Process And Modeling Of Concrete Cover-cracking Caused By Corner Located Rebar Corrosion

The research on the corrosion cracking process of reinforced concrete has a significant meaning for the accurate prediction of structure service life and maintenance or repair of concrete structure. The process and modeling of corrosion cracking has been studied by many scholars. However, most previous researches were focused on the rebar located in the central concrete, while the serial researches on corner located rebar were relatively deficient. Due to the differences of boundary conditions between corner and center located rebar, the corrosion laws are also different. In this paper, focused on the corner located rebar, the corrosion cracking process of reinforced concrete members is analyzed. Considering the different cover thickness of corner located rebar, the distribution rules of corrosion products around the rebar and the development rules of concrete surface cracks are summarized, and the corrosion cracking model of corner located rebar is established. The main research works are as follows.(1) Reinforced concrete specimens which are corroded in artificial environment are investigated. The distribution of corrosion products around the rebar is observed by using optical microscope. The time-varying laws of corrosion products distribution and the influence of different cover thickness of corner located rebar is analyzed. The result can provide a basis to characterize the corrosion cracking process of corner located rebar.(2) The development of cracks on concrete surface is monitoring by using crack observation instrument. The rules of crack width variation with time and corrosion rate are studied. The cracking time and crack development rate is analyzed considering the influence of different cover thickness of corner located rebar. The distribution of corrosion products within the crack is studied and the three forms of cracking development is proposed.(3) According to the non-uniform corrosion characteristics and the variation of circumferential cover thickness around the rebar, considering the actual state of corrosion products distribution, the variable stiffness board is used to simulate the variable concrete cover thickness. The corrosion cracking models of mid-located rebar and corner located rebar are established based on the method of elastic mechanics. The border issue of corner located rebar is solved in corrosion process.