Modeling coarse aggregate distribution in interfacial zone of new–old concrete in precast concrete structures

Abstract

AbstractThere are a large number of interfacial zones of new–old concrete in precast concrete structures, and the wall effect causes the reduction of coarse aggregate in the interfacial zones, which leads to the weaker physical, mechanical and durability properties of this part. In the present paper, some new–old concrete specimens with different chiseled depths at the interfaces were made to simulate the wet joints of precast concrete structures. The distribution characteristics of the coarse aggregate volume fraction in the interfacial zones of new–old concrete specimens were obtained by DIP (Digital Image Processing) technology. The results show that the distribution of the coarse aggregate volume fraction in the interfacial zones is similar to a positive V‐shape (no chiseling) or partial V‐shape (chiseled interface), and is generally lower than that of the noumenons of new and old concrete (constant values). With the increase of chiseled depth, the valley point (i.e., the minimum value) of the distribution curve of coarse aggregate volume fraction in the interfacial zone will move upwards and offset toward the old concrete. When the offset reaches 2 mm from the interface, it remains stable. The multiple irregular cone‐shape small pits on the actual chiseled surface are abstracted into a single bulging slope pit, and the area ratio of new–old concrete on the cross section within the chiseled range is derived. On this basis, the model of the coarse aggregate volume fraction in the interfacial zone varied with the distance from the interface is proposed.