The technical feasibility of using waste roofing products in asphalt concrete paving mixtures is addressed. Approximately 9 million tons of roofing waste are generated annually in the United States. Disposal costs are significant. Recycling represents an economical and, perhaps, environmentally attractive alternative to placing these wastes in landfills. The relatively large quantities of asphalt cement and "aggregate-type" materials present in roofing waste suggest that these materials have potential as a partial substitute for asphalt cement or aggregate, or both, in a paving mixture. A study that arrived at the following conclusion was conducted. (a) Acceptable paving mixtures, which contain up to 20 percent by volume of roofing waste, can be produced; (b) proper selection of binder type and quantity is critical to the performance of the mixture and depends on the type and quantity of the roofing waste in the mixture; (c) improved asphalt cement extraction and recovery processes need to be developed to effectively determine the properties of the asphalt cement in the roofing waste; (d) the total "active binder" content, depending on the effectiveness of the recycling agents, should be considered when designing asphalt concrete mixtures; (e) the gradations of conventional aggregates and roofing wastes should be considered when designing paving mixtures; and (f) the long-term field performance of paving mixtures containing roofing waste needs to be established.(A).
Abstract