University of California Pavement Research Center

This report, an interim report covering the work completed on the CAL/APT Project during the period June 1994 through July 1995 presents the results of laboratory tests on the pavement materials, and evaluates a number of different pavement-materialscharacterization and pavement-performance-prediction procedures. This information as well as additional data to be acquired subsequently will be used for complete analyses of response of the first two pavement sections (four test sections) to accelerated loading with the Heavy Vehicle Simulator (HVS). Experience gained from test-section construction suggests that the following guidelines might be of use for the construction of highway pavements by Caltrans: Reduce the length of mix that can be laid down prior to beginning compaction, Increase the minimum compaction thickness, especially for placement over cold existing surfaces and during night construction, Require simultaneous construction of adjoining lanes where feasible and, Install lateral confinement such as curbs or other similar devices prior to mix compaction where possible and economically feasible. Extensive analyses of the fatigue performance and resulting influences on subgrade strain of both the drained (ATPB) and undrained sections have been conducted. These analyses assumed the pavement to be represented as a multi-layer elastic solid and utilized a series of models for both fatigue and rutting. The predicted fatigue life is larger for the drained pavement than for the undrained pavement. This is due primarily to the increased stiffness of the ATPB compared to that of the aggregate base it replaces. However, the relative performance of drained and undrained pavements may be different under field conditions especially if severe moisture conditions reduce the effectiveness of the asphalt treatment. An increase in load from 40 to 100 kN (9,000 to 22,500 lb) causes a much larger reduction in the subgrade rutting life than predicted for the fatigue life.