Effect of Aggregate Mineralogy on Permanent Deformation

Abstract

Permanent deformation of asphalt road surfaces is a critical issue in Nordic
countries. The progression of this phenomenon is accentuated by the particular combination
of harsh climatic conditions and heavy loading cycles. In fact, the pavement is exposed to
temperature fluctuations of up to 80 °C throughout the year, and to a total traffic volume up to
5000 million vehicles thus causing severe distresses and shortening the pavement lifetime.
Therefore, it is necessary to assess how each characteristic of the bituminous mixture and its
components affects the performance of the pavement.
This study analyzes the relationship between the mineralogical composition of the
aggregates and the permanent deformation of the wearing course. In particular, the silicon
dioxide (SiO2) content has been selected as distinguishing factor in the selection of the stone
material, and used as control parameter to evaluate the pavement behavior when subjected to
heavy loadings at high temperature.
Four asphalt mixtures have been designed with the same type of binder and different
Norwegian aggregates having differing aggregate mineralogical properties. Subsequently the
mixtures have been subjected to the Wheel Track test at 50 °C in order to identify the
resulting permanent deformation. Depending on the aggregate mineralogy the test results will
determine the relation between the mineral content in the material and the correspondent rut
depth after 10 000 cycles, thereby indicating the dependency of the asphalt material
permanent deformation resistance on the aggregate mineralogy.