Potential water pollution from recycled concrete aggregate material

Abstract

Recycled concrete aggregates (RCA) are a widely used recycled building material. RCA materials have many uses such as a road base or backfilling trenches. Our study investigated the potential water-contamination risks of water exposed to RCA materials. We recirculated water for 60min through four different treatments. Two treatments were a PVC gutter filled with different size grades of RCA material (20mm and 45mm), the third treatment was a clean PVC gutter and the fourth and final treatment was an unused concrete water pipe. Results showed that RCA material exposed to water released a suite of contaminants that could be ecologically hazardous to aquatic species. RCA leached metals over the 60-min recirculation (aluminium, arsenic, barium, chromium, lead, manganese, molybdenum, titanium, lithium and strontium). Water exposed to RCA material exceeded aquatic ecosystem guidelines for aluminium by 50 times and lead by up to 12 times. RCA materials increased pH by up to 4.35 pH units and electrical conductivity (EC) by up to 11 times the starting EC (mean 27.9 µs cm–1). We suggest that RCA materials need to be used with caution in settings that could be exposed to water and flow to waterways of conservation value.