Dissipated energy analysis of four-point bending test on asphalt concretes made with steel slag and RAP

The paper discusses the results of an experimental study and a statistical analysis on the stiffness and the fatigue performance of recycled asphalt concretes, evaluated by the four-point bending test, at 20 °C and 10 Hz. The laboratory study was conducted on five different base-binder bituminous mixtures, made with recycled aggregates, namely Reclaimed Asphalt Pavement aggregate (RAP) and Electric Arc Furnace (EAF) steel slag, up to 70% by weight of the aggregate. In order to evaluate statistically the influence of the recycled aggregates on the stiffness of the mixes, the analysis of variance (ANOVA) has been performed on the modulus data. The fatigue tests were performed in stress and strain control mode, in order to describe completely the fatigue properties of the mixes. A dissipated energy method, based on the internal damage produced within the asphalt concretes, was used for the fatigue analysis. The damage curves, expressed in terms of the Plateau Value of the Ratio of Dissipated Energy Change, for both the stress and the strain control mode, were elaborated and statistically analyzed in order to unify the fatigue analysis. Compared to the control asphalt concrete, made exclusively with natural aggregate, the resulting mixes with RAP and EAF slag were characterized by improved stiffness and fatigue performance.