Influence of soiling phenomena on air-void microstructure and acoustic performance of porous asphalt pavement

Acoustical properties of porous asphalt and relationships with the structure of voids are analyzed. A special focus is put on the change of porous asphalt properties due to soiling, which is widely known as an essential problem of acoustical lifetime. Soiling mechanisms which are analyzed in artificially soiled samples with imaging techniques (thin sections and scanning electron microscopy) and their relevance to acoustical parameters are shown. Flow resistivities and sound absorption behaviour (frequencies and degree of sound absorption) are measured, structure factors and tortuosities are back-calculated with absorber models and compared according to mix design and changes due to soiling phenomena.