Characterization of the microstructure evolution features of various aggregates based on confocal laser scanning microscope

Abstract

To reveal the microscale structural evolution characteristics of aggregates, this study employs confocal laser scanning microscope (CLSM) to conduct the surface microstructures of six aggregates: limestone, basalt, granite, diabase, sandstone, and recycled aggregate (RA). Quantitative analysis was performed on the surface morphology, roughness parameters, and material ratio of the aggregates. The results indicate that the surface features of the aggregates vary with the type and treatment method, and these distinctions may be attributed to variations in diagenetic conditions. In the original state, the surface texture of limestone, basalt, and diabase is relatively minimal, with arithmetic mean height (Ra) distributed between 1.4 μm and 3.5 μm. Conversely, the surface texture of granite, sandstone, and RA is more complex, with Ra distributed between 7.5 μm and 9.5 μm. The roughness indices of basalt, limestone, and diabase show an increasing trend after lime treatment, indicating a more pronounced presence of microscopic peaks and pits. In contrast, all roughness indices of granite, sandstone, and RA exhibit a declining after lime treatment. After polishing, the Ra of the surfaces of the six different aggregates shows varying degrees of reduction. Specifically, Ra decreased by 43.89%, 33.11%, 26.52%, 30.14%, 29.80%, and 38.79% for limestone, basalt, granite, diabase, sandstone, and RA, respectively. Furthermore, the height distribution frequency and material ratio of aggregate surfaces vary with the type and treatment of aggregates. Through grey correlation analysis, the correlation degrees of root mean square slope (Rdq), kurtosis (Rku), and surface texture aspect ratio (Rtr) are 0.9524, 0.9522, and 0.9514, respectively, belonging to hybrid parameter, height parameter, and spatial parameter. This suggests a close relationship between these parameters and the polished stone value (PSV) of the aggregates. These findings offer valuable insights for improving aggregate selection and treatment processes, potentially leading to enhanced durability and performance of construction materials.