This report presents findings from prematurely failed pavement of Ring-Road II (Kehä II) in Espoo, Finland. The road had excessive potholes, cracking, raveling and stripping only five years after construction. Core samples taken for this study revealed also that pavement layers were partially separated due to the lack of bonding. Research focus was to determine the causes of Stone Mastic Asphalt surface layer failure. Documentation of mix design, construction and material quality analysis, prior to and after construction, was compared to the samples collected from the road. Traditional quality assessment of the pavement by means of binder content and aggregate gradation analysis, air voids content, Indirect Tensile Strength and Stiffness, as well as binder tests including Penetration, Ring and Ball Softening Point and rheological characterization by Dynamic Shear Rheometer (DSR) were performed. Discrepancy was found in filler composition and additional analysis was made by applying standard analytical procedure of hydrochloric acid solubility. The findings were confirmed by means of Thermogravimetral Analysis (TGA), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), supported by BET-adsorption surface area measurements. The investigation revealed presence of fly ash that was apparently used for extending limestone filler during construction. It can be concluded that the main reason for the pavement failure was due to this substitution and the consequent problems that followed in the construction and thereafter in the pavement performance.
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