Alkali activation of milled slag and its implications for the use of unmilled slag as a road stabiliser

Abstract

Paper presented at the 20th Annual South African Transport Conference 16 - 20 July 2001 "Meeting the transport challenges in Southern Africa", CSIR International Convention Centre, Pretoria, South Africa.

Un-milled GBS is widely used in France for stabilising gravels and sands and this stabilisation method is referred to as Grave-Laitier (GL) meaning gravel-slag. If sand is stabilised it is called Sable Laitier (sand-slag). In this process the GBS is mixed with the gravel or sand in a mixing installation (much like a concrete mixer). Because GBS will not hydrate in its own, but needs to be activated, lime and gypsum are added during the mixing process. Because un-milled slag has a gradation like sand and is used in relatively high percentages as a stabiliser (10 to 20%), the GBS not only provides chemical, but also a mechanical stabilisation. This stabilisation method has a number of advantages over conventional stabilisation using Ordinary Portland Cement (OPC) or bitumen.