ORCID Identifier(s)

0000-0002-3096-0489

Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

A Stefan Romanoschi

Abstract

Reclaimed asphalt pavement (RAP) and Reclaimed Asphalt Shingles (RAS) has proved to be an effective alternative to virgin materials in HMA production. Despite that recycling asphalt creates a cycle that optimizes the use of natural resources and sustains the pavement industry, State transportation departments have limited the maximum amount of RAP used in surface layers because of the variability concerns and lack of guidance provided. Even though at the moment, the United Stated recycles more RAP than Europe does in terms of percentage of the total RAP extracted from old pavements, it still lags Japan and other countries. A special concern is the use of RAP and RAS in asphalt surface mixes and overlays, which are subjected while in service to higher stresses from the action of vehicle traffic and environment than the mixes in the lower layers. More effort and evaluation of field performance are necessary to develop guidance on best practices when using RAP for surface layers. Currently, Texas Department of Transportation (TxDOT) allows RAP to replace up to 20 percent of virgin binder in surface course mixes, and up to 40 percent of virgin binder in the underlying layers. Despite many efforts, past asphalt recycling projects showed mixed results in terms of performance, even for mixes that fulfilled the requirements for maximum content of RAP/RAS and maximum percentage of recycled binder. In response to this need, an accelerated pavement test project was sponsored by the Texas Department of Transportation. For this project, eight pavement test sections were built and tested under accelerated loading conditions with the Pavement Testing Machine (PTM). The objectives of this research were to evaluate the field performance of the most commonly used mixes containing RAP/RAS in North-East Texas using Accelerated Pavement Testing (APT), to compare the results obtained from laboratory tests performed on the same mixes with the APT performance results and to evaluate the effect of artificial ageing of asphalt mixtures. A series of laboratory tests was conducted to evaluate the resistance to rutting and fatigue cracking. The results obtained in the laboratory testing were correlated with the field performance measured by the APT experiment. Rutting is not a problem for Texas mixes, regardless the percent of recycled materials incorporated. Out of all the tests performed to evaluate the resistance to rutting, the Hamburg Wheel Track Test correlated the best with the field performance. The addition of recycled materials increased the stiffness of the asphalt mix making it more prone to cracking. There was minimal or no correlations found between the laboratory cracking tests and the performance recorded by the APT.

Keywords

APT, RAP, RAS, Fatigue cracking, Rutting, Asphalt mix, Artificial ageing

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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