Modeling of asphalt durability and self-healing with discrete particles method

Asphalt is an important road paving material. Besides an acceptable price, durability, surface conditions (like roughening and evenness), age-, weather- and traffic-induced failures and degradation are relevant aspects. In the professional road-engineering branch empirical models are used to describe the mechanical behaviour of the material and to address large-scale problems for road distress phenomena like rutting, ravelling, cracking and roughness. The mesoscopic granular nature of asphalt and the mechanics of the bitumen layer between the particles are only partly involved in this kind of approach. The discrete particle method is a modern tool that allows for arbitrary (self- )organization of the asphalt meso-structure and for rearrangements due to compaction and cyclic loading. This is of utmost importance for asphalt during the construction phase and the usage period, in forecasting the relevant distress phenomena and understand their origin on the grain-, contact-, or molecular scales. Contact models that involve viscoelasticity, plasticity, friction and roughness are state-of-the art in fields like particle technology and can now be modified for asphalt and validated experimentally on small samples. The ultimate goal is then to derive micro- and meso-based constitutive models that can be applied to model behaviour of asphalt pavements on the larger macroscale. Using the new contact models, damage and crack formation in asphalt and their propagation can be modelled, as well as compaction. Furthermore, the possibility to trigger self-healing in the material can be investigated from a micro-mechanical point of view

Construction of experimental HMA test sections in order to monitor the compaction process

For getting better understanding about the process of HMA compaction, a test section was constructed while the governing process parameters, like; compaction progress, temperature of the material at which activities were employed, equipment properties and meteorological circumstances, were monitored. The test section consists of two constructed layers divided in two lanes A and B. The different lanes were compacted at different temperatures and with a different number of roller passes. In spite of the fact that common asphalt practice suggests that material temperature affect mixtures compactibility, the test section results indicated that no relationship between temperature and compaction progress could be identified. Different measuring techniques to monitor compaction progress were compared

Monitoring Hot Mix Asphalt Temperature to Improve Homogeneity and Pavement Quality

This paper describes how controlled compaction practices lead to better quality asphalt. Therefore, it is important that during compaction operations the mixture is at a suitable temperature in order to achieve the specified degree of compaction. The University of Twente’s Asphalt Paving Research and Innovation unit’s main aim is to professionalize the road construction industry. One of the focus research issues is developing a deeper understanding of the Hot Mix Asphalt (HMA) cooling process and the variation in the mix temperature during compaction and laydown operations. Temperature measurement has become easier over the last decade due to the development of new infrared cameras, line scanners and sensors. The authors used this new technology to study asphalt temperature characteristics on test sections constructed in 2007 and 2008. It provided several insights into the cooling and variation in temperature of some asphalt mixtures used in The Netherlands. This paper presents and discusses the temperature measuring equipment used and the techniques applied to analyze and visualize the temperature data. The trials show that asphalt surface temperature is a good indicator of temperature homogeneity and process control. Also, that contractors will pay more attention to enhanced integration of HMA temperature as operational parameter in the compaction process given that the measurement technology is now easily within their reach. In the future, the authors expect a revival of research into cooling processes of HMA

Runway paving: taking a different approach

Hot Mix Asphalt (HMA) paving of airport runways mostly requires multiple paving teams, multiple pavers, and a wide array of other equipment. The runway paving projects are typically renowned for the logistical effort and the tight margins for overruns, often requiring a relatively large part of the contractor’s resources. Due to the nature of airport operations the projects are of a fast-track nature and planned meticulously. The large-scale nature of the projects raise the attention of the media and contractors often use them as showcases. Although their project characteristics are well known and often appeal to the imagination, the projects have little attention in scientific journals from a process and operations management perspective. We present research ideas on operational matters, process and quality control issues relevant for runway HMA paving construction. It builds on our research experience in the area of highway asphalt paving. We describe the current state of the asphalt paving process and provide a brief overview of the sparse publications in the area. Based on a limited oral inquiry amongst Dutch experts – we present a first list of issues typical for runway asphalt paving operations. We hone in on variability encountered during HMA paving operations and operational strategies necessary for consistent paving and compaction. Lastly, we present technologies and approaches to improve the operational control and subsequent quality consistency during runway HMA paving operations