Performance of cold recycling materials with foamed bitumen and increasing percentage of reclaimed asphalt pavement

Abstract

The increasing use of bitumen-stabilised materials (BSMs) in the world and especially in Southern Africa necessitates further research into the fundamental properties and behaviour of BSMs. In particular, bitumen stabilisation is increasingly being used to rehabilitate base layers of pavements incorporating thick asphalt layers, resulting in higher percentages of reclaimed asphalt pavement (RAP) in the mixes. There is a significant need for improved understanding of these materials, which is the main objective of the study being undertaken. The extended knowledge gained from this research is intended to improve current mix design and structural design practices. The project's aim is to investigate the feasibility and suitability of producing BSMs that include RAP with relatively high blending ratios of recycled graded crushed stone. In this study, the RAP used in each mix design contains materials with relatively fresh binder. The proportions range from 100:0 to 0:100 of graded crushed stone: RAP. Tri-axial tests at different temperatures are carried out to determine shear properties, resilient modulus and permanent deformation behaviour of the mix. The findings show that the RAP type and percentage influence the rutting resistance, indirect tensile strength (ITS) and moisture susceptibility of the BSMs. A portion of this study is dedicated to the characterisation of the permanent deformation behaviour and to the moisture damage simulation.