The Bitumen Related Problems Observed on Soft Asphalt Concrete Pavements : Case Study

Abstract

Four roads paved with soft asphalt concrete during the autumn of 2017 by one contractor in a Nordic country, damaged during the following winter. The road users reported that bitumen detached from the surface and was sticking to the fur of pet animals, as well as to the surfaces of the vehicles. The article discusses aspects connected with production and paving, which may have affected the performance. In addition, the material analysis of the samples collected from the field was performed. The core samples were tested by Indirect Tensile Strength (ITS). Because of the low strength of the soft asphalt concrete the ITS is not routinely performed for this material. Therefore, the results of ITS were inconclusive due to the lack of reliable references. The gradation was analyzed after the bitumen extraction and recovery, and no abnormalities were discovered. The Zero Shear Viscosity at multiple temperatures and fractional composition was performed on both extracted and reference binders type V1500 and 650/900 (EN 12591) after evaluation of bitumen purity with infrared spectroscopy. The bitumen extracted from the most questionable pavement expressed comparable rheological behavior to references, but was characterized by the exceptionally high content of saturates. The short research project was unable to determine if the damage was a result or the reason for the altered binder composition. Nevertheless, the link between abnormal performance observed in the field and abnormal chemical characteristic of bitumen is reported.