Investigation of fatigue performance of asphalt mixtures and FAM mixes with high recycled asphalt material contents

Abstract Using a high content of recycled asphalt material, including reclaimed asphalt pavement (RAP) or recycled asphalt shingles (RAS), can be economically and environmentally beneficial. However, aged binder in RAP/RAS is a main concern for fatigue cracking resistance, therefore a reliable and efficient performance-related test for evaluating the effect of RAP/RAS on pavement performance is critical for the best use of these materials. In this study, four types of asphalt mixtures with various RAP/RAS contents higher than 20% were sampled from Southern California after different times at high temperature in the silo. To investigate the fatigue performance of these mixtures, four-point beam (4PB) fatigue testing was performed on full asphalt mixtures, and the linear amplitude sweep (LAS) testing was applied to their corresponding fine aggregate matrix (FAM) mixes. Testing results from FAM mixes have been analyzed within the viscoelastic continuum damage (VECD) framework. The relationships between fatigue life and strain level have been established for FAM mixes and full mixtures separately. The LAS testing results were compared among the FAM mixes with the same type of asphalt material but with different silo hours, which shows a good agreement with the observations from the 4PB testing results from full mixtures. Analyses of fatigue performance of both FAM mixes and full mixtures indicate that fatigue life decreases with the increase of RAP content, as expected, and that silo time shows an important effect. Finally, a strong linear correlation has been found between the strain value at failure of LAS tests of FAM mixes and the strain value at one million cycles to failure predicted from 4PB tests of full mixtures. This indicates that LAS fatigue testing on FAM mixes could predict the fatigue performance of asphalt materials containing high contents of RAP/RAS and potentially be developed as a surrogate performance-related test for asphalt mix design and/or QC/QA.