A. Arulrajah, 1 M. A. Rahman, 2 J. Piratheepan, 3 M. W. Bo, 4 and M. A. Imteaz 5 Interface Shear Strength Testing of Geogrid-Reinforced Construction and Demolition Materials REFERENCE: Arulrajah, A., Rahman, M. A., Piratheepan, J., Bo, M. W., and Imteaz, M. A., “Interface Shear Strength Testing of Geogrid-Reinforced Construction and Demolition Materials,” Advances in Civil Engi- neering Materials, Vol. 2, No. 1, 2013, pp. 189–200, doi:10.1520/ACEM20120055. ISSN 2165-3984. ABSTRACT: The interface shear strength properties of geogrid-reinforced recycled construction and demo- lition (C&D) materials were determined in this research to assess the viability of using geogrid-reinforced C&D materials as alternative construction materials. The C&D materials investigated were recycled concrete aggregate (RCA), crushed brick (CB), and reclaimed asphalt pavement (RAP). Biaxial and triaxial geogrids were tested as the geogrid-reinforcement materials. The interface shear strength properties of the C&D mate- rials were ascertained by using a large direct shear test (DST) equipment. Large-scale DST was conducted for unreinforced and geogrid-reinforced C&D materials. The interface peak and residual shear strength property of unreinforced and geogrid-reinforced RCA was found to be higher than that of CB and RAP. RAP was found to have the lowest interface shear strength properties of the C&D materials. The higher strength triaxial geogrids were found to attain higher interface shear strength properties than that of the lower strength biaxial geogrids. The DST results, however, indicated that the interface shear strength properties of the geogrid- reinforced C&D materials were less than that of the respective material without reinforcement. This can be attributed to the lack of interlock between the geogrids and the recycled C&D aggregates, as well as the cur- rent conventional testing method for DST that induces a shear plane at the boundary between the lower and upper boxes where the geogrid is placed. The unreinforced and geogrid-reinforced RCA, CB, and RAP were found to meet the peak and residual shear strength requirements for typical construction materials in civil en- gineering applications. KEYWORDS: geogrids, direct shear test, interface shear strength, recycled materials, construction, demolition Introduction Granular materials are commonly used in civil engineering applications, such as embankments, backfilling, road bases, road sub-bases, railway ballast, railway sub-ballast, gabion walls, and slope stabilisation. Typically, virgin aggregates from quarries are used as construction materials in these Manuscript received December 12, 2012; accepted for publication March 28, 2013; published online May 8, 2013. 1 Associate Professor, Faculty of Engineering and Industrial Sciences, Swinburne Univ. of Technology, Melbourne, Victoria, Australia 3000 (Corresponding author), e-mail: aarulrajah@swin.edu.au 2 Ph.D. Student, Faculty of Engineering and Industrial Sciences, Swinburne Univ. of Technology, Melbourne, Victoria, Australia 3000, e-mail: mdaminurrahman@swin.edu.au 3 Lecturer, Faculty of Engineering and Industrial Sciences, Swinburne Univ. of Technology, Melbourne, Victoria, Australia 3000, e-mail: pjegatheesan@swin.edu.au 4 Senior Principal, DST Consulting Engineers Inc., Thunder Bay, Ontario, P7B 5V5, Canada, e-mail: mwinbo@dstgroup.com 5 Senior Lecturer, Faculty of Engineering and Industrial Sciences, Swinburne Univ. of Technology, Melbourne, Victoria, Australia 3000, e-mail: mimteaz@swin.edu.au Copyright V C 2013 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 189 Advances in Civil Engineering Materials, Vol. 2, No. 1 Paper ID ACEM20120055 www.astm.org