Comparison of 2-D and 3-D shape analysis of concrete aggregate fines from VSI crushing

Abstract

The shape of concrete aggregate fine particles (fines), with particle sizes between 3 µm and 250 µm, produced by high-speed vertical shaft impact (VSI) crushing of 10 different rock types from quarries in Norway, has been studied by both dynamic image analysis (DIA), which is a two-dimensional (2-D) method, and X-ray computed microtomography (µCT) coupled with spherical harmonic (SH) analysis, which is a threedimensional (3-D) method. The 3-D µCT results serve as a check on the 2-D DIA results. The intent was to evaluate the applicability of the 2-D DIA method to extract shape parameters that could represent the actual 3-D shape of the VSI crushed concrete aggregate particles. The results show that the 2-D DIA method has problems correctly measuring the shape of particles smaller than about 40 µm due to too large of a pixel size and possibly some particle flocculation. The findings of this paper show, however, that if a large enough number of particles are analysed by the 2-D DIA method, a good but limited indication of the actual 3-D shape of the irregular crushed aggregate fines larger than 40 µm can be acquired and used for simple quality control in hard rock quarries.