Odours and Emissions from Bituminous Road Materials and their Mitigation
Creators: name: Deller, Zachary
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401605
subject: Functional materials

description: 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.