The first part of this dissertation is focused on comparing the mechanisms and fundamental properties that control the performance of asphalt mixtures during the uniaxial flow number testing. It is shown that aggregate packing, as measured using an image analysis method, is the key property affecting the failure and deformation characteristics in uniaxial testing. Additionally, it is shown that the main cause of tertiary flow of mixtures in the flow number test is structural instability and bulging (dilation) of aggregate skeleton. It is observed that dense graded mixtures with better aggregate packing showed a better rutting performance due to two principal mechanisms: first, lower stress level within the binder phase during loading due to aggregate skeleton serving as the main stress path, and second, the aggregates in proximity or contact showed a supporting structure (higher aggregate particle stability), which delays the tertiary flow in material, and reduces the rate of permanent deformation. The second part of this dissertation is focused on the mechanisms and factors controlling aggregate mobility and structure formation during compaction and their application for optimization of the construction process and for the development of a performance based mix design methodology. It is shown that for sufficient packing of aggregates during compaction, the viscosity of mastic should be low enough for lubrication, but high enough to prevent dry contacts of aggregates before the required aggregate packing is obtained. Depending on the stress state at the proximity zone of aggregates, there is a minimum mastic viscosity that is required to provide sufficient film thickness to prevent locking of the mixture at the early stage of compaction. A set of recommendations are proposed to estimate the optimum conditions for effective packing of aggregates. Based on the recommendations it is shown that packing of mixtures (as measured by total proximity zone length between aggregates) is a function of mastic viscosity, aggregate gradation, and compaction effort. The levels of these factors can be selected in order to achieve the required packing characteristic that is suitable for the design traffic loading.

A program has begun in Colorado to prove that HMA pavements can be effectively constructed at intersections and provide significant benefits to the owner. To many highway agencies, performance, construction speed, and cost are the three key issues to consider when rehabilitating or reconstructing high traffic intersections. Therefore, demonstration projects were organized by the Colorado Asphalt Pavement Association (CAPA) to demonstrate performance, construction speed and cost advantages over PCC pavements at high traffic intersections in Colorado. This paper documents the planning, design, and construction processes that were followed to successfully build an HMA pavement at an intersection carrying over 7.7 million 18 kip (8200 kg) ESALs for a 20-year design.

This dissertation integrates and assesses in-service hot mix asphalt pavement data from several typically available but disconnected data sources to inform pavement policy and specification development. This in-service pavement data approach captures connected pavement data from different stages of pavement projects (e.g. mix design, construction, performance after completion) to better understand the relationship between actual in-service performance and mix design, structural design, and construction variables. The dissertation addresses the following research question: what is the value of the in-service pavement data approach in developing hot mix asphalt pavement policy and specifications? To test this question, the dissertation applies this approach using data from 2007 to 2017 to investigate several current Washington State Department of Transportation (WSDOT) research questions. Using the in-service pavement data approach, WSDOT pavement performance questions regarding (1) 3/8-inch versus 1/2-inch nominal maximum aggregate size (NMAS) mixtures, (2) the influence of elevated in-place density mixtures and other mixture characteristics, and (3) high-reclaimed asphalt pavement (RAP) (> 20%) versus up-to-20%-RAP mixtures are analyzed. High level findings include: (1) there is no statistical evidence to suggest a difference in performance between 3/8-inch and 1/2-inch NMAS mixtures; however, the cracking/rutting performance of 3/8-inch NMAS mixtures may be trending higher for older mixtures (ages 9-10); (2) there is no field evidence to suggest an apparent trend between elevated density and increased cracking/rutting performance; however, fine-graded mixture cracking performance may be trending higher than coarse-graded mixtures for older contracts (ages 8-10) and no contracts with a density of 94% or higher perform poorly ([less than or equal to] 50 cracking/rutting condition value); and (3) there is no statistical evidence to suggest a difference in performance between high-RAP (> 20%) and up-to-20%-RAP mixtures. Ultimately, the in-service pavement data approach is a repeatable framework that can be used to better understand the relationship between actual in-service performance and mix design, structural design, and construction variables. Additionally, it is generalizable to any field with large data sets on in-service pavements (e.g. airfields, highways, etc.). Towards this end, the in-service pavement data approach and high-level findings of the WSDOT case studies may be applicable to the U.S. Air Force pavement program.

This volume highlights the latest advances, innovations, and applications in bituminous materials and structures and asphalt pavement technology, as presented by leading international researchers and engineers at the RILEM International Symposium on Bituminous Materials (ISBM), held in Lyon, France on December 14-16, 2020. The symposium represents a joint effort of three RILEM Technical Committees from Cluster F: 264-RAP “Asphalt Pavement Recycling”, 272-PIM “Phase and Interphase Behaviour of Bituminous Materials”, and 278-CHA “Crack-Healing of Asphalt Pavement Materials”. It covers a diverse range of topics concerning bituminous materials (bitumen, mastics, mixtures) and road, railway and airport pavement structures, including: recycling, phase and interphase behaviour, cracking and healing, modification and innovative materials, durability and environmental aspects, testing and modelling, multi-scale properties, surface characteristics, structure performance, modelling and design, non-destructive testing, back-analysis, and Life Cycle Assessment. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster new multidisciplinary collaborations.

This synthesis report will be of interest to state, local, and federal agency pavement materials, design, and construction engineers, as well as pavement research engineers and scientists. Those with supervisory oversight for pavement programs will also find it of interest. It describes the current practice for methods to achieve rut-resistant durable pavements. The synthesis documents current experience with permanent deformation of asphalt pavements and identifies methods to improve performance. Information for the synthesis was collected by surveying U.S. and Canadian transportation agencies and by conducting a literature search using domestic and international sources. This report of the Transportation Research Board describes the extent of the rutting problem on the National Highway System, pavement mixture design issues, and the design of rut-resistant mixtures. In addition, alternate mixture types, including stone matrix asphalt and porous asphalt, are discussed, as well as international approaches to mixture design. Finally, the construction of rut-resistant mixtures, including the role of quality control and quality assurance methods, are discussed. A summary of permanent deformation causes and solutions is included in the appendix.