LEACHING CHARACTERISTICS OF ASPHALT ROAD WASTE

Abstract

A proposed alternative for the management of reclaimed asphalt pavement (RAP) is use as fill material. However, two different types of environmental concerns relate to leaching of pollutants from RAP. The first is that the leachate produced when rainfall infiltrates RAP stockpiles could potentially be contaminated with trace amounts of organic compounds or heavy metals. A second environmental concern is that RAP used a fill material could potentially leach off contaminants when rainfall infiltrates the waste (unsaturated condition) or when used as fill below the water table (saturated condition). In both situations, the leachate produced could potentially be contaminated with trace amounts of the hazardous chemicals. Thus, a series of leaching tests were performed in Florida at both batch-scale and in leaching columns. The primary chemicals investigated were volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals. Results were consistent with previous studies showing that organic compounds do not leach from typical RAP. Heavy metals are sometimes encountered. The literature indicated the presence of chromium, lead, and barium; however, only lead was detected in this study and was ascribed to prolonged exposure to traffic and vehicle emissions. Results indicate that in most cases RAP would pose minimal environmental risk when used as fill in regard to the leaching of pollutants.