A study to evaluate low temperature performance of reclaimed asphalt pavement in hot mix asphalt at different degrees of blending

Currently New Jersey state specifications limit the percentage of Reclaimed Asphalt Pavement to 15 percent for surface courses and 25 percent for the intermediate and base courses. The limitations are placed because the interaction between the virgin and RAP binder is unknown in two ways. First, the amount of residual binder that is active in a mix, known as degree of blend-ing, is currently assumed to be 100 percent. Second, the effect that this blended binder will have on performance still needs to be investigated due to the fact that aged binder has a ten-dency to be stiffer. The low temperature performance was evaluated through the use of the disc shaped compacted tension test, modified bending beam rheometer, and tensile strength ratio test. These tests were performed on 25 and 35 percent RAP samples as well as a control mix and RAP samples from Delaware to determine if the current specifications for degree of blend-ing should be altered and if the amount of RAP can be increased. It was found that the assump-tion of full blending could lead to under-asphalting and decreased performance for 25 percent RAP. The use of softer binders to compensate for higher percentages of RAP can raise the fracture energy of a given mixture; however, it will also decrease the stiffness of the mixture due to partial degree of blending. The high RAP mixtures that fractionated the RAP and had an overall finer gradation appeared to have higher fracture energy and higher stiffness in the modi-fied bending beam rheometer.