Research on mechanical performance and micro-structural characteristics for large graded aggregates

Abstract

As a flexible base, large graded aggregates (LGA) have advantages in enhancing pavement performance, including cracking resistance, rutting resistance, and stability. Graduation composition is a crucial factor influencing the performance of the LGA. Therefore, this paper focuses on optimizing the gradation design of the LGA, as well as analyzing its mechanical performance and micro-structural characteristics. Firstly, new gradations of the LGA are optimized based on the Compressible Packing Model (CPM) theory. Then, the compact characteristics, California Bearing Ratio and triaxial compression performance are tested in the laboratory. Meanwhile, the micro-structural characteristics, including coordination numbers, pore and skeleton structural properties, are analyzed using the virtual three-dimensional discrete element specimen and Flat-Joint Contact (FJC) model. The result shows that the CPM for multi-particle systems is used to optimize the design of the LGA. Water content is one of the dominant factors affecting compaction and CBR value. The confining pressure would affect the maximal strength and negative pore pressure of the LGA. The specimen (LGA4) has smaller strain and higher strength and initial cohesion value. The aggregate compositions in different gradations have a significant influence on the structural skeleton and the mechanical performance of the LGA specimen. The coordination number and air void content of the LGA specimen can be evaluated as micro-structural, and the model between coordination number, air void content and CBR value can be established based on statistical analysis. The 13.2 mm and 26.5 mm are the key sieve sizes of the LGA based on the analysis of skeleton structural properties. Based on the research in this paper, the model of mechanical properties and micro-structural parameters is preliminary constructed.