Projekt BVFF - publicerade   BVFF nummer:  2013-029 Projekttitel  Improved Long-Term Rutting Prediction and Characterization Projektledare/Kontaktperson  Nicole Kringos Telefon  08790-8700 Utförarorganisation  KTH Medutförare  APRL-AASHTO: Advanced Pavement Research Laboratory of American Association of State Highway and Transportation Officials (represented by Dr. H. Azari - Director APRL) Bakgrund  With an increasing usage of performance-based contracts, contractors will make a consorted effort to ensure pavements fulfill their long-term performance criteria. From a societal point of view this is an important development towards more sustainable and environmental friendly infrastructure. With this new way of contracting, however, the tools that the contractors have available to design their pavement for enhanced long-term performance should also improve. If not, the risk arises for conservative over-design and an overall wasteful use of resources from an environmental perspective by trying to avoid financial penalties. For this reason, tests and computational tools would be needed that, together, can accurately characterize and predict the long-term material response and thus enable contractors to sharpen their design. In the USA recently a new test has been proposed by the Advanced Pavement Research Laboratory of AASHTO, called the ‘Incremental Repeated Load Permanent Deformation Test’. The test is based on a modification of the Flow Number test and is aiming at characterizing rutting performance of asphalt mixtures by taking into account the actual conditions of the road. The test has so far been tested extensively for American mixtures and has successfully been compared with know long-term field behavior and is currently going towards AASTO standardization. Considering the test is a damage-based test and is measuring at different conditions close to the field conditions, it seems to be an ideal test to enhance the long term rutting performance of mixtures. For this reason, this project is proposing to investigate the applicability of this test for the Swedish materials and heavier loading conditions. Additionally, the test is currently lacking a fundamental explanation of why it seems to work so well. Therefore it is also proposed to evaluate the test using X-ray tomography for monitoring the damage development as a function of mixture properties and test conditions and coupling that to simulations, utilizing the calibrated mechanics based design tool currently under development at KTH. The outcome of this project could be a fast new characterization test with a scientific basis that can be used in Sweden to support the performance-based contracts and to investigate the effect of heavy loads. Additionally, insight regarding the development of rutting damage in Swedish conditions will be generated in the project. Sammanfattning  This project is aiming at delivering a scientifically and field-validated rutting test protocol for Swedish conditions, based on a new test developed at AASHTO. In the project the test will be used for evaluation of the rutting potential of selected Swedish mixtures under various temperature and loading conditions. The scientific analyses of damage development inside the asphalt mixtures will give insight into optimized mix design as a function of temperature, moisture and load levels. The practical validation will give insight into the currently used mixtures as well as guidelines for optimized design. By involving a reference group from industry, the practical usability of the test will be ensured. Förväntat resultat  The following results will be expected: - A test validated protocol for Swedish conditions; - A detailed evaluation of the rutting potential of selected Swedish mixtures under various temperature and loading conditions: - Detailed scientific analyses of damage development inside the asphalt mixtures, as a function of mix design, temperature, moisture and load levels: - A coupling to the calibrated mechanics based framework developed at KTH to simulate the long term performance, based on the material characterization. Plan för resultatspridning och implementering  To ensure that the results of the project will move towards application in a rather short time-frame, the following steps will be taken: - An industry reference group will be formed at the start of the project. In this group various stakeholders will be invited. In addition to NCC (Jonas Ekblad) and Skanska (Roger Nilson) it can be anticipated that Trafikverket, material suppliers and equipment manufacturers may also participate. - During the project, it is anticipated that several publications will be submitted on the research to both international and national events, important for the pavement engineering community; - A calibrated, detailed, test protocol will be developed which can be readily used for implementation in a practical engineering setting, thus ensuring the application of the developed knowledge into modern-day engineering practise. - To advertise the results of the project and to demonstrate its application, an international workshop will be organized at the end of the project in which the results will be presented to the stakeholders. Tidsramar  This project can start as soon as it is granted and a PhD candidate has been selected in 2013. It could be anticipated that this is the case spring-mid 2013. The project will take place over 4 years. So the end is anticipated in 2017.