(57) A particulate waste material, for example a particulate contaminated material 1, is processed into a constructional material, such as an aggregate for use in the foundations of roads. The contaminated material 1 is mixed with cement powder 2, zeolite powder 4, and optional recycled aggregate 3 in a mixer 6, together with sufficient water to form a slurry. The slurry iss allowed to dry into a dry cake 8, which is then broken into fragments before it sets. These fragments are allowed to set partially, then are graded through a screen 9, oversize material being crushed by a jaw crusher 10 and recombined. Once setting is complete, this yields a solid coarse particulate building material in which the contaminated particulate material 1 is safely encapsuled. This method is suitable for processing contaminated materials such as treated drilling cuttings from boring oil wells, contaminated soils, road sweepings, furnace slags and ground lead glass, as well as other waste materials such as scrap plastics and plasterboard.
(71) Greenwod IP Ltd., Estuary farm, Off Edward Benefer Way, North Lynn, Kings Lynn, Norfolk, PE30 2HY, UK