Search Content

This project was performed to evaluate the performance of recycled aggregates and large stones used in the aggregate base/subbase layers of pavement systems and provide recommendations regarding pavement design and material selection. As part of this project, eleven test cells were built at MnROAD to evaluate the impact of recycled aggregates and large stones on the long-term pavement performance via a series of laboratory [permeability, soil-water characteristic curve (SWCC), stereophotography (image analysis), gyratory compaction, and resilient modulus (MR) tests] and field tests [intelligent compaction (IC), falling weight deflectometer tests (FWD), rutting measurements, international roughness index (IRI) measurements, light weight deflectometer (LWD) tests, and dynamic cone penetrometer (DCP) tests]. In addition, a pavement mechanistic-empirical (ME) design approach was used to provide recommendations for designs of pavement systems containing recycled aggregate base (RAB) and large stone subbase (LSSB) layers. Overall, this project found that finer recycled concrete aggregate (RCA) material would be preferable to coarser RCA material and a blend of RCA and recycled asphalt pavement (RAP) materials would be preferable to natural aggregate for aggregate base layers. RCA materials provided better performance than the blend of RCA and RAP materials, indicating that RCA materials would be preferable to the blend. For LSSB layers, this project found that geosynthetics would be required to successfully construct thinner LSSB layers. Overall, thicker LSSB layers provided better structural support than thinner LSSB layers both in the short term and the long term.

Poor drainage of roadway base materials can lead to increased pore water pressure, reduction of strength and stiffness, and freeze-thaw damage. Drainability is dependent on soil/aggregate physical properties that affect water flow and retention in the porous matrix, notably including particle-size distribution, particle shape, fines content, and density or porosity. The objective of this project was to quantitatively assess permeability and water retention characteristics of soil and aggregates applicable to pavement applications and to evaluate and derive predictive equations for indirect estimation of these properties. Samples of 16 materials used in transportation geosystems were obtained and laboratory tests were conducted to determine grain size distribution, index properties, saturated hydraulic conductivity, and soil-water characteristic curves. Results were analyzed to examine applicability of estimation equations available in the literature and to develop dataset-specific equations for the specific suite of materials. Procedures were provided to qualitatively assess base course drainability as "excellent," "marginal," and "poor" from grain size properties, thereby offering rationale to reduce pavement life- cycle costs, improve safety, realize material cost savings, and reduce environmental impacts.

These appendices pertain to report NRRA202103, Determining Pavement Design Criteria for Recycled Aggregate Base and Large Stone Subbase.