To evaluate the generation method of a digital asphalt-mixture specimen based on the discrete-element method, an algorithm for generating three-dimensional coarse aggregates is presented in this study. The simulation result shows that this algorithm can reflect the actual geometry (e.g., shape, size, fracture surface, and angularity) of aggregate particles. The digital three-dimensional specimen generated using this algorithm can model the three-phase system of coarse aggregates, air voids, and asphalt mastic for asphalt mixtures well. To estimate the distribution of coarse aggregates, both in the digital specimen and real asphalt mixture, the position and quantity of the coarse aggregates within a two-dimensional section of the asphalt mixture were adopted as evaluation indices. The results showed that the digital asphalt-mixture specimen was in good agreement with the real asphalt mixture, and the evaluation indices could be used to quantitatively analyze whether the digital specimen could reflect the real asphalt mixture. The proposed approach based on the discrete-element method can be used as a supplemental tool to evaluate the uniformity of asphalt mixtures for micromechanical analysis.

The indirect tensile test is commonly used to evaluate crack and fatigue resistance of asphalt mixtures. However, laboratory tests are time-consuming and laborious in general. Numerical simulation provides a technical way for studying the mechanical behavior of asphalt mixtures. In this research, a laboratory test and discrete element method were used to explore the effects of temperature, air void content, loading rate, and the homogeneity of a mixture on the splitting strength of asphalt mixtures. For asphalt mixtures, a three-dimensional random modeling method and two-dimensional modeling method based on X-ray computed tomography and digital image processing were developed. Also, a homogeneity evaluation index based on ring segmentation was proposed. The results show that an increase in loading rate and decrease in temperature resulted in a significant increase in splitting strength. With an increase in voids, the splitting strength of an asphalt mixture decreased. The Pearson correlation coefficient indicates that there seems to be no clear connection between splitting strength and homogeneity, but there is a significant correlation between the homogeneity and differences in the splitting strength.

The discrete element method is now increasingly used in the micro-mechanical analysis of asphalt mixtures. The digital image-based method is usually used to prepare the 2D discrete element sample. However, this method is costly and time-consuming. In this study, a series of algorithms were developed to generate the 2D discrete element sample of asphalt mixtures based on the probability analysis. Firstly, the shapes and sizes of the 2D aggregates cut from 3D aggregates were analyzed and their probabilities were computed. Based on this, an algorithm was proposed to generate the 2D aggregates. Secondly, a method was developed to calculate the number of 2D aggregates in the 2D asphalt mixture sample. Lastly, the algorithms for generating the 2D discrete element sample were summarized and discussed. With these algorithms, the 2D discrete element sample of asphalt mixtures can be generated directly and rapidly.

Green and Intelligent Technologies for Sustainable and Smart Asphalt Pavements contains 124 papers from 14 different countries which were presented at the 5th International Symposium on Frontiers of Road and Airport Engineering (IFRAE 2021, Delft, the Netherlands, 12-14 July 2021). The contributions focus on research in the areas of "Circular, Sustainable and Smart Airport and Highway Pavement" and collects the state-of-the-art and state-of-practice areas of long-life and circular materials for sustainable, cost-effective smart airport and highway pavement design and construction. The main areas covered by the book include: • Green and sustainable pavement materials • Recycling technology • Warm & cold mix asphalt materials • Functional pavement design • Self-healing pavement materials • Eco-efficiency pavement materials • Pavement preservation, maintenance and rehabilitation • Smart pavement materials and structures • Safety technology for smart roads • Pavement monitoring and big data analysis • Role of transportation engineering in future pavements Green and Intelligent Technologies for Sustainable and Smart Asphalt Pavements aims at researchers, practitioners, and administrators interested in new materials and innovative technologies for achieving sustainable and renewable pavement materials and design methods, and for those involved or working in the broader field of pavement engineering.

Pavement Design And Paving Material Selection are important for efficient, cost effective, durable, and safe transportation infrastructure Paving Materials and Pavement Analysis contains 73 papers examining bound and unbound material characterization, modeling, and performance of highway and airfield pavements. The papers in this publication were presented during the GeoShanghal 2010 International Conference held in Shanghai, China, June 3-5, 2010.