Asphalt Mixtures Compaction study: Field Tests and Numerical Modelling

Asphalt mixtures compaction, the last operation of the construction process, is considered to be one of the most important factors that influence its performance. Several types of rollers, mixtures and atmospheric conditions create a complex phenomenon for which there is not enough scientific and technical information. In this paper the two selected methods (field tests and numerical modelling) to study this matter are compared. A large field test was carried out to evaluate the influence of some variables in the final compaction, like the number of roller passes, the asphalt mixture type, the roller weight, the roller compaction mode, the vibratory and oscillatory dynamic parameters and the layer temperature. The statistical analysis of ten-thousand in-situ density measurements allowed to conclude that the mixture type, the temperature and the number of roller passes are the most important variables. Despite real paving and compaction operation representation in the experiment the high cost, the variable weather conditions and the organization difficulties are significant disadvantages. A numerical tool based on the Distinct Element Method (DEM) was used to perform the compaction process modelling. The methodology was adapted to the asphalt mixtures compaction study. Asphalt mixtures are modelled in two dimensions and its components (aggregate and bituminous mastic) are represented by circular rigid particles that interact with each other at soft contact points based on DEM, using PFC2D software. The results of lab and field asphalt compaction simulation are in agreement with the expected and described by others researchers. Up to now the numerical tool is not ready to predict every day compaction operations but in the future might be able to reduce the costs of the characterization tests in laboratory as well as validation tests in field.