Investigation of Low Temperature Cracking in Asphalt Pavements, National Pooled Fund Study - Phase II

Abstract

The work detailed in this report represents a continuation of the research performed in phase one of this
\nnational pooled fund study. A number of significant contributions were made in phase two of this comprehensive
\nresearch effort. Two fracture testing methods are proposed and specifications are developed for selecting mixtures
\nbased on fracture energy criteria. A draft SCB specification, that received approval by the ETG and has been taken
\nto AASHTO committee of materials, is included in the report.
\nIn addition, alternative methods are proposed to obtain mixture creep compliance needed to calculate thermal
\nstresses. Dilatometric measurements performed on asphalt mixtures are used to more accurately predict thermal
\nstresses, and physical hardening effects are evaluated and an improved model is proposed to take these effects into
\naccount. In addition, two methods for obtaining asphalt binder fracture properties are summarized and discussed.
\nA new thermal cracking model, called "ILLI-TC," is developed and validated. This model represents a
\nsignificant step forward in accurately quantifying the cracking mechanism in pavements, compared to the existing
\nTCMODEL. A comprehensive evaluation of the cyclic behavior of asphalt mixtures is presented, that may hold the
\nkey to developing cracking resistant mixtures under multiple cycles of temperature.