--ISAP Graduate Student Research Directory

Abstract

(Summary, conclusions, key achievements)

Reflective cracking is the dominant failure mode for asphalt concrete (AC) overlays, yet current design codes either do not explicitly account for it or else account for it in a purely empirical manner. The objective of this research is to develop a mechanistic model for reflective cracking that can be incorporated into future design codes. The mechanistic model is reached by identifying a suitable constitutive model for cracking in AC mixes and implementing it into a Finite Element program.

Non-local Continuum Damage Mechanics (CDM) is identified as the suitable framework for describing cracking in AC mixes under repetitive loading. The implicit gradient enhanced differential non-local CDM formulation is adopted. A damage evolution law for AC mixes is derived based on a Weibull-type phenomenological fatigue model. The model parameters are identified by fitting the stiffness reduction curves measured in third point beam bending fatigue tests.

A Finite Element analysis procedure is established to simulate reflective cracking in a Heavy Vehicle Simulator test on a full-scale AC on PCC overlay, whose crack pattern has been closely examined with a digital crack tracing technique. The procedure is then used in a parametric study that evaluates the effects of different factors on the reflective cracking performance of the overlay. It is found that while increasing overlay thickness and decreasing air void content always improve the performance, the effects of temperature depend on the mix type and overlay thickness. Similarly, debonding of the overlay to the PCC was found to be detrimental for all cases except thin, stiff overlays.

The framework of a new mechanistic-empirical design procedure against reflective cracking is also proposed.

John T. Harvey website

e-mail: jtharvey@ucdavis.edu

Rongzong Wu

email: rzwu@ucdavis.edu

M.E., Tsinghua University, China, 7/2000, B.E. Tsinghua University, China, 7/1997

Wu, R.Z., J. Harvey, and C. Monismith, (2006) Towards a Mechanistic Model for Reflective Cracking in AC Overlays, 81st Annual Meeting of the Association of Asphalt Paving Technologists (AAPT)

Wu, R.Z., and J. Harvey, (2003) Modeling of Cracking in Asphalt Concrete with Continuum Damage Mechanics, 16th ASCE Conference on Mechanics, Seattle, Washington, 16-18 July, 2003