Cracking And Spalling Of Reinforced Concrete Structures Under Simultaneous Loading And Chloride Penetration

It is widely known that the corrosion-induced concrete cracking,propagation of the cracks and the spalling of concrete cover have a large effect on the serviceability and durability of the concrete structures.After the corrosion of the steel bars,corrosion product,which has a larger volume of the original steel,will produce an expansive pressure on the surrounding concrete and leads to concrete cover cracking.The cracks provide paths for rapid ingress of aggressive agents into the reinforcement and accelerate the cracking propagation and even the spalling of concrete cover.However,most studies on the above corrosion-induced deterioration progress of reinforced concrete structures are made based on specimens without loading,which cannot reflect the situation of real structures.This paper focus on the durability deterioration progress of reinforced concrete structures under simultaneous sustained loading and chloride penetration,including the penetration of chloride ions,surface cracking of concrete cover,serious cracking damages on concrete cover and spalling of concrete cover.The main work of this paper can be summarized as follows:(1)A real port located in Zhoushan is investigated.The chloride penetration behavior of the components in the port under simultaneous loading and chloride environment is studied.Specimens are cast together with the port and subject to wetting and drying cycles.The differences in chloride penetration behavior between the components in situ and the specimens,and between the beams and columns in situ,are compared.(2)Surface cracking behaviour of concrete beams under simultaneous loading and chloride-induced steel corrosion is studied.The steel corrosion at surface cracking of beams under simultaneous sustained loading and steel corrosion is measured,and the influence of the stirrups on the crack patterns is discussed.A model,which can consider the influences of CP,loading and stirrups,is proposed to calculate the steel corrosion at the surface cracking.(3)Cracking damage and flexural behaviour of beams under simultaneous loading and chloride-induced steel corrosion are studied.The cracking parameters are investigated and the cracking area is proposed as the representations of the cracking damage.The effects of simultaneous sustained loading and chloride-induced steel corrosion on the cracking damage of beams are discussed.The flexural behaviours of the beams under different loading levels are compared.The mechanism of the corrosion on the longitudinal bars at the areas connecting with the stirrups is discussed.(4)The spalling behaviour of concrete cover of beams under simultaneous sustained loading and chloride-induced steel corrosion is studied.A model,which is to calculate the required moment for the spalling of the concrete cover,is proposed and verified.Factors which may influence the spalling of the concrete cover are discussed.Flexural behaviour of the beams with cover spalled off are measured and compared.A criterion for engineering is proposed to judge whether the concrete cover is spalling or not.