the urban heat island effect and impact of asphalt rubber friction course overlays on portland cement concrete pavements in the phoenix area

Larger volume of paving and building materials gives urban areas a much higher thermal storage capacity than natural surfaces. Satellite thermal imagery of the Phoenix region showed that paved surfaces, including parking lots, local roads, and highways play a significant role in regards to the Urban Heat Island (UHI). In the past few years, the Arizona Department of Transportation's (ADOT) "Quiet Pavements" program have been highly successful with the traveling pubic in addressing roadway noise; the urban freeway in the Phoenix metropolitan has been resurfaced with an Asphalt Rubber Friction Course (ARFC) layer to reduce the noise impact to the surrounding neighborhoods by as much as 4 to 6 decibels. This paper looks into the hypothesis that one consequence of the overlay program is to extend the life of the Portland Cement Concrete Pavement (PCCP) due to mitigation of daily thermal variances. Counterbalancing this benefit, the use of a dark material to overlay hundreds of lane miles in an urban setting plagued by a growing UHI may need consideration. It is hypothesized that by adding a "blanket" over the PCCP, the underlying material will experience higher low temperatures and lower high temperatures. Thermally induced stresses to PCCP can be very damaging, and anything that would lessen the temperature swings would be very beneficial. This study includes a field instrumentation effort with pavement temperature sensors to quantify the thermal behavior of the PCCP with and without the ARFC overlays. Thermally induced curling stresses are calculated, the benefit to the overall pavement service life is modeled, and the overlay strategy viewed as a pavement preservation tool is summarized. Copyright ASCE 2008.