Corrosion Of Steel Reinforcement In Concrete Research Articles

BASIC METHODS OF MONITORING OF CORROSION PROCESSES OF CEMENT STRUCTURES AND THEIR IMPLEMENTATION FOR PROJECTING OF POSSIBLE MINERALOGICAL CHANGES IN MATRIX COMPOSITION: REVIEW

Long time service of concrete constructions is accompanied by continuous impact of environment on its structural integrity and capability to carry project capacity of constructions. This influences are able to change not only chemical composition of cement matrix but itself activates corrosion processes that have place to occur on the joints of metal rebar and cement matrix in reinforced concrete (RC). Chemical initiation in the reinforced concrete begins due to the migration of water with parts of molecular oxygen in the thickness of concrete via porous structure of material. The same can be said about the injected compounds of either SO4 2- or Clcomponents that both can be present either in environment or concrete itself due to the modifications of slurry. Such occurrences usually accompanied by changes of pH of the environment that is crucial for the electrolytic environment to appear. Therefore, the process of the reduction of water/ proton may begin at rebar surface wich is the cause not only of the reinforced concrete rebar corrosion but also are reason of accelerated cement matrix degradation. Also, must be noted, that steel corrosion in RC accompanied by changes in current flow. Thus, by understanding the chemical processes and changes that occur in cement matrix of concrete and basics of steel corrosion initiation under the influence of aggressive solutions, the list of non-destructive methods of monitoring (NDM) based on electrical methods of monitoring are reviewed. Different approaches using electrical methods of corrosion monitoring has shown that the use of any of the technics either measurements of the corrosion potential or concrete resistivity or polarization resistance provides different results in mapping of areas with high corrosion risks, monitoring of the heterogeneity of concrete and insights on transport phenomena (e.g. water and salts ingress) in the material. Moreover, advances in potential monitoring without connection to the rebar as non-destructive measurements have shown their effectiveness. Nevertheless, colligation of the results of both numerical and NDM methods is necessary for assortment the results to provide a better data of the worktime of RC structures.

Signal-Based Acoustic Emission Clustering for Differentiation of Damage Sources in Corroding Reinforced Concrete Beams

Corrosion in reinforced concrete (RC) structures is a major durability issue that requires attention in terms of monitoring, in order to assess the degraded condition and reduce financial costs for maintenance and repair. The acoustic emission (AE) technique has been found to be useful to monitor damage due to steel corrosion in RC. However, further development of monitoring protocols is still necessary towards on-site application. In this paper, a hierarchical clustering algorithm based on cross-correlation is developed and applied to automatically distinguish damage sources during the corrosion process. The algorithm is verified on dummy samples and corroding RC prisms. It is able to distinguish two clusters of which the first one containing AE signals due to corrosion, absorption, hydration, and micro-cracking, and the second one AE signals due to macro-cracking. Electromagnetic interference can be distinguished as a third cluster and filtered subsequently. Due to overlapping characteristics, further differentiation of the first cluster is not possible. Afterwards, the algorithm is scaled up to two sets of RC beams, one set with a uniform corrosion zone, and the other set with a local corrosion zone. In addition, on this sample scale, the algorithm is able to successfully differentiate macro-cracking from corrosion and micro-cracking. It can therefore serve as an additional tool to assess the extent of corrosion-induced damage.

Stress distribution in thick‐walled cylinder due to non‐uniform radial pressure on the example of reinforcement corrosion in concrete

AbstractThis paper presents an analytical solution to the non‐uniform pressure on thick‐walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non‐uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non‐uniform pressure distributions. The results show that the corrosion‐induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non‐uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion‐induced stresses in concrete.

Improved numerical model for steel reinforcement corrosion in concrete considering influences of temperature and relative humidity

An improved numerical model for steel reinforcement corrosion in concrete was developed to investigate the influences of temperature and relative humidity on process control and corrosion rate of steel reinforcement in concrete. In order to overcome the limitations of current numerical corrosion models which oversimplify the activation overpotential, the influences of both forward and reverse electrode reactions on the activation overpotential were considered based on the original formulation of the Butler-Volmer equation. Meanwhile, the influences of temperature and relative humidity on the kinetic parameters of corrosion and the properties of concrete pore solution were considered simultaneously. Moreover, the applicability and efficiency of the proposed numerical model for steel reinforcement corrosion were verified by comparing with current empirical prediction models as well as available experimental data of both artificially accelerated and natural exposure corrosion tests. Finally, the influences of temperature and relative humidity on process control and corrosion rate of steel reinforcement in concrete were investigated comprehensively. Furthermore, the influences of temperature, water-to-cement ratio, concrete cover depth, and chloride content on the critical relative humidity were also discussed.

Non-Destructive Evaluation for Corrosion Monitoring in Concrete: A Review and Capability of Acoustic Emission Technique.

Corrosion of reinforced concrete (RC) structures has been one of the major causes of structural failure. Early detection of the corrosion process could help limit the location and the extent of necessary repairs or replacement, as well as reduce the cost associated with rehabilitation work. Non-destructive testing (NDT) methods have been found to be useful for in-situ evaluation of steel corrosion in RC, where the effect of steel corrosion and the integrity of the concrete structure can be assessed effectively. A complementary study of NDT methods for the investigation of corrosion is presented here. In this paper, acoustic emission (AE) effectively detects the corrosion of concrete structures at an early stage. The capability of the AE technique to detect corrosion occurring in real-time makes it a strong candidate for serving as an efficient NDT method, giving it an advantage over other NDT methods.

C10H18N2Na2O10 inhibition and adsorption mechanism on concrete steel-reinforcement corrosion in corrosive environments

C10H18N2Na2O10 (ethylenediaminetetra-acetic acid disodium salt) inhibition and adsorption mechanism on the corrosion of steel-reinforcement corrosion in concrete immersed in corrosive environments were investigated in this paper. For this, seven different concentrations ranging from 0% to 0.667% C10H18N2Na2O10 per weight of cement were admixed in steel-reinforced concretes immersed in saline and in acidic sulphate test-media and these were monitored using electrochemical techniques. Statistical analyses of the scatter of measured data from these, as per ASTM G16-95 R04, showed that C10H18N2Na2O10>0% admixtures portrayed excellent efficiency at inhibiting steel-reinforcement corrosion in the saline environment. However, attaining comparably high inhibition of steel-reinforcement corrosion in concrete immersed in the acidic sulphate environment exhibited greater dependency on high C10H18N2Na2O10 admixture concentration in the steel-reinforced concretes. Different models of adsorption isotherms bear indications of chemical adsorption, chemisorptions, as the prevalent adsorption mechanism of C10H18N2Na2O10 on steel-reinforcement in both of the corrosive environments.

Review of Physical Based Monitoring Techniques for Condition Assessment of Corrosion in Reinforced Concrete

Monitoring the condition of steel corrosion in reinforced concrete (RC) is imperative for structural durability. In the past decades, many electrochemistry based techniques have been developed for monitoring steel corrosion. However, these electrochemistry techniques can only assess steel corrosion through monitoring the surrounding concrete medium. As alternative tools, some physical based techniques have been proposed for accurate condition assessment of steel corrosion through direct measurements on embedded steels. In this paper, some physical based monitoring techniques developed in the last decade for condition assessment of steel corrosion in RC are reviewed. In particular, techniques based on ultrasonic guided wave (UGW) and Fiber Bragg grating (FBG) are emphasized. UGW based technique is first reviewed, including important characters of UGW, corrosion monitoring mechanism and feature extraction, monitoring corrosion induced deboning, pitting, interface roughness, and influence factors. Subsequently, FBG for monitoring corrosion in RC is reviewed. The studies and application of the FBG based corrosion sensor developed by the authors are presented. Other physical techniques for monitoring corrosion in RC are also introduced. Finally, the challenges and future trends in the development of physical based monitoring techniques for condition assessment of steel corrosion in RC are put forward.

Modelling the Performance of Sodium Nitrite and Aniline as Inhibitors in the Corrosion of Steel-reinforced Concrete

The performances of sodium nitrite and aniline inhibitors on the corrosion of concrete steel rebar partially immersed in sodium chloride and sulphuric acid media were investigated in this study. The open circuit potential corrosion monitoring technique was employed for the marine and acidic simulating environments and potential readings were taken in accordance with ASTM C 876. Inhibiting quality and uniformity of the inhibitors were then analyzed using the Weibull probability density distribution as an extreme value statistical modelling approach to study performance effectiveness and predict the most efficient inhibitor in each media. In the statistically analyzed experimental results for each of the inhibitor concentrations employed, (0.679 M) sodium nitrite is identified as exhibiting the best inhibiting quality in sodium chloride while (0.137 M) aniline was predicted as showing the lowest probability of corrosion risk in sulphuric acid medium. The synergetic admixtures employed in the study performed poorly in inhibiting effectiveness compared to the control specimens in the two media considered. The overall probabilistic results predicted preferences of sodium nitrite as inhibitors in the sodium chloride medium simulating saline environments and aniline in sulphuric acidic medium simulating sewage or underground microbial environments

Analysis of carbonation behavior in concrete using neural network algorithm and carbonation modeling

Carbonation on concrete structures in underground sites or metropolitan cities is one of the major causes of steel corrosion in RC (Reinforced Concrete) structures. For quantitative evaluation of carbonation, physico-chemo modeling for reaction with dissolved CO 2 and hydrates is necessary. Amount of hydrates and CO 2 diffusion coefficient play an important role in evaluation of carbonation behavior, however, it is difficult to obtain a various CO 2 diffusion coefficient from experiments due to limited time and cost. In this paper, a numerical technique for carbonation behavior using neural network algorithm and carbonation modeling is developed. To obtain the comparable data set of CO 2 diffusion coefficient, experimental results which were performed previously are analyzed. Mix design components such as cement content, water to cement ratio, and volume of aggregate including exposure condition of relative humidity are selected as neurons. Training of learning for neural network is carried out using back propagation algorithm. The diffusion coefficient of CO 2 from neural network are in good agreement with experimental data considering various conditions such as water to cement ratios (w/c: 0.42, 0.50, and 0.58) and relative humidities (R.H.: 10%, 45%, 75%, and 90%). Furthermore, mercury intrusion porosimetry (MIP) test is also performed to evaluate the change in porosity under carbonation. Finally, the numerical technique which is based on behavior in early-aged concrete such as hydration and pore structure is developed considering CO 2 diffusion coefficient from neural network and changing effect on porosity under carbonation.

Long-term factors influencing the adhesion of metallized zinc to concrete

Metallized zinc cathodic protection often is used to mitigate steel reinforcement corrosion in concrete. The zinc is flame or arc sprayed to the surface of the concrete structure to be protected. The metallized coating should be applied such that its adhesion to concrete is maximized. Factors believed to affect adhesion were investigated for pure zinc and a 85Zn-15Al alloy. On reinforced concrete samples polarized for more than 800 days at three different current densities, adhesion decreased. The reduction increased as a function of time and of the current density applied. When no current was applied, there was a small initial increase of adhesion with time. For the metallized samples that were freeze-thaw cycled, no loss of adhesion was found after 70 cycles.

Laboratory Performance of Zinc Anodes for Impressed Current Cathodic Protection of Reinforced Concrete

Abstract Cathodic protection (CP) is used increasingly to mitigate steel reinforcement corrosion in concrete. The performance of zinc materials as impressed current anodes was evaluated. The anode materials investigated included rolled zinc sheets, metallized zinc, and 85% Zn-15% Al. The circuit resistance and the adhesion of the anodes was monitored with polarization time. Overall performance of arc-sprayed zinc was good. However, its adhesion to the concrete surface slowly decreased as the current density, or the polarization period, increased. Penny blank sheets and metallized 85% Zn-15% Al were found unsuitable as impressed current anodes.