Large-Scale Direct Shear Testing of Recycled Construction and Demolition Materials

Laboratory large-scale direct shear tests were carried out on five different recycled construction and demolition materials, such as crushed concrete (CC), crushed rock (CR), crushed brick (CB), reclaimed asphalt pavement (RAP), and recycled glass (RG). The shear strength parameters were evaluated with a large shear test machine for different values of normal stress ranging from 30 to 200 kPa. Resulting values of cohesion were found to vary in a wide range between 8.55 kPa to 284.5 kPa, whereas coefficient of internal friction varies between 44.6 degrees to 52.1 degrees. The failure envelopes for all materials investigated are straight-line failure envelopes. Crushed rock and crushed concrete showed high cohesion of 284 kPa and 154 kPa, respectively, whereas reclaimed asphalt pavement and recycled glass showed low cohesion of 8.55 kPa and 14 kPa, respectively. Meanwhile, crushed brick showed a medium cohesion of 61.2 kPa. Further, the volumetric behaviours of the recycled materials are dilatancy except for reclaimed asphalt pavement at low normal stress. The results of the shear strength tests indicate that CR, CC, and CB and blends of RAP and medium recycled glass (MRG) with other materials can be viable materials to be sustainably used in pavement sub-base applications.