Non-destructive ultrasonic testing has attained popularity due to its robustness and cost-effectiveness in monitoring the structural health and performance evaluation of pavements, thus replacing traditional methods. This paper presents the application of an explicit finite element method for the modeling of ultrasonic wave propagation through asphalt concrete. Prior to modeling, non-destructive ultrasonic testing was conducted on four different types of asphalt concrete (AC-13, SMA-13, AC-20, and AM-20). Based on acoustic information (wave velocity) obtained in non-destructive testing (NDT) and density, the dynamic moduli of these asphalt concretes were evaluated and used in numerical modeling of ultrasonic wave propagation using the commercial software package ABAQUS. The ultrasonic wave results obtained by numerical modeling were compared with experimental results. This comparison showed a good fit between the finite element (FE) results and the experimental results and confirmed a good FE approach for ultrasonic wave propagation. In addition, the influence of varying dynamic moduli, density, varying location, and crack size/depth on ultrasonic wave propagation was analyzed.

Numerical simulation is an effective way to study the mechanical response of asphalt pavement, which is very important for the pavement structural design. In this study, a three-dimensional meso-structure discrete element model of asphalt pavement was generated with the FISH programming language and its meso-mechanical response under vehicle load was analyzed. The contact forces within the asphalt pavement, in asphalt mastic, in coarse aggregates and between asphalt mastic and coarse aggregates were studied. The results of the study show that the contact forces within the asphalt mixture are highly uneven. The number of contact points in coarse aggregates account only for about 10% of all contact points while the sum of the contact forces in coarse aggregates contributes to over 50% of all contact forces. This demonstrates that the coarse aggregates bear most of the vehicle load. The average normal contact force in coarse aggregates is about 5 N and the average tangential contact force in coarse aggregates is about 2 N. The modeling results provide a quantitative understanding of the distribution of loading in asphalt pavement.

A new type of porous sound-absorbing sound barrier was developed with quartz sand and self-developed polysiloxane resin. The forming process of the material was studied. The test specimens of the porous sound-absorbing sound barrier were prepared with different mesh numbers of quartz sand and different proportions of resin, and the void properties, compressive strength, durability, and acoustic performance were investigated. Based on the mix design results, it is suggested that 20-mesh quartz sand and a 10:1 mass ratio of quartz sand are used to prepare the porous sound-absorbing sound barrier. The durability study showed that the porous sound-absorbing sound-barrier material had good salt and alkali resistance, poor acid resistance, good water stability, and freeze–thaw stability. The laboratory acoustic test and practical engineering application results showed that the porous sound-absorbing sound barrier had excellent acoustic performance and good noise-reduction effects.

Surface texture is one of the most important morphology properties of coarse aggregates. It has an important effect on the performances of asphalt mixtures, such as the stiffness modulus and high temperature stability. Accurate characterization of the coarse aggregate texture is important for the quality control of coarse aggregates and the design of asphalt mixtures. The two-dimensional (2-D) image analysis method has been used to study the texture property of coarse aggregates in the past two decades. Because of the spatial and mesoscopic properties of the surface texture of coarse aggregates, the traditional 2-D image analysis method is not accurate enough to characterize the texture. In this study, a three-dimensional (3-D) image analysis method (Laplacian smoothing algorithm) was employed to study the coarse aggregate texture property based on the high-precision 3-D image. A minor improvement was added into the Laplacian smoothing algorithm to determine the smoothing scale. Three parameters (deviation limit, iteration number, and smoothness level) are used in the improved Laplacian smoothing algorithm to control the final smoothing result. The 3-D images with the precision of 0.05 mm and 0.1 mm of two sizes of limestone aggregates and two sizes of basalt aggregates were used to study the effect of the three parameters on the smoothing results. The optimal combination of the three parameters was determined based on the parameter study. The results indicate that the deviation limit should be set to 3%, the iteration number should be set to 1, and the smoothness level should be set to 1. A preliminary discussion on the scanning precision was presented based on the 3-D aggregate images with the precision of 0.05, 0.1, 0.2, and 0.5 mm. The results indicate that the 3-D images with average point spacing greater than or equal to 0.2 mm cannot provide sufficient texture details for the evaluation.