Assessment of Emissions of Crumb Rubber Modified Asphalt

The State of Michigan Department of Environmental Quality (MDEQ), Air Quality Division (AQD) is considering developing permit levels for crumb rubber modified asphalt for use on Michigan roadways. Several states already use crumb rubber modified asphalt. To determine how the addition of crumb rubber affects Volatile Organic Compound (VOC) releases, a series of field and laboratory tests were conducted. Field testing was conducted at the Hancock, MI asphalt plant operated by Payne & Dolan and tested both traditional and crumb rubber modified asphalt at both hot and warm mix temperatures. The field testing used the standard method for determining air emissions from asphalt plants, however, laboratory testing was done in an effort to accurately simulate field data without the time consuming and costly field methods. Laboratory testing procedures involved preparing and testing small mass samples, on the order of 1 g or less, using heated head space with gas chromatography couple (GC) analysis for benzene, toluene, ethylbenzene, xylenes (BTEX), and naphthalene, and Fourier Transform Infrared spectroscopy (FTIR) for formaldehyde. Laboratory test results are within the same order of magnitude as field test data for most substances and offer reasonable agreement to literature values