Spatial distribution characteristics of ellipsoidal coarse aggregates in concrete considering wall effect

In this work, an improved analytic algorithm was developed for generation of a random packing model of ellipsoidal coarse aggregates, which took the wall effect of concrete into consideration. The area fraction curve of aggregate obtained from the model was used to represent its spatial distribution characteristics, and the effects of aggregate volume fraction, aspect ratio, maximum (D-m) and minimum (D-0) equivalent diameters on the distribution characteristics were evaluated. The results demonstrate that the area fraction of aggregate first increases, then decreases and finally stabilizes with increasing distance from the boundary. The area fraction in the stable section (S-v) is slightly larger than the volume fraction regardless of aggregate aspect ratio and diameter. S-v increases as the aggregate volume fraction and diameter increase, or the aggregate becomes more spherical. The thickness of the wall effect layer (T-w) increases with increasing D-m , but does not vary with the volume fraction or aspect ratio. Empirical models for predicting T-w and S-v were proposed, indicating that T-w is almost 1.02 times larger than D-m. S-v can be accurately calculated using two equations for aspect ratios greater and smaller than unity, respectively.

Automated summary

An improved analytic algorithm was developed for generating a random packing model of ellipsoidal coarse aggregates considering the wall effect of concrete. The area fraction curve of the aggregate obtained from the model was used to represent its spatial distribution characteristics, and the effects of aggregate volume fraction, aspect ratio, and diameters on the distribution characteristics were evaluated.