A comprehensive laboratory evaluation of the geotechnical and geoenvironmental properties of five predominant types of Construction and Demolition (C&D) waste materials was undertaken in this research study. The C&D materials tested were Recycled Concrete Aggregate (RCA), Crushed Brick (CB), Waste Rock (WR), Reclaimed Asphalt Pavement (RAP) and Fine Recycled Glass (FRG). The geotechnical assessment included particle size distribution, particle density, water absorption, compaction, Los Angeles abrasion, post-compaction sieve analysis, flakiness index, hydraulic conductivity and California Bearing Ratio (CBR) tests. Shear strength properties of the materials were studied through a series of triaxial tests. Consolidated drained triaxial tests undertaken on the recycled materials indicated that the recycled materials had a drained cohesion ranging from 41 kPa to 46 kPa and a drained friction angle ranging from 49° to 51°, with the exception of FRG and RAP. The response of the materials under repeated load was investigated using repeated load triaxial (RLT) tests. The RLT testing results indicated that RCA, WR and CB performed satisfactorily at 98% maximum dry density and at a target moisture content of 70% of the optimum moisture content under modified compaction. The geoenvironmental assessment included pH value, organic content, total and leachate concentration of the material for a range of contaminant constituents. In terms of usage in pavement subbases, RCA and WR were found to have geotechnical engineering properties equivalent or superior to that of typical quarry granular subbase materials. CB at the lower target moisture contents of 70% of the OMC was also found to meet the requirements of typical quarry granular subbase materials. The properties of CB, RAP and FRG however may be further enhanced with additives or mixed in blends with high quality aggregates to enable their usage in pavement subbases.

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This paper presents the findings of a laboratory investigation on the characterization of recycled crushed brick when blended with recycled concrete aggregate and crushed rock for pavement sub-base applications. The engineering properties of the crushed brick blends were compared with typical state road authority specifications in Australia for pavement sub-base systems to ascertain the potential use of crushed brick blends in these applications. The experimental programme included particle-size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and repeated load triaxial tests. Laboratory tests were undertaken on mixtures of 10%, 15%, 20%, 25%, 30%, 40%, and 50% crushed brick blended with recycled concrete aggregate or crushed rock. The research indicates that up to 25% crushed brick could be safely added to recycled concrete aggregate and crushed rock blends in pavement sub-base applications. The repeated load triaxial test results on the blends indicate that the effects of crushed brick content on the mechanical properties in terms of permanent deformation and resilient modulus of both the recycled concrete aggregate and crushed rock blends were marginal compared to the effects on dry density and moisture content.

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.