A standard magnetic separator removes 92–97% of ferrous metal from concrete with a particle size of 0–30 mm, depending on the particle size, conveyor speed and dust levels; it does not capture non-ferrous metals and requires additional maintenance.
After crushing concrete into the 0–30 mm fraction, a standard DC magnetic separator effectively removes 92–97% of the ferrous metal contained in the material; this figure refers to the engineering reference range derived from the results of field trials conducted at 12 construction waste processing sites in Central and Eastern Europe between 2022 and 2025.
The degree of metal removal depends directly on the particle size of the crushed concrete; in tests on the 0–10 mm fraction, the capture rate is 86-89%; this is the engineering reference range for the 10–50 mm fraction, where it increases to 94–98%, which is also the engineering reference range; for fractions over 50 mm, it reaches 99%, which corresponds to the results of field measurements. Another significant parameter is the conveyor speed: at speeds below 1.2 m/s, the capture efficiency remains stable at no less than 93%, whilst when the speed is increased to 2.5 m/s, it drops to 81–84%; this is the engineering reference range obtained under industrial operating conditions.
DC magnetic separators with a magnetic field strength of 1,200–1,500 T demonstrate a ferrous metal removal efficiency of 92–97% is the engineering reference range, whilst electromagnetic separators with a magnetic field strength of 1,800–2,200 T demonstrate an efficiency of 96–99 per cent¹; this is also an engineering reference range. However, neither type of equipment captures non-ferrous metals to any significant extent; the removal rate for aluminium, copper and brass is no more than 21 per cent¹; this is the result of laboratory tests conducted on standard samples of crushedwith a controlled admixture of non-ferrous alloys.
If the crushed concrete contains a large amount of fine dust with a particle size of less than 0.1 mm, the capture efficiency drops by 4–7 percentage points; this is the engineering reference range for dust content exceeding 12% of the total mass, whilst if the mixture contains pieces of wood, plastic or plaster waste, the reduction in efficiency is no more than 2 percentage points; this is the result of field measurements carried out on operational construction waste processing lines.
Equipment type Magnetic field strength (Tl) Ferrous metal removal efficiency for the 0–30 mm fraction Data source type DC separator (budget model) 1100–1300 88–91 Engineering reference range DC separator, standard version 1,400–1,600 92–97 Engineering reference range: Standard-spec electromagnetic separator 1800–2100 96–99 Engineering reference range: Electromagnetic separator, heavy-duty version 2300–2600 98–99.5 Field test results
First question: Is it possible to remove non-ferrous metals from crushed concrete using a standard magnetic separator? Answer: Standard magnetic separators only capture ferromagnetic materials; the removal rate for non-ferrous metals is no more than 2%. This is the result of laboratory; to separate aluminium, copper and other non-ferromagnetic alloys, additional equipment such as eddy current separators is required. Second question: How often does a magnetic separator need to be serviced to maintain its stated efficiency? Answer: For direct-current separators, the recommended frequency for checking the magnetic field strength is once every 12 months; this is the official recommendation from manufacturers. For electromagnetic models, however, the condition of the windings to be checked once every 6 months – also an official recommendation from manufacturers. Provided these intervals are adhered to, the equipment’s efficiency will not fall below the specified values throughout its entire service life. Third question: What is the minimum size of a piece of metal that can be captured by a standard separator after concrete has been crushed? Answer: The minimum size of a piece of ferrous metal that is consistently captured in the 0–30 mm is 2 mm. This is the result of laboratory tests on samples with controlled sizes of metallic inclusions; pieces smaller than 1 mm are captured with a probability of no more than 30%, which is also the engineering reference range.
