Development of a laboratory test procedure for the evaluation of potential gaseous emissions of asphalt rubber bituminous mixtures

The superior performance of bituminous mixtures containing crumb rubber from end-of-life tyres has been widely documented from a structural and functional point of view. However, potential impact of the use of crumb rubber on the health of workers in pavement construction sites has been the subject of a limited number of investigations, with a consequent gap in currently available technical knowledge. Following previous research work focused on the chemical analysis of fumes sampled on site, in this paper the Authors present results obtained in the development of a laboratory test procedure for the evaluation of gaseous emissions of asphalt rubber bituminous mixtures in standard, controlled conditions unaffected by site-specific factors. The investigation included monitoring of emissions at the paver's driving seat and at the screed during the laying of gap-and dense-graded wearing course mixtures in three different sites. Laboratory tests were performed by following a fume-generation protocol and by measuring the contents of volatile organic compounds and polycyclic aromatic hydrocarbons in produced emissions. Comparison of results derived from laboratory and field data was carried out in absolute terms and within a carcinogenic risk assessment model. It was found that the proposed laboratory procedure yields emissions which in most cases are similar to those recorded on site at the paver's screed and that lead to a conservative risk estimate.