Characterization of the Geo-Environmental Properties of Untreated or Cement Treated Recycled Base Materials in Pavement Base Layer Applications

The use of recycled flex-base materials such as recycled crushed concrete aggregate (RCCA) and reclaimed asphalt pavement (RAP) are increasing considerably nowadays in pavement base layer applications. Increased use of these materials address the issues of depletion of natural resources and provide solution to the adverse effect on environment. The recycled materials utilized in this study was collected from the Texas Department of Transportation (TxDOT) approved sources. The properties of recycled base materials depend solely on the sources and their environmental aspects of using as base material needs to be analyzed. A comprehensive laboratory evaluation of geo-environmental properties of RCCA and RAP in untreated or cement treated condition were conducted in this study. The amount of RAP and RCCA varied from 0%-100% in the combination at 50% interval with cement content varying from 0% to 6% at 2% interval. The specimens were prepared at optimum moisture content and maximum dry density obtained from the test results. The geo-environmental tests included permeability and leaching tests. Leaching tests included pH, total and volatile dissolved solids, total and volatile suspended solids, turbidity and chemical oxygen demand (COD). Tests results were compared with the requirements of different environmental protection agencies. The comparison of tests results indicated that the recycled base materials were environmentally sound alternative to regular virgin aggregates and can be used in pavement base or sub-base layer.