Fatigue Performance of Stone Mastic Asphalt Designed with the Bailey’s Method

This paper presents the results of a laboratory analysis and a theoretical study on the fatigue performance of Stone Mastic Asphalt (SMA) mixtures, evaluated by the four-point bending test. The trial was performed on SMA mixes made with Electric Arc Furnace (EAF) steel slags and Coal Bottom Ash, integrated in the aggregate skeleton in partial substitution of natural limestone and filler, re-spectively. The Bailey’s method as well as a conventional trial and error approach, were used in order to design the grading curves of the mixes. The bitumen content evaluation was based on the optimization of the volumetric properties and the moisture resistance of the SMA mixtures, using the gyratory compactor and the indirect tensile test. The purpose was that to compare the fatigue resistance of the mixtures designed by means of Bailey’s and the trial and error procedures, considering both the empirical approach, related to a 50% reduction in the initial stiffness modulus and the dissipated energy analysis, which allows a more rational evaluation of the fatigue performance. Bailey’s SMA mixtures presented better fatigue behaviour than the reference mixes designed with the trial and error procedure. Moreover, with respect to the control SMA mixes prepared with natural aggregates, the mixes made with EAF slags and Coal ash showed improved fatigue properties.