Dan Chong

Bio: Dan Chong is an academic researcher from Hong Kong Polytechnic University. The author has contributed to research in topics: Asphalt & Environmental science. The author has an hindex of 10, co-authored 16 publications receiving 254 citations. Previous affiliations of Dan Chong include Shanghai University.

Volatile Organic Compounds Generated in Asphalt Pavement Construction and Their Health Effects on Workers

Abstract: Hot mix asphalt (HMA) is a major construction material used for building roads, airport runways, and parking lots. During HMA construction, a massive amount of volatile organic compounds (VOCs) is emitted from the hot asphalt mixtures, creating a potential health risk to on-site workers. Few studies have quantitatively investigated the constituents and potential health effects of the VOCs generated in HMA pavement construction. This paper presents the results of a study in which air samples were collected at multiple locations and time points of several projects during HMA pavement construction and were subsequently characterized for their chemical compositions and concentrations by using gas chromatography/mass selective detector (GC/MSD). The analysis results are compared with occupational exposure limits mandated or recommended by various agencies. Although the individual concentrations of the identified chemicals were found to be below various exposure limits, their collective effect on human health remains unknown and may not be ignored. This paper contributes to the knowledge of the types and concentrations of VOCs generated in asphalt pavement construction, their potential health risks to workers, and possible mitigation measures.

Connections between the Rheological and Chemical Properties of Long-Term Aged Asphalt Binders

Abstract: Asphalts aged in laboratory conditions have been extensively studied, but those aged in hot-mixed asphalt (HMA) mixtures in the field receive less attention. Particularly missing are the aging characteristics of asphalts in long-life HMA pavements. In this study, the rheological and chemical properties of asphalts that were aged in HMA pavements for 7 and 36 years were examined, including the variations of these properties with pavement depth and their interrelationships. The analysis results suggest that (1) severe asphalt binder aging occurred at the deepest pavement layer, (2) material type and pavement depth affect aging rate, (3) asphalt binder from the deepest layer showed a loss of saturates, (4) binders’ two important rheological properties are well related to asphaltenes content and ketone formation, and (5) age hardening apparently is affected more by the increase of dispersion volume and size than by the viscosity of the suspension medium. These findings not only prove that asphalt bind...

Asphalt mixtures emission and energy consumption: A review

Abstract: The objective of this paper is to assess carbon dioxide emissions and energy consumption for the production of road pavements by means of a literature review. The construction of the main types of pavements requires energy and generates greenhouse gas emissions that impact the environment. Different types of asphalt mixtures such as cold mixtures, warm mixtures, asphalt rubber mixtures and mixtures with reclaimed asphalt pavement were assessed. The fuel used in the burners that heat and dry the aggregates is the main source of emissions. Also, the aggregates moisture content is an important parameter that influences the energy consumption. On the other hand, the energy consumption and emissions to produce Portland cement mixtures are related to the process of cement production. For both asphalt and Portland cement mixtures, the extraction, manufacturing and placement were also evaluated. Moreover, the energy consumption of the pavements structures was evaluated. Pavements composed of Portland cement concrete consume more energy than hot mix asphalt. But, warm mix asphalt technologies can save 20–70% of the energy consumption when compared to hot mix asphalt, mainly due to the temperature reduction in the warm mix processes. In addition, the emissions caused by different fuels used to produce pavement mixtures were compared. Asphalt mixtures and their alternative technologies consumed less energy and emitted fewer gases than Portland cement mixtures. Carbon dioxide emissions for hot mix asphalt and asphalt rubber mixtures can be 70% lower than emissions for Portland cement concrete. Some alternatives to reduce energy consumption and greenhouse gas emissions in asphalt mixtures production are the decrease of aggregates moisture content, reduction of the asphalt mixtures production temperature and use of waste materials in pavement construction. Switching from hot mix to warm mix technologies would reduce the carbon footprint generated by the asphalt industry.

Monitoring of volatile organic compounds (VOCs) from an oil and gas station in northwest China for 1 year

Abstract: . Oil and natural gas are important for energy supply around the world. The exploring, drilling, transportation and processing in oil and gas regions can release a lot of volatile organic compounds (VOCs). To understand the VOC levels, compositions and sources in such regions, an oil and gas station in northwest China was chosen as the research site and 57 VOCs designated as the photochemical precursors were continuously measured for an entire year (September 2014–August 2015) using an online monitoring system. The average concentration of total VOCs was 297 ± 372 ppbv and the main contributor was alkanes, accounting for 87.5 % of the total VOCs. According to the propylene-equivalent concentration and maximum incremental reactivity methods, alkanes were identified as the most important VOC groups for the ozone formation potential. Positive matrix factorization (PMF) analysis showed that the annual average contributions from natural gas, fuel evaporation, combustion sources, oil refining processes and asphalt (anthropogenic and natural sources) to the total VOCs were 62.6 ± 3.04, 21.5 ± .99, 10.9 ± 1.57, 3.8 ± 0.50 and 1.3 ± 0.69 %, respectively. The five identified VOC sources exhibited various diurnal patterns due to their different emission patterns and the impact of meteorological parameters. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models based on backward trajectory analysis indicated that the five identified sources had similar geographic origins. Raster analysis based on CWT analysis indicated that the local emissions contributed 48.4–74.6 % to the total VOCs. Based on the high-resolution observation data, this study clearly described and analyzed the temporal variation in VOC emission characteristics at a typical oil and gas field, which exhibited different VOC levels, compositions and origins compared with those in urban and industrial areas.