Experimental Study On Degradation Of Basic Mechanical Properties Of Corroded Reinforced Concrete

Reinforcement corrosion and cracking of concrete will appear when it suffers from erosion of chlorine ion. Corrosion of reinforcement steel will result in decreased cross-sectional area, reduction of load- carrying capacity and cracking of concrete protective layer. In addition, corrosion of steel will affect the bond-slip between reinforcement and concrete. Moreover, corrosion of stirrups will weaken the lateral confinement on concrete and rebar, and thus decrease the structure bearing capacity. Previous studies have indicated that the corrosion of steel has a great influence on the basic mechanical properties of reinforced concrete structures. However, only a few literatures are available which considered the effects of concrete strength on basic mechanical properties of corroded reinforced concrete. Further studies to identify these effects are urgently needed.In this thesis, the author study on the two aspects. The first was experimental study of bond-slip performance of corroded rebar. The test has been designed that made two batches different concrete strength cubic concrete specimens(120 specimens). After the specimen electricity accelerated corrosion test, research the relations of corrosion specimen concrete cover cracking and rebar corrosion rates in the different concrete strength. Through drawing pull out loading and cyclic loading tests, to research the effect of bond-slip properties of reinforcement concrete for rebar corrosion in different concrete strength. The results show that: the higher the concrete strength will lead to specimen surface cracking more obvious for steel corrosion. With the increase of rebar corrosion rates, the maximum bond stress has the trend of first increasing and then decreasing. When the steel corrosion rates is greater than 3.5%, the higher the strength of concrete will result greater decline rate of maximum bond stress. Moreover, the strength of concrete has a great influence on the residual bond stress, initial stiffness and energy dissipation of the rebar corroded specimens. The second was to study the axial compressive performance confined concrete of corroded stirrups, a total of 15 stirrups confined concrete cylindrical specimens were made and then axial compressive test. Combined with the existing data, to research the influence of reinforced concrete cylindrical specimen axial compression performance with different concrete strength when stirrup has corroded. The results show that: when the stirrup corrosion rate is more than 15%, the stirrup corrosion cross-sectional area substantially reduced and seriously reduce the restriction ability of stirrups. In addition, with the increase of stirrup corrosion rate, cylindrical specimen maximum load, ductility coefficient and initial tangent stiffness has decreased, while the compressive strength more lower lead to the greater decline rate of maximum load, ductility coefficient and initial tangent stiffness. With the increase of stirrup corrosion rate, the energy consumption of cylindrical specimen is more and more small. When the stirrup corrosion rate of specimen is 20.65%, the stirrup energy decreased 57.98%, compared with non corroded cylindrical specimens.