Concrete meso-structure characteristics and mechanical property research with numerical methods

•Fractal theory is introduced as a representative index of concrete meso-structure.•The average fractal dimension increases with the size increases.•The whole fractal dimension decreases with the size increases.•Maximum bearing capacity rises with aggregate volume fraction and specimen size.•Nominal strength rises with aggregate volume, but declines with specimen size.

Concrete meso-structure significantly affects its mechanical property, as crack generally starts and develops basically along the interface between aggregate and mortar on the meso-scale. The cracking path is highly dependent on the interface structure, the main component of concrete meso-structure. Since the interface is formed due to aggregate distributing in mortar mix, the relation between aggregate surface area and interface perimeter could be considered as a representative index of concrete meso-structure. As it is too complicated to adopt traditional methods to represent this relation, in order to better understanding the influence of meso-structure change on mechanical property, fractal theory is introduced to explore the relationship, with the main focus on the characteristics of the concrete meso-structure and its influence on mechanical property. Results show that the specimen size has great impact on meso-structure and mechanical property, while the influence of aggregate volume fraction can be neglected. It is more obvious in larger specimen size that aggregate volume fraction increase could contribute a lot to bearing capacity improving and whole stress level descending. Besides, aggregate volume fraction increase could improve the local cracking stress, but reduce the cracking strain, resulting in cracking brittleness.