Texture changes in crushed basalt road base

Abstract

Summary The internal texture of undisturbed samples of granular road base has been studied by microscope examination of pet-rological thin sections prepared from samples impregnated with epoxy resin. The study of compacted crushed basalt road base materials subjected to repeated loading from traffic and in laboratory tests, showed that the -75 μm particles become rearranged to give local accumulations of finer particles. A ‘Texture Factor’ (TF), assessed by a point counting method, was developed to quantitatively describe and follow such changes in the internal texture. The TF increases progressively with repeated loading and the increase is more rapid at higher moisture contents. The TF in road pavements is highest near the surface and a possible relationship between TF and existing pavement condition is described. Possible applications of TF measurements on existing roads to problems of material durability and pavement performance are discussed.