Degree Name

Doctor of Philosophy


Department of Civil and Mining Engineering


The following research focuses on the effect of the basecourse properties on the performance of slag pavements.

Slag, a by-product of iron/steel manufacturing, has been utilised as a pavement material in Australia for at least the last two decades. Its performance has been noted by various road building authorities. Slag materials are being judged for their effectiveness by the same criteria used for natural materials. These types of verifications resulted limited use of slag. One reason for its limited use is a lack of understanding of slag properties in the pavements and, in particular, as a basecourse material.

To address this issue, a wide spectrum of basecourse attributes were investigated with respect to the properties of slag materials. Four promising test blends from a number of preliminary slag blends were selected for further investigation. The use of these blends in the field and the availability of feedback on their performance justified their selection.

In this study, the slag properties' influence on pavement performance, evaluation of their numerical values, applicability of test methods, correlation of laboratory and field results, as well as the reasons for inclusion of a particular property in the current material supply specification, were investigated.

The investigations led to identification of major basecourse properties for which further research was required. These properties were: Anisotropy, Healing, Elastic Modulus, Permeability, Plasticity, Shrinkage, Unconfined Compressive Strength and Wet - Dry Strength. The above properties were further investigated by reviewing current Australian Standards and their test methods, where applicable, to obtain their numerical values. Wherever necessary, modifications were suggested for particular test methods. In some instances computer analysis was carried out.

After completing laboratory and related field investigations, the research work was then focused on the field performance of slag pavements. Two case studies were considered. The first was based on a review of performance of existing slag pavements constructed since 1970 in the lllawarra Region, South Coast of NSW , Australia. The second case study involved one of the test blends, selected for this research, which was subsequently used by Federal Airport Corporation as a pavement material for runway and taxiways of the Parallel Runway Project, Sydney. The behaviour of slag material during preliminary trials and then later at the construction stage and through field performance highlighted many important basecourse properties of the slag test blend affecting its performance. The consistency of physical and chemical properties of slag was also reviewed in this case study.

The analysis was focused on applicability of the test method, the co-relation of laboratory and field results and their influence on field performance. The analysis of results included integration of laboratory/field test results and conclusions derived from the case studies with regard to the basecourse properties.

The investigations led to many conclusions and recommendations such as: 1. Wet - Dry Strength property is not applicable to slag materials. 2. Consistent chemical and physical properties in the specified ranges are observed for slag materials. 3. Elastic Modulus for slag pavement basecourse is greater than 5000 Mpa and at times can exceed 10000 M P a depending on blend. 4. Cracking in slag pavements does not necessarily represent a failure of the pavement. 5. At a comparative cost, slag pavements offer longer pavement life than pavements made of traditionally used materials. 6. Slag materials can be worked in wet conditions and require less compactive effort. 7. Performance based specifications for slag materials and material selection recommendations for the road building authorities, were formulated.