Multiple slag/lime blends have been used in the road stabilisation industry for multiple decades, mainly on the east coast of Australia. Common slag/lime blend proportions are 85/15, 70/30, 60/40 and 50/50. These blends are frequently applied in the rehabilitation and recycling of existing pavement base course materials for strengthening purposes.
Selection of the most appropriate slag/lime blend in the mix design phase of a project, for a given material type does not have a documented process. Empirical evidence supports the notion that selection of one slag/lime blend over another in the mix design phase is based largely on experience rather than on engineering principles.
There were three objectives associated with this research. They were:
- Quantification of which slag/lime blend is the most appropriate to select for a given source material, based on achieving an optimal strength outcome.
- Provision of documented selection criteria for practitioners to use and reference.
- Provide a basis for Austroads to incorporate the outcomes of this work into AGPT4D, specifically Table 2.4, which provides guidance for preliminary binder selection, but does not provide direction regarding the various slag/lime blends.
An experimental laboratory testing program was established where materials with differing properties were mixed with the slag/lime blends at three application rates (2%, 4% and 6%). Two source basecourse materials from NSW and VIC formed the foundation of all the trials. These were blended with two clays at varying proportions to generate materials with plasticity indexes ranging from 5 to 20. 168 UCS mix design trials were carried out.
This research work generated a framework to optimise a stabilisation mix design trial so that asset owners could benefit from having the lowest quantity of binder, whilst still achieving design requirements.