Foam bitumen stabilization is a viable alternative to reduce aggregate consumption in New Zealand. An accelerated full-scale experiment on foam bitumen pavements was conducted in the Canterbury Accelerated Pavement Testing Indoor Facility (CAPTIF), as part of a Transit New Zealand research project to study the effects of foam bitumen on unbound granular materials. Six pavement sections were tested. Three were constructed using foam bitumencontents of 1.2%, 1.4% and 2.8% respectively, plus a common active fillercontent of 1.0% cement. Two more pavements were constructed adding cementonly (1.0%), and foam bitumen only (2.2%). In addition, one control section with the untreated unbound material was tested. Strains were collected using a 3D Emu soil strain system installed in each pavement section. Results showed that surface deflections decreased at sections with higher bitumen contents. After the application of 5,710,000 Equivalent Standard Axles(ESAs), the sections stabilized with cement only, bitumen only, and the control section all showed large amounts of rutting. Conversely, little rutting was observed in the three sections stabilized with foam bitumen and 1.0% cement. Water was introduced into these three pavements plus additional accelerated loading, and caused the section with the lowest foam bitumencontent to fail. These results showed that foam bitumen and cement had a significant effect on improving the performance of the materials studied. Material samples taken for Indirect Tensile Strength (ITS) and Repeat LoadTriaxial (RLT) for laboratory tests showed that the ITS test was a good predictor of the pavement performance giving a clear trend, while RLT results were not conclusive.
Abstract