Durability Of Reinforced Concrete Structures Research Articles

Machine learning algorithms in the environmental corrosion evaluation of reinforced concrete structures - A review

Accurate corrosion assessment of reinforced concrete (RC) structures is expected to improve the service life and durability of structures. However, traditional evaluation methods rely on simple regression and assumption models, which are easy to lead to unreliable evaluation results. The time-consuming and complex calculations in corrosion assessment are particularly suitable for machine learning (ML) and have already been deeply affected by the application of existing ML algorithms. The review analyzes recent ML methods for corrosion assessment of RC structures. These algorithms have recently had a significant impact on the estimation of the corrosion process, significant mechanical properties and durability of RC structures. In addition, some challenges that have emerged in corrosion evaluation and could be solved by ML algorithm are discussed critically. Through the detailed analysis of the challenges and future directions, researchers and engineers related industry will gain vital insight on the sustainable durability design of RC structures.

Corrosion Effects on Durability of RC Structures

The corrosion of steel reinforcement is recognized as one of the most important degradation problems in reinforced concrete (RC) structures [...]

Dynamic bond stress‐slip model for smooth bars in concrete under transverse tensile‐compressive stresses

AbstractMost old‐type reinforced concrete (RC) buildings reinforced with smooth bars are often subjected to dynamic loads and the structural joints are usually in a complex tensile‐compressive stress state. To evaluate the safety and durability of RC structures with the finite element method, the dynamic bond performance of smooth bars in concrete under transverse tensile‐compressive stresses needs to be well understood. Therefore, an experimental study including 248 pull‐out specimens is performed to characterize the dynamic bond properties of smooth bars in concrete under transverse tensile‐compressive stresses. Based on the experimental results and other data, the effects of various factors on the peak bond stress, the slip at the peak bond stress, and the shape of the softening branch are analyzed in detail. With two bond parameters and one shape parameter, a simple bond stress‐slip model is proposed. Through comparison with experimental results, the validity of the model is verified.

A review on performance‐based specifications toward concrete durability

AbstractConcrete is the most popular and widely used construction material due to its relatively low cost, versatility, and adaptability. Recent past experiences show that the reinforced concrete (RC) structures deteriorating prior to the expected service life when exposing to aggressive chloride or carbonation‐induced environments. This is because of the general assumption that if the strength criteria are satisfactory, the concrete would be sufficiently durable. This assumption does not take into account the variability in concrete resulting from the actual concreting practices, such as placement, consolidation, finishing, and curing. In other words, concrete in the specimens cast for compressive strength bear little resemblance to the concrete in the actual structure. This paper presents a detailed review on the developments that are taking place globally toward the performance‐based specifications for achieving the long‐term durability of RC structures. Also, based on the in‐house experimental studies and available knowledge, a durability performance criterion is suggested for structures exposed to chloride or carbonation‐induced environments toward enhancing the service life.

Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods

The review article investigated failure, design issues, repair and strengthening of reinforced concrete (RC) silos, primarily in agricultural set-ups. The durability of RC structures was influenced by the nature of the bulk solids, materials used in the reinforcement of the structures. Traditionally, high-grade steel has been used in silo wall reinforcement because it is affordable and readily available. However, it is susceptible to corrosion. In contrast, fiber-reinforced polymers (FRP) have better mechanical properties (tensile strength, elastic modulus, and Poisson’s ratio) and are not corroded. Additionally, there are limited scalable and facile methods for commercial production. The low ductility elevates the risk of brittle fracture in external pre-stressing concrete repair/strengthening. Beyond the material factors, the existing silo design codes such as BS EN 1991-4:2006, Australian Standard AS 3774-1996, and American Society of Agricultural Engineers ANSI/ASAE EP433 DEC1988 (R2011), and American Concrete Institute ACI 313-97 are limited by simplified characterization of loading/unloading scenarios and exclusion of specific hopper geometries and configurations. The funnel and mass flow scenarios and accumulation of bulk materials contribute to silo failure. In brief, the present repair/strengthening strategies (external pre-stressing, insertion/removal of inserts, shear columns, and FRPs alternatives to steel) do not adequately address the diverse variables that elevate the risk of material failure.

Durability of RC Structures against Carbonation-Induced Corrosion under the Impact of Climate Change

The factors associated with concrete carbonation can be classified in three major categories of environmental factors, concrete's internal-structural factors, and construction-operation conditions. Climate change is expected to cause gradual change in many primary environmental factors, which may accelerate reinforcement corrosion in reinforced concrete (RC) structures. Studies show that CO2 concentration in the atmosphere may rise from 379 ppm in 2005 to 1,000 ppm in 2100. Hence, adoption of suitable measures to protect exposed RC members against carbonation-induced corrosion is essential for countering the future environmental effects which, in turn, requires further investigation on the effect of critical structural factors, such as water-cement ratio and cement content in the concrete mix design, and construction-operation factors, such as concrete cover depth and surface protection, on the durability of RC members. In this study, these factors were investigated through Monte Carlo simulation. The results showed that slight adjustments in some structural and operational factors can significantly reduce the risk of corrosion initiation and ultimately improve the durability of concrete members against corrosion. The effect of each parameter on the probability of corrosion initiation during the design life of a RC structure was analyzed and interpreted using numerical examples.

Corrosion performance of mild steel and epoxy coated rebar in concrete under simulated harsh environment

PurposeThe purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides.Design/methodology/approachThe blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure.FindingsMild steel BB showed a high corrosion current density of 1.24 µA/ cm2 in Tafel plots and a very low polarization resistance of 4.5 kΩ cm2 in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm2 is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl− solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions.Originality/valueThe corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.

Effect of Aggregate of Electric Arc Furnace Slag on Durability of Reinforced Concrete Structures in Chloride Environment (Part I)

Durability of reinforced concrete structures including electric arc furnace slag as aggregate in chloride environment is a significant topic to enable their performance stable in their service period. In this study, chloride penetration in recycled concretes including gradation of fine and coarse aggregate that is electric arc furnace (EAF) slag is tested and compared with that of reference concrete including just natural aggregate gradation. To observe chloride penetration effect, concrete samples are exposed to a saline attack firstly; and then, total chloride content and chloride penetration profiles are tested. The Part I of the study argues the effect of aggregate of electric arc furnace slag on durability of reinforced concrete structures in chloride environment in the Introduction and Background section and the Materials and Methods section. Second part of the study is going to present the Results and Discussions section and the Conclusions section. Both part have the Abstract section and Reference section differently each other.

Effect of Aggregate of Electric Arc Furnace Slag on Durability of Reinforced Concrete Structures in Chloride Environment (Part II)

Second part of the study presented argues the effect of aggregate of electric arc furnace slag on durability of reinforced concrete structures in chloride environment based on the Results and Discussions section and the Conclusions section. Both part have the Abstract section and Reference section differently each other. Results display that the EAF slag aggregate is favorable because of increasing the durability against chloride damage and of stoping the penetration of free chloride measured with method of the colorimetric test as well as wet chemical analysis. However, the study also answers that the wet chemical analysis is still the best method to measure the penetration of free chloride in concretes.

RBSM-BASED ANALYSIS OF CRACK CONTROL EFFECTIVENESS OF POLYMER CONCRETE OVERLAY FOR REINFORCED CONCRETE STRUCTURES

This paper presents a method for numerical analysis of the effectiveness of using the engineered cementitious composites with polyvinyl alcohol fibers for concrete cover repairs. The numerical analysis utilizes a nonlinear three-dimensional Rigid-Body-Spring Model which has strong capabilities to assess the crack width and crack patterns in the concrete structures. The applicability of the analysis is demonstrated on a reinforced concrete frame corner which is subjected to both the action of the positive and the negative bending moment. The effectiveness of the added overlays is shown in a comparison of the frame corner with and without the engineer cementitious composite overlays. The added overlays reduce the crack width and thus extend durability of rein-forced concrete structures. DOI: http://dx.doi.org/10.5755/j01.mech.23.6.18931

Structural Monitoring Techniques for the Largest Excavation Section Subsea Tunnel: Xiamen Xiang’an Subsea Tunnel

AbstractBecause of the particular and complex engineering environment of subsea tunnels, effective monitoring techniques should be adopted to ensure the operation security of subsea tunnels. Also, monitoring the condition of steel corrosion in reinforced concrete (RC) of subsea tunnels is especially imperative for ensuring structural serviceability and durability of RC structures. In this paper, monitoring the largest excavation section subsea tunnel, Xiamen Xiang’an Subsea Tunnel, is studied. It includes the layout of monitoring sections and monitoring contents, selection of monitoring locations, and the monitoring instruments. The design of corrosion monitoring system is especially focused on because of its complexity. Both commercial corrosion sensors and developed corrosion sensors based on electrochemical and fiber Bragg grating techniques, respectively, are adopted. The arrangement of corrosion monitoring section and locations as well as the installations of sensors and the establishment of corrosio...

Advances of Monitoring Corrosion in Reinforced Concrete Based on UGW

Monitoring the condition of steel corrosion in reinforced concrete (RC) is imperative for ensuring structural serviceability and durability of RC structures. The techniques based on ultrasonic guided wave (UGW) gain more and more popularities as they have many advantages for monitoring corrosion in reinforced concrete. In this paper, UGW based monitoring techniques in the past decade are reviewed, including corrosion monitoring mechanism and feature extraction, monitoring corrosion induced deboning, monitoring pitting corrosion, monitoring corrosion induced interface roughness. Finally, the challenges and future trends in the development of UGW based monitoring techniques for condition assessment of corrosion inreinforced concrete are put forward in this paper.

Analytical modeling for corrosion-induced cover cracking of corrosive reinforced concrete structures

An analytical model for predicting the corrosion-induced cracking of concrete cover of reinforced concrete (RC) structures was developed. The effects of influence factors such as practical initial defects, corrosion rate, strength and elastic modulus of concrete on the corrosion-induced cracking of concrete cover were investigated. It was found that the size of practical initial defects was the most effective factor. Therefore, improving the compactness of concrete is an effective way to improve the durability of RC structures. It was also demonstrated that the accelerated corrosion tests may be unfavorable in the study of the relationship between cracking time and crack width.

Influence of Cracks on the Durability of RC Structures

To carry out maintenance and assessment of reinforced concrete (RC) structures, a good understanding of the effect of the change in bond behaviour of reinforcement during service life is essential. Steel reinforcement is subjected to corrosion due to carbonation and chloride attack. The former ordinarily induces uniform corrosion, the latter induces generally localised corrosion at cracks level. The existence of cracks and the crack width affect the starting points of corrosion, as indicated by the results of the exposure test carried out by Shiessl et al.[1]. Corresponding techniques, such as non-destructive in-situ testing for concrete cover thickness, permeability and the positions of the reinforcing bars, are helpful to model the real behaviour. Cracked portion around the tensile reinforcement in a flexural member can be considered to be equivalent to a concrete member having a single reinforcement subjected to pull-out force at both ends. In this paper a damage process model is proposed based on slip crack propagation in order to evaluate the effective load capacity.

A Method for the Evaluation of the Durability of Reinforced-Concrete Structures from the Viewpoint of Fracture Mechanics

We develop a method for the evaluation of the durability of reinforced-concrete beams based on the concepts of fracture mechanics. A model of fracture of cracked structures taking into account the process of creep of concrete is constructed. We deduce dependences describing the influence of crack opening displacement on the growth of its length under long-term loading and present formulas for the crack-mouth opening displacement under short-term and long-term loads. The development of a periodic system of cracks is described for different types of concrete subjected to long-term loading.

Consideraciones sobre la repasivación de las estructuras corroídas de hormigón

An analysis is made of the responses of clean and precorroed steel electrodes in Ca(OH) 2 saturated solutions and in cement mortar, using gravimetric, metallographic and electrochemical techniques, essentially polarisation resistance measurements. The paper aims to answer some important questions about the corrosion of reinforced concrete structures (RCS) which, though seemingly elementary, continue to arouse controversy in scientific, technical and economic circles, such as the following: What corrosion rates are dangerous in RCS? What concrete resistivities guarantee sufficient durability of RCS? Is it possible to detain corrosion once it has begun? Can corroded RCS be repassivated? Are electrochemical RCS rehabilitation methods efficient, and if so, when? The results obtained indicate that electrochemical chloride removal and realkalisation cannot repassivate heavily corroded steel surfaces, however they can be effective methods to prevent corrosion provided they are used before the transition from the passive state to the active one occurs. If applied to late, are useless for this purpose.