Pavements are the largest civil infrastructure on earth. They have huge impacts on economy, society and environment. Starting from my PhD study, I have been working on pavement-related research for over 20 years. My research in pavement covers pavement materials and structures, pavement management from the perspective of life-cycle assessment and optimization, smart pavements, and health issues in pavement construction. Here are some highlights of our pavement research.

Dr. J. Claine Petersen, a prominent asphalt scientist at Western Research Institute, once stated that “The study of these (asphalt) molecular interactions at the nanoscale level, and their effect on physical and chemical properties measured at the macro level, is what is meant by physicochemical characterization. This is asphalt’s “black box” in which its most guarded secrets are kept.”Over the years, our group has been trying to disclose

this “black box” by revealing the physicochemical origins of asphalt property variations. We invented new methods to assist the characterization of asphalt binders at the molecular level and nanoscale. Using such methods, we are the first research group that discovered the interesting asphaltene microstructures in asphalt binders and how the microstructures change with binder aging. We found that nearly all the engineering properties of asphalt binders (stiffness, fatigue, relaxation) can be well explained through the nanoscale microstructures and their interactions with binders’ liquid phase. Such findings can help us identify and develop more durable asphalt binders. We also developed methods to evaluate and improve the durability of asphalt mixtures from the perspective of anti-aging.

Perpetual road is made of pavement structure that can last at least 50 years. I was involved in incorporating the mechanistic-empirical pavement design principles into pavement design in Kentucky. In Hong Kong, I assisted in the development of flexible pavement design guide based on the mechanistic principles. In these studies, we found that the perpetual road is the most environmentally friendly solution, because material, energy, and green-house gas emission can be greatly reduced. However, perpetual road pavement structure is difficult to be built. Through existing road pavements and theoretical research, we try to identify the key factors that affect the performance of perpetual pavement. We are in the process of developing new design criteria for perpetual roads and develop new materials for perpetual pavements.

A large proportion of urban areas are covered with road and street pavements. Current urban pavement systems are similar to those used on rural roads, and pavement design and construction have been emphasized on engineering performance and cost savings.

A key issue that affects the sustainable development of cities is limited lands to meet the demands from growing population and economic activities. In addition, conventional pavements in urban areas cause various problems. This poses a challenging question to government, industry and researchers: Can a paradigm shift be made on pavement technology to maximize the value of urban lands and tackle various issues associated with the current urban pavements?

This research is funded by the Research Impacts Fund in Hong Kong. It aims to develop technologies to create fundamentally different urban pavement systems for effective use of the pavements and their occupied spaces. The new pavement systems have the following characteristics: 1) Prefabricated structures for convenient construction, maintenance, and replacement and for hosting integrated electronic and electrical systems; 2) Hybrid pavement surfaces for enhanced performance and environmental stewardship; 3) Integrated intelligent transport systems (ITS) and Internet of Things (IoTs) sensors for smart city development; 4) Integrated solar energy harvesting and light-emitting diodes (LEDs) systems for traffic signage and city beautification.

Asphalt is widely used in construction applications, especially in paving jobs. In most paving applications, asphalt mixtures need to be heated to high temperatures to satisfy workability requirements. During the mixture production and construction processes, enormous amount of asphalt fumes is generated. Asphalt fumes are a mixture of volatile organic compounds (VOCs) and aerosols, and they are hazardous to construction workers and even nearby passengers. Asphalt fumes generated in pavement construction have been extensively studied from the perspective of occupational health. However, with evolving pavement materials and technologies, their impacts on fume composition and hazardous potentials are less researched. Our research group has been continuously working in this research area over the past years. We are developing refined methods to better analyze asphalt fumes and evaluate their health impacts.