A new viscoelastic method of calculation of low-temperature thermal stresses in asphalt layers of pavements

Abstract

The paper presents a new method of calculation of thermal stresses in asphalt layers of pavements induced by cooling or heating. The method, developed by the author, is based on the analytical solution for the linear viscoelastic Burgers model extended numerically for the case of asphalt layers whose rheological parameters are strongly dependent on temperature. The coefficient of thermal expansion and Poisson’s ratio may optionally be taken either as constant or varying with temperature. Two equivalent numerical methods have been developed, named as ‘the incremental method’ and ‘the stress increase and relaxation method’. The computer program was developed for calculation of thermal stresses in several different cases of temperature impact, included constant rate cooling and heating, change of temperature and relaxation and a cycle of first cooling, relaxation and second cooling. What the most important practically, the solution for any change of temperature, modelling real winter changes in long period of time, was also developed. Several examples of calculations are presented. The results obtained with use of this method are promising and appear to be acceptable. The advantages of the new method in comparison with existing methods are that it takes fully into account the viscoelastic properties of a layer and the method is correct if the material does not meet the time–temperature superposition principle.

Keywords:

• Calculation of thermal stresses in asphalt
• theory of thermal stresses
• viscoelastic asphalt mix properties
• Burgers model
• low-temperature asphalt cracking

Acknowledgment

It is to gratefully acknowledge that during preparation of the computer application of the new method the author worked closely with Filip Biedrzycki a student of the informatics at the Gdansk University of Technology who contributed greatly to the development of the computer program for thermal stress calculations. The refinement of the computer program was done by Lukasz Szatkowski MSc in informatics.