Construction techniques and mix design methods are subjected to continuous development along with new inventions, technologies, and related implementation strategies. Due to recent materials introduced into asphalt mixtures such as modified asphalt binders, high percentages of Reclaimed Asphalt Pavement (RAP), warm mix technologies, recycling agents, and others, the asphalt industry is rapidly moving toward the Balanced Mix Design (BMD) method. Current asphalt mixture design methods are structured around meeting a range of volumetric requirements and sometimes other properties such as stability and/or moisture sensitivity. Although this allows for volumetric parameters to be monitored and controlled during production, it does not give much engineering insight as to how the mixture will perform under field conditions. The objective of this research was to assist the local agencies in Nevada with the transition from the Marshall method to the BMD, the latest methodology for designing asphalt mixtures, using the Superpave gyratory compactor and performance tests. Based on experimental data, the research team aimed to create an approach for an optimised, and high-performing mix designs with the use of 15% RAP along with an implementation plan that could be adopted by local agencies and serve as an example for other agencies.

The sustainability of roadway construction has rapidly been gaining attention within the pavement industry. The pavements examined in this study are in a Northern Nevada county with many of the roadways categorized as low volume roads. The county began surfacing rural roads with 100% Reclaimed Asphalt Pavement (RAP) millings, without any design considerations for decades. These pavements have provided satisfactory performance with little to no maintenance for their intended purpose for 25–30 years. The presented research revealed RAP milling surfaced roads with layer coefficients between 0.18 and 0.30, and design thicknesses ranging from 5 to 11 inches.

The Federal Aviation Administration (FAA) is considering implementation of a balanced mix design (BMD) method for asphalt concrete (AC) of airfield pavements in a future specification update. One of the key elements toward implementing BMD, is setting adequate conditions for laboratory mechanical testing that best simulate actual field conditions. In this study, representative air void (AV) levels were identified for laboratory mechanical testing by analyzing quality control (QC) data of plant-mixed laboratory-compacted (PMLC) samples along with in-place density measurements for multiple existing airfield pavements. The laboratory compaction effort in the Superpave gyratory compactor (SGC) required to reach the recommended AV levels was evaluated for different specimen heights. The specimen height and AV level were then experimentally verified with the Ideal Rutting test (ASTM D8360-22) for these airfield mixtures. Based on analysis of field density, laboratory compaction effort, and mechanical test data, it was recommended to test 62 mm thick gyratory specimens at 7 ± 0.5% AV (directly molded) or at 5 ± 0.5% AV (after cutting), which should help capture the different aspects of the asphalt mixture’s resistance to rutting with reference to aggregate skeleton and binder properties.

The Federal Aviation Administration (FAA) is investigating the development of a balanced mix design (BMD) framework with rutting and cracking laboratory mechanical tests for airfield asphalt concrete (AC) mixtures. This project specifically focuses on the rutting aspect of the FAA BMD framework, by establishing proper rutting test protocols and deriving relevant criteria for four laboratory rutting test methods. The manuscript presented the experimental plan data including laboratory and plant produced samples of several airfield mixtures at two air voids (AV) levels. Robust trends were found amongst different rutting tests, whereas for the Hamburg wheel track test (HWTT), the data were significantly influenced by the variability of the rut depth with stripping failure, especially in the case of cut specimens. Thus, additional parameters from the HWTT that could isolate the stripping failure from the mixture rutting characterization were investigated in this study. Based on the developed regression models and statistical analyses, the research team was able to derive initial criteria for the explored rutting tests based on the current FAA specification of maximum 10 mm asphalt pavement analyzer (APA) 250 psi/250 lb rut depth after 4,000 cycles.

This study aims to establish a comprehensive mechanistic framework to refine the current Federal Aviation Administration (FAA) specification of the Asphalt Pavement Analyzer (APA) test method at 250 pounds per square inch (psi) tire pressure and 250 lb wheel load, for different aircraft load levels and speeds. The criteria adjustments were based on airfield pavement mechanistic responses coupled with rutting performance models, developed from the repeated load triaxial (RLT) test conducted on airfield asphalt mixtures. The first step in the framework involved numerical modeling using 3D-Move to evaluate airfield pavement responses under different loading conditions. A sensitivity analysis was performed based on 3D-Move responses including three temperatures, three speeds, and five aircraft load levels. The state of stresses generated by 3D-Move was utilized to determine the range of deviatoric (σ _d ) and confining (σ _c ) stresses that covers different airfield loading conditions. Subsequently, the RLT test was performed under three selected sets of σ _d and σ _c . This effort aims to quantify the sensitivity of the calculated rut depth to speed, temperature, and gross aircraft weight using the laboratory-developed, mix-specific performance models. Based on the APA 250 psi/250 lb test thresholds refined from the FAA Advisory Circular 150/5370-10H, new test criteria were established for different rutting mechanical tests, including APA 100 psi/100 lb, the Hamburg Wheel Track Test, High Temperature Indirect Tensile Test, and Ideal Rutting Test. As a preliminary verification of the recommended criteria, field cores from airfield pavements with varying field rutting performance were evaluated using laboratory mechanical tests. The test data was then compared against the refined test thresholds to ensure that the proposed test criteria can effectively identify airfield mixtures with poor field performance in rutting.