Migration of Subgrade Salts Damages Thin Pavements

In moisture deficient areas, soluble salts contained in road aggregates may be leached to the surface by evaporation gradients. The growth of salt crystals beneath the surfacing layer of a pavement may cause damage by blistering and cracking the surface. Salt damage can be prevented by selecting materials that contain less than 0.2% of soluble salts or else by controlling surfacing permeability so that the ratio of permeability to layer thickness is less than 30 microsecond. Salt damaged pavements may be repaired by overlaying to render the surfacing impervious. A conductivity method is suggested as a means of detecting excessive percentages of soluble salts in road-making materials, and a method of measuring surfacing permeability in situ is described.