Reduced emissions of warm mix asphalt during construction

Abstract

Warm mix asphalt (WMA) is produced at lower temperature and hence its production in the asphalt plant is favourable in terms of energy consumption and CO2 emission. As a side effect, it is expected that the emissions during pavement construction are reduced too, which is highly relevant for workplace hygiene and for environmental protection. In a field trial five pavement sections were constructed with different warm-mix asphalt types and one hot mix asphalt (HMA) used as a reference. During construction, several road workers were equipped with personnel samplers to determine their exposure to pollutants relevant for occupational health. Particular attention was paid to the total particulate matter (TPM) and the polycyclic aromatic hydrocarbons (PAH). In addition, emissions of TPM, PAH, and other organic pollutants (volatile organic compounds, TVOC) were sampled on the paver and rolling compactor. To evaluate total emissions of road construction, an integrative pollutant sample was collected downwind of the construction site and mass emissions were estimated using a tracer gas technique with constant dosing at known source strength. In parallel, a series of laboratory experiments were carried out on the same material to elucidate differences in the emission behaviour between the warm mix asphalt types and in relation to HMA under more controlled conditions. The laboratory experiments indicate a 90% reduction of TPM and 50–70% lower TVOC values by the use of WMAs in comparison to hot mix asphalt. Emissions of pollutants during road construction, however, were low for all asphalt types, mostly below the occupational health limits and the detection limits of the applied analytical techniques. The study demonstrates the benefit of temperature reduction during road construction for occupational health and the environment.