Emissions of tar-containing binders: a laboratory study

Abstract

In Switzerland, hot recycling of tar-containing pavements is a subject of much dispute between environmentalists, road authorities and constructors. The main reason for this controversy comes from a lack of knowledge about the amount of hazardous compounds emitted, especially polycyclic aromatic hydrocarbons (PAHs), and the resulting health risk for road workers. On this background we decided to initiate a research project to study the emission behaviour of tar-containing materials. Mixtures of tar and bitumen with variable PAH content were heated in an open reactor flask at different temperatures to identify and quantify the key parameters of PAH emissions. The expected linear correlation between PAH concentration in the fumes and in the binder was found only for binder mixtures with PAH concentrations above 5000 ppm. This was traced back to the problem that a change of the PAH content in the binder was always accompanied by a change of other parameters, like viscosity. In the experiments with temperature variation, emissions of individual PAHs correlated well with vapor pressure. However, for Naphthalene and, in a lesser degree, for 3-ring PAHs too, a partial depletion of these compounds in the vapour was observed in some experiments. The effect is a slower increase with temperature for these compounds compared to 4-6-ring PAHs. This is one reason why the commonly used set of EPA-PAHs, which includes naphthalene and 3-ring PAHs, is considered inappropriate for the assessment of the health hazard in the case of tar-containing materials in hot recycling.

ENCORT-CDW - Evaluation of the European recovery target for construction and demolition waste

“…For pure bitumen binders the emission of benzene-soluble particulate matter (BSM) (EAPA & NAPA, 2011) and PAH (Brandt et al, 2000) increases nonlinearly by a factor 2 per 12 ˚C. However, lower temperature dependencies have been shown for tar-contaminated binders (Hugener et al, 2007). Evident temperature dependency has been found also in occupational exposure (Cavallari et al, 2012).…”

“…The presence of PAH-16 and carcinogenic PAH compounds is often used as indicators to support the hazard assessment of tar contaminated pavements. PAH-16 contents at up to 15-23 % have been estimated for coal tar (Hugener et al, 2007;KFA, 2010).…”

Skin disease after occupational dermal exposure to coal tar: a review of the scientific literature

“…Coal tar is currently used in many industries, particularly in manufacturing and primary production. Therefore, workers in aluminum production, steel and iron foundries, tar refineries, road paving, roof insulation, pavement sealcoat, and wood surfaces painting experience high exposure to coal tar and its components. The exposure is mainly through inhalation and dermal contact .…”

Experimental study on shear fatigue behavior and stiffness performance of Warm Mix Asphalt by adding synthetic wax

“…The ability to generate asphalt mixtures that reduce production and application temperatures also yields a number of environmental benefits [1,2], along with economic and operational advantages. Lower temperatures during asphalt production inevitably lead to reducing CO 2 /CO 2 equivalent and fume emissions [3], which in turn guarantees better working conditions and less energy consumption during the production phase. The economic and operational benefits encompass: lower production costs, less fuel required for production, greater emissions control, potentially longer hauling distances, and extended construction schedules with tighter constraints [4].…”