The project was designed to develop (1) a better quantitative understanding of the relation between laboratory accelerated binder aging and field aging, (2) a test procedure to measure properties of an aged binder that relate to failure on the road and (3) a proposed specification for estimating the relative durability of binders in the presence of oxidative aging. Tests were conducted on original base and polymer modified binders, laboratory compacted mixtures, and pavement aged binders. The project necessarily evolved to a more comprehensive approach to improving pavement service life.

"ASTM Publication Code Number (PCN) 04-011080-08. - "Sponsored by ASTM Committee D-4 on Road and Paving Materials."-- Foreword. - Includes bibliographical references and indexes. - Electronic reproduction; W. Conshohocken, Pa; ASTM International; 2011; Mode of access: World Wide Web; System requirements: Web browser; Access may be restricted to users at subscribing institutions.

In recent years an increased use of polymers has occurred to modify asphalt binders, mainly to decrease pavement rutting but also to improve binder failure strain in direct tension. Whereas all of these effects positively impact the durability of polymermodified pavements, a need exists to quantify these improvements and the duration in the presence of oxidative aging. This research evaluated the durability of polymer modified asphalt (PMA) through a number of determinations that included the characterization of the original binder property and pavement-aged binder for modified and unmodified binders. Changes in styrene-butadiene-styrene (SBS) polymer modified binder properties from oxidation were analyzed using dynamic shear rheometry, ductility, and force ductility. Previous literature reports using size exclusion chromatography showed that degradation of the molecular weight profile of SBS accompanied the loss of PMA ductility. Yet base binder embrittlement also occurred, as evidenced by ductility and force ductility. Testing aged PMA binders at higher temperatures to soften the base binder restored the polymer modulus to the force ductility measurements as did blending with a softer deasphalted oil. These measurements indicate that the more significant cause of PMA degradation with aging is base binder embrittlement rather than polymer degradation. Sixteen pavements in 11 Texas Districts, plus four MnRoad pavements were evaluated in order to obtain a more detailed profile of binder oxidation in pavements. Slices of each core provided detail on binder oxidation and air voids. The data confirm that binders can oxidize at least several inches into the pavement. However, oxidation also can be significantly slowed, apparently by very low accessible air voids. Interestingly, the data indicate that the air voids that are relevant to the binder at a specific depth of the pavement are those in the immediate vicinity of the binder; low air voids above or below the binder do not seem to significantly affect the binder oxidation rate. Furthermore, that binders oxidize inches below the surface shows that temperature conducts well into the pavement, consistent with a heat conduction model that is used to calculate ground temperatures as a function of depth.

Following the five-year study performed to investigate the behavior of binders and asphalt mixtures containing polymer modifiers, it was determined that an insufficient amount of time had elapsed to allow any determinations to be made based upon the special field test sections. The study reported herein was to extend that initial time and to study in depth those special test sections, using visual observations coupled with resulting tests performed on samples extracted from the sections and comparisons with the original data developed in the original research. The research includes laboratory testing of field samples, determining the aging effect on the control and modified binders and corresponding effect on the mixtures, and visual evaluations. Retained samples of the original asphalts were also evaluated for potential performance as determined by the performance-based asphalt binder specification developed by the Strategic Highway Research Program. Four hot mix pavement field projects were constructed in the Tyler, Lufkin, San Antonio, and Childress Districts (10, 11, 15, and 25, respectively), and two seal coat projects were placed in the Odessa and Bryan Districts (6 and 17).

Asphalt Pavements provides the know-how behind the design, production and maintenance of asphalt pavements and parking lots. Incorporating the latest technology, this book is the first to focus primarily on the design, production and maintenance of low-volume roads and parking areas.Special attention is given to determining the traffic capacity, re

Ohio Department of Transportation has adopted the hot mix asphalt concrete containing polymer modifiers for use in the interstate highway pavement. Among the various reasons cited for the adoption of polymer modifiers are the favorable field experiences by ODOT, extensive literatures reporting enhanced performance, such as rutting resistance, low temperature thermal cracking resistance, and possibly fatigue endurance. However, despite these favorable findings, there are still cases involving premature failure of hot mixtures containing polymer modifiers. Concerns regarding optimum polymer content, compatibility between polymer additives and asphalt cement, proper mixing and compaction procedure remain to be resolved. Furthermore, performance based specifications to ensure production of desirable final asphalt concrete product require additional development. Questions regarding the suitability of Superpave binder testing procedures for the polymer-modified binders need to be clarified.

Polymer modified asphalts have recently been the focus of much attention in the U.S. due to claims that polymer additives will lengthen the life of an asphalt pavement. Much of the published research on this topic has been concentrated on the effects of polymer modifiers on binder and mixture properties. The goal of this testing is to predict from laboratory testing the actual field performance of an asphalt concrete. Over the years, specifications have been developed for conventional asphalts that allow pavement performance to be predicted from certain binder tests. These conventional binder tests do not fully address the special characteristics of polymer modified asphalt binders and need revision to be an effective tool in predicting pavement service life. This paper presents the findings of a two-part laboratory research program intended to relate binder and mixture properties of polymer modified asphalts. The preliminary testing involved five asphalt binder types and a variety of binder and mixture tests. Promising test procedures were further investigated in the final testing program where ten asphalt binders were examined. Simple linear regression was used to determine the strength of a relationship between pairs of binder properties and mixture properties. The preliminary testing showed penetration, toughness and tenacity, and force ductility to have the most promise in predicting mixture performance. The final testing contained enough data to be analyzed with both simple linear regression and multiple regression. Penetration, toughness and tenacity, force ductility again were the test procedures that had binder properties that correlated well with mixture properties.