In-situ micro-characteristics of fiber at the mortar transition zone in asphalt mixtures

Abstract

Due to certain differences in physical and chemical properties of fibers used, there will be various defects in the internal structure of the resulted mixture from a microscopic perspective. The establishment of correlation between the microstructure characteristics and road performance of asphalt mixture has certain scientific research value. In this research, the proposed method of Resin Impregnated Mixture Slices was successfully used for the in-situ micromorphology, chemical heterogeneity and micro-mechanical properties investigation of lignin fiber, polypropylene (PP) fiber and polyester (PET) fiber at the mortar transition zone in asphalt mixtures. The box dimension presented by Fluorescence Microscope (FM) images indicates the most uniform distribution of polyester fibers. It is possible to trace methoxy group and ester group as an indicator on lignin fiber and polyester fiber in the thermodynamic distribution images of Attenuated Total internal Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). And it was found that the fibers mainly concentrated in the inner region of asphalt mortar. In the testing mortar region of lignin, polypropylene and polyester fibers by Atomic Force Microscope-Quantitative Nano Mechanical (AFM-QNM), DMT-modulus in the areas containing fibers is 2.0 ∼ 18GPa, 1.0 ∼ 2.5GPa and 2.5 ∼ 5.0GPa, adhesion ranges from 50 ∼ 75nN, 20 ∼ 35nN, 30 ∼ 60nN, and the Dissipation values are 5.0 ∼ 15KeV, 0.5 ∼ 3.5KeV, 3.5 ∼ 7.0KeV, respectively. The mechanical properties of PP fiber modified asphalt mixture are considerably 0.5 ∼ 1.0 time lower than those of other samples due to the low-density and weak mechanical properties.