Laboratory Evaluation of Emulsion-Treated Base Layer Mixes Incorporating Reclaimed Asphalt Pavement Materials

Emulsion-Treated Base (ETB) is one of the most preferred base layer stabilization methods in which dense graded aggregates are treated with a slow setting bituminous emulsion. To reduce the cost of ETB and minimize the need for virgin aggregates, it is essential to evaluate the possibility of incorporating higher dosages of Reclaimed Asphalt Pavement material (RAP) in ETB. The present study evaluates the effect of RAP incorporation in ETB at dosages of 0%, 25%, 50%, 75%, and 100%. The effects of RAP incorporation were studied in terms of RAP mixing and RAP blending methods. RAP mixing is a process in which a definite proportion of RAP is added to virgin aggregates of a given gradation without a target gradation, while in RAP blending, virgin aggregates of required aggregate sizes are blended to RAP with the objective of achieving a targetted dense aggregate gradation. In this study, RAP was characterized using cohesion tests, fragmentation tests, and other physical properties recommended by the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM) Technical Committee. When 50% RAP was added to ETB using the RAP mixing method, the Maximum Dry Density (MDD) of the mix decreased by 4.4%, but in using RAP blending, the reduction in MDD was only 1.3%. ETB prepared with up to 75% RAP, 3% emulsion, and 1% cement, using the RAP blending method, was found to satisfy the minimum indirect tensile strength requirement of $225\mathrm{kPa}$ (specified by TG 2 2009 and IRC 37 2012), and exhibited appreciable rutting resistance and a tensile strength ratio of more than 0.7. This study identified that 50% RAP incorporation in ETB using blending gives the best performance in terms of cohesive and adhesive strength, moisture resistance, and resistance to permanent deformation.