Developments in Rapid Set Lean Concrete Subbase

The technology and practice for single shift high strength concrete base replacement, mainly at night, using rapid set concrete has been established in Australia for ten years. Since 2017 this technology has now been adapted and extended to developing a rapid set lean concrete and related registered mixes. This has arisen from a need in recent years to not only replace the upper pavement layer alone, be it concrete, asphalt or unbound material, but the lower pavement layer as well. This material is being used in as a subbase for either deep asphalt or concrete. This paper describes the development, laboratory testing, registering of mixes of this material, related field practice and site coordination in replacing both the lower and upper pavement layers in the constraint of single shift operations often at night. Relevant applications are in works such as carried out in widening, replacing old concrete bases constructed before 1970 without substantial subbases or other improvement works associated with the NSW Sydney Region “Pinch Point Projects”.