Influence of Crushing Conditions on Recycled Concrete Aggregates (RCA) Leaching Behaviour

The French construction industry generates almost 250 million tons of mineral waste per year. This waste can be used, after preparation, to replace natural materials used for construction work. This can preserve natural resources by contributing to a circular economy. A better understanding is necessary with regards to the deconstruction waste behaviour when used in redevelopment project or construction work, as backfill or embankments. This article intends to better understand how crushing influences recycled concrete aggregates leaching behaviour. Four concrete samples were studied from French power plant deconstructions. The leaching behaviour, of different grain size classifications, was tested with standard (i.e. with size reduction < 4 mm) and non-standard leaching tests (i.e. without size reduction). The samples were crushed with different industrial tools. The results showed that the final products maximum grain-size (Dmax) for crushing operation seems to have an influence on fine grain production. The role of the crushing technique used still remains uncertain. The analytical results from the leaching tests showed that the major elements leached are calcium, sulphates, carbonates, potassium, aluminium and silica. The trace elements were usually found in the smallest grain-size classification (0–6 mm). For the standard leaching tests, the total dissolved solids rose for the larger grain size classifications, whereas for non-standard leaching tests (performed without size reduction) the opposite occurred. All samples followed the environmental acceptability requirements. It seems essential to control the crushing parameters to sustain and strengthen continued concrete waste recovery to help improve French and European waste recovery objectives.