University of Leeds University of Nottingham

A process is described for the manufacture of a new building material from soil and bitumen which has the potential to be competitive with conventional masonry products in both compression and tension and possesses excellent water repellence and freeze-thaw resistance. Selected soil, which is preheated to 150ºC, is charged to a pug-mill mixer, where molten straight run bitumen, at a maximum viscosity of 0.2Pa.s is then added. The two constituents are mixed until all the soil particles are fully coated with bitumen. The mixture is then cooled and the resulting free flowing powder is placed and compacted in a mould to form the required shape of unit suitable for the purposes of construction. The unit is then removed from the mould and cured by heating in an oven for up to 1 day. During curing, the blocks undergo no warping and practically no shrinkage. This process of soil – bitumen mixing, compacting and curing is critical, but entirely practicable. The nature of the soil and bitumen constituents, and the percentage of bitumen that is combined with the soil, have also been found to be important. Test results of the standard basic properties of the unit are also presented.