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Title:Evaluation of Aggregate Subgrade Materials Used as Pavement Subgrade/Granular Subbase
Author(s):Kazmee, Hasan; Tutumluer, Erol
Subject(s):aggregate subgrade
subgrade stability
permanent deformation
accelerated pavement testing
construction platforms
low-volume roads
Abstract:With recent focus on sustainable construction practices and the ever-increasing transportation costs and scarcity of natural resources, integration of large-size and marginally acceptable aggregates and recycled materials (e.g., reclaimed asphalt pavement [RAP]) with current construction specifications is becoming imperative. As an incentive, the Illinois Department of Transportation has been using large-size rocks, popularly known as aggregate subgrade. However, adequate scientific knowledge about material performance is largely unknown. To this end, a research study was undertaken at the Illinois Center for Transportation to evaluate the adequacy and field performances of IDOT’s new aggregate subgrade specifications. A state-of-the-art image analysis technique was used to characterize the size and shape as well as the texture and angularity properties of selected aggregate subgrade materials. For field evaluation, 24 combinations of pavements were constructed over subgrade with controlled low immediate bearing value (IBV) or unsoaked California bearing ratio (CBR) strength properties. Construction quality control was achieved through in-place density and modulus measurements on aggregate layers using a nuclear gauge, lightweight deflectometer, and soil stiffness gauges. Periodic rut measurements were carried out on the pavement surface throughout the accelerated loading process using an Accelerated Transportation Loading Assembly (ATLAS). Contributions of the underlying pavement layers to the total rut accumulation were evaluated through innovative applications of ground-penetrating radar (GPR), a lightweight variable-energy penetrometer device, known as the PANDA, and a geo-endoscopy probe. Layer intermixing and material migration at the aggregate subgrade– subgrade interface improved the foundation layer stiffness properties and pavement performance results significantly. RAP-capped construction platforms consistently exhibited a higher magnitude of rutting. Performances of flexible pavement sections were governed by the as-constructed HMA thicknesses, which varied considerably during the paver operation because of RAP subbase sinkage and the weak subgrade. Adequate validation and potential revisions to current IDOT specifications were recommended
Issue Date:2015-07
Publisher:Illinois Center for Transportation/Illinois Department of Transportation
Citation Info:Kazmee, Hasan, and Erol Tutumluer. 2015. Evaluation of Aggregate Subgrade Materials Used as Pavement Subgrade/Granual Subbase. A report of the findings of ICT-R27-124. Illinois Center for Transportation Series No. 15-013. Research Report No. FHWA-ICT-15-013. Illinois Center for Transportation, Rantoul, IL.
Series/Report:Illinois Center for Transportation Series No. 15-013/Research Report No. FHWA-ICT-15-013.
Genre:Technical Report
Sponsor:Illinois Department of Transportation, R27-124
Rights Information:No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161
Date Available in IDEALS:2015-09-18

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