Numerical and Experimental Investigation of the Appropriate Geometry of Asphalt Specimens for Quality Control Using Impact Resonance Tests

ABSTRACT This article investigates the appropriate geometry of asphalt concrete specimens for quality control purposes using the impact resonance test (IRT). The research was divided into two phases, covering numerical and experimental studies at room temperature (23°C) and −20°C. In the first phase, numerical modal analysis and frequency domain analysis studies, with plausible values of moduli and phase angles, were used to make predictions about the range of fundamental frequencies to expect in experimental tests, whereas the second phase intended to adjust and/or confirm decisions suggested from the numerical study. Advanced computational modeling software was used to examine a Superpave gyratory compactor (SGC) specimen with a height of 120 mm and a diameter of 150 mm. Further cylindrical (both 120 mm in height, one with a 60-mm diameter and the other a 76-mm diameter) and disc specimens (both 150 mm in diameter, one with a 40-mm height and the other a 60-mm height) were produced from the SGC original specimen for additional tests. Then, the experimental studies revealed that SGC specimens with such a high-damping material are not suitable for IRT experiments at 23°C due to their inability to produce a clear fundamental resonance frequency peak. At −20°C, multiple peaks were detected, which could be a consequence of the specimens’ geometry. Hence, much care should be taken to define the fundamental frequency. For the cylinder geometries at 23°C, the numerical study showed a well-separated peak. Conversely, in the experimental study, no clear resonance peaks, only fluctuations, were detected. Therefore, caution is advisable when interpreting test results. At −20°C, both numerical and experimental studies confirm the detection of single resonance peaks. For the disc geometries with the approximately 60-mm height and 150-mm diameter, both numerical and experimental studies confirm the presence of well-separated antisymmetric and symmetric modes at both temperatures, which suggests using such geometry for quality control.