Impact of Impurities on the Properties of Recycled Aggregate for Use in Civil Engineering Work and Road Construction. Part 2: Environmental Assessment

Abstract

Recycled concrete aggregate fraction 0/63 mm is used as unbound materials in several construction works, for which the environmental soundness is of a great importance. The present study aims to evaluate the influence of impurities such as asphalt, bricks, soil, and lightweight materials on the environmental properties of recycled concrete aggregate. The chemical characteristics are determined as per EN 13242+A1 requirements. The environmental performance is evaluated based on a batch leaching test according to EN 12457-1 (L/S =2) and on the content of organic materials such as PAHs, PCBs, C10-C40. The two sets of tests were found to give conflicting results: no problematic chemical characteristics were found even at a high percentage of impurities in the recycled concrete aggregate, while the environmental performance was not satisfactory; the recycled aggregates were found not inert because of the significant amounts of sulphates, chlorides and total dissolved solids, sometimes heavy metals and, when blended with ground asphalt, organic compounds such as hydrocarbons. Thus, backfills and road facilities can be a source of soil and groundwater pollution if a pre-demolition audit, identification of contaminated CDW, decontamination activities and selective demolition are not implemented. Some improvements in the regulatory framework are proposed.