Evaluation of the mechanical performance of recycled concrete aggregates used in highway base layers

Concrete waste is one of the most abundant waste materials and remains in the environment for a long period of time, which, if not recycled, can significantly reduce the life of municipal landfill facilities. The use of recycled concrete aggregate materials in highway constructions as compared with the use of conventional materials is more economic, profitable, and reduces virgin natural resource demands on the environment. To evaluate their potential reuse in highway bases, two different recycled concrete aggregate base course (RCA) materials were tested for their resilient modulus, permanent deformation, and durability in the laboratory. The same tests were also conducted on a conventional graded aggregate base (GAB) material and the mixtures of RCA-GAB. The summary resilient moduli (SMR) of RCAs were 2.6 and 2 times higher than that of the GAB material, and their stiffness increased when subjected to freezing and thawing cycles. Consistent trend could not be observed with CBR and SMR values and percent RCA addition. Overall, GAB yielded lower permanent deformations compared with the RCA materials. However, a consistent trend could not be observed with CBR, SMR, permanent deformation, and percent RCA addition. The stiffness of RCAs increased with an increase in the number of freezing and thawing cycles.