Performance-Based Pay Factors for Asphalt Concrete Construction; Comparison with a Currently Used Experience-Based Approach

摘要

The paper briefly summarizes a procedure to quantitatively establish pay factors for asphalt concrete pavement construction using performance models for fatigue and rutting based on the analysis of accelerated pavement tests from the Caltrans Heavy Vehicle Simulator (HVS) and the WesTrack accelerated pavement performance test program. For rutting, the influence of asphalt content, airvoid content, and aggregate gradation are considered. For fatigue, airvoid content, asphalt content, and asphalt concrete thickness are included. Costs are established using a cost model considering only agency cost consequences of delaying or accelerating the time to the next rehabilitation. For the as-constructed mix, the relative performance (RP)-the ratio of off-target ESALs to target ESALs-is determined for both fatigue and rutting. The shortest RP for the combined RP's for mix and pavement characteristics considered for a specific distress mode permits determination of the pay factor from the cost model. Pay factors determined by this methodology are compared with those that have been used by the California Department of Transportation (Caltrans), termed an experience-based approach. This set of pay factors has been in use since 1997 for Quality Control/Quality Assurance projects. Comparisons are included for approximately 80 projects constructed in the period January 1997 to June 2000. Only a limited number of these contained measured rutting and fatigue cracking data that had been incorporated in the Caltrans Pavement Management System. Comparisons of pay factors for these projects determined by the two methodologies are also included. An analysis is presented which compares pay factors calculated at the end of the project based on the total tonnage to the average of the pay factors based on the daily total tonnage. A computer application using the performance based approach is also included.