No abstract

No abstract

The interface shear strength properties of geogrid-reinforced Construction and Demolition (C&D) aggregates were determined using a modified large scale direct shear test (DST) apparatus. Comparisons were made between the results of the various C&D aggregates reinforced with biaxial and triaxial geogrids as well as with the unreinforced aggregates by means of the modified and conventional DST methods. The modified DST method employed, sought to increase interlocking between the C&D aggregates with the geogrids and thus ascertains the true interface shear strength properties of the recycled demolition aggregates. Biaxial and triaxial geogrids were used as the geogrid-reinforcement materials. The C&D aggregates tested with the DST were Recycled Concrete Aggregate (RCA), Crushed Brick (CB) and Reclaimed Asphalt Pavement (RAP). The modified DST results indicated that the interface shear strength properties of the geogrid-reinforced C&D aggregates were higher than that of the conventional test method as well as the respective unreinforced materials. Geogrid-reinforced RCA was found to have the highest interface peak and residual shear strength property of the C&D materials. RAP was found to have the smallest interface shear strength properties of the C&D aggregates. The higher stiffness triaxial geogrid attained higher interface shear strength properties than that of the lower stiffness biaxial geogrid. The modified device also showed some increased measured interface coefficients compared to a conventional DST. The geogrid-reinforced recycled C&D aggregates was found to meet the peak and residual shear strength requirements for typical construction aggregates used in civil engineering applications.

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 has yet to be established. This research investigates the resilient moduli (M R) and permanent deformation characteristics of C&D materials reinforced with biaxial and triaxial geogrids with the use of a 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 M R properties of the geogrid-reinforced RCA and CB were found to be higher than that of the respective unreinforced material. The M R 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 M R 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 was found to have 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.

No abstract