15 Sept 99
percent, compared to new paving materials, have been demonstrated (Thirumalai 1992).
One state DOT study showed that the costs of using RCP would be equal to using virgin
aggregates, when disposal and all other costs were considered (Ahmed 1991). This
would make RCP more attractive in areas that do not have access to low cost, quality
aggregate. True life-cycle analysis must include not only the initial cost, but also the
increased performance and the effects of the waste material on the pavement materials
recyclability at the conclusion of its useful life.
d. Finally, state and federal regulations and policies can have a strong influence on
the use of waste materials in pavement construction. Federal programs such as the 1976
Resource Conservation and Recovery Act and the 1984 Hazardous and Solid Waste
Amendments promoted the use and recycling of waste materials. The 1991 Intermodal
Surface Transportation Efficiency Act (ISTEA) required that all DOT's use a certain
percentage of crumb rubber in asphalt mixtures. This was later rescinded through the
significant opposition of many states (Shelburne and DeGroot 1998).