Reuse of Linz‐Donawitz (LD) Slag in Asphalt Mixtures for Pavement Application

Standard asphalt mixtures for road infrastructures consist of natural aggregate and bitumen. A number of research efforts have successfully investigated the possibility of replacing the conventional aggregate skeleton with industrial by-products such as slag originating from steel production process. However, little is known on the effect of steel slag on the mixtures functional performance and properties such as resistance to low temperature cracking and to permanent deformation, stiffness and fatigue. This paper presents a comprehensive and extensive investigation on the fundamental performance properties of different types of asphalt mixtures prepared with 100% LD slag aggregate. A conventional asphalt mixture containing natural Gabbro aggregate was also prepared for comparison purposes, while sophisticated testing methods and procedures were used to evaluate the key performance parameters for the set of asphalt mixtures investigated. Low temperature cracking represents a serious distress for asphalt pavements built in cold regions. This phenomenon is induced either by single low temperature event or multiple freeze thaw cycles and it is associated to further damage due to traffic loading. In this study, low temperature cracking was addressed through Thermal Stress Restrained Specimen Tests. Penetration Tests and Cyclic Compression Tests were used to evaluate the response of asphalt binder and asphalt mixture to permanent deformation due repeated loading, respectively. The Cyclic Indirect Tensile Test was selected for investigating both stiffness properties and fatigue resistance. For this purpose the complex stiffness modulus was measured to quantify material stiffness under different temperature and loading conditions providing information on the visco-elasto-plastic material behavior. Fatigue tests were used to determine the progressive and localized material damage caused by cyclic loading. In addition, skid resistance properties were analyzed with the Wehner/Schulze Polishing machine and by calculating the Polished Stone Value. The experimental results and the analysis conducted in the present investigation indicate that asphalt mixtures prepared with LD slag are suitable for asphalt pavement construction and that in most cases they perform better than conventional asphalt mixtures prepared with Gabbro aggregate.