

  • Larry Michael, Larry L Michael LLC

While Route 66 may be the most road in the US, few roads are more famous world-wide than the Autobahn in Germany. This high performance road is known for allowing its drivers to push the limits of speed in some areas requiring a pavement which will perform in this high octane environment. In the past, when the Autobahn was repaved, then entire roadway was shut down and multiple pavers were used in echelon to provide a high quality surface; however, on the latest SMA repave, the entire leveling and surface courses were paved full width (with just one paver) to eliminate joints. This presentation discusses why SMA was chosen in this application and how this “wide-open” paving was completed.


Panel Session: The Future of SMA

  • Dennis Bonds, P.E., Director of Quality Control, APAC-Mississippi Inc.
  • Carsten Karcher, Dr.-Ing., Director, European Asphalt Pavement Association
  • Matteo Pettinari, PhD, Specialist in Asphalt Materials and Flexible Pavements, Danish Road Directorate
  • Horst Erdlen, Business Unit Manager, J. Rettenmaier & Söhne, Germany
  • Rebeccah Smith, Assistant Division Chief, Office of Materials Technology, Maryland State Highway Administration
  • Craig Parker, Executive Vice President, Silver Star Construction Co. Inc. (moderator)


Closing Comments

  • J. Richard Willis, PhD, Senior Director of Pavement Engineering & Innovation, NAPA