SALT DAMAGE TO BITUMINOUS SURFACINGS: RESULTS FROM ROAD TRIALS IN BOTSWANA

The paper discusses the results of research undertaken in Botswana to provide design criteria to avoid damage inflicted on thin bituminous surfaces by soluble salt. The damage, characteristic of warm arid or semi-arid regions of the World, occurs when the salt crystallizes within the pavement, physically disrupting the bituminous surfacing and causing premature deterioration of the road. The criteria were worked out from observations made on a road trial constructed in May 1990 in northern Botswana where the salt levels at which damage occurred and the nature and development of the damage were determined. Some preventative measures were incorporated in the trials to determine their efficacy in avoiding damage. The results from the trials have enabled a revision of the current Botswana road design standards with respect to salt limits in pavement materials to be proposed. (A) For the covering abstract of the conference see IRRD 873950.