ASSESSMENT OF MATERIAL GRADATION OF FLEXIBLE PAVEMENTS USING RADIOMETER

Abstract

Gradation or Grain size distribution is one of the key property of aggregates. ,The flexible pavement layers transmit the vertical compressive stresses to the lower layers by grain to grain transfer through the points of contact in the granular structure. A granular material designed for maximum stability should possess high internal friction to resist deformation under load. A well graded granular structure consisting of strong graded aggregates can transfer the compressive stresses through--`a wider area and thus forms a good flexible pavement layer. The load spreading ability of this layer therefore depends very much on type and gradation of material. Gradation has enormous influence on the desirable properties of a pavement layer such as stability, density, drainage, permeability etc.. It is to be decided whether to. increase the drainage sacrificing the stability or to use densest gradation possible for maximum stability at the risk of poor drainage and increased frost susceptibility in the pavement system. In weak pavement layers, there will be a change in material gradation due to many reasons, such as application of heavy wheel loads, poor drainage system etc. This will disturb the fabric of road structure by affecting the strength and drainage patterns. . In the present investigation using pavement models, correlations have been developed between reflectance, grain size, density and moisture content from the spectral responses obtained by Radiometer. The material gradation in layer(s) of flexible pavement model has also been obtained from the spectral response using Radiometer. A model of pavement section was prepared and tested for observing t rchange in the strength pattern due to the application of loads. (