Recent Australian Experience with In Situ Stabilization

Abstract

For reasons of climate and economy, Australia’s roads are typically of light construction. However, new challenges are emerging as the primary road network nears completion and the volume, mass, and tire pressures of road freight vehicles increase. In 1986, Austroads issued their “Guide to Stabilisation in Roadworks” and, since that time, a great deal of research has been conducted in Australia to improve the in situ stabilization processes from the point of view not only of pavement thickness design but also of construction and rehabilitation practice. In situ pavement recycling by incorporating a cementitious binding agent has long been recognized as an economical way to strengthen pavements. The main problems have been the use of thin layers combined with short working times, resulting in high roughness and subsequent delamination of layers, pumping of fines, and excessive cracking. However, the recent development of deep-lift recycling equipment and specialized binder spreaders, together with the more ready availability of a range of slow-setting binders (granulated slag, fly ash, and lime) and high-performance compaction equipment, have allowed the development of deep-lift stabilization techniques. A brief background of Australia’s roads and recent developments in the use of in situ stabilization in Australia are presented, and recent tests with the accelerated loading facility to assess the suitability of bitumen/cement and slag/lime blends, the latter incorporated in both thin (200 mm) lifts and thick (400 mm) lifts, and the impact of this research on practice, are summarized.