Laboratory Fatigue Characterization of Foamed Bitumen Stabilized Granular Base and Recycled Blends for Pavements

Foamed bitumen stabilization offers a sustainable solution for the construction of new pavements or rehabilitation treatments while also improving the performance of pavement structures. This technique allows up to 100 % of the existing pavements to be used, which will lead to lower use of quarry resources and reduced material transportation cost. In recent years, there have been advances in the use of foamed bitumen stabilized (FBS) pavements. However, prior to the research in this paper, no specific Australian performance relationship had been developed for FBS materials. Also, there was a lack of test procedures specifically developed to manufacture and evaluate the fatigue cracking resistance of FBS conventional and recycled pavement materials. This paper presents the laboratory characterization and development of a fatigue relationship to predict performance of FBS materials. For this purpose, laboratory experiments were undertaken including flexural fatigue, modulus, and strength tests using a four-point bending beam system. Five different host materials were selected for laboratory investigations, including three crushed rocks and two recycled blends incorporating 50 % reclaimed asphalt pavement and 80 % recycled cement-treated crushed rock. A total of eight FBS mixes were tested with varying host materials, foamed bitumen content from 2 to 4 %, and hydrated lime content of 1 or 2 %. A testing procedure to measure and analyze the fatigue performance of FBS granular base and recycled blends was produced. Using the laboratory test results, a specific laboratory fatigue relationship for FBS materials, including recycled blends, is developed. The flexural modulus, flexural strength-to-modulus ratio, and volume of bitumen were found to be major parameters affecting the fatigue life of FBS materials and were consequently employed to develop the predictive model. This research will assist with the subsequent development of a performance-based in-service fatigue model for thickness design of FBS flexible pavements.