Characterization of the shape and size of coarse aggregates by photogrammetry for the design of self-compacting concretes

Geometrical characteristics of coarse aggregates have a direct influence on the rheological properties of self-compacting concretes, with and without fiber reinforcement. In particular, their shape and size are related to their maximum particle packing fraction and their intrinsic viscosity. These parameters intervene in the analytical equation of Krieger and Dougherty, used to obtain the plastic viscosity of fresh concrete as a suspension of particles. However, traditional characterization methods of aggregates have limitations in providing the information necessary to determine them. In this article, photogrammetry is used to define with precision the main particle dimensions of three types of coarse aggregate. It is demonstrated how their morphological characterization can be done by a simple procedure of image processing of the orthophoto of a sample of the aggregates. The provided measurements make it possible to estimate the intrinsic viscosity through the circularity of particles. The results of the size distribution of their minor axis are found to reproduce the granulometric curve of the sieving method. These distributions are used to determine the maximum packing fraction for which, the approximation of different available empirical formulas are also discussed regarding the roundness or angularity of the aggregates. • Precise and simple geometrical characterization of aggregates by photogrammetry. • Direct measurements on non-distorted orthophotographs by digital image analysis. • Size distribution of particle minor axis approaches the sieving granulometry curve. • Angularity in crushed aggregates increases the intrinsic viscosity. • Rounded aggregates reach higher maximum packing fraction values.