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Asphalt mastic is known to play an important role when determining the fatigue performance of asphalt mixture. Time sweep test using a Dynamic Shear Rheometer can be used. However, a long testing t...

A laboratory study was done on three bitumen of penetration grade 50/70 from three sources and three corresponding mastics made using these three base bitumen and one filler – Limestone. The tests ...

Utilisation of recycled construction and demolition waste (CDW) within pavements is a beneficial substitution technique towards sustainability. Following this approach, this research investigates t...

The present study was carried out to evaluate effects of regular sized hydrated lime (RHL) and Nano-sized hydrated lime (NHL) on rutting resistance performance of asphalt mastic related to stiffnes...

The long-term effects of SBS-modified binders and rejuvenators on the properties of high-RAP mixtures, especially the cracking resistance, have not been resolved. Therefore, this paper evaluates th...

The microstructures of asphalt mastic have been considered as an important micromechanical mixture property related to the macro performance of asphalt mixtures based on the multi-scale analysis me...

On 18 October 2011, the International Agency for Research on Cancer (IARC) revealed its conclusions of an eight-day comprehensive review of bitumen (asphalt) and bitumen emissions (fumes). The working group concluded that occupational exposures to oxidized bitumens and their emissions during roofing are ‘probably carcinogenic to humans’ (Group 2A); occupational exposures to hard bitumens and their emissions during mastic asphalt work are ‘possibly carcinogenic to humans’ (Group 2B); and occupational exposures to straight-run bitumens and their emissions during road paving are ‘possibly carcinogenic to humans’ (Group 2B) These evaluations and supporting data have been published as Volume 103 of the IARC Monographs. The IARC process is described, as well as details of the conclusions, hazard versus risk, prominent human, animal and mechanistic studies, routes of exposures and ways to reduce exposures. Implications for the asphalt pavement industry include communication to workers and product users, and pote...

During compaction of asphalt mixtures, aggregate structure starts building up by proximity and direct contact of aggregates. In the previous studies, it has been shown that the aggregate structure directly affects the service performance. However, the mechanisms of the aggregate structure formation are not clearly understood. This study is focused on the mechanisms affecting aggregate mobility during compaction and the effect of material properties on the aggregate structure formation. At the initial stages of compaction, there is a relatively thick layer of mastic (i.e. mix of binder and filler) between aggregates, which allows for a shearing mobility in the mix, if the mastic viscosity is sufficiently low. However, as compaction proceeds, the mastic layer at proximity zone of aggregates becomes thinner due to high stress intensity and the higher viscosity of thin mastic film or the aggregates dry contact effect increases the shearing resistance against compaction (i.e. mix becomes locked). In this study...

This study quantifies moisture damage at the asphalt mastic–aggregate interfaces using finite element method modelling technique in ABAQUS. A model aggregate surrounded by a layer of mastic is subjected to static loads of varying magnitudes and patterns. Using dynamic shear and elastic moduli of wet and dry mastic and aggregate as model inputs, moisture-induced damage is quantified through parameters such as contact stresses at interface, load to initiate damage and de-bonding at the interface. Results show that contact stresses are significantly higher in dry samples than wet samples. It is revealed that damage initiates at a smaller magnitude of deformation (0.0508 mm) in the wet sample than that (0.508 mm) in the dry sample. That is, a stiffer dry sample carries more loads and deforms less before damage initiation than a softer wet sample. In addition, approximately 6.8% interface de-bonding occurs in the dry sample, whereas 49.1% de-bonding occurs in the wet sample.

In our research project entitled "Chemical irritative and/or genotoxic effect of fumes of bitumen under high processing temperatures on the airways," 73 mastic asphalt workers exposed to fumes of bitumen and 49 construction nonexposed workers were analyzed and compared with respect to polycyclic aromatic hydrocarbons (PAHs) exposure and exposure-related health effects. In order to assess the internal exposure the monohydroxylated metabolites of pyrene, 1- hydroxypyrene (1-OHP), and phenanthrene, 1-, 2- and 9-, and 3- and 4-hydroxyphenanthrene (OHPH) were determined in pre- and post-shift urinary samples. Significantly higher concentrations 1-OHP and OHPH were detected in the post-shift urine samples of 7 mastic asphalt workers working on the same construction site compared to the reference workers and all other 66 mastic asphalt workers. The adjusted mean OHPH in the reference, 66 mastic worker, and 7 worker subgroups was 1022, 1544, and 12919 ng/g creatinine (crn) respectively, indicating a marked rise in the 7 worker subgroup. In addition, there was a more than 12-fold increase of PAH metabolites from pre- to post-shift in these 7 workers, whereas in the other mastic asphalt workers there was only a twofold rise in PAH-metabolite concentration between pre- and post-shift values. The analysis of a drilling core from the construction site of the seven workers led to the detection of the source for this marked PAH exposure during the working shift as being coal tar plates, which were, without knowledge of the workers and coordinators, the underground material of the mastic asphalt layer. The evaluation of the stationary workplace concentration showed enhanced levels of phenanthrene, pyrene, fluorene, anthracene, and acenaphthene during working shifts at the construction site of these seven workers. Our study shows that biological monitoring is also a useful tool for the detection of unrecognized sources with high PAH concentrations.

Two different types of mineral fillers were mixed with two different grades of asphalt binders to investigate the effect of filler surface on the rheological properties with respect to their long-term aging characteristics. The rheological properties of unaged and aged asphalt-filler systems were studied as a function of aging time. Different modeling techniques were evaluated to construct the aging master curves to investigate the effect of fillers on the long-term aging characteristics of asphalt binders. The results indicate that the generalized power law model can be successfully used to characterize the aging time–temperature effects for asphalt mastics. The results also indicate that the Williams–Landel–Ferry (WLF) model can be used to develop the aging shift factors. In addition, the aging master curves of asphalt-filler systems were also developed to characterize the effect of fillers on the aging kinetic curves of asphalt binders. Furthermore, the results show that stiffness effect of asphalt-fil...

Mastic asphalt workers may be exposed to polycyclic aromatic hydrocarbons (PAH) present in bitumen. We conducted a cross-shift study to determine genotoxic effects after exposure to bitumen. For this purpose, external and internal exposure of 202 mastic asphalt workers exposed to bitumen and 55 construction workers without exposure to bitumen was assessed. Exposure by inhalation to fumes of bitumen during the shift was measured by personal ambient monitoring. To assess overall exposure to bitumen (by inhalation and dermal absorption), 1-hydroxypyrene (1-OHP) and the sum of 1-, 2 + 9-,3-,4-hydroxyphenanthrene (OHPhe) were determined in pre- and postshift urine. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) adducts, anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (anti-BPDE) DNA adducts, DNA strand breaks and alkali-labile sites, and micronucleus frequencies were determined as biomarkers of genotoxic effects in white blood cells (WBC). Concentrations of fumes of bitumen were correlated with a moderate associati...

Since the mid-1990s the German BITUMEN Forum has worked on a comprehensive program on the safety and health at work with bitumen. Determining the concentration of emissions arising from handling hot bituminous substances has been one of the main priorities of the forum's work. Almost all branches of industry in Germany that use bitumen have been examined. More than 2000 samples were gathered between 1991 and 2006. The measuring method determined vapors and aerosols emitted from hot bitumen. With the results of these measurement data it is possible to show how exposures to vapors and aerosols of bitumen vary with production and different uses e.g., rolled asphalt, mastic asphalt, roofing, and joint fillers. With the exception of work with mastic asphalt, all uses of bitumen show exposures to vapors and aerosols of bitumen of less than 10 mg/m 3 . The situation for mastic asphalt is entirely different. At the workplaces at mechanical as well as manual work with mastic asphalt very often exposures above 10 m...

A recent decision of the German Committee on Hazardous Substances (AGS) not to establish an occupational exposure limit for vapors and aerosols emitted by hot mastic asphalt was tied to an industry commitment that all mastic asphalt workers would be intensively screened medically so that technical or personal protection measures can be promptly put in place to reduce occupational exposure. In the meantime, almost 80% of all active mastic asphalt workers in Germany have been examined and questioned about work-associated health complaints. The results of this comprehensive survey of mastic asphalt workers compared to a parallel unexposed control cohort indicate significant irritation of the breathing airways and itching eyes. The survey has furthermore indicated that more individuals from the exposed cohort suffered from health restrictions, as diagnosed by their physicians. The investigation has provided a general view and is considered to be a basis for more detailed examinations.

Data concerning the irritative effects of current exposure to fumes of bitumen on the airways in humans are limited. To assess the effects of fumes of bitumen on the airways a cross-shift study was conducted with monitoring of inflammatory process in upper and lower airways of workers exposed to fumes of bitumen and a reference group. All workers were examined immediately before and after shift. At both time points, spirometry was performed and nasal lavage fluid (NALF), induced sputum and spot urine were collected. Cellular composition and inflammatory mediator profile of the NALF and sputum samples were analyzed. Personal air sampling in each mastic asphalt worker's breathing zone was carried out to measure exposure to fumes of bitumen. The present cross-shift study with 202 mastic asphalt workers exposed to fumes of bitumen and 55 roadside construction workers as the reference group showed that fumes of bitumen released under high processing temperatures by mastic asphalt handling can exert acute and (...

The mechanical properties of mastic asphalt are highly affected by the rheological properties of the respective mastic binder. Trinidad Lake Asphalt (TLA), which comprises naturally weathered bitumen and filler, is often used for modifying the mastic binder properties in order to obtain improved performance of the respective mastic asphalt mixture (such as stiffness and deformation resistance). Increased traffic loading and severe environmental conditions often demand more stringent requirements for the mixture performance; in these cases, further modifications of the mastic binder by polymer modification may be required. This paper demonstrates the potential use of polymer modified binders for mastic asphalt bridge surfacing for enhancing the mixture performance for use under more severe environmental conditions and/or to carry increased traffic loading. Rheological analysis showed that the “stiffening” effect caused by addition of TLA into mastic binder, which is normally anticipated in the cas...

Epidemiological studies [1,2] have reported elevated cancer incidences and mortality in the Danish mastic asphalt industry, and have associated these elevations with exposure to asphalt fumes. The strength of the causal association depends heavily on the claim that coal tar was not used in the industry after World War II; otherwise, exposure to coal tar pitch volatiles would have seriously confounded study results. Yet, other reports [3,4,5] indicate coal tar was used well into the 1970's. To clarify the issue, the Copenhagen Road Institute collected core samples from sites where the history of mastic application was known. Coded samples were extracted, and subjected to HPLC separation, GC-MS, fluorescence fingerprinting and the Diazo test for phenolics. The extracts were also tested in the Modified Ames Assay. The results of the study show that the composition and mutagenicity of the core samples until 1970 were consistent with the presence of coal tar.