This paper discusses the evaluation of Superpave binder specification using pavements constructed with polymer-modified asphalt binders. Performance data collected from pavement test sections constructed in Sherman and Texarkana, Texas, were used in this evaluation. The Sherman pavement sections were overlays constructed in 1986 on US-75 whereas the Texarkana sections were all new construction on US 59/71 in late 1986 and early 1987. Dense-graded hot-mix asphalt (HMA), which contained 16-mm (5/8-inch) maximum size aggregate, was used. The aggregate comprised crushed limestone and field sand. Traffic loading and performance data were collected for both sites. Superpave binder tests were conducted on original asphalt binders saved from the construction projects. Superpave Performance Grade (PG grade) were then established for these binders. Predicted performance from the Superpave PG grades was compared against the field performance. Results indicate that the Superpave rutting parameter predicts rutting resistance reasonably accurately. It was found that the accuracy of prediction of thermal cracking is improved if failure properties are also considered. Finally, it was shown that the Superpave fatigue parameter needs reevaluation.
A major result of the research conducted under the Strategic Highway Research Program from 1987 to 1993 was the development of the Superpave (Superior Performing Asphalt Pavement) system for the comprehensive design of asphalt pavements. These 14 contributions describe the experience to date in the
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).
The primary objective of this full-scale accelerated pavement testing was to evaluate the performance of unmodified and polymer modified asphalt binders and to recommend improved specification tests over existing SUperior PERforming Asphalt PAVEment (Superpave) binder performance grading methodologies. Candidate replacement tests were evaluated via their ability to discern fatigue cracking resistance and rutting. Two fatigue cracking specification tests were identified as more capable in capturing performance than others: binder yield energy and critical tip opening displacement. Two rutting specification tests that quantify irrecoverable deformations exhibited the best strength to capture rutting: multiple stress creep and recovery and oscillatory-based nonrecoverable stiffness. Based on the full-scale performance and laboratory tests, crumb rubber (recycled tires) modified asphalt (Arizona wet process) was shown to significantly slow or stop the growth of fatigue cracks in a composite asphalt pavement structure. A hybrid technique to modify asphalt with a combination of crumb rubber and conventional polymers (terminally blended) exhibited good fatigue cracking resistance relative to the control binder. Also, a simple addition of polyester fibers to asphalt mix was shown to have high resistance to fatigue cracking without the use of polymer modification. The research study also quantified the capabilities of the National Cooperative Highway Research Program's mechanistic-empirical pavement design and analysis methodologies to predict rutting and fatigue cracking of modified asphalts that were not captured in the calibration data from the Long-Term Pavement Performance program. Falling weight deflectometer, multidepth deflectometer, and strain gauge instrumentation were used to measure pavement response. The results illustrated that the nationally calibrated mechanistic-empirical performance models could differentiate between structural asphalt thickness but had difficulty differentiating modified from unmodified asphalt binder performance. Nonetheless, the mechanistic-empirical performance ranking and predictions were enhanced and improved using mixture-specific performance tests currently being implemented using the asphalt mixture performance tester.
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
In the recent past, new materials, laboratory and in-situ testing methods and construction techniques have been introduced. In addition, modern computational techniques such as the finite element method enable the utilization of sophisticated constitutive models for realistic model-based predictions of the response of pavements. The 7th RILEM International Conference on Cracking of Pavements provided an international forum for the exchange of ideas, information and knowledge amongst experts involved in computational analysis, material production, experimental characterization, design and construction of pavements. All submitted contributions were subjected to an exhaustive refereed peer review procedure by the Scientific Committee, the Editors and a large group of international experts in the topic. On the basis of their recommendations, 129 contributions which best suited the goals and the objectives of the Conference were chosen for presentation and inclusion in the Proceedings. The strong message that emanates from the accepted contributions is that, by accounting for the idiosyncrasies of the response of pavement engineering materials, modern sophisticated constitutive models in combination with new experimental material characterization and construction techniques provide a powerful arsenal for understanding and designing against the mechanisms and the processes causing cracking and pavement response deterioration. As such they enable the adoption of truly "mechanistic" design methodologies. The papers represent the following topics: Laboratory evaluation of asphalt concrete cracking potential; Pavement cracking detection; Field investigation of pavement cracking; Pavement cracking modeling response, crack analysis and damage prediction; Performance of concrete pavements and white toppings; Fatigue cracking and damage characterization of asphalt concrete; Evaluation of the effectiveness of asphalt concrete modification; Crack growth parameters and mechanisms; Evaluation, quantification and modeling of asphalt healing properties; Reinforcement and interlayer systems for crack mitigation; Thermal and low temperature cracking of pavements; and Cracking propensity of WMA and recycled asphalts.
The overall objective of this study was to determine if the Superpave high-temperature rheological properties of polymer-modified asphalt binders correlate to asphalt mixture rutting resistance. An emphasis was placed on evaluating polymer-modified asphalt binders with identical (or close) high-temperature performance grades (PG's), but varied polymer chemistries. Eleven asphalt binders were obtained for this study: two unmodified asphalt binders, an air-blown asphalt binder, and eight polymer-modified asphalt binders. High-temperature asphalt binder properties were measured by a dynamic shear rheometer (DSR). Mixture rutting resistance was measured by repeated shear at constant height (RSCH), and the French Pavement Rutting Tester (French PRT). The first objective was to verify the findings of a previous study using a different aggregate. In the previous study, it was found that the Superpave high-temperature asphalt binder properties correlated to mixture rutting resistance with few outliers, and a change in high-temperature PG from 70 to 76 increased rutting resistance. However, the correlation between RSCH and asphalt binder G*/sind (delta) depended on DSR frequency. The data suggested that a low DSR frequency, such as 0.1 rad/s, might provide a better grading system than the standard DSR frequency of 10.0 rad/s. This would require a change in the current asphalt binder specification. A diabase aggregate was used in a previous study. The data using a second aggregate, a limestone aggregate, in combination with four of the asphalt binders, agreed with the findings from the diabase mixtures. The second objective was to retest the diabase mixtures at 70 degrees Celsius using RSCH. The test temperatures used in the previous study were 50 degrees Celsius for RSCH and 70 degrees Celsius for the French PRT. The polymer-modified asphalt binders had continuous high-temperature PG's ranging from 71 to 77. Therefore, it was recommended that the test temperature for RSCH be increased to 70 degrees Celsius. Again, the correlation between RSCH and G*/sind was dependent on DSR frequency. The data suggested that a low DSR frequency, such as 0.1 rad/s, might provide a better grading system. However, it is not known whether this finding applies to pavements, or is related to the accelerated nature of the RSCH test. Furthermore, G*/sind (delta) at 0.1 rad/s did not clearly provide a better correlation to RSCH than the high-temperature PG's of the asphalt binders. The degree of correlation between the French PRT and G*/sind at 70 degrees Celsius did not depend on DSR frequency, and there was only one outlier. A correlation between the French PRT and high-temperature PG provided no obvious outliers. No changes to the specification are recommended based on the French PRT results.
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.
"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.
