Development of guide specifications for recycled aggregates in concrete construction

Abstract

Recycling of construction materials is growing along with the demand for recycled materials. However, this growth is often constrained by specifiers` insufficient knowledge of material performance, low awareness of benefits, and perceived risks. Until recently, in Australia, the use of crushed concrete derived from building demolition has been restricted to granular subbase layers in road pavement construction and drainage, or excavation fill applications. However, improved crusher technologies, rubble screening and aggregate washing, and tighter regulation of the recycling industry, have contributed to significant improvements in the quality of recycled concrete products. Consumer acceptability of recycled materials, however, largely depends on products being technically suitable, cost competitive and meeting environmental impact requirements. This paper discusses the proposed Guide specification document which will cover existing technical information and potential uses of recycled concrete and masonry waste into a structured format, required for specification guidelines. This includes information on recycled material properties and performance, and examines technical and market considerations of construction and demolition (C a. D) waste recycling, based on field trials of premix recycled concrete. Different sources of aggregate batches are assessed in relation to existing Australian Standards for natural aggregates, in particular AS 1141, to establish conformance of recycled products. The proposed Guide specification document will provide engineers with product specification information and the tools required for conventional design with graded recycled C a. D waste material