Discrete element modelling of asphalt mixtures compaction

Abstract

Asphalt mixtures compaction is considered to be one of the most important factors that influence asphalt layers durability, as has been shown by many studies in the past. However, it is still not clear how compaction should be carried out. In the present paper, a computer simulation based on the Distinct Element Method (DEM) is adopted to study this matter. Asphalt mixtures are modelled as an assemblage of circular rigid particles that interact with each other at soft contact points based on DEM, using Itasca-PFC2D software. Up to this point, the influence of several parameters has been investigated, namely the generation process, the assembly dimensions, the initial conditions, the type of contact model, the material properties and the loading conditions. A mixture with median predicted compactability, AC 0/16, was selected from the study "FGSV: Merkblatt für das Verdichten von Asphalt", 2004, in which the compactability of several kinds of asphalt mixtures were evaluated. The numerical model is initially validated against laboratory data (static compaction). As expected the Burger's contact model is shown to give a better agreement than the obtained with an elastic contact model. The model has been further improved with two different techniques. First a contact hardening effect was introduced as function of the particle aspect ratio. Secondly, the formation of rigid bodies in the assembly was considered as result of the particles overlap. Both techniques proved to be useful. In accordance to the previous encouraging results one presents the field tests that were carried out to acquire the necessary data for the following simulations (roller compaction). The preparation procedure for the simulations is shown and the preliminary results presented. The initial results for the static roller compaction seem reasonable. It is shown that the presented study is a good insight in the complex behaviour of asphalt mixtures compaction.