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[NTC2015-SU-R-11] Hydraulic and Environmental Behavior of Roadway Millings in Highway Shoulder Applications



Description: 

Most of the previous studies indicate that the roadway millings, i.e., RAP, is an excellent material for use as a base course aggregate or HMA aggregate. Several studies have investigated gradation, hydraulic and strength properties of RAP as a base course material; however, limited information exists on use of RAP material as a shoulder backup material. The objectives of the proposed study are to evaluate the hydraulic and leaching characteristics of RAP materials in Maryland highway systems.  These objectives will be addressed employing a combination of hydraulic conductivity and leach tests. The research study will consist of five main elements:  (1) collection and characterization of RAP samples from different sources in Maryland, (2) evaluation of hydraulic conductivity of Maryland RAPs, pollutant leaching on several RAPs through (3) toxicity characteristic leaching procedure tests and (4) column tests, and (5) evaluation of the fate and transport of pollutant leaching in surface waters nearby the highways.

The important deliverables from the study will be definition of hydraulic (permeability) and pollutant leaching characteristics of RAP in a constructed highway geochemical environment.  A final deliverable with be a set of guidelines for SHA use, describing acceptable usage RAP in highway environments in Maryland.  Included will be any RAP specifications that are necessary to meet desired and required properties, along with possible methods available to meet these specifications.  Meeting these objectives will facilitate the reuse of this recycled material, because State engineers and contractors are more amenable to using a geotechnical construction material if its engineering properties and environmental suitability have been previously characterized. 

Meeting implementation plan defined above will facilitate the reuse of this recycled material, because State engineers and contractors are more amenable to using a geotechnical construction material if its engineering properties and environmental suitability have been previously characterized.