ABSTRACT
The source rocks which are currently used to provide crushed products for use in the Melbourne Region are: basalt, acid volcanics, hornfels, granitic rocks, scoria, and sedimentary rocks. Hard rock products can be subdivided into two broad categories – 'specified' and 'non-specified'. If a material is not durable, the crushed particles may break down or disintegrate significantly due to the alteration and subsequent decomposition of the mineral components within the rock. The placement and performance characteristics of a crushed product are related to the size distribution and shape of the component particles. Modification of the properties of crushed rock products can be achieved by the addition of stabilising agents such as Portland cement, hydrated or quick lime, bituminous materials, pozzolan with lime or cement and certain chemicals. The terminology used by different specifying authorities to describe source rock quality or to identify a crushed product often differs from that traditionally used by the quarrying industry.
