Said S.F.,Swedish National Rd And Transport Research Institute |
Hakim H.,Swedish National Rd And Transport Research Institute |
Eriksson O.,Swedish National Rd And Transport Research Institute
Journal of Testing and Evaluation | Year: 2013
Pavement deformation in bituminous layers is mainly caused by shear deformations. There is a need for a practical shear test for routine use, which can be used to evaluate the shear properties of bituminous materials. Shear properties are related to pavement performance and needed in viscoelastic pavement evaluation models. The main objective of this work is to determine the rheological properties of asphalt concrete materials for use in viscoelastic models and performance evaluation of bituminous pavement layers. This paper describes an asphalt concrete shear box test for determining the shear modulus and phase angle of asphalt mixtures and estimating their viscosity. The sensitivity of the test method was determined by testing cylindrical asphalt concrete specimens of varying mix composition. A procedure is presented for rheological characterization of asphalt concrete materials for use as a performance indicator. It is also concluded that the asphalt concrete shear box is reliable for measuring the shear modulus, phase angle and viscosity of asphalt concrete at different temperatures and frequencies for use in evaluating pavementmodels and discriminating between asphalt mixes. Copyright by ASTM Int'l (all rights reserved).
Hjort M.,Swedish National Rd And Transport Research Institute |
Jansson J.,Swedish National Rd And Transport Research Institute
Accident Analysis and Prevention | Year: 2010
Accident statistics assembled by the Swedish National Road and Transport Research Institute (VTI) have shown that buses are overrepresented when it comes to accidents on icy and snowy roads. For a better understanding of the problem, the performance of modern summer and winter tyres on winter road conditions had to be assessed. The objective of this work has been to go beyond standard road grip studies, and instead investigate how the driver's possibility to deal with one challenging situation depends on the tyres and tyre configuration. This paper describes a novel methodology where measurements with different tyres on ice in VTI's tyre test facility, enabled a simulator study for evaluating the impact of different tyre characteristics when driving in conditions with strong side wind on a slippery road. The main results of the study are: to deal with strong side wind, good front wheel grip is most important, and while non-studded winter tyres provided little or no improvement over summer tyres, studded winter tyres significantly reduced the risk to run off the road. Furthermore, it is very difficult for the drivers to judge, beforehand, whether a vehicle with a particular tyre configuration will perform good or bad. © 2009 Elsevier Ltd. All rights reserved.