Welcome to the 501 Series!

INCREASED SINGLE-LIFT THICKNESSES FOR AGGREGATE BASE COURSES

Pavements usually require at least two layers, or lifts­—the base course (often an unbound aggregate layer) and an additional surface layer. If it were possible to lay aggregate layers in one lift (12 to 14 inches thick), the greater thickness would give stronger support to the pavement and be more economical.

 This project was initiated specifically to investigate the potential for placing unbound aggregate base courses in thicker lifts to improve pavement performance, reduce costs, and increase the amount of aggregates used.

During the project, a total of six test pads were constructed- two in a limestone quarry in Texas and two at a gravel production site near Memphis, Tennessee. Lift thicknesses at these sites ranged from 6 to 21 inches, and density and seismic data were recorded for varying moisture conditions.

The project also included two crushed granite test sections constructed in Georgia.

Based on the results of this study, researchers recommend the new specifications be adopted to allow the placement of thicker lift bases. Those specifications are included in the ICAR 501-5F report.  In this 501 series you will find the following reports:

501-2, “A Study on the Feasibility of Compacting Unbound Graded Aggregate Base Courses in Thicker Lifts than Presently Allowed by State Departments of Transportation,”  Jaime L. Bueno, Kenneth H. Stokoe, II, and John J. Allen.

501-3, “Prediction of Working Load Displacements Under Plate Loading Tests from Seismic Stiffness Measurements,” Michael L. Myers, Kenneth H. Stokoe, II, and John J. Allen.

501-5F, “Increased Single-Lift Thicknesses for Unbound Aggregate Base Courses,” John J. Allen, Jaime L. Bueno, Michael E. Kalinski, Michael L. Myers,  and Kenneth H. Stokoe, II.

Reports 501-1 and 501-4 were internal documentation only and were not published.

Please click on the above references to go to the individual reports.