scholarly journals CARBONIZATION OF CONCRETE AND CORROSION OF REINFORCEMENT OF REINFORCED CONCRETE STRUCTURES OF UNDERGROUND SEWERAGE SYSTEMS

2021 ◽  
pp. 47-56
Author(s):  
Valeriy Makarenko ◽  
Volodymyr Gots ◽  
Tetiana Khomutetska ◽  
Yulia Makarenko ◽  
Tetiana Arhatenko ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Diffusion Processes ◽  
Concrete Structures ◽  
Corrosion Damage ◽  
Exposure Period ◽  
Chloride Ions ◽  
Reinforced Concrete Structures ◽  
Term Operation ◽  
Nace Solution

The process of carbonization of concrete with different ratio of water to cement (W/C) was studied, and the influence of the environment on corrosion damage of reinforced concrete reinforcement was studied. The results of the study of carbonization of concrete on specially prepared model samples of concrete with a size of 250x250x250 mm with an exposure period in NACE solution for 500 days without external load are presented. Measurements of corrosion damage of reinforcing rods, which were placed inside concrete cubes, were performed. The method of estimating the amount of carbonization of concrete and corrosion of reinforcement is described in detail in known scientific papers. The obtained data testify to the active carbonization of concrete during the whole exposure period of the samples in NACE solution, however, concrete prepared at the ratio W/C = 0.5 and 0.6 is particularly significant in terms of carbonization intensity. Concrete with a ratio of W/C = 0.7 is less susceptible to damage. Moreover, a similar trend is observed for corrosion of fittings. This is due to the fact that the increase of the aqueous medium in the concrete mass facilitates diffusion processes of delivery to the reactive zone of chemically aggressive ingredients such as carbon dioxide, chloride ions, hydrogen, sulfur, sulfate ions, various types of bacteria and the like. The kinetics of concrete carbonization and corrosion of reinforcing bars in chemically aggressive NACE medium depending on the exposure period of the samples in the model solution was experimentally studied. It is established that with the increase of the water-cement ratio W/C from 0.5 to 0.7, the depth of carbonization and the layer thickness of corrosion products increase sharply. The flooding of the surface layers of the reinforcement and their strong embrittlement in the process of long-term operation of the reinforcement in the structure of reinforced concrete, which causes a decrease in crack resistance in general of reinforced concrete structures. The degradation of reinforcing steel during long-term operation in aggressive environments, which leads to premature corrosion damage to the reinforcement with subsequent destruction of the structure, was investigated experimentally with the involvement of high-precision metallographic equipment.

scholarly journals Investigation of the relationship between the strength limit and the long time fatigue of steel reinforcements of reinforced concrete structures

2021 ◽  
pp. 28-40
Author(s):  
Denys Chernyshev ◽  
Yulia Makarenko ◽  
Tetiana Khomutetska ◽  
Valeriy Makarenko
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Hydrogen Content ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Reinforcing Steel ◽  
Term Operation ◽  
Strength Limit

The results of experimental studies have shown a strong effect of diffusion hydrogen on the static and cyclic parameters of crack resistance of reinforcing steel. It was found that with increasing flooding, especially when the hydrogen content exceeds 5 cm3/100g, both static strength and long-term strength (fatigue) decrease sharply. Moreover, these areas of hydrogen solution in reinforcing steel are characterized by a viscous nature of fracture, while for heavily flooded reinforcement (from 5 to 12 cm3/100g) is characterized by brittle fracture by the mechanism of microcracking in the hardened (martensite or troostite structure). The analysis of the obtained experimental results allowed to determine the optimal hydrogen content in the reinforcing steel (3…5 cm3/100g), the excess of which can cause a decrease in the crack resistance of the reinforcement during long-term operation, especially in corrosive environments. The mechanism of hydrogen influence on crack resistance of metal at static and alternating loading which consists in diffusion and dislocation movement of hydrogen in structure of a reinforcing core that as a result that causes strong flooding of steel and its embrittlement is offered. It is established that carbon and low-alloy sieves, which are characterized by ferritic-pearlitic and sorbitol structure provide high resistance, especially to long-term fatigue, and the transition to steels with a structure of martensite or tempered (transient structure of bainite) structure of bainite sharply reduces reinforcing steel, which makes it impossible to use in the manufacture of reinforcement involved in reinforced concrete structures designed for long-term operation (more than 50…60 years). Thus, the obtained diagram can be recommended to designers of reinforced concrete structures for hydraulic purposes, as it greatly facilitates the reasonable choice of reinforcement in the development of reinforced concrete structures for responsible and long-term use.

scholarly journals The electrochemical performance and modification mechanism of the corrosion inhibitor on concrete

2021 ◽  
Vol 28 (1) ◽  
pp. 352-562
Author(s):  
Meiyan Hang ◽  
Minghui Jiang ◽  
Junwei Xu ◽  
Teng Cheng ◽  
Hao Wang ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Electrochemical Performance ◽  
Corrosion Inhibitor ◽  
Electrode Potential ◽  
Concrete Structures ◽  
Corrosion Damage ◽  
Chloride Ions ◽  
Reinforced Concrete Structures ◽  
Chloride Corrosion ◽  
Chloride Environment

Abstract The purpose of this study was to solve the chloride corrosion damage problems of the rebar in reinforced concrete structures under the chloride environment. The effects of 1.0% triethanolamine (abbreviated as 1.0% TEA), 1.0% Ca(NO2)2, and 0.5% TEA + 0.5% Ca(NO2)2 (abbreviated as 1.0% composite corrosion inhibitor) on the electrochemical performance and modification mechanism of the mortar specimens were investigated by combining macro experiment and microanalysis. The results showed that the electrode potential of the rebar was effectively improved by incorporating the 1.0% composite corrosion inhibitor. This composite corrosion inhibitor displayed the ability to stabilize the electrode potential of the rebar; it also formed a passive film on the surfaces of the rebar, protected the rebar from chloride attack, and achieved satisfactory electrochemical performance. In addition, it could also effectively improve the strength of the mortar specimens and possessed the strong ability to bind chloride ions, thus signifying that it could promote cement hydration and accelerate the formation of cement to form AFt crystals. Therefore, the results of this investigation confirmed that this composite corrosion inhibitor could be effectively used in practical engineering to prevent the corrosion of reinforced concrete structures.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

scholarly journals Experimental study of the influence of crack width due to corrosion behaviour using different measurement methods and different exposures

2019 ◽  
Vol 289 ◽  
pp. 08005
Author(s):  
Martin Schneider ◽  
Georg Gardener
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Corrosion Behaviour ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Chloride Ions ◽  
Reinforced Concrete Structures ◽  
Reinforcing Steel ◽  
Surface Corrosion ◽  
Potential Mapping

Corrosion of reinforcing steel has a great influence in reducing the lifetime of concrete structures; Carbonation of the concrete pore solution causes surface corrosion on the steel and diffusion of chloride ions through the capillary system of the concrete cover causes pitting corrosion on the steel surface. Corrosion of metals is highly dependent on the environmental conditions. Exposure to chloride ions can be critical to the service life of reinforced concrete structures. The durability of reinforced concrete structures exposed to deicing salt or marine environments can be affected by impact of chloride ions. Detection methods for the rate of corrosion of non-destructive and destructive procedures were analysed. The potential mapping applied on the concrete surface was discussed as a standard method for corrosion detection and will be explained in detail including the application boundaries of the method. It is assumed that the corrosion behaviour of reinforcing steel depends on crack widths. To analyse that, 8 coated and 8 uncoated test samples with different concrete strength classes were used. The concrete objects were exposed to a 3% sodium chloride solution. The corrosion behaviour of reinforcing steel is analysed by using potential mapping with different reference electrodes (Ag/AgCl and Cu/CuSO4). The results show a significant correlation between crack size and protection system on the surface. The maximum crack width with a low indication of corrosion was found to be 0.1 mm.

scholarly journals Long-Term Efficiency of Two Organic Corrosion Inhibitors for Reinforced Concrete

2010 ◽  
Vol 636-637 ◽  
pp. 1059-1064 ◽  
Author(s):  
E.V. Pereira ◽  
R.B. Figueira ◽  
Manuela M. Salta ◽  
I.T.E. Fonseca
Keyword(s):  
Reinforced Concrete ◽  
Environmental Conditions ◽  
Corrosion Inhibitors ◽  
Electrochemical Techniques ◽  
Concrete Structures ◽  
Concrete Slabs ◽  
Reinforced Concrete Structures ◽  
Reinforcement Corrosion ◽  
Organic Corrosion Inhibitors

In this paper the efficiency of two organic corrosion inhibitors, a migratory and an admixture inhibitor, was evaluated by electrochemical techniques in solutions simulating the interstitial electrolyte of concrete and on concrete slabs exposed to natural environmental conditions over a five-year period. From obtained results, the usefulness of the two products is discussed aiming its application in new structures to prevent chlorides induced corrosion and as a curative method for repairing reinforced concrete structures contaminated with chlorides and affected by reinforcement corrosion.

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