research has already shown that although the high-alumina (rasc) grade of calcined bauxite from guyana is one of the best aggregates for skid-resistant road surfacings, other calcined bauxites are also very good and might be even better if they were calcined differently. the report gives details of a series of calcination trials that have been carried out at the laboratory on three raw bauxites, together with the results of laboratory tests and of a road trial of the materials produced. one (from ghana) gave results which were very similar to those given by rasc bauxite, and another (from australia) also showed considerable promise. the third (from northern ireland) gave poorer results, but was better than most natural high-psv road stones. the results showed that good performance is associated with high alumina content (over 65 per cent), that a moderate amount (not more than 20 per cent) of iron is beneficial, and that the silica content should be low (under 10 per cent). (a).

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