Stockpiling Recycled Concrete Aggregate: Changes in Physical Properties and Leachate Characteristics Due to Carbonation and Aging

The produced recycled concrete aggregate (RCA) often is stockpiled at the facility at which is produced and is maintained for more than a year before the material is utilized. This time period is referred to as aging in this study and this article is describing a methodology developed to simulate aging of RCA under laboratory conditions and its effects on RCA’s physical properties and characteristics of leachate extracted following batch water leach tests. The laboratory aging tests were performed for a period of one year. When samples of aged and non-aged RCA were compared, it was observed that unlike aged RCA, non-aged RCA has a measurable plastic limit. This is attributed to the existence of un-hydrated cement paste, which hydrates with aging. The data showed that the changes in other physical properties and mortar content were negligible. However, there were notable differences in the collected leachate. A decrease in pH was observed over time, which is attributed to an increase in carbonate content of the material. The leaching concentrations of Ca, Al, and Fe fluctuated within the first two months and approached to a steady value thereafter. However, the leached concentrations of Mg showed slight but consistent increase with time.