Odours and Emissions from Bituminous Road Materials and their Mitigation

To manage emissions and odours from bitumen, a clear understanding of the causes of these phenomena is crucial to developing mitigation strategies. Bitumen is a complex product that is extracted from crude oil. The occurrence of fuming or highly odorous events is currently unable to be predicted, leading to disruptions of projects and residents when these events occur. The complex chemical composition of bitumen adds difficulty in deciphering the causes of odour and emission. To date, no published work has provided predictive models that can be widely employed to manage bitumen emissions and odour through pre-emptive strategies. This thesis aims to investigate chemical and physical metrics that can be used within the industry to implement proactive management strategies in the management of odour and emissions. To investigate fuming in bitumen, a multimethod approach was used by quantifying benzene, toluene, ethylbenzene, and m, o, p-xylene (BTEX), measuring the partition coefficients of these analytes, and finally, a novel method to measure the volatile mass of bitumen utilising thermogravimetric analysis (TGA). It was found that the concentration of BTEX varied significantly between bitumen samples. The partition coefficients of these analytes are essentially the same regardless of the sample. Finally, the volatile mass of each sample varied significantly between samples, independent of bitumen grade or country of origin. The volatile masses of the bitumen correlate strongly with fuming events in bitumen and can reliably be used as predictors of bitumen fuming risk, allowing pre-emptive management of high-emission bitumen. To enable the prediction of poor odour in bitumen, this work introduces a Linear Discriminant Analysis (LDA) method, utilising data from headspace gas chromatographymass spectrometry (HS-GC–MS) of bitumen samples to forecast the likelihood of odours in bituminous road binders. The LDA model, developed using HS-GC–MS results from sixteen straight-run binders of known odour status collected globally, demonstrates high accuracy in odour prediction through two cross-validation techniques. This accuracy enables the rapid identification of odorous bitumen samples using GC–MS data. Furthermore, this method suggests alkanes and arenes contribute directly or indirectly to odour in a significant way. The proposed approach provides a simple and practical tool, offering the potential for selective use or pre-treatment of bitumen, thereby reducing the introduction of highly odorous binders into paving projects. This methodology presents an innovative step towards proactive odour management in asphalt paving, contributing to community well-being, environmental quality, and the efficiency of paving operations. Additives that can reduce fuming or odour offer a strategy to mitigate excessive fuming and odour in products known to cause these events. The effectiveness of additives in managing these events is poorly catalogued in current literature. This thesis investigated a range of additive classes, including commercial additives, natural products, synthetic chemicals, biomolecules, and solid adsorbents. Headspace gas chromatography-mass spectrometry (HS-GC-MS) was used to measure the release of volatile organic compounds (VOCs) from bitumen after adding these additives. Among the additives investigated, solid adsorbents were the most effective in mitigating the emissions of the monitored VOCs. These results suggest that solid adsorbents such as carbonaceous materials may be prioritised for managing VOC emissions in asphaltrelated projects. This thesis greatly contributes to understanding emissions and odour in bitumen materials. Strategies that reduce the entry of poor-quality products into projects are essential in controlling emissions and improving air quality in construction. These findings allow a proactive approach to mitigate emissions through product selection and management strategies by employing safe additives in emission control.