Recycled plastic modified bitumen: Evaluation of VOCs and PAHs from laboratory generated fumes

Study on the effect of different aldehyde modifiers on the fume suppression effect, mechanism and road performance of SBS modified asphalt

In order to curb asphalt fume emissions during the heating process of styrene-butadiene-styrene (SBS) asphalt, three aldehyde modifiers [vanillin (X), citral (N) and amyl cinnamaldehyde (J)] were blended into SBS-modified asphalt to prepare aldehyde-modified asphalt in this paper. By collecting solid particles and volatile organic compounds (VOCs) in asphalt fumes to conduct relevant experiments, we have analyzed the fume suppression effect and suppression mechanism of aldehyde modified asphalt, and finally examined the road performance of aldehyde modifiers with the best fume suppression effect. It was found that the average VOCs concentration of aldehyde modified asphalt was reduced by about 78 % after 30 min. Aldehyde modifiers significantly reduce the compositional type and content of VOCs in SBS asphalt and reduce the risk of carcinogenicity by curbing the emission of substances such as benzene and phenol. J asphalt reduced solid particle emissions from SBS asphalt fume by 31.4 % and outperformed both X and N asphalt in inhibiting the escape of solid particulate matter and carcinogens from asphalt fume. Polymer networks and the cross-linking of chemical molecules are the main reasons for inhibiting the escape of asphalt fume molecules. In addition, the J modifier enhanced the high-temperature stabilization and water-stability properties of asphalt mixtures, but slightly reduced the low-temperature cracking resistance. The results showed that the three aldehyde modifiers were effective in inhibiting the volatilization of fumes from SBS modified asphalt. Among them, with the best effect of curbing fume emissions and a better road performance, J-modified asphalt is promising for the application in asphalt fume prevention and emissions reduction, and provides a new solution to reduce construction pollution and physical harm caused by asphalt fume in the construction process.

Multimethod Approach to Investigate the Factors Influencing High-Temperature Fuming of Bitumen

Bitumen is heated at high temperatures during asphalt paving applications. In these circumstances, there is the possibility for fuming. These fumes can vary in intensity and, if significant, may attract complaints. The bitumen's chemical composition depends on the crude oil from which it originates. A tool to screen bitumen and evaluate its potential to release fumes would be highly beneficial. In this study, three methods have been employed to investigate a series of bitumen samples that were known to produce complaints by (a) quantifying benzene, toluene, ethylbenzene, and m, o, p-xylene (BTEX), (b) measuring the partition coefficients of these analytes, and (c) measuring the volatile mass of bitumen exposed to isothermal heating. It was found that the concentration of BTEX varied significantly between bitumen samples. The partition coefficients of these analytes are substantially the same between samples. Finally, the volatile mass of each sample varies significantly between samples, independent of bitumen grade or country of origin. These volatile masses correlate strongly with fuming complaints from bitumen and can be used as predictors of bitumen fuming risk.

Analysis of possible carcinogenic compounds in recycled plastic modified asphalt

The incorporation of recycled plastics in asphalt mixtures is getting a growing interest, however, exposing recycled plastics to the high working temperatures of asphalt has posed health and safety concerns. Few studies have paid attention to assessing health and environmental risks concerning recycled plastic-modified asphalt. This study investigates the release of 6 carcinogenic compounds from asphalt modified with recycled plastics, 4 volatile organic compounds (VOCs) and 2 polycyclic aromatic hydrocarbons (PAHs). The concentration of each compound was quantified by GC-MS. Human health risk assessments were conducted using probabilistic methods to assess the risk for an average Australian construction worker to get non-carcinogenic and carcinogenic health issues when exposed to conventional and plastic-modified asphalt fumes. Results showed that non-carcinogenic and carcinogenic risks related to VOC carcinogens (benzene, trichloroethylene, tetrachloroethylene and styrene) are negligible while PAHs (benzo[a]pyrene and dibenz[a,h]anthracene) constitute a possible non-carcinogenic risk and low carcinogenic risk for workers exposed to asphalt fumes. Overall the incorporation of recycled plastic in asphalt reduced the risk for workers to get non-carcinogenic and carcinogenic health issues compared to conventional asphalt mixes. ENVIRONMENTAL IMPLICATION: With increasing trends of using recycled plastics as road materials, concerns about the exposure of workers to carcinogenic gaseous emissions have been raised. This study demonstrates a non-carcinogenic and carcinogenic risk assessment on exposure to recycled plastic modified asphalt fumes. The findings suggest that recycled plastics decrease non-carcinogenic and carcinogenic risks compared to conventional asphalt.

Characterization, Properties and Mixing Mechanism of Rubber Asphalt Colloid for Sustainable Infrastructure

Rubber asphalt has always been considered to have the most potential for the disposal of waste tires as sustainable infrastructure. However, the covalently cross-linked tire rubber presents an extreme challenge in reusing waste rubbers in roads. Rubberized asphalt with finely dispersed or colloidal structure has been regarded as a potential binder used as road material because of the improved properties in terms of storage stability, easy processing and high content of incorporation. However, the mixing mechanism between the finely dispersed rubber on micro-nano scale with asphalt is still not clear, which restricts its further development as value-added material. Devulcanized rubber (DR) was introduced to improve the compatibility between asphalt and rubber. The basic chemicals of DR and asphalt were introduced based on their structures. Furthermore, the interactions between DR and asphalt were discussed according to the functional elements at different levels, and the concept of DR as “the fifth component” of asphalt was put forward. Finally, high performance, environmental and economic effects and applications of devulcanized-rubber-modified asphalt (DRMA) were discussed. The review is expected to provide a guide for the wide application of DRMA, which is still restricted by poor compatibility and bad stability during processing, storage and recycling.

Sample Preparation and Analytical Methods for Identifying Organic Compounds in Bituminous Emissions

Bitumen is a major construction material that can emit harmful fumes when heated. These fumes pose health risks to workers and communities near construction projects or asphalt mixing plants. The chemical complexity of bitumen fumes and the increasing use of additives add to the difficulty of analytically quantifying the harmful chemicals emitted using a single technique. Research on bitumen emissions consists of numerous sample preparation and analytical methods. There are a range of considerations to be made when deciding on an appropriate sample preparation method and instrumental configuration to optimise the analysis of specific organic contaminants in emissions. Researchers investigating emissions from bituminous materials may need to consider a range of analytical techniques to quantify harmful chemicals and assess the efficacy of new additives. This review summarises the primary methodologies for sample preparation and analytical techniques used in bitumen research and discusses future challenges and solutions.