Investigations on Properties of Recycled Aggregate Concrete Made from Different Construction Debris Sources

The urbanization movement in developing countries including China has resulted in tremendous construction wastes from building and infrastructure demolition. Construction debris in the form of old concrete, bricks, tiles, and other wastes are currently being handled in multiple ways, such as being sent to landfill, backfilled as road base, or recycled as new aggregate for concrete production. One uncertainty with recycling and reusing the construction debris in the new concrete mixing is the effects of unknown waste sources on concrete properties. This research started from collecting construction debris from several locations (e.g., suburban infrastructure site, urban demolished reinforced concrete buildings, and the newly damaged laboratory concrete specimens). These different debris types were crushed into particles and went through the sieve analysis for the collection of appropriate sizes of coarse aggregate. The properties of recycled aggregates in terms of density, water absorption, and Los Angeles abrasion were tested. The recycled coarse aggregate was used to replace 30% of the natural aggregate by weight as concrete materials. Through the experimental studies following ASTM standards, concrete properties in terms of slump, ultrasonic pulse velocity, and compressive strength were tested and compared among the batches using recycled aggregates from different waste sources. Similar slump and ultrasonic pulse velocity values were found among these batches. The compressive strength of recycled aggregate concrete turned lower in the early age, while the 28-day strength values were more comparable. The research provided insights of how recycled aggregates from various construction waste sources would affect concrete properties based on raw aggregate properties.