Associate professor of civil engineeringMember of ASTM, Clemson University, Clemson, S.C.
The performance of graded aggregate bases can normally be determined from the property indexes of the aggregate materials such as compressive strength, density, abrasion, hardness, and absorption. All these values can be systematically obtained through standardized laboratory operations.
A simple impact technique is advocated for characterization of base materials in the field. This technique, modified from one successfully used in fragmentation operations, uses a cylinder nearly 3 in. (76 mm) in diameter and 26 in. (660 mm) high. A sample of the material is placed on the bottom and impacted with a standard weight. The change in size distribution of the material as a result of several impacts is used to determine the impact strength index (ISI). The value of ISI correlates with unconfined compressive strength and specific energy. Progress is being made to determine correlation of the results of a multisize sample with compressive strength and the Los Angeles number.
Paper ID: JTE11703J