Performance Evaluation Methods for Balanced Design of Asphalt Mixtures

Abstract

The environmental and economic benefits of using reclaimed asphalt pavement (RAP) and/or recycled asphalt shingles (RAS) in asphalt mixtures are well known. The use of RAP/ RAS can reduce production costs, improve permanent deformation resistance, and support sustainability. However, the use of RAP/RAS could result in a significant increase in an asphalt mixture’s stiffening and embrittlement, and thus, subsequently increase pavement susceptibility to cracking. To meet these challenges, mixture adjustments are recommended including the use of softer asphalt binder, recycling agents, and/or warm mix asphalt (WMA) additives. Such adjustments could significantly change the mixture performance that cannot be captured when the Superpave volumetric mix design method is used alone. The main objectives of this study were to select and verify an aging protocol (time and temperature) that can be used with the selected cracking test; evaluate the effectiveness of the selected performance tests to capture asphalt mixture performance; suggest an integrated and practical balanced mix design (BMD) framework ensure balanced performance during design and production stages; and investigate the differences in results between laboratory-mixed laboratory-compacted (LMLC) specimens and reheated plant-mixed laboratory-compacted (RPMLC) specimens. The First Chapter of this study summarizes the current knowledge related to the Superpave volumetric mix design and BMD methods, research objectives, motivation, and scope. In Chapter Two, four aging protocols (various times and temperatures) after short term oven aging (STOA) were evaluated and correlated to field aging. In this effort, one aging protocol, practical and suitable to the IDEAL cracking test (IDEAL-CT), was selected and verified. In Chapter Three, asphalt binder and mixture performance tests along with associated indicators were used to evaluate the mixtures’ sensitivity to materials combinations and their ability to capture the performance. The Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) were used for asphalt binder evaluation and the IDEAL-CT and IDEAL Rutting Test (IDEAL-RT) for asphalt mixture evaluation. Asphalt mixtures designed with different materials components including the use recycled materials, softer asphalt binder, and WMA additive were selected for evaluation. In Chapter Four, BMD approaches as well as the advantages and challenges of each method were presented. The IDEAL-CT and IDEAL-RT along with their preliminary acceptance criteria were evaluated as primary performance tests for the proposed BMD framework. In Chapter Five, previous research studies on differences between LMLC specimens RPMLC specimens using different laboratory tests were presented. A wide spectrum of materials and mix designs were evaluated to identify the relationship between the LMLC and the RPMLC specimens. This effort aims to explore if the same IDEAL-CT and IDEAL-RT acceptance criteria can be used during design and production stages. Finally, Chapter 6 summarizes the main findings and conclusions of this study. In addition, recommendations and future research are provided.