Evaluation of the laboratory prediction of surface properties of bituminous mixtures

Abstract

An experimental and analytical investigation was carried out both in laboratory and in situ on wearing courses. The approach presented in this paper aims to predict the in situ density and surface properties of bituminous layers, during the phase of mix design in laboratory. Therefore, the main attempt of this study is to identify, amongst the commonly available laboratory equipments, the most adequate for producing specimens that, used for carrying out simple and reliable laboratory test, allow the prediction of the surface characteristics of the mixture as laid on site. This is done by comparing the data collected from an experimental site with those calculated from laboratory specimens compacted with the superpave gyratory compactor (SGC). Typical laboratory tests (such as the sand patch method and the skid test) as well as the surface data obtained with a laser profilometer have been considered for characterizing the properties of a standard Italian wearing course, laid in two different final thicknesses and produced with the most common raw materials, according to the currently used techniques for mixtures production and laying process for maintenance work. An evaluation of the SGC ability to represent the density and surface properties of the mixture once on site is then discussed.