Laboratory evaluation of noise - Dampening properties of asphalt mixtures

The objective of this research study was to recommend laboratory test procedures to identify pavement materials properties that are indicative of tyre / pavement noise dampening characteristics in the field. Test parameters from two laboratory test procedures were examined in depth for potential dampening properties. The first test was the Dynamic Complex Modulus test, which provides valuable information about the viscoelastic properties of asphalt mixtures. Of specific interest was the phase angle parameter, which is indicative of the viscous behavior of the material. Over 215 asphalt mixtures were analyzed, constituting different types of asphalt mixtures. The phase angle was determined to be a good potential laboratory parameter to distinguish the asphalt mixture's tyre / pavement noise characteristics in the field. Furthermore, phase angle test parameter master curves and predictive equations were developed. The second test was aimed at evaluating the dampening properties of pavement materials using a nondestructive ultrasonic pulse velocity technique. The Ultrasonic Pulse ime (UPT) was measured and the Effective Flow Resistivity for the various asphalt mixtures was calculated. In addition, a mathematical model to predict the UPT based on the asphalt mixture volumetric properties was developed. The UPT experimental program encompassed 18 mixtures including several field cores obtained from national and international pavement sections. Correlations between predicted and laboratory measured dampening properties were good to excellent. In addition, ield noise measurements were obtained to validate the noise characteristics in the laboratory using the recommended test parameters. Correlations between both the phase angle and UPT test parameters with field measurements were good. In the USA, highway noise is predicted using the Traffic Noise Model (TNM) developed by the Federal Highway Administration (FHWA). Since the FHWA TNM does not incorporate specific properties of asphalt pavement materials in tyre / pavement noise estimations, recommendations on how to incorporate such input properties based on test parameters nalyzed in this study were provided.