Abstract
Rapid urbanization and population growth have caused a substantial rise in the generation of all kinds of waste globally. The use of recycled waste not only can replace the enormous volume of virgin materials used in construction but also alleviate environmental concerns by lowering landfilling loads. This study aims to evaluate the feasibility of using non-treated and cement-treated recycled concrete aggregates (RCA) in pavement base and subbase layers. A detailed study focused on the strength, durability and microstructural aspects of treated RCA. To fulfill this, experimental test program and analysis covered particle-size distribution, Los Angeles abrasion, aggregate impact value, modified Proctor compaction, unconfined compressive strength (UCS), weight loss under wet-dry cycles, and scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. The recycled aggregates are found to show excellent physical and mechanical characteristics in terms of abrasion and aggregate impact values. Cement treatment has shown to significantly enhance the strength and durability characteristics of RCA, rendering it suitable for pavement base/subbase layer application. RCA samples treated with a cement content of 3% and above (by weight) are found to satisfy the minimum specified unconfined compressive strength (UCS) values of 2MPa at 7 days of curing, according to the Texas Department of Transportation (TxDOT) and Austroads guidelines for pavement base and subbase layer applications. However, a relatively higher cement contents (5% and 7%) is required to meet the minimum 7-days UCS criterion of 3 and 4.5MPa for base layer applications of low- and high- volume roads, respectively, according to Indian road standards (IRC SP 72 (2015) and IRC 37(2018)). Cement-treated samples with 2% cement or above showed minimal weight loss after 12 alternate wet-dry cycles, which was well within the maximum permissible limit (14%) specified in various standards for stabilized materials. Additionally, microstructural investigations have clearly showed formation of hydration products corroborating the mechanism behind strength gain with time. Findings from this study provide references to promote the use of RCA in construction of pavement base and subbase layer, contributing towards the goal of net zero set by the United Nations.
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