Corrosion Of Steel Bars Research Articles

Three-Dimensional Reconstruction and Damage Localization of Bridge Undersides Based on Close-Range Photography Using UAV

Abstract Damage inspection on the undersides of bridges is an important and challenging part of routine bridge inspections. A method for 3D reconstruction and damage localization of bridge undersides based on close-range photography by UAV and stereo vision combined with deep learning algorithms is proposed, the specific contributions include: (1) proposing a close-range photography method for acquiring high-resolution images from multiple perspectives of the bridge underside by UAVs, serving as the data source for damage analysis; (2) applying a deep learning-assisted segmentation method to optimize the multi-view geometry-based 3D reconstruction method, improving the efficiency of three-dimensional reconstruction, and defining the projection direction from the 3D reconstruction results to obtain ultra-high-resolution panoramic images of the bridge underside; (3) addressing the issue of detecting minor damages in large panoramic images by using a slice-assisted reasoning module and a lightweight convolutional YOLO v8 network to identify exposed steel bars corroded due to concrete damage in the panoramic images, and defining a coordinate system to localize the damages on the bridge underside. The proposed method was applied to damage detection and localization on the underside of a 160m span main span of an in-service concrete bridge. The results demonstrate that the proposed method can quickly and accurately identify exposed steel bar corrosion on the bridge underside and output reports, proving the practicality of the proposed method.

The coupling effect of calcined layered double hydroxides and impressed current cathodic protection system on chloride ion binding and migration of sea sand mortar

Chloride introduced by sea sand and sea water leads to steel bar corrosion. Calcined Layered double hydroxides (CLDH) and impressed current cathodic protection (ICCP) system were used to adsorb chloride ion and control steel bar corrosion in chloride abundant environment. In this research, chloride binding effect of two kinds of CLDH were investigated in simulated concrete pore solution. Besides, chloride absorption capacity and steel bar corrosion resistance of Mg-Al CLDH was explored in mortar. Further, hydration degree of mortar installed ICCP system and migration of ions around the anode and cathode were detected. Results show that Mg-Al CLDH exhibits excellent chloride binding capacity and corrosion resistance. After installing the ICCP system, corrosion of steel bars in mortar mixed Mg-Al CLDH was controlled. And ions in mortar specimen around anode or cathode exhibits migration phenomenon in different degree. A two stage-four step model was established to explain the degradation of hydration products and ion migration in CLDH-ICCP system. Under the ICCP system, Cl− in pore solution increased at early stage and then decreased both around anode and cathode, the increment process was controlled by desorption of Mg-Al CLDH and decreased process was controlled by degradation of hydration products. Therefore, the CLDH-ICCP system was recommended to solve the problem of steel bar corrosion introduced by marine environment.

Flexural reliability of corroded RC beams strengthened with CFRP sheets considering longitudinal corrosion non-uniformity of steel bars

The corrosion of steel bars in RC beams along the longitudinal direction is usually non-uniform, thereby increasing the variabilities of failure mode and flexural behavior of corroded RC beams strengthened by CFRP sheets. This paper analyzed the flexural reliabilities of CFRP sheet-strengthened corroded RC beams, which considered the corrosion non-uniformities of longitudinal steel bars along the beam length. Based on the failure mode-based calculation method and Monte-Carlo simulation, the beams were discretized into a series of units along the beam length and the failure probabilities of the beams were considered as the failure probabilities of the serial units. Meanwhile, the occurrence probabilities of failure modes at bending failure were also studied. Parametric analysis results showed that the occurrence probabilities of failure modes were affected by steel reinforcement corrosion degrees, CFRP strengthening ratios and initial strains at concrete tensile edge. Meanwhile, the longitudinal corrosion non-uniformity could significantly affect the occurrence probabilities of different failure modes and degrade the flexural reliabilities; e.g., for RC beams under third-point bending, when the corrosion degree is 0.3, the predicted reliability index with considering longitudinal corrosion non-uniformity can be 28.3% lower than that without. The proposed reliability calculation method could accurately assess the impacts of longitudinal corrosion non-uniformity on flexural reliabilities and lay a solid foundation for calibrating design factors used in CFRP sheet-based strengthening designs, thereby contributing to both evaluating the safety of existing CFRP sheet-strengthened corroded RC beams and designing the strengthening CFRP sheets for existing corroded RC beams, which improve the safety and maintenance of existing RC structures in corrosive environments.

Experimental Study on the Mechanical Properties of Squat RC Shear Walls with Corrosion Along the Base

In corrosive environments containing chloride and sulfate, the corrosion of steel bars is common along the base of squat RC shear walls (SRCSW) due to problems such as construction quality, concrete stress concentration, local defects, and accumulation of water and corrosive media. In this paper, three SRCSWs are designed and constructed and their mechanical properties assessed. One side of each SRCSW was exposed to a corrosive environment for 70 days, while the other side was subject to the same conditions over different corrosion times (i.e., 0 day, 42 days, and 70 days). Then, the corrosion-induced cracking process, the mechanical properties of SRCSWs corroded along the base, the relationship between the mass loss of total steel bars (MLTSB) in the corroded area and the wall mechanical properties, and the relationship between the average width of corrosion-induced cracks (CICs) and the wall mechanical properties were studied through an accelerated corrosion test and a loading failure test. The results indicate that the area of corrosion-induced cracking on SRCSWs increased with the corrosion time, and the cracking area on the different SRCSWs was approximately identical when the SRCSWs were exposed to the same corrosion time. When the degree of corrosion was different, the loading failure characteristics of the SRCSWs were obviously different, but the failure mode always corresponded to shear failure. The load–displacement curves of the SRCSWs with different degrees of corrosion along the base basically coincided and were linear when the loading was in the elastic stage. Compared to SW-1, the peak load of SW-2 decreased by 4.0%, but that of SW-3 increased by 2.7%. Compared to SW-1, the yield loads of SW-2 and SW-3 decreased by 22.4% and 11.8%, respectively. When the MLTSB increased from 13.05% to 16.71%, the crack, yield, and peak loads of the SRCSWs corroded along the base decreased by 8.8%, 22.4%, and 6.8%, respectively. The cracking, yield, and peak loads of the SRCSWs corroded along the base decreased linearly with the increase in MLTSB and the average width of the CICs, and the corresponding fitting relations were established. The results of this study can serve as a reference for the durability design of SRCSWs in corrosive environments.

Degradation law of bond strength of reinforced concrete with corrosion-induced cracks and machine learning prediction model

During long term operation service, reinforced concrete (RC) structures are subjected to corrosive media such as chloride salts, which results in the degradation of interface bond performance, subsequently reducing the load bearing capacity and service life of the structures. To accurately assess the durability of RC structures in environments such as oceans and salt lakes, this study combines experimental methods with machine learning (ML) techniques to explore the degradation patterns and predictive models of bond performance under chloride salt corrosion. Accordingly, a series of central pull-out tests were conducted based on an electrochemical accelerated-dry-wet cycle corrosion regime to investigate the degradation patterns of bond performance between corroded steel bars and concrete under different corrosion degree and corrosion-induced crack widths. By comparatively analyzing the evolution patterns of cracks and the morphology of the steel bars in reinforced concrete specimens and their failure modes, and integrating the mechanical degradation mechanism with chemical and microscopic corrosion mechanisms, an in-depth analysis of the corrosion-induced degradation patterns at the bond interface was performed. The internal relationships between corrosion degree, corrosion-induced crack width and bond strength were discussed, and the variation patterns of bond strength with corrosion-induced crack width and corrosion degree were explored. Moreover, the bond strength patterns were analyzed from an energy perspective. The results indicate that bond strength and bond energy decrease with an increase in the corrosion-induced crack width of the concrete. Additionally, based on the experimental data from this study, ML predictive models for bond strength were established using corrosion-induced crack width as the control variable. The results show that the ML-based bond strength predictive models fit well with the experimental data, offering higher accuracy and reliability compared to traditional bond strength models. The research findings provide significant theoretical basis and practical guidance for safety assessment, maintenance, reinforcement, and full-life design of corroded RC structures.

Effects of interlayer-modified layered double hydroxides with organic corrosion inhibiting ions on the properties of cement-based materials and reinforcement corrosion in chloride environment

Developing novel, environmentally friendly, and efficient corrosion inhibitors is of great significance for improving the durability of marine concrete against chloride ion erosion. This paper aims to explore the potential of layered double hydroxides (LDHs) as nanocontainers, incorporating organic corrosion inhibitors between LDHs layers to synergistically enhance their effectiveness. In this study, Mg/Al-pAB-LDH was synthesized through the interlayer modification of LDHs with an organic corrosion inhibitor, p-aminobenzoic acid (pAB), employing a calcination-rehydration method. Chloride ion (Cl−) adsorption behavior was quantitatively and qualitatively analyzed and the effect on mortar properties was investigated. The corrosion resistance of steel bars in the mortar was assessed under chloride salt simulated concrete pore solution (SCPs) and chloride salt wet-dry cycles via electrochemical tests and microscopic characterization of Mg/Al-pAB-LDH. The results demonstrate that Mg/Al-pAB-LDH efficiently captures Cl− and releases corrosion-inhibiting ions pAB, with the adsorption process conforming to pseudo-second-order kinetics and Langmuir adsorption isotherm. Mg/Al-pAB-LDH enhances the pore structure of mortar, effectively improving mechanical properties and resistance to chloride ion penetration, with the optimal effect observed at a 4 % addition rate. Mg/Al-pAB-LDH demonstrates outstanding corrosion resistance to steel bars in both SCPs and mortar. In SCPs, it serves as a corrosion inhibitor by adsorbing Cl− and releasing pAB, whereas in mortar, it functions as a corrosion inhibitor by enhancing the physical barrier effect of mortar, adsorbing Cl−, and releasing pAB. This study demonstrates the promising potential of utilizing Mg/Al-pAB-LDH as a novel corrosion inhibitor to mitigate the corrosion of steel bars in marine concrete.

Research on the Fatigue Damage Mechanism of Corroded Steel Bar

Reinforced concrete bridge structures are prone to unpredictable brittle failure under fatigue loads, posing a serious threat to their safety. And its fatigue performance depends on the fatigue performance of the steel bars inside the concrete. At the same time, the corrosive environment in which the bridge structure is located can cause premature corrosion of the steel bars inside the bridge structure, and a certain degree of corrosion can significantly reduce the fatigue life of the steel bars. This article summarizes the current research status of fatigue damage mechanisms of steel bars in both non corroded and corroded states, analyzes the existing problems, and proposes suggestions for further in-depth research.

Contribution of spatially variable pitting corrosion on fatigue life prediction of RC beams

Pitting corrosion induces stress concentration in steel bars, significantly reducing the fatigue life of reinforced concrete (RC) beams. Moreover, spatially variable pitting corrosion can cause fatigue fractures in tensile steel bars at various cross-sections of beams, not just at the mid-span section. This will further increase the failure probability of beams but is rarely considered by existing studies. Thus, this study proposes a fatigue life prediction method for RC beams experiencing spatially variable pitting corrosion. First of all, the spatial variability of pitting corrosion in tensile steel bars in RC beams is simulated through the three-dimensional laser scanning method and the spectral representation method, in which the steel bar diameter, length, distance, corrosion level, and the correlation between corrosion pits are systematically considered. Subsequently, the fatigue crack initiation and propagation of pitting corroded steel bars are modeled based on fracture mechanics. The spatial analysis is then conducted on corroded RC beams until fatigue failure occurs. The proposed prediction method is verified with results from existing references. The findings highlight that neglecting the spatial variability of pitting corrosion leads to an overestimation of the fatigue life of corroded RC beams, especially under uniformly distributed loadings and high corrosion levels. This study provides a reasonable prediction for the lifespan of corroded RC beams.

Photothermal superhydrophobic coating for concrete: Highly effective anti/deicing performance and corrosion resistance

Superhydrophobic concrete is an effective method to prevent corrosion of internal steel bar. However, existing superhydrophobic concrete is difficult to remove the ice on the superhydrophobic concrete surface. Here, we overcame this problem by developing a photothermal superhydrophobic coating for concrete, which obtained from polydimethylsiloxane (PDMS), multi-walled carbon nanotubes (MWCNT) and further superhydrophobicity. This photothermal superhydrophobic coating showed the excellent superhydrophobicity, self-cleaning property, anti-fouling property, and the long anti-icing time. In addition, the ice on the coating would rapidly melt into the water which easily rolled off the surface under the irradiation of infrared light. This coating not only had the good chemical durability and mechanical durability, but also had the corrosion resistance performance. This work will enrich superhydrophobic concrete technology and promote the application of superhydrophobic concrete in practical building.

Behavior of corroded HSC beams repaired by sprayed UHTCC and textile: Experimental study and theoretical analysis

Behaviors of twelve high strength concrete (HSC) beams were studied, including one control specimen, five corroded but non-repaired beams, and six corroded beams repaired by sprayed ultra-high toughness cementitious composites (UHTCC) with or without textile reinforcement. Galvanostatic accelerated corrosion technique was adopted, and three targeted corrosion levels (5 %, 10 %, and 15 %) were selected for each tensile steel bar. Corrosion-induced results, such as voltage change, crack initiation, concrete spalling, corrosion crack length and width, and non-uniform corrosion of steel bars were studied and compared with the results observed in normal strength concrete (NSC) beams. Structural behaviors, including failure modes and load-displacement responses were investigated through four-point bending tests. Results revealed that compared to NSC beams, HSC beams sustained more severe damages under a comparable corrosion level. Spalling was observed at a relatively lower corrosion ratio of 4.43 % and the maximum non-uniform corrosion coefficient, which was defined as the ratio of the maximum corrosion ratio to the average corrosion ratio, was 4.28. Corrosion-induced bonding degradation can alter the failure mode of corroded specimens in bending tests from bending to debonding. For repaired beams, however, the bonding degradation effect was reduced and bending failure was observed for all specimens. The bearing capacity of the beams repaired with sprayed UHTCC cannot be restored with a 12.42 % corrosion ratio, while the beams repaired with sprayed UHTCC/textile can recover their capacity even at a 13.6 % corrosion ratio. Furthermore, an improved theoretical model based on the fiber section analysis and virtual work method was developed to predict structural bending responses. The comparison of the experimental and theoretical results indicated the average corrosion ratio-based method may overestimate the loading capacity, especially for the beams with severe corrosion.

Chloride corrosion resistance of wet joints in manufactured sand reinforced concrete prepared in plateau environment

The durability of three types of wet joints in manufactured sand concrete prepared in simulated plateau environment was investigated. And the accelerated corrosion test on specimens in the chloride salt solution and the static tensile test on corroded steel bars in specimens were carried out by sequence. The durability of different types of specimens prepared in plateau environment was compared by analyzing the development of concrete cracks, the corrosion morphologies of internal steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. The results demonstrate that the development of concrete cracks and the distribution of crack width are affected by wet joint. The nonlinearity of variation of average crack width with actual corrosion rate is enhanced by wet joint. The strength and elongation of steel bars in concrete decrease evidently by wet joint. The strength and elongation loss of steel bars after corrosion is effectively reduced by the punched treatment on joint interface. There is no clear superiority or inferiority pattern for the durability of wet joint specimens with untreated interface (UI) and chiseled interface (CI), and the durability of wet joint specimen with punched interface (PI) is better than that of UI and CI specimens.

Study of endogenous chloride ion content on the behavior of steel bar depassivation in sea sand concrete

In this study, we investigated the chloride concentration in sea sand that induces corrosion in steel bars, as well as the corrosion mechanisms of steel bar within sea sand concrete. Different analytical techniques indicated that the chloride concentration for steel bar corrosion in sea sand concrete was 0.03 % (when the water-binder ratio was in the range of 0.4–0.6). First, the calcium silicate in sea sand concrete reacted with Fe3+ to reduce the compactness of the oxide layer and increase the corrosion risk of steel bars. Second, as the water-binder ratio and chloride concentration gradually increased, the loose structure of the passive film increased, and the relatively dense structure decreased, which made it easier for chloride ions to penetrate the outer layer of the passive film to erode the steel matrix. Besides, the reaction of chloride ions with C3A to form Friedel's salt optimized the pore structure and reduced the content of free chloride ions. However, the adverse effect of chloride ions on the passive film of steel bars exceeded the beneficial impact of porosity reduction. These findings allow us to better apply sea sand to improve the sustainable development of environment.

A new prediction model for residual deformation capacity of corroded steel bars

Corrosion of reinforcing steel bars (rebar) is one of the primary factors leading to the performance degradation of reinforced concrete (RC) structures. It is essential to take into consideration the deteriorating effects of corrosion when it comes to assessing the performance of existing RC structures. However, due to the uncertainties and randomness associated with the degree and distribution of corrosion, accurately assessing the residual deformation capacity of corroded rebar is a significant challenge. This paper presents a comprehensive theoretical model for the prediction of the residual deformation capacity of corroded rebar. Taking into account the mechanical characteristics of the steel material, three classes of non-uniform corrosion in rebar are firstly defined on a quantitative basis to characterize the deformation distribution patterns under tension. Based on the concept of deformation accumulation, a simplified theoretical model is proposed for evaluating the residual deformation capacity of corroded rebar, incorporating both the non-uniformity of corrosion and the sample (or gauge) length; thus, a length scale is built into the nominal strain measure to accommodate the use of different sample or gauge lengths. Numerical tensile tests on 500 randomly generated samples of rebar with varying corrosion levels are conducted, and the parameters of the theoretical model for the three corrosion classes are determined based on a regression analysis of the tensile test results. Comparisons with actual experimental results and existing degradation models demonstrate that the proposed theoretical model provides a more accurate estimation for the deformation capacity of corroded rebar. The model offers a reliable reference for accurately assessing the tensile performance of corroded rebar in subsequent engineering applications.

Numerical modeling of non-uniform corrosion of concrete reinforcement considering calcium leaching and chloride diffusion coupling effect

A novel numerical model is proposed for characterizing the nonuniform corrosion of steel bars. The proposed model corrects the anodic Tafel slope through the concentration of chloride and accounts for the adsorption-binding impact of chloride. The viability of the presented model is confirmed with regard to chloride diffusion and the distribution of steel corrosion products. The rebar-concrete interface's non-uniform distribution of oxygen and chloride concentrations along the circumferential direction influences the corrosion current density. Calcium leaching influences the migration of oxygen and chloride, and speeds up the electrochemical corrosion of the rebar.

Study on seismic behavior of corroded reinforced concrete walls in flexural-shear failure

In this study, artificial climate-accelerated corrosion tests and pseudostatic loading tests were conducted on six reinforced concrete (RC) shear walls subjected to flexural-shear failure. The effects of the corrosion degree and axial compression ratio parameters on the seismic performance of RC shear walls were investigated. The corrosion conditions (corrosive cracks and corroded steel bars), failure process, bearing ability, deformation capacity and energy consumption capacity were compared. The test results showed that chlorine salt erosion induced severe deterioration of the properties of the RC shear wall. The internal reinforcement of the specimen was severely corroded near the protective layer. The failure mode of the severely corroded specimens changed from the original flexural-shear failure mode to the bending failure mode. Rebar corrosion markedly decreased the bearing ability, deformability and energy dissipation capability of the specimens. Based on the limited test data in this study, the existing equations for calculating the parameters of the characteristic points were modified, and equations for calculating the parameters of the skeleton curve of the corroded RC shear wall were proposed. The cyclic corrosion degradation index was utilized to define the degradation of various mechanical properties of the specimen (yield load, hardening stiffness, reloading stiffness, peak load, unloading stiffness, etc.). With cyclic loading, and considering the pinching characteristics, a restoring force model of a corroded RC shear wall was established based on the Ibarra-Medina-Krawinkler (IMK) model. The comparison illustrated that the built restoring force model was in good agreement with the skeleton curve and hysteresis rules and could accurately reflect the hysteresis performance of corroded RC shear walls to a certain extent.

Study on Seismic Behavior and Component Vulnerability of Corroded RC Shear Walls Subjected to Flexural Shear Failure

ABSTRACT The impact of corrosion degree, axial compression ratio, reinforcement ratio of longitudinal bar and horizontal distribution rebar, and stirrup of boundary column on seismic performance of RC shear walls were investigated. The corrosion forms (rust expansion cracks and corroded steel bars), failure process, hysteretic characteristics, bearing capacity, and deformability were compared. Subsequently, a numerical model of corroded RC shear walls was established adopting shell elements. Finally, according to the numerical simulation method, considering the uncertainty of corrosion degree and material parameters, the vulnerability models of RC shear wall components with different corrosion degrees were built. The results show that the mechanical properties of the shear wall were seriously deteriorated due to the corrosion of steel bars, and the ultimate displacement and ductility coefficient of severely corroded specimens were reduced by 28.5% and 12.27% respectively, compared to non-corroded specimens. A proposed numerical modeling method for corroded RC shear walls based on shell element is accurate, and the bearing capacity error and energy dissipation error of the simulation and test results were less than 20%. As the degree of corrosion grew, the probability of shear wall components experiencing more severe failure added significantly. When the displacement angle was 1/120 (This is the limit value of elastic-plastic displacement angle specified in the code), the probability of DS3 and DS4 occurring in the shear wall with a corrosion degree of 0% were 56% and 39.44%, and the probability of DS4 and DS5 occurring in the shear wall with a corrosion degree of 10% were 41.1% and 38.44%.

Research Progress in Corrosion Behavior and Anti-Corrosion Methods of Steel Rebar in Concrete

The corrosion of steel rebars is a prevalent factor leading to the diminished durability of reinforced concrete structures, posing a significant challenge to the safety of structural engineering. To tackle this issue, extensive research has been conducted, yielding a variety of theoretical insights and remedial measures. This review paper offers an exhaustive analysis of the passivation processes and corrosion mechanisms affecting steel rebars in reinforced concrete. It identifies key factors such as chloride ion penetration and concrete carbonization that primarily influence rebar corrosion. Furthermore, this paper discusses a suite of strategies designed to enhance the longevity of reinforced concrete structures. These include improving the concrete protective layer’s quality and bolstering the rebars’ corrosion resistance. As corrosion testing is essential for evaluating steel rebars’ resistance, this paper also details natural and accelerated corrosion testing methods applicable to rebars in concrete environments. Additionally, this paper deeply presents an exploration of the use of X-ray computed tomography (X-CT) technology for analyzing the corrosion byproducts and the interface characteristics of steel bars. Recognizing the close relationship between steel bar corrosion research and microstructural properties, this paper highlights the pivotal role of X-CT in advancing this field of study. In conclusion, this paper synthesizes the current state of knowledge and provides a prospective outlook on future research directions on the corrosion of steel rebars within reinforced concrete structures.

Valorization of industrial wastes for sustainable cement-based materials with enhanced chloride binding

Improving the chloride binding capacity of cement-based material can effectively slow down the corrosion of steel bars in concrete. This study investigated the valorization of two industrial wastes, carbonated sintering red mud (CSRM) and bauxite tailings (BT), as supplementary cementitious materials (SCMs) to enhance the chloride binding capacity of cement-based materials. CSRM and BT were incorporated separately and in combination to prepare cement paste mixtures, replacing 10–30 % of ordinary Portland cement. The bound chloride contents were determined, and the hydration products were characterized using X-ray diffraction and thermogravimetric analysis. Both CSRM and BT promoted the formation of Friedel's salt (FS) through increased aluminum dissolution and conversion of monocarbonate/monosulfate phases. In the early ages, the synergistic effect of CSRM and BT resulted in the highest FS content. At later ages, BT demonstrated superior chloride binding due to its high alumina content facilitating continued FS formation. Furthermore, the adverse effect of CSRM on the composite system was less than that of BT. At 28d age, when the SCMs content was 30 %, the compressive strength of cement-BT system was 34.5 % lower than the control, while the compressive strength of cement-CSRM system was only 20.9 % lower than the control. The findings highlight the potential of valorizing CSRM and BT as sustainable SCMs for developing chloride-resistant cement-based materials.

Performance repair of building materials using alumina and silica composite nanomaterials with electrodynamic properties

Abstract In recent years, the service life of building materials has become the focus of attention. Among them, the service life of concrete and steel bars is particularly affected by the corrosion of external ions (such as Cl−) in the environment. To solve this problem, a new type of composite nanocolloid was prepared through a controllable preparation method. The composite nanocolloid is prepared from aluminum chloride sol and silica sol as raw materials. The prepared colloidal particles have a particle size distribution between 10.5 and 17.5 nm, exhibiting excellent stability and dispersibility. In order to verify the improvement effect of the composite nanocolloid on the properties of building materials, the influence of it on the porosity of concrete and the anti-corrosion performance of steel bars was experimentally studied. The results indicate that the moisture absorption and dehumidification speed of concrete treated with composite nano colloids is slower, and the pore size distribution is mainly concentrated in 100–1,000 nm, indicating that the colloids can effectively optimize the pore structure of concrete. In addition, the processed steel plate samples showed high AC impedance values and low corrosion current logarithmic values in electrochemical testing, indicating that composite nanocolloids have a significant protective effect on the corrosion of steel bars, which can effectively improve the performance of building materials and extend their service life.

Factors Influencing Chloride Ion Diffusion in Reinforced Concrete Structures.

Reinforced concrete structures are prone to the corrosion of steel bars when exposed to chloride-rich environments, which can severely impact their durability. To address this issue, a comprehensive understanding of the factors influencing chloride ion diffusion in concrete is essential. This paper provides a summary of recent domestic and foreign research on chloride ion transport in concrete, focusing on six key factors: water-binder ratio, additive content, crack width, ambient temperature, relative humidity, and dry-wet cycles. The findings show that the diffusion coefficient of chloride ions in concrete increases with a higher water-binder ratio and decreases with increased additive content. Additionally, wider cracks result in a greater diffusion of chloride ions. The permeability resistance of concrete to chloride ions decreases with rising temperature and humidity, and dry-wet cycles further accelerate the diffusion of chloride ions. The article concludes by discussing various anti-corrosion measures, such as the use of corrosion inhibitors, surface coatings, and electrochemical treatments, to ensure the longevity of the structure. Finally, directions for future research are proposed.