CPTP update: highlights from the past year demonstrate that the Concrete Pavement Technology Program is continuing its progress in making road surfaces that are safer, smoother, and more durable

Public Roads, Sept-Oct, 2003 by Cheryl Allen Richter, Suneel Vanikar

Humans have been building roads since the Romans, so some may assume that the highway community knows everything there is to know about pavement. Not so. Pavements are highly variable in smoothness and durability, depending on the origin of the materials used to construct them, weather conditions such as temperature and humidity during and after construction, and how well (or not so well) the materials were compacted. Construction of pavements that are safe, smooth, and durable requires good design, sound selection of materials and mix design, and well-controlled construction processes.

The Federal Highway Administration's (FHWA) Concrete Pavement Technology Program (CPTP) is helping designers, material suppliers, contractors, and State agencies improve portland cement concrete (PCC) pavements by addressing some of the critical gaps in knowledge. The CPTP authorized under the Transportation Equity Act for the 21st Century (TEA-21) is funding research on approximately 30 projects for 6 years to improve the performance and cost-effectiveness of concrete pavements. During the first years, FHWA and the Innovative Pavement Research Foundation conducted the CPTP jointly. In the summer of 2002, FHWA assumed sole responsibility.

The CPTP will produce practical and readily usable tools, guidelines, methods, and software to be used in the selection of materials, mix and pavement design, construction, and operation. The goals are to reduce user delays and costs, improve performance, and foster innovation. The July/August 2002 issue of PUBLIC ROADS discussed selected CPTP projects in depth, and this follow-up article describes the program's progress and highlights over the past year, starting with selected CPTP projects in advanced pavement design systems.

The Concrete Pavement Technology Program was developed and is being implemented by FHWA in cooperation with the State departments of transportation (DOTs), American Association of State Highway and Transportation Officials (AASHTO), industry, :rod academia. "This program is an excellent example of a public-private partnership," says Tommy L. Beatty, FHWA's director of pavement technology. "The CPTP has produced numerous technologies that will make a significant impact on the transportation program."

Advanced Pavement Design Systems

These projects are pioneering changes in structural design, materials, and cost analysis. The industry can expect guidance, tools, and test methods to support the design and evaluation of highly cost-effective and durable concrete mixtures and analytical tools to perform sound economic evaluation of alternative pavement designs.

Joint Sealing

currently, nearly all State highway agencies require transverse joint sealing, which adds about 2 to 7 percent to the initial construction costs of pavements and even more in resealing activities. If narrow, unsealed joints on short-jointed concrete pavements can perform as well as sealed joints, States may save millions of dollars in construction and maintenance costs. By eliminating or reducing the need for joint maintenance, this change also will improve safety by reducing the need for lane closures that are inherently dangerous to both drivers and maintenance crews.

A 3-year CPTP study on the cost effectiveness of scaling transverse contraction joints is one of several projects that will help agencies determine when, where, and how to seal pavement joints. In this study the lead on the program, Dr. Katie Hall, and her colleagues will take a close look at the performance of 35 to 40 experiments in 12 States on sealed and unsealed joints. CPTP-funded demonstrations in Illinois, Kansas, and Ohio on high-performance concrete pavements, for example, are comparing sealed versus unsealed joints.

In the 1950s Wisconsin DOT (WisDOT) engineers questioned the cost effectiveness of sealing joints in PCC pavements. Since that time Wisconsin has built numerous test sections and documented findings to determine the effects of unsealed joints on pavement performance. In 1990 WisDOT adopted a department policy of not sealing PCC joints in new construction and maintenance. "We are convinced that leaving joints unsealed is the most cost-effective way to deal with joints in PCC pavements," says Steve Krebs, WisDOT pavement engineer.

A 1997 report, Stephen E Shober's The Great Unsealing: A Perspective on PCC Joint Sealing, documented Wisconsin's findings and started a national controversy. "Although Shober took a lot of heat for his stand, this research intrigued us in Illinois because we have the same weather conditions," says Matt Mueller, Illinois Department of Transportation (IDOT) pavement engineer.

At that time IDOT was conducting a study of how much water was passing through its concrete and full-depth bituminous pavements. A flow meter on the under drains revealed the presence of significant water passing through the typical sealed joint pavements. Recognizing that seals fail to keep the water out, IDOT decided to do its own joint sealing studies and asked crews on then-current projects to install a few 61-meter (200-foot) sections with narrow unsealed transverse joints. In 1997 the first test section on IL 64 near St. Charles compared three variations: joints with no seals, preformed elastomeric (rubbery) joint seals, and a reservoir sealed with rubberized hot sealant. Three subsequent test sections of unsealed and sealed joints followed in 1997 on IL 59 at Naperville, in 1999 on US 67 at Jacksonville, and in 2000 on IL 2 at Dixon.