|Project Name:||Characterization of Open-Graded Aggregates|
Office of Infrastructure Research and Development |
|Team:||Bridge and Foundation Engineering Team|
|Project Description:||This project will characterize natural aggregates based on the American Association of State Highway and Transportation Officials (AASHTO) Designation: M43-05 (and the American Society for Testing and Materials (ASTM) Designation: D 448-03a). State Departments of Transportation (DOT) and counties use this designation (or an equivalent) to specify the aggregates used in the construction and maintenance of highways and bridges (e.g. the Geosynthetic Reinforced Soil Integrated Bridge System). To accurately obtain the strength properties of these materials, a large-scale test device, such as a large shear box or a large diameter triaxial cell, must be used. Many transportation agencies do not have access to these large-scale devices and often use a scalped sample or a default low value for the friction angle, leading to a conservative design. This project will provide engineers with more accurate friction angles for their commonly used materials. Since the friction angle is based on other factors besides gradation and size, the influence of saturation, angularity, and maximum density will also be investigated. A correlation to the repose angle of the materials will also be investigated so that a designer can more accurately estimate the friction angle of granular material without performing a large-scale direct shear test. To date, this characterization of the AASHTO open-graded aggregates has not been performed. Future work includes characterization of common well-graded aggregates. The results of this applied research will immediately benefit transportation agencies.|
|Start Date:||March 1, 2011|
|End Date:||August 19, 2013|
The objectives of this research are:
(1) Provide engineers with the strength properties of the common open-graded aggregates used in construction.
(2) Describe the influence of saturation, angularity, and source on the strength of common aggregate blends.
|Test Methodology:||Laboratory testing|
|Expected Benefits:||This research will provide transportation agencies (e.g. departments of transportation) with strength properties of commonly used open-graded aggregates.|
|Deliverables:||Name: TechBrief: Friction Angles of Open-Graded Aggregates from Large-Scale Direct Shear Testing|
Product Type(s): Techbrief
Description: The deliverable will be a TechBrief outlining the strength properties of the American Association of State Highway and Transportation Officials (AASHTO) aggregates. Recommendations will also be provided on a preliminary default friction angle in the absence of testing.
Bridges and other structures|