Increased nighttime temperatures caused by retained heat in urban areas is a phenomenon known as the urban heat island (UHI) effect. Urbanization requires an increase in pavement surface area, which contributes to UHI as a result of unfavorable heat retention properties. In recent years, alternative pavement designs have become more common in an attempt to mitigate the environmental impacts of urbanization. Specifically, porous pavements are gaining popularity in the paving industry because of their attractive storm water mitigation and friction properties. However, little information regarding the thermal behavior of these materials is available. This paper explores the extent to which porous asphalt pavement influences pavement temperatures and investigates the impact on UHI by considering the diurnal temperature cycle. A one-dimensional pavement temperature model developed at Arizona State University was used to model surface temperatures of porous asphalt, traditional dense-graded asphalt, and portland cement concrete pavements. Scenarios included variations in pavement thickness, structure, and albedo. Thermal conductivity testing was performed on porous asphalt mixtures to obtain values for current and future analysis. In general, porous asphalt exhibited higher daytime surface temperatures than the other pavements because of the reduced thermal energy transfer from the surface to subsurface layers. However, porous asphalt showed the lowest nighttime temperatures compared with other materials with a similar or higher albedo. This trend can be attributed to the unique insulating properties of this material, which result from a high air void content. As anticipated, the outcome of this study indicated that pavement impact on UHI is a complex problem and that important interactions between influencing factors such as pavement thickness, structure, material type, and albedo must be considered.

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The NCHRP 9-19 panel recommended the repeated load permanent deformation test as a laboratory procedure that could be used to evaluate the resistance of a hot-mix asphalt (HMA) to tertiary flow. No standard test protocol addresses the required laboratory stress to be applied. The test can take several hours until tertiary flow is reached and in many cases the sample may never fail. A model capable of predicting or providing general guidance on the flow number characteristics of a mix can be of great value. The model can be ideally used as a guideline to determine the stress–temperature combination that will yield tertiary flow within a reasonable testing time. In this study, an effort was undertaken to develop a flow number predictive model. The model uses HMA mixture volumetric properties and stress–temperature testing conditions as predictor variables. The laboratory test data used are a combination of two valuable databases. The first one included tests conducted at Arizona State University; the second one included tests conducted by the FHWA Mobile Asphalt Material Testing Laboratory. Ninety-four mixtures were evaluated, and 1,759 flow number test results were available. Various regression models were evaluated by combining several independent variables. The final model selected had fair statistical measures of accuracy, and it covered a wide range of mixtures, gradations, and binder properties, as well as laboratory-applied stress. As more testing data become available, the model could be refined and recalibrated for better accuracy.

The objective of this study was to evaluate the material properties of a conventional (control) and fiber reinforced asphalt mixtures using advanced material characterization tests. The laboratory experimental program included: triaxial shear strength, dynamic (complex) modulus, repeated load permanent deformation, fatigue, crack propagation, and indirect tensile strength tests. The data was used to compare the performance of the fiber modified mixture to the control. The results showed that th performance in several unique ways against the anticipated major pavement distresses: permanent deformation, fatigue cracking, and thermal cracking.

In 1999 the Arizona Department of Transportation (ADOT) started outlining and developing a long-range pavement research program. This research program was established in cooperation with Arizona State University (ASU) and had the ultimate goal of implementing the Mechanistic–Empirical Pavement Design Guide (MEPDG) for Arizona. Since ADOT uses asphalt rubber (AR) mixes for new and rehabilitation pavement designs, an integral part of the MEPDG calibration effort must include AR mixtures, which were not included in the MEPDG's development. The objective of this study was to perform a comparison between AR properties and those of the conventional dense graded asphalt mixtures typically used for MEPDG development, calibration, and validation. Another important task was to evaluate how these mixes could be implemented into the MEPDG in the short term and to make recommendations on how to use them in future designs. A total of 23 AR mixtures were available for analysis from a joint ADOT-ASU database. The database contains several engineering properties of AR mixes and binders. These data were used to compare properties, select MEPDG input parameters, generate design analysis for permanent deformation and fatigue cracking, run case studies to predict performance, and compare results with field performance data. Several issues were identified pertaining to the implementation of AR mixes in the MEPDG, and recommendations were provided.