ASSESSMENT OF SECONDARY MATERIALS FOR PAVEMENT CONSTRUCTION - TECHNICAL AND ENVIRONMENTAL ASPECTS

Current research at the University of Nottingham to enable the use of secondary materials in road construction covers technical aspects, mec hanical properties of waste materials and the environmental implicatio ns of their use. Materials studied are minestone, china clay sand, sla te waste, pulverised fuel ash and furnace bottom ash. The laboratory p rogramme set up for this research and the methodologies suggested for the study of the properties of these materials are presented. The test methods currently used to select pavement aggregates are presented al ong with current methods for the assessment of the environmental impac t of secondary aggregates. The potential of the secondary aggregates i s assessed within the current technical and environmental procedures p reviously presented. Two new methodologies are presented, one for the mechanical examination of secondary aggregates and one for the environ mental assessment. The mechanical assessment encompasses conventional characterisation and classification tests on both unbound and lightly treated pavement materials, and fundamental tests such as repeated loa d triaxial tests (RLTT) and repeated load indirect tensile tests (RLIT T). Some sample results are presented, suggesting the feasibility and adequacy of this methodology for material discrimination, and evaluati on of mechanical properties for design purposes. The environmental ass essment indicates how the leaching concentration of contaminants from intensive testing can be used as the first step in assessing the envir onmental acceptability of a secondary material, and the means of deter mining a more realistic measure of in situ performance is discussed. T he advantages and advancements of the presented methodologies over the basic and inappropriate techniques currently used to assess the suita bility of secondary aggregates for use as pavement construction materi als are discussed. Copyright (C) 1996 Elsevier Science Ltd