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Determination of the particle size and surface area of the raw materials

Bepaling van de deeltjesgrootte en de oppervlakte van de grondstoffen


The joint research project "Environmental implications of useful applications of primary and secondary materials to be used on or in the ground", was carried out by four institutes i.e. RIVM, ECN, TNO and INTRON. In this research project an estimation had been made of the environmental implications when primary materials (natural materials) are replaced by secondary materials (waste materials) in road constructions and building materials. For this estimation the standard leaching test was used. The standard leaching test is applicable to materials with particles smaller than 3 mm. Therefore, some materials have to be reduced by crushing and grinding. This report concerns the determination of the size distribution of the raw materials and materials after grinding by dry sieving and wet sieving. On the basis of the results of the test sieving an estimation of the surface area's was made. In general, it was found that the particles smaller than 20 mum contributes more than 90% to the total surface area and less than 10% to the mass weight of the materials. Grinding hardly affects the percentage of mass weight of the fractions > 20 mum and < 20 mum. A relatively small increase of the fraction < 20 mum results in a considerable increase of the total surface area. The surface area of waste incinerator slag had been measured by the BET-method too. It was found that it wasn't expedient to determine accurately the surface area of particles larger than 1 mm. Moreover, the relation between the particle size of the material and the leaching behaviour of Cd, Cr, Cu, Mo, Ni, Pb, and Zn had been investigated by the column-tests on waste incinerator slag, which had been grinded to different particle sizes. No significant relationship was found between the leaching behaviour and the particle size.

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