Evaluating Laboratory Compaction Techniques of Reclaimed Asphalt Pavement

Abstract

Reclaimed asphalt pavement (RAP) is a byproduct of roadway resurfacing. A limited amount of RAP can be recycled into new hot-mix asphalt; the rest is stockpiled. Some states allow the use of RAP–aggregate blends as base course material. Because of RAP's low strength and susceptibility to creep deformation, the Florida Department of Transportation (DOT) excludes RAP from being used as pavement base course for high-traffic areas. The research objective was to determine whether the strength characteristics of RAP could be improved through compaction and thereby make its base suitable in high-traffic areas. Modified Proctor, vibratory, and gyratory compaction data were compared. Four RAP sources were used. Specimens compacted by the three methods were tested with the limerock bearing ratio (LBR), unconfined compressive strength, and indirect split tensile strength. LBR is Florida's variation of the California bearing ratio. Specimens were compacted to either a density or a compaction energy level. Vibratory compaction produced the lowest densities and strengths. Modified Proctor produced higher densities and strengths than vibratory, but the LBR strengths for all RAP types were consistently below Florida DOT standards. Gyratory compaction produced the highest densities and strengths. Gyratory RAP specimens were two to four times as strong as modified Proctor specimens at the same density. The compaction method did not have as significant an effect on creep, although gyratory-compacted samples produced less creep than modified Proctor–compacted samples.