State of the art volumetric mix design Stone Mastic Asphalt (SMA)

At the moment a straightforward volumetric mix design is used for SMA in the Netherlands, which gives sometimes problems with regards performance in the field. The largest problems are early rutting. A renewed volumetric mix design method was developed. In the method, the determination of the stone quality is priority one. Development of a test to determine HRS voids in the stone skeleton (FIRS) and the abrasion of the stone fraction is discussed, together with the implementation of gyratory compaction. The consequence of the change from Marshall compaction to gyratory compaction is also shown. Five test trials are followed by the working group to compare the design with the mix in the road. Three test sites with so-called SMA 0/11 (maximum stone size 11 mm) mixes were followed and two test sites with SMA 0/8 mixes. The next coming years will show the effect of the new mix design method.