Resilient Modulus and Permanent Deformation Responses of Geogrid-Reinforced Construction and Demolition Materials

Extensive amounts of natural quarry aggregates are currently being used in road and pavement applications. The use of construction and demolition (C&D) materials such as recycled concrete aggregate (RCA), crushed brick (CB), and reclaimed asphalt pavement (RAP) as an alternative to quarry aggregates has generated interest in recent years, particularly as a pavement base or subbase material. However, the resilient moduli responses and performance of these C&D materials reinforced with geogrids under repeated loads have yet to be established. This research investigates the resilient moduli (MR) and permanent deformation characteristics of C&D materials reinforced with biaxial and triaxial geogrids with the use of repeated load triaxial (RLT) equipment. The effects of varying deviatoric stress on the resilient modulus of unreinforced and geogrid-reinforced C&D materials were also investigated. Regression analyses of resilient modulus test results were performed using the two- and three-parameter models. The MR properties of the geogrid-reinforced RCA and CB were found to be higher than that of the respective unreinforced material. The MR value of RCA+biaxial increased by 24% and of RCA+triaxial increased by 34% when compared with unreinforced RCA. The permanent deformation value obtained from RCA+biaxial decreased by 29% and of RCA+triaxial decreased by 36% when compared with unreinforced RCA. The MR value of CB+biaxial increased by 16% and of CB+triaxial increased by 55% when compared with unreinforced CB. The permanent deformation value decreased by 29 and 37% for CB+biaxial and CB+triaxial, respectively, when compared with unreinforced CB material. The incorporation of geogrids had significant effects on the resilient modulus and permanent deformation characteristics of C&D materials. The three-parameter resilient moduli model was found to provide a good fit for the geogrid-reinforced C&D materials.