Visualization of the three-dimensional structure and stress field of aggregated concrete materials through 3D printing and frozen-stress techniques

Characterization of the three-dimensional stress field of concrete materials is crucial to understanding their mechanical properties and failure mechanisms, but their hidden and complex meso-scale structure makes physically extracting and visualizing this information intractable. This paper therefore presents a new approach that uses 3D printed models based on X-ray microfocus computed tomography (CT) imaging of a concrete sample to replicate its complex aggregate structure in a transparent matrix. The associated three-dimensional stress field is visually characterized at mesoscale through uniaxial compression tests and photoelastic techniques that incorporate a three-dimensional frozen-stress test to analyse the effects of randomly distributed aggregates. These results are used to validate the accuracy of simulated data created using the finite element method, which allows a comparison to be made between two-dimensional and three-dimensional heterogeneous aggregated models. The study indicates that meso-heterogeneity has more influence on the stress state of localized areas than the entire field. Compared to 2D structures, 3D structures possess a lower stress concentration due to the lateral inertial confinement effect. The difference in stress field between the two structure types is therefore attributable to a combination of structural heterogeneity and lateral inertial confinement.