Cement Stabilization of Unpaved Roads

In an effort to address the local citizens’ preference for preserving existing gravel roads, personnel of the Northern Virginia District of the Virginia Department of Transportation (VDOT) have been exploring various options for improving the effectiveness of current maintenance practices. The purpose of this study was to explore the effectiveness of chemical stabilization practices on unpaved roads. A 550-ft-long segment of Hurley Lane, a gravel road in Loudoun County, was selected for testing. Traffic counts measured by VDOT personnel in early 2016 indicated approximately 340 vehicles per day, including 3% trucks. The construction technique known as full-depth reclamation (FDR) was used. The existing unpaved road section was pulverized to a depth of 12 in and subsequently blended with 5% cement by weight using road reclaiming equipment. The surface was then covered with a double chip seal. The main objective of this project was to provide stability while still maintaining the appearance and “feel” of a gravel road. Construction was completed in mid-November 2015, and problems with surface durability became evident approximately 3 months later. Excessive rutting and soil contamination at the surface were observed. Follow-up field testing was conducted to determine the cause of failure. A falling weight deflectometer was used to measure the response of the road section to impulse loads. Test results and visual observation indicated that the lack of durability of the chip seal was the most likely cause of substandard performance. Prior to stabilization, the test section at Hurley Lane required frequent maintenance activities. The need for extensive road maintenance decreased substantially after completion of the project, indicating that the underlying cement-stabilized road section was performing adequately. The study concluded that cement stabilization using the FDR approach is a viable option for improving some unpaved roads. It can be particularly attractive in situations where placement of conventional cement-treated aggregate is impractical because of time constraints on delivery. The study recommends that VDOT consider using FDR with chip seal surfacing for maintenance of areas identified as maintenance nuisance (each road segment under 0.1 mile long) and for roads qualified under the Rural Rustic Road Program (designed to keep a traditional rural lane appearance while improving the riding surface within the current right of way). FDR projects need to be planned adequately and monitored during construction. Particular attention should be directed to field testing of compaction, weather-related limitations on construction activities, and chip seal application procedures. The study also recommends the use of a falling weight deflectometer to prioritize maintenance needs. FINAL REPORT CEMENT STABILIZATION OF UNPAVED ROADS Edward J. Hoppe, Ph.D., P.E. Associate Principal Research Scientist Harikrishnan Nair, Ph.D., P.E. Research Scientist Virginia Transportation Research Council (A partnership of the Virginia Department of Transportation and the University of Virginia since 1948) Charlottesville, Virginia May 2017 VTRC 17-R19