A Simplified Testing Approach for Recycled Coarse Aggregate in Construction

Abstract

Recycled aggregate (RA) is the end product of recycling process of properly treated concrete waste. It is also being one of the heaviest portions in the construction and demolition (C&D) waste stream (Environmental Protection Agency, 2005). As any other construction materials, engineering properties of aggregate products are always one of the major concerns. Traditionally, to obtain engineering properties of aggregate products, it is involved numbers of destructive and non-destructive tests. But most of the tests can only provide limited information of aggregate properties. As a result a large number of tests have to be done to obtain all necessary information required. RA is a recycled product, which tends to have a high consistence variation (Tam and Tam, 2008), compare with virgin materials. These directly increase time and resources involve in RA testing processes for high-grade applications such as recycled aggregate concrete (RAC). This paper investigates the methods of testing RA products. A simplified testing approach is established by constructing a correlation among different aggregate test results. Twelve physical, mechanical and chemical properties of aggregate are being investigated: (1) particle size distribution; (2) particle density; (3) water absorption; (4) wet strength; (5) dry strength; (6) Los Angeles value; (7) aggregate crushing value; (8) weak particle; (9) particle shape; (10) flakiness index; (11) chloride content in concrete aggregate; and (12) sulfate content in concrete aggregate. The experiments conducted are based on Australian Standard 1141 (AS 1141, 1974). Eight RA samples (Samples 1 to 8) collected from C&D sites and centralised recycling plants in Brisbane and Gold Coast, Australia are used in this study and their properties are compared with virgin aggregate (Sample 9). A linear regression analysis is used to construct the correlation among the aggregate properties. From the result, it is refined six groups of tests: (1) particle size distribution; (2) particle density and strength; (3) strength and abrasiveness; (4) weak particle; (5) particle shape; and (6) chemical contents. By understanding these six groups of tests for aggregate, it will be able to fully understand the aggregate properties. Approximately 30% reduction of test number is achieved, which can save both time and resources required for examining RA quality.

Keywords:

• Recycled Aggregate
• Construction and Demolition Waste
• Correlation
• Construction
• Australia