Damage Evolution Study of Modeled Recycled Concrete Based on Orientation of Recycled Aggregate

Abstract:

The modeled recycled concrete containing modeled square aggregates in different directions were applied to study the propagation of cracks at compression loading. The strain distribution and development were analyzed using digital image correlation and the finite element method， and the influence of the direction of aggregates on its damage evolution was investigated. The results show that when the modeled aggregate is placed horizontally， the strain concentration first appears in the interface on both sides of the aggregate. When the aggregate is placed in the direction of 22.5°， the strength and secant modulus are higher than the other two cases， and the strain concentration first propagates at the upper and lower vertices of the aggregate and develops into cracks along the interface on both sides of the aggregate. When the aggregate is placed in the direction of 45°， the upper and lower vertices of the aggregate have the highest strain concentration. Before the load reaches 80% of the peak force， the strain concentration of modeled recycled concrete is lighter than that of modeled normal concrete. For three directions of the aggregate， the strain concentration of modeled recycled concrete is 15%， 32%， and 39% smaller than that of modeled normal concrete. Because the elastic modulus of old mortar is in between the natural aggregate and new mortar， the strain concentration of the modeled recycled concrete is reduced. Based on the research on the influence of the direction of recycled aggregate on its damage evolution， it is proven that the methods of removing tips of aggregates and reducing needle flake aggregates can optimize and modify the recycled aggregates.

Key words:modeled recycled concrete;modeled normal concrete;modeled aggregate;mechanical properties;damage evolution