J. Piratheepan

Geotechnical Properties of Recycled Crushed Brick in Pavement Applications

This paper presents the findings of a laboratory investigation of the characterization of recycled crushed brick and an assessment of its performance as a pavement subbase material. The properties of the recycled crushed brick were compared with the local state road authority specifications in Australia to assess its performance as a pavement subbase material. The experimental program was extensive and included tests such as particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio, Los Angeles abrasion loss, pH, organic content, static triaxial, and repeated load triaxial tests. California bearing ratio values were found to satisfy the local state road authority requirements for a lower subbase material. The Los Angeles abrasion loss value obtained was just above the maximum limits specified for pavement subbase materials. The repeat load triaxial testing established that crushed brick would perform satisfactorily at a 65% moisture ratio level. At higher moisture ratio levels, shear strength of the crushed brick was found to be reduced beyond the acceptable limits. The results of the repeat load triaxial testing indicate that only recycled crushed brick with a moisture ratio of around 65% is a viable material for usage in pavement subbase applications. The geotechnical testing results indicate that crushed brick may have to be blended with other durable recycled aggregates to improve its durability and to enhance its performance in pavement subbase applications.

Reclaimed Asphalt Pavement and Recycled Concrete Aggregate Blends in Pavement Subbases: Laboratory and Field Evaluation

In recent years, efforts have been made to incorporate reclaimed asphalt pavement (RAP) into pavement base or subbase applications by means of cement binder stabilization. This approach, however, may not be an environmentally friendly solution due to the high carbon footprint involved in the production of Portland cement. Recycled concrete aggregate (RCA), on the other hand, has been widely accepted in pavement applications. The sustainable solution of blending RAP with RCA was investigated in this research in an attempt to facilitate the usage of this blend as an alternative pavement subbase material. An extensive suite of geotechnical laboratory tests was undertaken on RAP with contents of 100, 50, 30 and 15% in blends with RCA. Results of the research study indicated that RAP/RCA blends with a low 15% RAP content meet the repeated load triaxial requirements for use in pavement subbase layers. Results of field performance of a pavement subbase constructed with untreated 100% RAP, at a private haul road field-demonstration site, confirmed that it had insufficient strength requirements to meet local road-authority pavement-subbase requirements. RAP and RAP/RCA blends, although found in this study to be not fully compliant with the local road-authorities requirements, could be potentially considered for lower traffic usage, such as haul roads and footpaths.

Geotechnical Performance of Recycled Glass-Waste Rock Blends in Footpath Bases

Laboratory and field experiments were undertaken to investigate the possible application of recycled crushed glass blended with crushed basaltic waste rock as a footpath base material. The laboratory experimental program included basic and specialized geotechnical tests including particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and triaxial shear tests. A field demonstration footpath comprising two sections of recycled glass-waste rock blends with 15% and 30% recycled glass content and a third control section with only waste rock was subsequently constructed on the basis of the outcomes of the initial laboratory tests. Subsequently field tests with a nuclear density gauge and Clegg impact hammer were undertaken, as well as laboratory testing of field samples to assess the geotechnical performance of the trial sections. The field and laboratory test results indicated that adding crushed glass may improve the workability of the crushed waste rock base material but subsequently results in lower shear strength. The blend with 15% glass content was found to be the optimum blend, in which the material presented good workability and also had sufficiently high base strength. Higher recycled glass content (30%) resulted in borderline, though still satisfactory, performance. The research findings indicate that recycled crushed glass in blends with crushed waste rock is a potential alternative material to be used in footpath bases. A separate study is recommended to evaluate the environmental risks associated with the usage of these recycled materials.

Evaluation of Interface Shear Strength Properties of Geogrid-Reinforced Construction and Demolition Materials Using a Modified Large-Scale Direct Shear Testing Apparatus

AbstractThe 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 and 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 and the r...

Geotechnical Properties of Waste Excavation Rock in Pavement Subbase Applications

AbstractThis paper presents the findings of an extensive laboratory investigation on the geotechnical properties of waste excavation rock in pavement subbases. The waste excavation rock used in this study originated from “basalt floaters,” or surface excavation basalt rock (basalt). Traditionally, this material would have been disposed as waste, often into landfill. The engineering properties of the crushed basaltic waste rock were compared with the local road authority specifications to assess its performance as a pavement subbase material. The experimental program was extensive and included tests such as particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio, Los Angeles abrasion loss, pH, organic content, static triaxial, and repeated load triaxial tests. The Los Angeles abrasion loss value obtained indicated that the crushed basaltic waste rock is durable. California bearing ratio values were found to satisfy the local state road authority...

Geotechnical Properties of Recycled Concrete Aggregate in Pavement Sub-Base Applications

This paper presents a laboratory investigation of the geotechnical properties of recycled concrete aggregate (RCA). The properties of RCA were compared with state road authority requirements to assess its performance as a pavement sub-base material. The experimental programme included tests such as particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion loss, pH, organic content, static triaxial, and repeated load triaxial tests. The Los Angeles abrasion loss tests indicated that the RCA is durable. CBR values were found to satisfy the local state road authority requirements for sub-base material. Repeated load triaxial tests established that the RCA would perform satisfactorily as a pavement sub-base material in the field. The results of the laboratory testing undertaken in this research indicated that RCA satisfied the criteria for use in pavement sub-base applications.

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

AbstractExtensive 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 mode...

Resilient Moduli Response of Recycled Construction and Demolition Materials in Pavement Subbase Applications

AbstractResults of an extensive series of repeated load triaxial tests performed on three major recycled construction and demolition (C&D) materials at various moisture contents and stress levels were analysed to ascertain their performance in pavement subbases. The development of the resulting permanent deformation that accumulates with the repeated loading and the determination of resilient modulus by two phases of the test are described. The experimental study shows that the C&D materials perform satisfactorily at a moisture content of about 70% of their optimum moisture contents. Furthermore, the C&D materials also satisfy the two-parameter and three-parameter models. The results of this study indicate that, at a density ratio of 98% compared to maximum dry density obtained in the modified proctor test and with moisture contents in the range of 65–90% of the optimum moisture content, most of the recycled C&D materials produce comparatively smaller permanent strain and greater resilient modulus than na...

Suitability of Using Recycled Glass - Crushed Rock Blends for Pavement Subbase Applications

Construction and demolition materials such as recycled crushed rock and recycled glass account for a major proportion of the waste materials present in landfills in Australia. Using recycled glass and crushed rock in road pavement applications would significantly reduce the need for quarry-based virgin materials. Furthermore, recycled materials could be used in parts of the country where aggregate sources are scarce. This paper discusses the suitability and applicability of recycled glass when used in blends with crushed rock for road pavement applications. Performance of the blends was measured using an extensive suite of geotechnical engineering laboratory tests including basic classification tests along with modified compaction, California Bearing Ratio and Los Angeles abrasion tests. Repeated load triaxial tests were also conducted on blends. The test results indicated that the recycled glass could be blended with recycled crushed rock by up to 30% by mass and provide satisfactory engineering performance to be used as a pavement subbase material.

Interface Shear Strength Testing of Geogrid-Reinforced Construction and Demolition Materials

The interface shear strength properties of geogrid-reinforced recycled construction and demolition (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 materials 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 current 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 engineering applications.