LAUSR

The impact of asphalt cement ageing on pavement durability is a well-known phenomenon for pavement engineers, yet due to complexity in the chemical structure of asphalt cement, not understood thoroughly. Accelerated laboratory ageing procedures usually consider aggregates as inert material, which are insensitive to environmental effects. While in most cases this assumption is not far from reality, there are some cases where the aggregates could play a significant role. Iron Sulfide exists in many aggregate sources in different forms such as pyrite and pyrrhotite. Products of the reactions from such aggregates may have a catalytic effect on the ageing procedure of asphalt cement. In this research, three different sources of Iron Sulfide-containing aggregates were selected to produce laboratory mixes, which were conditioned under moisture and heat. Complex modulus tests were performed on unconditioned and conditioned samples, and the parameters of the rheological behaviour of each mix were determined using the 2S2P1D model. After each step of conditioning, recovered asphalt was subjected to chemical and rheological analysis. The 2S2P1D model was also employed to determine the rheological parameters for recovered asphalt cement from different mixes. Shift factors determined as part of developing master curves were also used to investigate the temperature susceptibility of samples. Carbonyl and sulfoxide indices and the ratio between them were also used to study the chemical path of reactions. The results of this study showed that for samples that were subjected to both heat and moisture, mixes containing Iron Sulfide minerals seem to follow somehow different ageing kinetics resulting in an important change in the behaviour, which is reflected through different rheological parameters and chemical indices.