Abstract:
Internationally, recycled glass (RG) cullet has been widely utilised in road pavements from the basecourse to the surfacing. However, in the Auckland region of New Zealand, this trend has not been taken up mainly due to the lack of understanding on behaviour and performance of RG blended mixtures, and the incentive to recycle material. In this research, a comprehensive laboratory study was undertaken from locally sourced aggregates and RG cullet to illustrate the viability and influence on inclusion of RG into the basecourse. In the study, RG was introduced into the natural aggregates samples at different replacement rates, 5%, 15% and 30% by weight. The particle size distribution (PSD), optimum moisture content (OMC), pH value and Los Angeles (LA) abrasion index were determined for each of the mixtures. Standard California Bearing Ratio test (CBR) and modified double decker CBR test, or Todd Bearing Ratio test (TBR) were carried out on the natural aggregates and mixtures as a comparative test to determine the influence of the RG cullet. The CBR test is normally used in the field to evaluate pavement thickness and is a measure of the stiffness of the pavement. To ensure consistency in the results and reduce variability, the PSD conforming to TNZ M/4 specification for both aggregates and RG cullet were reconstituted for each of the tests. The OMC percentage, pH value and LA abrasion index increased as RG replacement increased. These patterns were in accordance with other studies conducted in the past. The CBR and TBR values reduced as more RG cullet was added into the mixtures. There is no such specification to evaluate the TBR test yet; however, based upon the current study, 30% RG blended mixtures reached TBR value of 73%, which was considered as marginal aggregates for pavement source material. The relationship between CBR value and TRB value was investigated. The TRB value was 63% of the value of CBR test on average. Since the PSD was pre-selected, the coefficient of variation for all the tests kept below 11%, which was considered very low for geotechnical material.