Analytical methodology to determine the composition of filler used in Hot-Mix asphalt: Case study

For more understanding about asphalt pavement deterioration in Finland, a premature failure of major arterial Ring Road II surface layers was investigated. Documentation of mix design (MI)), construction, and material quality analysis, before and after construction, was reviewed and compared with samples collected from the road. The traditional quality assessment of the pavement by means of hinder content and aggregate gradation analysis, air void content, and indirect tensile stiffness and strength, as well as binder tests (penetration, ring and ball softening point, and dynamic shear rheometer), did not provide information on the possible reasons for failure. A discrepancy was then found in the filler composition; the discovery was made by applying the standard analytical procedure of hydrochloric acid solubility, coupled with material composition simulations. This finding (and forensic technique) was positively verified by means of thermogravimetral analysis and X-ray diffraction. Scanning electron microscopy, supported by the BET-adsorption (Brunauer-Emmet-Teller) surface area measurements, suggested that, between the stage of MD and construction, the limestone filler was substituted with a mixture of limestone and fly ash. The filler blends were reconstructed on the basis of the MD report and established forensic laboratory findings. The comparative analysis of reconstructed fillers, by means of Fourier transform infrared spectrometry, verified that an almost ideal match was obtained with the latter. Alteration of construction material is suggested as the main reason for discrepancies between the Ml) and actual properties of the analyzed performance of the wearing course.