Investigating the Design and Fatigue Performance of Stone Mastic Asphalt

Stone mastic asphalt (SMA) is recognized as an ideal surface layer in heavy traffic situations, due to good rut resistance properties attributed to the stone on stone contact of the mix skeleton. Methods of ensuring that the stone skeleton is not overfilled with mastic were investigated in this research. In Queensland, thin surfacing layers (less than 40mm for SMA10) are used, often over old, weak pavements that exhibit high deflection. Under such conditions, fatigue failure of SMA, rather than rutting, may be the limiting design factor. This paper reports on an investigation into the fatigue performance of typical Queensland SMA mixtures using UMATTA equipment. The fatigue properties of SMA incorporating flyash, hydrated lime and ultra fine dust as the mineral filler and a SBS polymer modified binder are also investigated. The study included Queensland dense graded asphalt as a reference for quantifying any benefits obtained by using the various SMA mixtures. Some fatigue relationships for the SMA mixtures studied are proposed and the benefits of using SMA in combined creep-fatigue situations investigated. It was found that SMA mixes provided excellent value for money in whole of life costing terms. (a) For the covering entry of this conference, please see ITRD abstract no. E205976.