Damage analysis of semi-flexible pavement material under axial compression test based on acoustic emission technique

Semi-flexible pavement (SFP) material has been promoted to apply in pavement engineering mainly for its excellent performance in rutting resistance. But its mechanical behavior is complicated due to its heterogeneity and interlocking structure. According to the present study, the damage process of SFP (with and without fiber), as well as its porous asphalt (PA) matrix, under uniaxial compression test was detected employing acoustic emission (AE) technique. The heterogeneity and the interlocking effect were varied by changing the matrix porosity and the gradation, respectively. The stress-strain curves reveal that cement grouting could decrease the material's failure strain distinctly, while the addition of fiber made no effect on the results. Nevertheless, both the cement grouting and the addition of fiber caused medium and high amplitude (50-65 dB) AE signals during the AE detection. Besides, the Rise Angle (RA) value and energy distribution both illustrate that there was increasing trend in the amounts of shear cracking in SFP during compression, which was different from asphalt mixtures. And the addition of fiber could restrain the shear cracking to improve the crack resistance. Quantificationally, heterogeneity was characterized by standard deviation of compositions' modulus and an interlocking index was extracted from a modulus micromechanical model to characterize the interlocking effect. The Weibull distribution was adopted to characterize the damage evolution, where the cumulative AE energy was chosen as the damage variable. The result shows the two Weibull parameters m, n had obviously positive correlation with the matrix porosity and the interlocking index, respectively. (C) 2019 Published by Elsevier Ltd.