Papers by Keyword: Reinforcement Corrosion

Abstract: In order to determine the inhibitory additives concentration influence degree on the corrosion degradation rate, we studied the anode behavior of steel reinforcement made of steel grade St3 in a 10% solution NaCl with and without the inhibitors additives of various concentrations. As inhibitory additives, nitrates of potassium, sodium, magnesium, calcium and zinc were introduced into the aggressive environment, since they are often introduced into concrete compositions to accelerate their hardening. Polarization curves have been obtained for steel reinforcement in an aggressive environment, allowing the corrosion rate calculation. It was established that the introduction of potassium and zinc nitrates in an amount of 0.5% into an aggressive environment has the greatest effect on the corrosion processes’ inhibition. When nitrates of alkali and alkali-earth metals are introduced into an aggressive environment, the change in the reinforcing bars mass made of St3 steel occurs 7-8 times slower. Increasing the concentration to 1 and 1.5% is shown to be impractical, due to the small difference in the effect on the reinforcing steel anodic dissolution. A study on the effect of combining inhibitory additives on the corrosion resistance of steel reinforcement in a 10% solution NaCl was made. It was found that the combined action of inhibitors is less effective than the single effect of additives on the corrosion rate.

Abstract: The impact-echo method is commonly used for detection of flaws in concrete elements based on the shift in the thickness frequency of a plate-like member. However, there is a need to develop this efficient technique for other applications. This paper investigates the feasibility of using the impact echo-method for identifying corrosion of steel reinforcement in concrete structures. For this purpose, 180 reinforced concrete cubes were cast and tested. The main parameters studied were the amount of recycled aggregate (i.e. 0%, 25%, 50% and 100%), nanosilica (1.5% and 3%) and the steel bar diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. The impact-echo results were correlated against the actual corrosion levels obtained by the mass loss method. The experimental results showed that the response of impact echo in terms of frequency peaks is found to be sensitive to the high and moderate levels of corrosion. However, no clear trend was observed at the initial stage of corrosion. It is demonstrated that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion phenomenon in reinforced concrete structures.

Abstract: The reinforcing steel embedded in concrete is generally protected against corrosion by the high alkalinity (pH = 12.5 to 13.5) of the concrete pore solution. The structural degradation of concrete structures due to reinforcement’s corrosion has an impact on the safety, serviceability and durability of the structure. The corrosion of reinforcements in the construction of a transport infrastructure (especially bridges), parking areas, etc., is primarily initiated by chlorides from de-icing salts. When corrosion is initiated, active corrosion results in a volumetric expansion of the corrosion products around the reinforcing bars against the surrounding concrete. Reinforcement corrosion causes a volume increase due to the oxidation of metallic iron, which is mainly responsible for exerting the expansive radial pressure at the steel–concrete interface and development of hoop tensile stresses in the surrounding concrete. When this tensile stress exceeds the tensile strength of the concrete, cracks are generated. Higher corrosion rates can lead to the cracking and spalling of the concrete cover. Continued corrosion of reinforcement causes a reduction of total loss of bond between concrete and reinforcement.

Abstract: Cover cracking from reinforcement corrosion is one of the major causes of deteriorations in reinforced concrete structure. If the cover cracking time can be predicted, it would be useful for maintenance planning and budget allocation. The objective of this paper was to find the influence of repair materials on concrete cover cracking time. In this study, the corrosion of concrete reinforcement was accelerated by electricity. Using three types of materials, it was found that the cover cracking time of repair mortar was the shortest followed by those of concrete and non-shrink cement grout respectively. In addition, specimens simulating repaired concrete were prepared. The cracking times of the repaired specimens were found to be about the same and were of the same order as those of repair materials only.

Abstract: Reinforcement corrosion can lead to a severe damage in reinforced concrete columns with subsequent loss of bearing capacity. This condition can be deleterious in case of a seismic event. The possibility of repairing and strengthening damaged columns with high performance fiber reinforced concrete (HPFRC) jacketing has been experimentally investigated by some of the authors in previous papers, through full-scale tests on specimens under cyclic loads. The main aim of the intervention was not only to restore the original bearing capacity but also to increase the column durability. In the present paper, a numerical model is developed with the FEM software Diana in order to simulate the cyclic behaviour of corroded r.c. columns reinforced with HPFRC. Particular attention is devoted to the simulation of the corrosion phenomenon and to the strain localization due to the jacket presence. The chemical attack is defined in such a way to account for both the geometrical and mechanical variations of the bar properties. The numerical analyses represent a very useful tool for highlighting the main parameters that have to be considered in evaluating the behaviour of the damaged and then repaired elements. Finally, they constitute a support for the design and, as a consequence, for the reinforcement optimization.

Abstract: Almost all reinforced concrete structures which are exposed to weather effects are threatened by corrosion. The corrosion of steel elements in structures has an influence on lifetime these constructions and adversely affects their properties. However, the steel in concrete structures is protected against corrosion due to the properties of concrete such as high pH or impermeability, but if the concrete is of poor quality and his protective properties are insufficient the corrosion can occur. A problem causes the action of carbon dioxide which has the effect of lowering the pH below the critical value and thereby accelerating the corrosion.Non-destructive methods such as Impact-echo method offer the possibility of easy and quickly detection of initial damage of structure and thus can prevent the occurrence of permanent damage to the whole construction.This article describes the development of corrosion which is caused by carbonation of the concrete and supported by action of chlorides by using Impact-echo method. The paper presents results obtained on the reinforced concrete samples with one steel rod passing through the center. After carbonation concrete the samples were exposed accelerated controlled degradation in aqueous NaCl solution for 4 months.

Abstract: Based on the mechanism of reinforcement corrosion in concrete structures and the experimental measurements of corrosion potential and resistance, this paper investigates the impact of concrete cover thickness and chemical alkalinity on reinforcement corrosion. Experimental results show that the rate of reinforcement corrosion decreases as the thickness of concrete cover of reinforcement increases. Moreover, given no risk of alkali-aggregate reaction, raising the chemical alkalinity of concrete cover helps maintain passivation of reinforcement. Additionally, under general atmospheric conditions, cracks that are not along bars barely affect structural durability if the width of cracks is smaller than its standard limit.

Abstract: Abstract: The paper, by using various electrochemical methods, conducts non-destructive quantitative testing towards currently-used bridges, analyzes reinforcement corrosion characteristics under natural environment, concludes the influencing rule of natural environment on reinforcement corrosion, and reveals differences accelerated simulation environment by contrasting with preliminary laboratory results. The real bridge measurement results show that: weight loss ratio of reinforcement under humid environment can reach a maximum of 33% and a minimum of 18%; while weight loss ratio of reinforcement under dry environment falls between 8%-15%. The actual measurement results also show that: box girder and guard bar coated with waterproof layer help to protect reinforcing bars inside the concrete and effectively reduce the corrosion rate inside reinforcing bars with weight loss ratio around 4-8%. It contrasts the precision of two testing methods and comes to a conclusion that testing precision of linear polarization method is higher than that of impulse current method.

Abstract: This paper analyzes the whole deterioration process of the concrete structural performance caused by reinforcement corrosion, and given the three setting conditions which are corrosion cracking conditions and collapsed condition, and the corresponding performance function for such structural durability limit state. The relevant content can provide a reference for the design of structural durability and related specifications.

Abstract: In order to achieve internal reinforcement of concrete bridges quantitative nondestructive testing, this paper has adopted linear polarization method to test reinforcement passivation in the pore solution of simulated concrete and corrosion current density value in the corrosion process under different external environments and has built calculation model for amount of reinforcement corrosion based on detection signal. That is to say a new idea, which makes the evaluation results more effective, has been put forward to efficiently correspond with reinforcement corrosion ratio with potential signal, and the quantification evaluation for damage of reinforced concrete can be carried directly. It has modified theoretical model and analyzed the error through weightlessness tests. The research result shows that the calculation model after modified can significantly improve the detection accuracy for the actual rate of reinforcement corrosion. CLC: TU528.33 Document code: