Abstract
In the case of existing prestressed concrete structures, information about the actual state of prestressing is an important basis for determining their load-carrying capacity, as well as remaining service lifetime. This is even more important in the case of existing prestressed concrete bridges, which are exposed to a more aggressive environment than the other prestressed concrete structures. The level of prestressing is affected and reduced by prestress losses at a given time. In calculating the internal forces and stresses, required for the assessment of the Ultimate Limit State and the Serviceability Limit State, it is necessary to know not only the prestressing level but also the cross-sectional area of the prestressing steel (wire, strand or cable), which can change in time due to corrosion. In practice, in the case of the pre-tensioned concrete members, it has often happened in the past that cable ducts have been grouted only partially, or not at all, due to poor grouting technology. Experts did not realize what this could cause in the future—the penetration of water with aggressive agents directly into the cable duct and consequently corrosion of the prestressing steel, which means not increased protection of the steel, but rather acceleration of degradation. On the other hand, in many cases, corrosion also occurs in ducts that are not grouted and no water has entered them. This paper deals with this phenomenon—the formation of corrosion of prestressing steel in cable ducts in ungrouted ducts due to moisture. This problem was investigated experimentally and numerically in the simulation program ESP-r. Experimental measurements and numerical simulations have shown that the water vapor condenses in the cable ducts, which can subsequently cause corrosion of the prestressing steel.
Highlights
Deterioration of structural materials is an inevitable and challenging fact in the field of engineering
Corrosion can be defined as an electrochemical phenomenon, in which steel essentially returns to its original form—ore—by creating iron oxides on its surfaces [12]
All engineering materials will return to their original state, the forms which are found in nature [14]
Summary
Deterioration of structural materials is an inevitable and challenging fact in the field of engineering. One particular form of deterioration—corrosion of prestressing steel—affects the load-carrying capacity and remaining service lifetime of structures [1,2,3,4,5,6] This kind of deterioration is difficult to detect through the regular inspection and belongs among the most critical types of damage in prestressing tendons (wires, strands, or cables) [7,8,9,10,11]. Corrosion can be defined as an electrochemical phenomenon, in which steel essentially returns to its original form—ore—by creating iron oxides on its surfaces [12]. It means that the corrosion is physicochemical reaction between a metal and the environment. Four fundamental components are important for corrosion to take place—an anodic reaction, a cathodic reaction, an electrolyte and an electronic path [14]
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