Characteristics of CRM Binders and Mixtures Used in Nevada
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The use of crumb rubber modified binders to improve the performance characteristics of hot mixed asphalt (HMA) mixtures have shown mixed results throughout the U.S. Some studies showed improved performance properties such as added resistance to rutting, fatigue, and low temperature cracking while some field performances have shown problems with raveling bleeding and aging of the CRM HMA mixtures. Before the Nevada Department of Transportation (NDOT) can assess the merit of using CRM HMA mixtures, it must have the following: 1-A system to evaluate the CRM binders in order to assign the binder most suitable for the environmental and traffi.c loading conditions of a particular pavement segment; 2-A procedure for mix design to select the most appropriate proportioning of binder and aggregate; 3-A mixture analysis system to predict the long-term performance of CRM mixtures under the combined action of environment and traffic loadings. It is necessary to develop a system that enables NDOT to predict the performance of CRM pavements before construction (as is done for traditional HMA mixes) and to select better pavement alternatives. In 1994, NDOT initiated a multi-year research project to develop a system for the evaluation of CRM binders and mixtures under Nevada's environmental and traffic conditions. The project started on January 1, 1994 and was completed on August 31, 1997.