Pure brick sand from Construction and Demolition Waste (CDW) through magnetic sorting

In the processing of construction and demolition waste (CDW), the sorting of the delivered mixtures is one of the decisive process steps in order to produce pure recyclates, which can be used, for example, as a cement substitute or as a raw material component for the brick production. A previously unused method for the separation of fine brick particles as sand utilises rare-earth magnets. This method is based on differences in magnetic susceptibility, which have been confirmed by measurements on bricks and concretes. Sorting tests carried out using a roll magnetic separator with a field strength of 1,4 Tesla at a belt thickness of 0,7 mm confirmed the separability of brick-concrete-mixtures and provided insights into the most important influencing variables. In addition to manual sorting the quantification of the contents of concrete or brick in the magnetic and non-magnetic fractions was determined with laser-induced breakdown spectroscopy (LIBS) and artificial intelligence-based optical quality assurance. Thus, in addition to the proof of seperability, a first step to faster ways for quality control has been accomplished.