TECHNOLOGY OF SLAG UTILIZATION IN HIGHWAY CONSTRUCTION

Research and applied utilization activities for the increased use of ferrous and nonferrous slags in civil and highway construction are presented. The overall use of blast furnace slag is relatively well known for a range of highway construction applications from granular base to supplementary cementitious materials. In contrast to blast furnace slag, which is volumetrically stable and straightforward in its construction uses, steel slag contains hydratable oxides that can result in volumetric instability that must be dealt with through appropriate steel slag aging, testing and quality control to ensure its appropriate use in highway construction. Particular care must be taken to prevent potential steel slag expansive behaviour in confined applications. Quality requirements and guidelines on steel slag expansivity to further the use of appropriate quality steel slags, with demonstrated acceptable performance, in aggregate and cementitious applications are outlined. There is a full range of proven civil and highway construction uses - from aggregate to cementitious materials - for copper, nickel and phosphorus nonferrous slag. The use of air-cooled nickel slag is presented, based mainly on practical highway experience and in the Dominican Republic with ferronickel slag. It has been shown in the laboratory, and more importantly during highway construction, that air-cooled, crushed nickel slag can be an excellent aggregate in granular base, engineered fill and hot-mix asphalt. There is a good potential for increased ground, granulated copper and nickel slags use as supplementary cementitious materials that is being developed, which takes advantage of the 'latent energy' content. The scope of a new technical text on the technology of slag utilization is reflected throughout to provide a practical context for the highway engineer.