Reflective Cracking Study: Second-Level Analysis Report

This report follows a series of seven first-level Heavy Vehicle Simulator (HVS) testing reports, two laboratory reports on shear and fatigue testing, a forensic investigation report, and a report on the backcalculation of deflection measurements, all of which document an investigation undertaken to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It presents the findings from a detailed analysis of the laboratory fatigue and shear results, and a series of simulations using CalME mechanistic-empirical design software and continuum damage mechanics implemented using a finite element method. The work was conducted by the University of California Pavement Research Center (UCPRC) as part of Partnered Pavement Research Center Strategic Plan Item 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking.” This work was originally requested by the Caltrans/Industry Rubber Asphalt Concrete Task Group (RACTG) to compare the performance of one set of examples of thin overlays of cracked asphalt pavement containing different types of binders modified with recycled tire rubber. This work, included as Appendix H of the Rubber Modified Binder Pilot Projects Review prepared by the RACTG is part of a more comprehensive work plan prepared by the Task Group that included evaluation of pilot projects and construction and monitoring of field test sections (undertaken by Caltrans). The objective of this UCPRC project will be met after completion of the following four tasks: 1. Develop improved mechanistic models of reflective cracking in California, 2. Calibrate and verify these models using laboratory and HVS testing, 3. Evaluate the most effective strategies for reflective cracking, and 4. Provide recommendations for reflective cracking strategies. This report addresses all the tasks and consists of six main chapters. Chapter 2 provides an overview of the HVS testing program for the study. Chapter 3 summarizes a second-level analysis of the laboratory fatigue and shear test results. Chapter 4 discusses mechanistic-empirical modeling and simulations of the HVS results using CalME software, which is currently being developed for Caltrans by the UCPRC. Chapter 5 discusses modeling and simulations using continuum damage mechanics implemented using finite-element models. Chapter 6 lists key findings of the study, and provides recommendations for implementation.