Multi-scale Evaluation Method To Determine Aggregate Abrasion Resistance For Asphalt Pavement

Asphalt pavement is the prevalent pavement type in China.With the surface course directly bearing traffic load,surface texture properties significantly influence the skid resistance and durability of asphalt pavement.Therefore,it is essential to investigate the wearing of asphalt pavement surface.This study develops a comprehensive evaluation method that is capable to measure surface texture of asphalt pavement at multiple spatial scales.The comprehensive evaluation method consists of a series of experimental and numerical approaches.Experimental approaches include laser scanning,aggregate polishing test,abrasion test,optical profilometer,scanning electron microscope,and X ray diffraction test.Numerical approaches include imaging analysis,reverse modeling,finite element analysis,and molecular dynamics.Utilizing the comprehensive evaluation method,different influencing factors for the skid resistance have been investigated to reveal the wearing mechanism.Analysis results elucidate the wearing mechanism of aggregate texture at different spatial scales,which can improve our understanding of skid resistance performance of asphalt pavement.Major findings in this study are expected to provide theoretical supports for improving pavement design and maintenance planning.(1)At the macroscale,surface texture of asphalt pavement is measured by a laser scanner.Based on the measurement results,reverse modeling is used to establish the three-dimensional pavement surface with actual texture.After that,the surface texture model is input into ANSYS,commercial software for finite element modeling.The finite element model from ANSYS simulates the distribution of contact stress under traffic loading.Based on the stress result and the aggregate fatigue damage theory,the evolution of pavement macrotexture is predicted using FE-SAFE,finite element software for durability analysis.In this way,the fatigue life of pavement texture can be determined.In the macroscale analysis,a three-dimensional characteristic parameter ? is proposed as the ratio between the macrotexture variation and the mean macrotexture depth,in order to quantitatively evaluate the skid resistance of pavement surfaces.(2)At the microscale,three types of aggregate commonly used in Chinese pavements are selected for the Wehner/Schulze test to measure the skid resistance.In the polishing process,the surface texture of aggregates at microscale is captured by an optical surface profilometer.Twelve morphological parameters are used to represent microtexture according to the captured results.A correlation analysis is carried out between the morphology parameters and skid resistance of aggregate.The correlation analysis yields quadratic polynomial regression models to quantify the relationship between microtexture and skid resistance of aggregate.(3)Four types of aggregates that are commonly used in Chinese pavements are tested in the Micro-Deval abrasion test.Aggregates of different abrasion degrees are prepared into specimens to determine the Polishing Stone Value(PSV)and the pendulum slip resistance.Aggregates are comprehensively evaluated to effectively distinguish good ones from fair and poor,and this comprehensive analysis process facilitates aggregate selections.(4)X-ray diffraction is used to analyze the mineral compositions in aggregates.Using results from the polishing test and abrasion test of aggregate,the relationship between aggregate mineral composition and aggregate performance is analyzed based on the grey correlation theory.Analysis results show that the content of calcium-and magnesium-compositions in aggregates are closely correlated to both skid resistance and abrasion resistance.That is to say that aggregates containing more calcium-and magnesium-compositions are more likely to be more resistant to skid and abrasion.(5)Based on the X-ray diffraction test results of aggregates,molecular dynamics models of major minerals,such as quartz,are established in LAMMPS,open-source software for molecular dynamics modeling.The wearing between quartz crystals and other mineral crystals in the polishing test is simulated in the molecular dynamics model.Simulation results are validated by the tests,demonstrating that mineral abrasions at finer spatial scale are related to aggregate skid resistance at macroscale.Achieved results refined the mechanism of pavement aggregate wear evolution at different scales,and can further promote the existed understanding of skid resistance performance of asphalt pavement,so that to provide theoretical and methodological support for pavement design,construction,maintenance and driving safety.