| Author: | Mo, Shicong |
| Title: | Characterization of inhaled hazardous particulates in asphalt pavement construction |
| Advisors: | Wang, Yuhong (CEE) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Pavements, Asphalt -- Design and construction Asphalt cement -- Toxicology Gases, Asphyxiating and poisonous -- Toxicology Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | viii, ix, 190 pages : color illustrations |
| Language: | English |
| Abstract: | The construction industry is a pillar industry of the national economy. As an important sector of the construction industry, roadway construction plays a vital role in creating employment opportunities, promoting economic growth and encouraging social development. A large amount of money is invested in the processes of construction, maintenance and repair of roadways every year. Therefore, a large number of workers are involved in construction activities. Although many efforts have been made to make roadway construction "greener" and "more sustainable", less attention is paid to occupational health hazards produced during roadway construction by construction professionals and researchers. To explore this less researched field, this study firstly identifies and prioritizes the occupational health hazards of roadway construction. The top two hazards in the prioritized hazard list are identified to be asphalt fumes and dust. An in-depth literature review suggests that existing knowledge on the characterization of the two health hazards is insufficient. Therefore, two studies related to asphalt fumes were conducted to analyze their emission characteristics due to the effects of binder sources, paving temperature and aging conditions. One study related to inhalable particulate matters in asphalt pavement milling was performed to evaluate their morphological characteristics and chemical components. The main contents of this dissertation are summarized as follows: 1. Identification and prioritization the key occupational hazards in roadway construction: Three approaches were used to identify and prioritize key health hazards in roadway construction, including bibliometric analysis, questionnaire survey, and analytic hierarchy process (AHP). Bibliometric analysis indicates that submicron particles and polycyclic aromatic compounds (PACs) are the primary concerns by researchers, and ergonomics also attract some attention. Survey results suggest that the most frequently encountered occupational disorders by roadway construction workers are Musculoskeletal Disorders (MSDs), heat stroke, respiratory health issues, and hearing loss, and the most commonly encountered hazards are noise, dust, asphalt fumes, heat stress, and some adverse working conditions. Perceptions on associations between the health hazards and disorders were obtained. Although there are some discrepancies between the AHP scores provided by two groups of professionals, the commonly agreed top occupational hazards include dust, asphalt fumes, noise, high/low-temperature stresses, and chronic injuries. 2. Effects of asphalt source and mixing temperature on the generated asphalt fumes: Asphalt fumes generated in pavement construction have been extensively studied from the perspective of occupational health. This chapter examines these issues from the perspective of material and construction. Asphalt binders from different sources were used to create standard asphalt mixtures. An asphalt fume generation and collection system were built for generating fumes at simulated construction conditions and collecting fumes similar to the procedure used in field exposure studies. The total particulates (TP) in the fume samples were analyzed gravimetrically, and the chemical components of the samples were identified by using GC/MS. Results indicate that the TP concentration and chemical component of asphalt fumes are highly dependent on asphalt source and temperature. The TP concentration from one asphalt can be several times higher than that from another. At 140 °C, the total number of detected polycyclic aromatic hydrocarbons (PAHs) ranges from 4 to 9; at 160 °C, the number ranges 108 from 4 to 12. 3. Changes of asphalt fumes in hot-mix asphalt pavement recycling: Hot-mix asphalt pavement recycling is widely practiced for its economic and environmental benefits. Existing studies are mainly focused on the engineering properties of reclaimed asphalt pavement (RAP) materials, without considering their impacts on the generated asphalt fumes-a widely recognized environmental hazard. In this chapter, asphalt mixtures made of asphalt binders from four different sources were used to systematically create RAP materials in three aging conditions. Asphalt fumes were generated and collected from non-aged asphalt materials as well as RAP materials, followed by gravimetric and chemical analysis of the collected asphalt fumes. RAP materials were found to generate greater amount of particulates in asphalt fumes as compared with non-aged asphalt materials. In general, RAP materials are associated with increase in the types and concentrations of PAHs in asphalt fumes, especially those PAHs with more than three aromatic rings. PAHs increase in asphalt fumes is particularly noticeable for RAP created in the natural aging condition. It is reasonable to believe that asphalt fumes generated from RAP are more hazardous. The mechanisms of the increase in PAHs are discussed through the oxidization of hydroaromatics in asphalt binders. 4. Evaluation of exposure to PAHs in inhalable milling wastes: Millions of tons of old asphalt pavements are milled when road resurfacing is performed in the world. Existing studies are mainly focused on respirable silica in inhalable particles generated from the milling process and its mitigation measures, without considering the organic fractions and their potential health risk to workers. In this part of the study, respirable particles were collected from six types of milling wastes. Several analyses were conducted to obtain the surface morphology, organic fraction proportion, and chemical components of these collected particles. The results show that the concentration of respirable silica is relatively low in collected particles due to the small percentage of Si and Al. The ratios of organic fractions are approximately 2 times higher than the content of asphalt binder in asphalt mixture. In general, particles from different types of milling wastes have different types and concentrations of PAHs. The compounds of PAHs in these particles are dominant by PAHs with more than 3 aromatic rings. Therefore, it is reasonable to believe that workers exposed to such particles are affected by more types of carcinogenic PAHs. The research shows that asphalt fumes are significantly affected by asphalt source and mixing temperature, and recycled asphalt pavements emit more dense and harmful fumes when it is reheated to be used again. The dust from milling wastes contains approximate 10% of organic fractions and some trace of PAHs. Therefore, it is necessary to take mitigation measures to safeguard the health of road construction workers. |
| Rights: | All rights reserved |
| Access: | open access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991022385358503411.pdf | For All Users | 5.42 MB | Adobe PDF | View/Open |
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