Use of Blended Binder Tests to Estimate Performance of Mixtures with High Reclaimed Asphalt Pavement/Recycled Asphalt Shingles Content

The purpose of this study is to assess the use of blended binder tests to estimate mixture performance properties of high reclaimed asphalt pavement (RAP)/recycled asphalt shingles (RAS) mixtures utilizing recycling agents as a means to evaluate different recycling agents and estimate their doses for a given mixture. Blended binder properties are measured by using standard performance grading (PG) and PG+ test methods and correlating the results with corresponding performance properties of mixtures. Blended binders consisting of virgin and recovered binders and recycling agents were prepared and tested for PG grading properties, multiple stress creep recovery grades, and linear amplitude sweep fatigue life after the rolling thin-film oven and pressure aging vessel aging. Mixtures were tested for rutting resistance and cracking resistance at intermediate temperature and at low temperatures after being subjected to short-term oven aging and long-term oven aging. The correlation between the blended binder properties and mixture performance properties is used to identify the binder test parameters that can be used to predict the long-term performance of high RAP/RAS mixtures and the effects of various recycling agents. Results generally indicate that use of direct testing of recovered binders with recycling agents is an effective means to estimate required initial dose for recycling agent, and testing actual blended binders can be used to predict mixture performance-related properties for the testing conditions used in this study.

Performance Evaluation of Asphalt Mixtures with Reclaimed Asphalt Pavement and Recycled Asphalt Shingles in Missouri

This study investigates the performance of eighteen different dense-graded asphalt mixtures paved in Missouri. The sections contain a wide range of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), and different types of additives. The large number of sections investigated and the associated breadth of asphalt mixtures tested provided a robust data set to evaluate the range, repeatability, and relative values provided by modern mixture performance tests. As cracking is one of the most prevalent distresses in Missouri, performance tests such as the disk-shaped compact tension test (DC[T]) and Illinois flexibility index test (I-FIT) were used to evaluate the cracking potential of the sampled field cores. In addition, the Hamburg wheel tracking test (HWTT) was employed to assess rutting and stripping potential. Asphalt binder replacement (ABR) and binder grade bumping at low temperature were found to be critical factors in low-temperature cracking resistance as assessed by the DC(T) fracture energy test. Six sections were found to perform well in the DC(T) test, likely as a result of binder grade bumping (softer grade selection) or because of low recycling content. However, all of the sections were characterized as having brittle behavior by the I-FIT flexibility index. Service life and ABR were key factors in the I-FIT test. Finally, a performance-space diagram including DC(T) fracture energy and HWTT rut depth was used to identify mixtures with higher usable temperature interval (UTImix), some of which contained significant amounts of recycled material.