Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.

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Gradation measurement is important for quality control of pavement construction. Computed tomography (CT) can capture the microstructure images of asphalt mixture. However, an accuracy digital image processing method should be developed. In this study, fuzzy network, multilevel threshold and morphological methods are utilized to reduce the noise, enhance the contrast and segment images. The 2D aggregate gradation obtained from the digital image segmentation procedure is transferred into 3D gradation by stereological method. The results show that fuzzy network can balance the noise reduction and contrast enhancement. The multilevel Otsu's threshold method can obtain the two thresholds automatically. The morphological processing and watershed transformation can fill the holes in the image and break the aggregate connections. By comparing the calculated gradation and the designed gradation, the image processing procedure proposed in this paper can be utilized to obtain the gradation information of AC, SMA and OGFC accurately and effectively.@en