Effect of CO₂ Curing on the Physical Properties of Recycled Coarse Aggregate with Different Attached Mortar Contents

Abstract

The effects of carbon dioxide (CO₂) curing conditions (temperature, relative humidity and CO₂ curing time) on the physical properties of recycled coarse aggregate (RCA) with varying attached mortar (AM) contents were studied. Before and after CO₂ curing, the physical properties in terms of the apparent density, water absorption and crushing value of RCA were tested and the quality of RCA was determined. Besides, scanning electron microscope was used to observe the microstructure of RCA. Results show that the physical properties variation of RCA with higher AM content are more significant, and the quality of RCA with lower AM content is easier to be upgraded during CO₂ curing. The physical properties of RCA with 40.8% AM content are earlier stable than that with no less than 44.5% AM content during CO₂ curing. The optimal temperature and relative humidity are 50 °C and 55% for CO₂ curing, respectively. CO₂ curing is incapable of upgrading the quality of RCA with AM no less than 50.6%. The quality of RCA with 44.5% AM content can be upgraded only under the optimum CO₂ curing conditions. Under relative humidity higher than 40% and the CO₂ curing time more than 12 h, CO₂ curing upgrades the quality of RCA with 40.8% AM content.

Keywords

recycled coarse aggregate / attached mortar content / carbon dioxide curing / curing time / relative humidity / temperature

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