Study the use of reclaimed asphalt pavement (RAP) with foamed bitumen in Hong Kong

The primary objectives of this research were to investigate laboratory properties of the foamed asphalt mixes (FA mixes) which contains reclaimed asphalt pavement (RAP) materials and are stabilized by foamed bitumen. In this research, two bitumens (Shell 60 and Shell 100) and two RAP materials (RAP#1 and RAP#2) were selected, and four RAP contents (0%, 20%, 40%, 60%) were considered in mix design and property investigation (including permanent deformation, fatigue and moisture susceptibility). Bitumen foamability under 140 combined testing conditions for Shell 60 bitumen and Shell 100 bitumen, including the foaming properties and decay functions, were comprehensively studied. Permanent deformation of FA mixes was evaluated in laboratory by repeated load axial creep (dynamic creep) test. As well as the ultimate strain, the creep strain slope (CSS) and secant creep stiffness modulus (SCSM) were initially used to investigate the susceptibility of FA mixes to permanent deformation. The indirect tensile fatigue test (ITFT) was firstly used to test FA mixes. Fatigue lives between FA mixes and the hot-rolled mixes were compared, characteristic of the fatigue failure and materials' effects on fatigue properties were analyzed, nonlinear characteristic of FA mix was discussed. Moisture susceptibilities of FA mixes were firstly and comprehensively studied. The soaked indirect tensile strength (ITS) test, the soaked dynamic creep test, the soaked ITFT test, and the freeze-thaw ITFT test were conducted in order to investigate and evaluate the moisture susceptibilities of FA mixes to permanent deformation, ITS and fatigue under the moisture conditions.; From tests and evaluations of permanent deformation, fatigue and moisture susceptibility of FA mixes presented in this study, it can be found FA mixes stabilized by the harder bitumen (e.g. Shell 60) and containing the less aged RAP materials (e.g. RAP#1) have better engineering properties and can be recommended as road base layer under the heavy moisture condition in southern China. Group D has the best overall properties, which contains 60% RAP#1 and is stabilized with 3% Shell 60.