Rebecca S McDaniel

Investigation of Properties of Plant-Produced Reclaimed Asphalt Pavement Mixtures

The influence of reclaimed asphalt pavement (RAP) content on the mixture and recovered binder properties of plant-produced hot-mix asphalt (HMA) was examined by studying the complex moduli of RAP mixtures and binders. RAP was added at 15%, 25%, and 40% levels to HMA with PG 64-22 and at 25% and 40% levels to HMA with PG 58-28 binder. In addition, control mixture samples with PG 64-22 and no RAP were also collected and tested for comparison. Compacted specimens were tested to determine the complex dynamic moduli (|E*|) at three temperatures. Complex shear moduli (|G*|) of the binders recovered from these HMA samples, RAP samples, and original binders were determined at the same test temperatures. Low-temperature creep compliance and indirect tensile strength of the mixtures were also determined, and these results were used to estimate the critical cracking temperature of the pavement. Statistical analysis indicated that there were no differences in mean strength and |E*| of the mixtures at the 15% and 25% RAP levels. Some differences between the control mixture and the 40% RAP mixtures were found only at the higher test temperatures.

Long-Term Monitoring of Noise and Frictional Properties of Three Pavements: Dense-Graded Asphalt, Stone Matrix Asphalt, and Porous Friction Course

Three highway test sections were monitored for friction, texture, and noise properties over a period of 4 years. The monitored highways were constructed from dense-graded asphalt (DGA), stone matrix asphalt (SMA), and porous friction course (PFC) mixes. The PFC was intended to reduce tire–pavement noise. It was found that the PFC and SMA pavements exhibited comparable frictional properties (international friction index and skid number), which were significantly higher than those observed in the DGA section. It also was found that the PFC section was the quietest and that SMA was louder than DGA. In general, all three sections performed well, and no failures were noticed in any of the monitored pavements during the course of this study.

Identification of Laboratory Technique to Optimize Superpave HMA Surface Friction Characteristics

This report summarizes an investigation into various options for polishing, testing and analyzing pavement surface frictional properties in the laboratory. Devices were sought that could assess the effects of both microtexture and macrotexture of hot mix asphalt (HMA) surfaces in the laboratory and the field. The investigation consisted of a detailed literature review and consultations with users of existing devices for polishing and testing pavement materials. The recommended devices include the Dynamic Friction Tester (DFT) and the Circular Texture Meter (CTM). This study is the first phase of a planned three-phase research program to examine the frictional characteristics of Superpave HMA mixtures. A plan for continuing with Phase II of the project, using the recommended devices and funded by the Indiana and Iowa Departments of Transportation, is also outlined.

High-Temperature Properties of Asphalt Binders: Comparison of Multiple Stress Creep Recovery and Performance Grading Systems

The Superpave® high-temperature test protocol has been shown to be inadequate for characterizing the high-temperature behavior of asphalt binders, particularly those that are polymer modified. Recently, a specification based on the multiple stress creep recovery (MSCR) test was proposed to address the shortcomings of the Superpave high-temperature binder specifications. This study aimed to investigate the merits of implementing the current MSCR test protocol as a replacement for the performance-graded high-temperature test. A statistical analysis was conducted on a data set from the Indiana Department of Transportation to see how MSCR and performance grading procedures differ in grading various binders. In addition, an experimental study was conducted with 16 modified and unmodified binders. The results indicated that the MSCR test was a suitable replacement for the performance grade test because it provided a better tool to rank modified asphalt binders as well as unmodified ones. That is, creep compliance from the MSCR test more fundamentally represented binder behavior at high temperatures compared with the performance grade rutting parameter. In addition, the simplified approach—known as grade-bumping—used in the current Superpave mix design system to account for high traffic levels and low speed limits can be eliminated when the MSCR test is used.

Evaluation of Reclaimed Asphalt Pavement for Surface Mixtures

The Indiana Department of Transportation has successfully used Reclaimed Asphalt Pavement (RAP) for decades because of its economic and environmental benefits. Because of uncertainties regarding the types of aggregates contained in RAP and their resulting frictional properties, however, INDOT has until recently disallowed the use of RAP in asphalt surface mixtures. In addition, the hardened asphalt binder in the RAP could potentially increase the occurrence of thermal cracking. This research was conducted to explore the effects on RAP with poor or unknown aggregate qualities to establish maximum allowable RAP contents to provide adequate friction. The effects of RAP on thermal cracking were then investigated at the potential allowable RAP contents. Laboratory testing showed that the addition of poor quality RAP materials did impact the frictional properties and cracking resistance of the mixtures, but that lower amounts of RAP had little effect. The frictional performance of the laboratory fabricated and field sampled RAP materials was acceptable at contents of 25% but may be questionable at 40%. Field friction testing was also conducted on existing roadways with RAP to explore their field frictional performance. Several low volume roadways and one experimental interstate project were tested. The field results showed acceptable performance after 3 to 5 years of low volume traffic at RAP contents of 15‐25% and after more than 10 years of interstate traffic with 15% RAP. The low temperature testing showed an increased susceptibility to thermal cracking as the RAP content increased but the change in critical cracking temperature was relatively small at the 25% RAP level. At 40% RAP without a change in the virgin binder grade, the critical cracking temperature was about 6°C warmer than the control mixture. This finding supports the need for a binder grade change for RAP contents greater than 25%, as indicated in other research and as required by the current INDOT specifications.

Modified Ignition Oven Test Procedure for Determination of Binder Content in Hot Mix Asphalt Containing Dolomite Aggregate

The binder content of hot mix asphalt (HMA) is most commonly determined either by solvent extraction or ignition oven (IO) methods. Generally, the IO method has worked well with various HMA mixtures except those containing certain types of high mass loss (decomposing) aggregates, especially dolomite. For these aggregates, the high temperatures experienced during the ignition process initiate chemical changes within the aggregate particles, which result in variable mass losses. This, in turn, causes difficulties in calculating a consistent correction factor and determining a repeatable binder content. This paper presents a modified IO binder content determination method, which involves lowering the test temperature to 427°C and reducing the sample mass by half. In addition, only the bottom material basket of the typical IO test setup is used to avoid errors in the results due to temperature differentials that develop when, upon ignition, mixture from the lower basket starts heating the mixture in the upper basket. The proposed method was successfully verified by using six different plant-produced mixtures.

Research on a laboratory technique for tire-pavement noise assessment of asphalt mixes

Abstract Communication noise is classified as one of the pollutions for the current environment. Experimental techniques to measure tire-pavement noise generation from asphalt pavements in the laboratory have been limited. A series of experiments were conducted on six different asphalt mixtures to determine if Purdue University’s Tire-Pavement Test Apparatus (TPTA) could be used to overcome these limitations. The procedure produced samples with low tire-pavement noise; however, the air void contents of the samples were higher than designed. Despite these difficulties, the sample preparation technique and the TPTA testing protocol were shown to offer an effective approach for quick laboratory assessment of tire-pavement noise characteristics of hot mix asphalt pavements at a substantially reduced cost compared to field testing.

Investigating the Feasibility of Integrating Pavement Friction and Texture Depth Data in Modeling for INDOT PMS

Under Indiana Department of Transportation (INDOT) current friction testing program, friction is measured annually on interstates but only once every three years on non-interstate roadways. The state’s Pavement Management System, however, would require current data if friction were to be included in the PMS. During routine pavement condition monitoring for the PMS, texture data is collected annually. This study explored the feasibility of using this pavement texture data to estimate the friction during those years when friction is not measured directly. After multiple approaches and a wide variety of ways of examining the currently available data and texture measuring technologies, it was determined that it is not currently feasible to use the texture data as a surrogate for friction testing. This is likely because the lasers used at this time are not capable of capturing the small-scale pavement microtexture. This situation may change, however, with advances in laser or photo interpretation technologies and improved access to materials data throughout the INDOT pavement network.

Longitudinal Joint Specifications and Performance

Deterioration of longitudinal joints is widely recognized as one of the major factors contributing to failure of asphalt pavements. Finding ways to improve the durability of longitudinal joints will lead to improved service lives and lower life cycle costs. Research and field trials have been directed towards improving joint performance since at least the 1960s. Most of that work was addressed improving the density at and around the joint. This report summarizes an extensive review of the pertinent literature, a review of state specifications and inspection of several trial projects in Indiana related to longitudinal joint construction and performance. Recommendations are given for new and continuing efforts to encourage or require the construction of durable longitudinal joints.

Determining of the Binder Content of Hot Mix Asphalt Containing Dolomitic Aggregates Using the Ignition Oven

The binder content of an HMA mix is one of the critical factors affecting the quality of the mix. The ignition oven is one widely used method for determining the binder content, however, its use is problematic with some types of aggregates, including dolomites. With these aggregates, the mass loss continues after the binder is burned off as the aggregates decompose and the test does not terminate at a stable mass. This study investigated the factors that affect this mass loss in problematic aggregates and developed a modified ignition oven procedure to limit this mass loss. The mass loss in the ignition oven was found to be both time and temperature dependent. The mass loss is also related to the binder content in the mixture. When the binder in the mixture ignites, the oven temperature increases and exceeds the pre-set test temperature. Temperature variations inside the ignition oven result in higher temperatures in the vicinity of the upper basket; these temperature differences are even more pronounced when the binder ignites. These higher temperatures can result in increased mass loss with problematic aggregates. A test temperature as low as 427°C was found to be effective for removing the binder from a mixture. Therefore a modified ignition oven procedure was developed to control the temperatures and limit the additional mass loss for problematic aggregates. The method involves placing half the total sample mass in the bottom basket only and running the ignition oven at a temperature of 427°C. This method was verified by testing six different plant produced mixes containing problematic aggregate and by comparing the results to results of the standard ignition oven method and to solvent extraction. The modified method is recommended for use with problematic aggregates or where the standard test method yields calibration factors greater than 1.0 or the test does not terminate automatically.