Utilisation of aggregate materials in road construction and bulk fill

In the UK, at present, the majority of aggregate materials, for all construction applications, are obtained from primary resources such as crushed rock and sand and gravel. Material extraction results in many adverse environmental impacts and utilisation consumes a finite natural resource. In the UK we also produce large quantities of waste and by-product materials, from industrial and domestic activities, that require management or disposal. To maintain levels of development and construction but reduce the utilisation of primary aggregates, two principal options are available: optimise the use of primary materials or utilise alternative materials. This paper summarises ongoing research at the University of Nottingham, UK, which addresses both of these issues for aggregates used in road construction and bulk fill. Predictions of the in situ performance of alternative and conventional aggregate materials have been investigated as regards both mechanical and environmental loading. Performance based mechanical specifications have been developed using a repeated load triaxial test and indirect tensile test for assessing untreated and treated materials. For the investigation of environmental performance, a tank-leaching test and lysimeter trials have been utilised. In addition, the CoURAgE project (a European-wide research collaboration, centred at Nottingham) has investigated possibilities for optimising the use of aggregate materials in the unbound layers of roads. Aspects of that project cover the importance of good design and construction techniques and, thus, are also focused on minimising the required quantity of natural aggregate material.