Comparative Study of Hammer Type on Frequency Response in Bituminous Mixture Impact Resonance Test

This study investigates the influence of hammer type on the frequency response of asphalt mixture slab subjected to the Impact Resonance Test (IRT). Two impact hammers with different tip materials were used: a miniature steel-tipped hammer (SH) and a plastic-tipped hammer (PH). The impact was applied at the center of the slab surface, while acceleration was measured at several positions. The Frequency Response Function (FRF) results show that the PH hammer provides stronger low-frequency excitation, efficiently capturing the flexural modes that carry the relevant information for characterizing the viscoelastic behavior of asphalt mixtures, while the SH hammer excites higher modes but with limited energy at low frequencies. The results confirm that selecting an appropriate hammer configuration is essential to ensure reliable excitation over the frequency range relevant to the characterization of bituminous materials.