Field Performance Evaluation of Roadway Drainage System Installed in Recycled Concrete Aggregate Base Course

This study presents findings from a 33-month field evaluation of a roadway drainage system installed adjacent to a base course constructed with recycled concrete aggregate (RCA). One paved and one unpaved RCA section, with dimensions simulating roughly a two-lane roadway, were constructed. The drainage system consisted of corrugated and perforated underdrain pipe embedded into a free-draining natural aggregate wrapped around with a nonwoven geotextile. The objective of the field evaluation was to monitor changes in the filtration characteristics of the geotextile and the drainage capability of the underdrain pipe. The major finding of the study is that both test sections continued to discharge infiltrated rainwater throughout the study. However, geotextiles exhumed from test sections indicated some reduction in permittivity due to both migration of fine particles and chemical precipitation (tufa) from RCA. When compared with results from previously completed laboratory study, migration of fine particles from RCA onto geotextile surface was found to be similar. However, the chemical precipitation observed from the field geotextile samples was significantly less than what was observed previously from the laboratory study. The tufa precipitation within the drainage pipes was also insignificant in terms of impeding the hydraulic ability of the drainage system. These findings indicate that while using RCA in the field may result in modest reductions, overall hydraulic performance of the drainage system remains acceptable, supporting the use of RCA as a base course. However, it is important that the properties of the geotextile must be compatible with the gradation of the RCA.