NCHRP 01-41 [Completed]
Models for Predicting Reflection Cracking of Hot-Mix Asphalt Overlays
| Project Data
||Texas A&M Research Foundation|
||Robert L. Lytton|
BACKGROUND: Reflection cracking is one of the primary forms of distress in hot-mix asphalt (HMA) overlays of flexible and rigid pavements. In addition to affecting ride quality, the penetration of water and foreign debris into these cracks accelerates the deterioration of the overlay and the underlying pavement, thus reducing service life. The basic mechanism causing reflection cracking is strain concentration in the overlay due to movement in the existing pavement in the vicinity of joints and cracks. This movement may be induced by bending or shear action resulting from traffic loads or temperature changes and is influenced by traffic volume and characteristics, daily and seasonal temperature variations, and other factors (e.g., pavement structure and condition, HMA mixture properties, the degree of load transfer at joints and cracks). Preliminary models for predicting the extent and severity of reflection cracking in HMA overlays have been developed; however, only limited research has been performed to evaluate and validate these models.
Research is needed to address the issues associated with reflection cracking and to develop mechanistic-based models for use in mechanistic-empirical procedures for the analysis and design of HMA overlays. This research will help account for the effects of reflection cracking on performance thus improving the analysis and design of HMA overlays of flexible and rigid pavements.
OBJECTIVE: The objective of the research was to identify or develop mechanistic-based models for predicting reflection cracking in HMA overlays of flexible and rigid pavements and associated computational software for use in mechanistic-empirical procedures for overlay design and analysis.
Status: The project is complete. The research reviewed available information relevant to reflection cracking of hot-mix asphalt (HMA) overlays, considered the factors that contribute to reflection cracking, and developed mechanistic-based models for predicting the extent and severity of reflection cracking in HMA overlays. These models were developed for use in the design and analysis of HMA overlays; they can be incorporated into the Mechanistic-Empirical Pavement Design Guide (MEPDG) software. The final report has been published as NCHRP Report 669. The CD-ROM containing the software referenced in the report is available as an ISO image which can be downloaded and burned to a blank CD. (Here is some help on burning an ISO image.)