Mechanical behaviour of asphalt mixtures to be used in infrastructures

Abstract

Most transport infrastructures, including road and airport pavements, include bituminous mixtures which allow a 3 good performance and an adequate durability under ordinary service conditions. 4 Due to the need to improve the performance of railways, allowing a more durable high-speed lines and a 5 maintenance cost reduction, several studies to promote the use of new materials, mainly through the incorporation of 6 bituminous mixtures as sub-ballast layer have been developed, instead of the classical section, which only includes 7 granular setting beds. 8 The present work aims to characterize the mechanical behaviour of bituminous mixtures in order to be applied in 9 railway infrastructures. 10 As a methodology to study the mechanical behaviour of the bituminous mixtures, laboratory repeated loading tests 11 were performed, namely four-point bending tests (4PBT) to determine stiffness and fatigue behaviour, and cyclic 12 triaxial compression tests to evaluate the permanent deformation behaviour. 13 The fatigue behaviour of the studied bituminous mixtures was evaluated by the 4PBT, with controlled strain and the 14 application of a sinusoidal loading with different frequencies, according to the European Standard EN 12697-24. 15 The permanent deformation behaviour of the bituminous mixtures was analyzed with the cyclic triaxial compression 16 test, by subjecting the samples to a static confinement stress through the application of vacuum and applying a 17 rectangular cyclic axial pressure stress, according to the European Standard EN 12697 -25. 18 For this study several samples were cored from a physical model built at LNEC’s test pit, built in order to test 19 different unconventional railway substructures, namely using bituminous mixtures as sub-ballast layer. 20 The results obtained showed that the bituminous mixture AC20 base 50/70 (MB) applied in the sub-ballast layer is 21 suitable for application in transport infrastructure because it presents an adequate performance to fatigue and permanent 22 deformation. Through the tests carried out it was also possible to understand the importance of volumetric 23 characteristics, especially the bulk density to a good behaviour of bituminous mixture.