Pavement
- Publication no: AP-T377-24
- ISBN: 978-1-922994-28-8
- Published: 30 August 2024
- PDF (free) Download
This report, which focuses on the reflective cracking of asphalt overlays, documents the findings of project APT6330. The project comprised two main phases. The purpose of the first phase was to undertake a laboratory testing program to characterise the cracking resistance of typical asphalt overlay mixes based on the Texas overlay tester. Nine typical asphalt materials with conventional and polymer modified binders were selected for the testing.
The second phase focused on understanding the available Texas Transportation Institute (TTI) methodology and, particularly, the associated software for asphalt overlay thickness design and analysis. The suitability of adopting the TTI methodology and models within the context of Australian and New Zealand design methods for flexible pavements was assessed, and an exploratory assessment using a targeted sensitivity analysis was undertaken with TTI-associated software for a specific case example.
Based on the findings, the project provided general guidance and recommendations. It identified that research on the in-service reflective cracking performance is necessary to calibrate the currently available models, and develop a method for temperature characterisation across the wide range of Australian and New Zealand climates.
- Summary
- 1. Introduction
- 1.1 Purpose
- 1.2 Scope
- 1.3 Methodology
- 2. Laboratory Characterisation Program
- 2.1 Selected Mixes
- 2.2 Laboratory testing on asphalt mixes – NTRO laboratory manufactured mixes
- 2.2.1 Binder testing
- 2.2.2 Aggregate testing and volumetrics
- 2.2.3 Specimen preparation and testing for indirect tensile modulus testing
- 2.2.4 Overlay tester specimen preparation
- 2.2.5 Principles of the overlay test and test procedures
- 2.3 Laboratory testing on asphalt mixes – Industry supplied test specimens
- 3. Laboratory Tests Results
- 3.1 ITT modulus results
- 3.2 OT results
- 3.3 Summary of overlay testing
- 4. Prediction of Reflective Cracking Life
- 4.1 Introduction
- 4.2 Existing approach to reflective cracking for asphalt overlays (based on the Paris Law and Fracture Mechanics
- Principles)
- 4.2.1 Determination of A and n fracture parameters
- 4.3 Mechanistic-empirical reflective cracking prediction model overview
- 4.4 Texas overlay thickness design and analysis software
- 4.4.1 Introduction
- 4.4.2 TxACOL software
- 5. Reflective Cracking Sensitivity Analysis Outcome
- 5.1 Overview and assumptions
- 5.2 Reflective cracking life at different climates and thicknesses
- 5.2.1 Method
- 5.2.2 Results
- 5.3 Effect of mixes with A15E binder on reflective cracking life
- 6. Conclusions and Recommendations
- References
- Appendix A Target and Measured Combined Gradings and Particle Densities
- Appendix B Overlay Test Results Data
- Appendix C Example of SIF Regression Equation for One Axle Load Case