Corrosion map of zinc in Slovakia

The subject of this research was influence of the environmental parameters, like temperature, humidity and pollutants, on the corrosion rate of the zinc protective coating of the steel structural elements. Zinc is usually used to protect those elements against corrosion. The idea was to study the corrosion of zinc in different parts of Slovak Republic in order to create the so-called corrosion map of the country. The corrosion rate of zinc rcorr was calculated according to standard ISO 9223. Results have shown that both the input parameters, as well as the corrosion rate of zinc, are changing with time

Innovative strengthening of RC columns using a layer of a fibre reinforced concrete

Reinforced concrete structures that are influenced by degradation, overloading, the thawing and freezing cycles, abrasive damage and corrosion of reinforcement, should be repaired or strengthened. Each of those mentioned situations lead to decreasing the load-carrying capacity of the construction. The damage of a structure or its member causes exceeding the serviceability limit states and ultimate limit states. For this reason, for further use of the structures, they have to be strengthened to increase the load-carrying capacity and to extend the remaining lifetime. A new method for strengthening the vertical members, e.g., columns, is using the fibre reinforced concrete layer and its increased tensile strength in comparison to common RC concrete. This article deals with the theoretical design of dimensioning the columns using a layer of fibre concrete around a column (wrapping). In this case, it is necessary to calculate the residual strength of fibre concrete, which is a crucial factor for the tensile strength of the element

Influence of the type of cement and the addition of an air-entraining agent on the effectiveness of concrete cover in the protection of reinforcement against corrosion

The concrete cover is the basic protection of the reinforcement against the influence of external factors that may lead to its corrosion. Its effectiveness depends mainly on the composition of the concrete mix, including the cement used. Depending on external environmental factors that may aggressively affect the structure, various types of cements and concrete admixtures are recommended. The paper presents the results of tests that allow us to assess the effect of the type of cement used and the air-entraining agent on the effectiveness of the concrete cover as a layer protecting the reinforcement against corrosion. In order to initiate the corrosion process, the reinforced concrete specimens were subjected to cycles of freezing and thawing in a sodium chloride solution. The degree of advancement of the corrosion process was investigated using the electrochemical galvanostatic pulse technique. Additionally, the microstructure of specimens taken from the cover was observed under a scanning electron microscope. The research has shown that in the situation of simultaneous action of chloride ions and freezing cycles, in order to effectively protect the reinforcement against corrosion, the application of both blast-furnace slag cement and an air-entraining agent performed the best.Web of Science1416art. no. 465

Measurement of corrosion rates on reinforcement using the field test

Reinforcement corrosion is a phenomenon that affects not only the durability and serviceability of the structure itself but the economy of the countries, as well. In many cases, structures and bridges must be repaired or reconstructed as a result of corrosion of the reinforcement. In extreme cases, when maintenance is neglected, it is necessary to completely replace the structures with new ones, even if their planned service lifetime has not been reached - it is not enough to strengthen them or it is economically inefficient. Corrosion of the reinforcement primarily causes a reduction in the cross-sectional resistance of the load-bearing elements by reducing the cross-sectional area of the reinforcement, which means a reduction in the force in the reinforcement that it transmits. For this reason, it is necessary to know the rate of corrosion over time depending on the environment in which the element is located. The paper is focused on the experimental measurements of corrosion losses due to atmospheric corrosion on reinforcement samples using the field test. As a part of experimental measurements, corrosion rates on reinforcements of four diameters (diameters 6, 10, 14, and 25 mm) of steel for reinforcement, grade B 500B, are monitored at measuring stations and bridges in various aggressive environments.This research was supported by Research Projects No. 1/0623/21 of the Slovak Grant Agency

Experimental verification of real behavior of bridge structures using proof-load tests

The aim of the paper is to point out the inevitability of the proof-load tests for the real and correct behavior of bridge structures in ultimate limit state and maximum allowable deformations in serviceability limit states. It is needed to point to the most consequences of resistance, reliability, durability and lifetime of the bridge structures. Using the proof-load tests for new bridges is prescribed by the Slovak standard STN 73 6209

ANALYSIS OF PROPERTIES OF THE FRP REBAR TO CONCRETE STRUCTURES

The application of the FRP (Fiber Reinforced Polymer) rebar is presented in this paper. The various kinds of fibers, depending on the types of the FRP rebar and types of matrix of FRP are listed. The main tasks of matrix and fibers are specified. The two methods of FRP bars production are explained. The selected physical and mechanical properties of the various types of the FRP rebar are shown and compared. The long-term properties of the FRP rebar, as relaxation and creeping processes, are also introduced. The FRP properties were compared to conventional steel reinforcement properties. Moreover, the typical disadvantages of traditional reinforced concrete, as the susceptibility to corrosion were presented. It is shown that the FRP reinforcement is quite opposite, since it has almost total resistance to corrosion. The corrosion factors, to which the FRP is resistant, are presented and explained

Diagnostic and Analysis of Selected Masonry Railway Bridges on Slovak Railways

The paper presents an overview of the current state of railway masonry arch bridges that are in operation on Slovak Railways. The material of the vault is either stone or brick. It also presents the current possibilities of diagnostics, monitoring and evaluation of failures, the method of measuring selected material characteristics of masonry elements (especially the determination of compressive strength). Within the cooperation of our department and the Research and Development Institute of ŽSR, applications of diagnostic measurements and evaluation of the current state of these bridges are presented on selected bridge structures

Influence of Fatigue Crack Formation and Propagation on Reliability of Steel Members

During the years of bridge exploitation, many degradation processes and external influences attack its structure. Therefore, bridge reliability and durability is decreasing in time. On the other hand, the traffic load remains almost the same or even higher than in the past. However, bridges should not to become the limiting component of communication capacity and traffic reliability. Regarding to reliability, bridges should be assessed from the viewpoint of the Ultimate Limit States (ULS) and Serviceability Limit States (SLS). Within the ULS, cross-sections and members are verified for various types of stressing and their combinations, and also for fatigue at the same time. The cross-sectional verification, e.g., for bending stresses and fatigue, is done independently according to corresponding criteria of the ULS determined for strength verification a fatigue assessment separately. The presented article deals with the steel railway plate girder bridge with bottom member deck, in which there is an effort to prove the effect of the crack in tension bottom flange due to fatigue stressing on the change of bending resistance over time. The analytical calculation was derived and at the same time, the probabilistic approach of the influence of the fatigue crack size on the change of the cross-sectional resistance and reliability over time was used

Influence of Corrosion on Crack Width and Pattern in an RC Beam

AbstractThe paper is concerned with numerical modeling of corrosion of steel reinforcement in the reinforced concrete. The cracking response of the reinforced concrete beams due to the corrosion effect of the steel reinforcement and due to the load effects was analyzed. The effect of corrosion was simulated by the nonlinear numerical analysis with the FEM program using the 3D model