|FHWA > Engineering > Pavements > Looking at Long-Term Results|
Pavement Preservation Compendium II
Looking at Long-Term Results
Performance of Test Section After 13 Years
by Gary Hildebrand and Scott Dmytrow
To evaluate the "preventive maintenance effectiveness of flexible pavement treatments," the Strategic Highway Research Program placed sections for Specific Pavement Studies 3 (SPS-3) throughout the United States and Canada in the late 1980s and early 1990s. Each SPS-3 project included test sections that received different treatments. The project test sites were in four climate zones; exhaustive information was recorded at construction; and performance data were captured periodically by the Long-Term Pavement Performance team and stored in the DataPave software.
After 13 years, what conclusions can be drawn? What is the effectiveness of the preventive maintenance treatments? Following is a report on one SPS-3 project in California,1 observed on May 23, 2003.
A brief history of the California SPS-3 project is as follows:
Treatments and Conditions
Different preventive maintenance strategies were applied to 11 segments of the test section in 1990. One segment was routed and crack sealed, one was slurry sealed, five had different chip seals applied, and four received different overlays of hot-mix asphalt (HMA). The control section received no preventive maintenance.
After 13 years, the segment with rout and crack seal was only in marginally better condition than the control section. The entire rout-and-crack-seal test section had to be crack-sealed during the first few years (circa 1992) and again in 2000 to fix adhesion problems. Ride quality on the rout-and-crack-seal section is similar to that on the control section. In addition, part of this test section has deteriorated badly, possibly because of an underlying condition.
The slurry seal has performed well, with no delaminating (i.e., separation from the surface) or raveling (i.e., loss of aggregate from the surface) - the roadway remains protected. Most of the cracks seem to have reflected through the slurry but have been crack-sealed, preventing moisture intrusion and base damage.
Overall, the five different chip seals have performed well, with minimal raveling, bleeding (i.e., a layer of asphalt binder migrating to the surface), or flushing (i.e., minor bleeding of binder). Some chip seals, however, had more reflective cracking than others.
The four HMA overlays also have performed well, although reflective cracking has occurred in the two sections with conventional HMA overlays. The fiber and asphalt rubber HMA overlays, however, appear to have an increased resistance to reflective cracking.
In contrast to the 11 test segments, the control or "do nothing" section is in very poor condition. The ride quality is bad and the section is in need of more than preventive maintenance. The crack filler appears to be the only thing keeping this section intact.
Between each test section is an unofficial control section. Each of these is also in very poor condition and will require more than preventive maintenance.
With the exception of the rout-and-crack-seal section, all of the maintenance strategies are performing well. The treatments have extended the life of the pavement and have kept the roadway in a condition acceptable to the motoring public. Each of the maintained sections could gain extended life with the application of another maintenance treatment.
The slurry and seal coat sections require a thin blanket or leveling course to restore ride quality. The thin overlay sections could benefit from either a slurry seal or another seal coat, because the ride quality generally is good. To obtain long-term service from the rout-and-crack-seal or control sections, extensive and costly rehabilitation strategies may be necessary.
The treatments applied to this test section demonstrate the benefits of PM for roads in good condition. When the SPS-3 strategies were applied in 1990, the 1985 chip seal was in good shape, the ride quality was good, and the distress consisted of transverse and longitudinal cracks approximately one-quarter inch wide. After 13 years, almost all of the PM-treated sections are still serviceable.
The test site is a very low-volume roadway in a non-freeze-thaw area. Achieving the same magnitude of success elsewhere with any of these strategies, therefore, requires comparable traffic and weather conditions.
The test sections prove the viability of PM treatments. Another PM treatment on the test sections could extend the life of this roadway another 5 to 10 years. This site shows that a pavement placed in 1980 can be maintained for more than 30 years in a condition acceptable to the general public - and to taxpayers - at the cost of a few PM treatments.
For more information contact Gary Hildebrand, Telfer-Windsor Fuel Co., P.O. Box 38, Windsor, CA 95492 (telephone: 916-354-9760; e-mail: firstname.lastname@example.org).
1 06A300; GPS Section 061253; Butte County, California; State Route 32; PM 15.96-18.71; average annual daily traffic: 2,900 vehicles.
Hildebrand is Pavement Preservation Specialist, Telfer-Windsor Fuel Company, Windsor, California; Dmytrow is Technical Marketer, Koch Pavement Solutions, Sacramento, California.
From TR News, September-October 2003, pp. 4-15. Copyright, Transportation Research Board (TRB), National Research Council, Washington, D.C. Reprinted with permission of TRB.