J.L.M. Voskuilen ; Ministerie van Verkeer en Waterstaat, Rijkswaterstaat, Dienst Weg- en Waterbouwkunde (RWS, DWW); M.F.C. van de Ven ; Tu Delft
In the Netherlands a CROW working group has developed a new mix design for SMA based on a volumetric approach. A software program can calculate the realised void content in SMA with the following input data: mix composition, densities of the components, air voids content of the compacted stone skeleton. The theoretical voids content in SMA, based on filling the air voids in the stone skeleton with a volume of mortar, can be translated into the realised air voids content in SMA with a socalled shift factor. This shift factor takes into account the enlarging effect of air voids content of the stone skeleton in SMA due to the presence of mortar between the stones in SMA. In this way the desired SMA mixture can be calculated based on air voids content requirements. This mix design procedure has to be validated by compacting three SMA mixtures: one mixture with the calculated required air voids content and two mixtures with a stone content +/- 2,5 % the calculated stone content. Based on the realised air voids content in SMA and the stone content in SMA the required mixture can be chosen by interpolation. To validate the new mix design procedure two mixtures from test sites were studied. To study the effect of filling the air voids content of the SMA stone skeleton with mortar on the resistance to rutting different variations of filling of those SMA mixtures were investigated with the wheel-tracking and triaxial test. For the mixture of each test site 5 different compositions were tested varying from strongly underfilled to strongly overfilled with mortar. The 5 different mix compositions were volumetrically kept constant. For one test site the normal crusher sand in the mixture was substituted by Scottish granite crusher sand and in the other case by fine natural sand. This was done to investigate the effect of the sand on the enlarging effect of the stone skeleton and on the resistance to permanent deformation. In this paper the results of wheeltracking and triaxial tests on these mixtures are discussed.
Paper Rilem Rhodes SMA