Chapter 47 Hydraulically bound mixtures for local roads

Whether clay, industrial by-product, recycled product or processed natural aggregate, hydraulic binders are unique in their versatility to treat such materials to produce durable, sustainable and cost-effective pavement layers. This chapter describes how this is achieved with hydraulic binders to produce materials with the mechanical properties and performance attributes for use from capping layers to bases. The guidance presented here, which is in accord with European standards, covers treatment using the full range of hydraulic combinations based on air-cooled steel slag, cement, coal fly ash, granulated blast-furnace slag and lime. The resulting materials are known as hydraulically bound mixtures (HBM). HBM in their various forms have been used in road, airfield, port and other pavement construction for over 50 years. Here, however, the focus is on pavements for local roads, whether new or for alignment improvement, whether for their rehabilitation or trench reinstatement, and the chapter describes the behaviour of HBM and their applicability and design for local roads.