Evaluation of Melter Slag as a Base Course Material

Abstract

The demand for quality natural aggregates for use in pavement construction is approaching a critical state in some parts of New Zealand and other countries around the world. The search for alternative sources of aggregate to minimize the utilization of natural aggregates and provide a high quality substitute has led to slag. The purpose of this study was primarily to examine the engineering, environmental and economical issues relating to the utilization of melter slag as a base course material. New Zealand pavements are predominantly thin-surfaced unbound granular flexible pavements where the main design criterion is the vertical compressive strain at the top of the subgrade imposed by each axle load. Laboratory testing used Repeat Load Triaxial apparatus to determine the resilient modulus and permanent deformation characteristics of the melter slag aggregate and two traditional aggregate materials. The principles of multi-layer elastic theory were then used in a pavement design exercise to determine the engineering and economic benefits of the slag. Additives were also attempted in the laboratory testing to investigate the effect they would have on the melter slag aggregate. Results showed the performance of the slag exceeds that of the natural aggregates in terms of both resilient modulus and permanent deformation characteristics, and the addition of lime and cement binders enhanced these characteristics even further. The study also investigated various environmental and economic factors associated with the use of the slag and concluded that melter slag should be considered as an adequate substitute for traditional premium aggregates in road construction.