The American Association of State Highway and Transportation Officials (AASHTO) classifies open-graded aggregates according to the M43 gradation based on standard sizes for processed aggregates.(1) Despite common use of these aggregates, their strength characteristics have not been systematically measured or used in design. Instead, engineers frequently use a default friction angle of Thirty four Degrees, leading to potential of Conservatism in retaining wall and foundation design. The primary purpose of this course is to present research results on the strength properties of standard open aggregates tested in a large-scale direct shear (LSDS) device to improve the state of practice for the design of structures using these materials. This course material is based on FHWA Publication Number FHWA-HRT-13-068: Friction Angles of Open Graded Aggregates from Large Scale Direct Shear Testing.

At the conclusion of this course, the learner will have a better understanding about the Direct Shear Testing on Friction Angles of Open Graded Aggregates as well as an understanding of the following topics:

• Knowledge of various friction angles of open graded aggregates
• Knowledge of different testing procedures for the performance of aggregates
• Knowledge of comparative analysis of testing results
• Knowledge of performance monitoring based on friction angle of aggregates