In 1991, the U.S. Congress passed the Intermodal Surface Transportation Efficiency Act, or "ISTEA" as it is commonly refered to. Section 1038 of the ISTEA, required the Secretary of Transportation and the Administrator of the U.S. Environmental Protection Agency (EPA) to jointly conduct studies to determine the economic savings, technical performance qualities, threats to human health and the environment, and the environmental benefits of using recycled material in highway devices and appurtenances, as well as highway projects. A wide variety of waste materials have been or could be appropriate for use as a highway construction material. A symposium held in October of 1993 presented information presented information on the wide variety of worldwide research that is now underway in the area of recycling. Based on the results of that symposium, this paper provides information on some more promising and innovative uses for what would other wise be considered waste material. Materials covered in this paper include: Blast furnace and steel slags; Carpet fibers; Coal-ash by-products including fly ash, botton ash and flue gas desulfurization waste; Glass; Municipal solid waste combustion ash; Recycled plastic; Roofing shingle wastes; and Rubber tires for uses other than in asphalt pavements. Each material is briefly described and some of the current research projects using these materials are presented. Information regarding performance is also presented, as available. Material availability, environmental concerns, and disposal problems are also briefly described. (A)
Samenvatting