Petrographic assessment of re-textured road surface aggregates

Abstract

Since the costs of structural maintenance of slippery road surfaces are very high, re-texturing offers the potential for economically increasing a road's surface life without the addition of new material. Correctly using mechanical re-texturing techniques improves mechanical properties of the road stones. These techniques can be used in more sensitive areas to provide adequate surface skidding resistance. The main objective of the present research is to investigate material properties and performance in the laboratory of aggregates subjected to mechanical treatments (sand blasting) with a view to establish the cause of some aggregate material to benefit in terms of their Polished Stone Value (PSV) enhancement. Samples of aggregate from 35 quarries have been assembled and in the first stage a thin section of each aggregate was prepared (from at least six rock fragments of each individual aggregate) and their petrological properties determined. In the second stage, test specimens were made in accordance with the procedures described in BS812 Part 114 1989. Initially, the PSV of each aggregate sample was measured in a program of standard tests. The test specimen was subjected to a program of sand blasting treatments. The type of mechanical processes involved in re-texturing suggest the relevance of geological structure and properties in determining their degree of enhancement of surface texture for each specific aggregate. It was found that the surface texture resulting from erosion of the aggregates during re-texturing not only depends on their mineralogy, petrographic properties, differential wear, but, above all, mainly depends on the percentage of the soft mineral distribution over the whole matrix of the rock mass. The relationship between different surfacetexture (natural and re-textured) and their new PSV (after treatment) of aggregates is also evaluated. © 2010 WIT Press.