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The residual cross-sectional areas of corroded rebars and their uniformity are the main indexes to evaluate the safety and durability of concrete structures in the marine environment. To evaluate corrosion characteristics of naturally corroded rebars, nineteen corroded rebars were extracted from the prototype components of a high-pile wharf with 35 years of service. The apparent morphology characteristics of corroded rebars were obtained using 3D scanning. The results indicate that the corrosion is non-uniform along both the longitudinal and cross-sectional directions of the corroded rebars. In the marine environment, the residual cross-sectional areas of corroded rebars along the length adhere to a three-parameter Weibull distribution; however, no specific probability distribution model or clear correlation with the distribution pattern exists for rebars with varying corrosion degrees. The spatial heterogeneity factors of the rebars are characterized by a three-parameter Frechet distribution. [ABSTRACT FROM AUTHOR]

Corrosion protection of steel bars in alkaline concrete environments poses a common challenge in marine engineering. One approach to mitigate steel bar corrosion is the addition of corrosion inhibitors to the concrete. In alkaline environments, the passivation of rebars occurs through anodic passivation coupled with the cathodic oxygen reduction reaction (ORR). The catalysis of ORR can expedite anode passivation. To investigate the corrosion inhibition of steel bars in alkaline environments, meso‐tetra(4‐carboxyphenyl)porphine (TCPP), known for its ORR catalytic properties, is selected. TCPP forms adsorption films on the surface of steel bars, facilitating the formation of passivation films. TCPP primarily adsorbs onto active sites on the surface of the passivation film, where lattice iron ions have leached. The adsorbed TCPP accelerates the formation of the passivation film through ORR catalysis, inhibiting the development of passivation film defects and enhancing the integrity and protection of the passivation film. The most significant effect is observed when the concentration of TCPP is 0.5 mmol/L. The physical adsorption of TCPP is primarily determined by the negative charge centers, namely the carboxyl group O and the pyrrole N. However, due to steric hindrance caused by the unrestricted rotation of the carboxyl benzene, the pyrrole N does not play a dominant role in chemical adsorption. Instead, the active site for chemical adsorption is the carboxyl group O. The adsorption process significantly reduces the diffusion coefficient of TCPP molecules, providing a robust and stable adsorption binding. Phthalocyanine molecules without carboxyl benzene groups adopt a planar structure, allowing them to form stable adsorption configurations on the iron surface through flat adsorption. This observation provides guidance for the design of novel metal phthalocyanine molecules. Specifically, the development of metal phthalocyanine molecules with modifying groups that are coplanar with the phthalocyanine ring and possess restricted rotation can achieve flat adsorption, improve coverage rate, and enhance adsorption configuration stability. [ABSTRACT FROM AUTHOR]

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Fatigue tests were performed on a full-scale deck slab (15,240 × 3,890 × 210 mm) supported by steel girders spaced at 3.05 m using a rolling load simulator for up to 6 million equivalent cycles under two half axle moving loads of 90 kN each, spaced at 1.2 m. The loads were designed to produce the equivalent effect of the CL625 design truck of the Canadian Highway Bridge Design Code (CHBDC). The deck had several sections featuring three different reinforcement designs; namely, steel rebar, glass fiber–reinforced polymer (GFRP) rebar, and GFRP structural permanent form. The steel rebar was designed in accordance to the empirical method in Section 8 of the CHBDC. This paper focuses primarily on the performance of the 3,810 × 3,890 mm steel-reinforced section and compares it to the two adjacent GFRP-reinforced sections. It also introduces a method to define the loading cycle based on vertical deflection and recovery at the center of a section, which could differ from the vehicle travel cycles. As a result, it was shown that the middle steel-reinforced section experienced 6 million cycles, double that of the two end sections. It experienced a 71% reduction in stiffness and its live-load deflection increased by 2.36 times. The live-load strain of its bottom transverse reinforcement reduced from 384 to 264 με, while the strain of the top transverse reinforcement over the support increased from 20 to 301 με after 6 million cycles. The deflection limit of L/800 was satisfied up to 4.47 million cycles. A dense grid-pattern of cracks occurred at the bottom. Few transverse cracks occurred on top and longitudinal cracks developed above the girders. Practical Application: The empirical design methods in bridge codes provide a convenient way for engineers to design bridge decks with steel or glass fiber–reinforced polymer (GFRP) reinforcement. This paper verifies the fatigue performance of such deck designs under realistic rolling load that simulates the full life of a bridge. The study quantified changes in deflection, stiffness, and strains over time throughout the life of the bridge deck along with the development of cracking patterns. The study is also the first to compare the performance of a GFRP-reinforced deck to that of the traditional steel-reinforced deck under rolling load cycles. A method to quantify the number of cycles the deck experiences is also proposed. [ABSTRACT FROM AUTHOR]

AbstractThe connection of steel elements to concrete is typically achieved through embedded shear connectors (anchors) placed at the interface of concrete and steel. These shear connectors come in various types, such as headed studs, welded or coupled rebars, shear lugs, or a combination of these, designed to handle large shear forces. Shear connectors primarily resist shear forces and bending loads. However, when the load is not applied along the centroid of the shear connector, it generates a torsional moment in addition to shear- and flexure-induced moments, impacting the performance of shear connectors. To address this phenomenon, this experimental study assesses the behavior of shear connectors, including studs, shear lugs, and rebars, both individually and in combination, under three different load eccentricities relative to anchors spacing connectors (0, 0.25, 0.50, and 0.75). The results are then compared with the control specimen (without eccentricity). The findings revealed that vertical shear lugs can significantly enhance the shear capacity, and ACI 318-19 is conservative in this regard by 41.5% for a relative load eccentricity of 0.75. Nonetheless, it gives good estimations of the shear capacity of connectors without vertical shear lugs. HIGHLIGHTSContributing to the very limited data on the performance of anchors under the combined action of shear and torsion.ACI 318-19 [1] provides reliable estimations of shear strength for studs/rebars, both with and without eccentricity. However, it tends to be conservative by 41.5% (for a relative eccentricity of 0.75) when horizontal and vertical shear lugs are utilized.Contributing to the very limited data on the performance of anchors under the combined action of shear and torsion.ACI 318-19 [1] provides reliable estimations of shear strength for studs/rebars, both with and without eccentricity. However, it tends to be conservative by 41.5% (for a relative eccentricity of 0.75) when horizontal and vertical shear lugs are utilized. [ABSTRACT FROM AUTHOR]

The residual cross-sectional areas of corroded rebars and their uniformity are the main indexes to evaluate the safety and durability of concrete structures in the marine environment. To evaluate corrosion characteristics of naturally corroded rebars, nineteen corroded rebars were extracted from the prototype components of a high-pile wharf with 35 years of service. The apparent morphology characteristics of corroded rebars were obtained using 3D scanning. The results indicate that the corrosion is non-uniform along both the longitudinal and cross-sectional directions of the corroded rebars. In the marine environment, the residual cross-sectional areas of corroded rebars along the length adhere to a three-parameter Weibull distribution; however, no specific probability distribution model or clear correlation with the distribution pattern exists for rebars with varying corrosion degrees. The spatial heterogeneity factors of the rebars are characterized by a three-parameter Frechet distribution.

In this article, a review focusing on the frost resistance of recycled coarse aggregate concrete (RAC) and the bond performance of RAC with rebar under freeze–thaw environment is carried out. The results show that there are still some controversies about the advantages and disadvantages of the frost resistance of RAC, and many influencing factors have not been considered. The mass of the RAC pullout specimens shows a trend of first increasing and then decreasing after freeze‒thaw cycles. The failure modes of the RAC pullout specimens after freeze‒thaw cycles include pullout failure, pullout-splitting failure, splitting failure, and rebar yielding failure. The bond performance of RAC with rebar shows a degradation trend after freeze‒thaw cycles, mainly in the decrease in bond strength and the increase in bond slip. The bond performance of RAC specimens is inferior to that of natural aggregate concrete specimens after freeze‒thaw cycles. The bond strength prediction models and the bond–slip constitutive relation prediction models of RAC with rebar after freeze‒thaw cycles have been summarized to ensure that engineers can better understand their applicability. The bond stress distribution between the RAC and rebar in the anchoring area is not uniform and constantly changes with the number of freeze‒thaw cycles. The degradation mechanism of the bond performance of RAC with rebar after freeze‒thaw cycles is analyzed.

Structural durability is critical for building and civil engineering safety, wherein the arrangement and distribution of reinforcing bar (rebar) is crucial. Improperly aligned rebar impacts bearing capacity, whereas uniform spacing optimally distributes loads, reducing stress. We introduce a computer-vision based Deep Vision Net (DVNet) model for real-time evaluation of rebar placement. A customized dataset is prepared in an environmental setup and augmented to address overfitting issues. This research conducts a comparative analysis of the learning performance exhibited by the proposed DVNet model against several other pre-trained models, such as Mask-RCNN and YOLOv5. The proposed DVNet model is built on a customized DeepCNN architecture, achieving a commendable precision of 88.6 % and recall of 89.3 %. Utilizing the DVNet model, the real-time assessments of rebar placements were performed at various spacing intervals. Experimental results demonstrate that the DVNet-based model excels at ensuring the structural arrangements of the rebar intervals.

Ultra-high-performance concrete (UHPC) with a low steel fiber volume fraction offers lower material costs than UHPC with typical steel fiber volume fractions, and has the potential to mitigate the ductility degradation of rebar-reinforced UHPC (R-UHPC). This study explores the reinforcement effect on the tensile behavior of UHPC with a low fiber volume fraction with the aim of facilitating more cost-efficient UHPC applications. The axial tensile behavior of 30 UHPC specimens with low fiber volume fractions at different reinforcement ratios was tested through direct tensile tests. The findings indicate that adopting UHPC with a low fiber volume fraction can significantly mitigate the ductility deterioration of rebar-reinforced UHPC (R-UHPC), and both increasing the reinforcement ratio and decreasing the fiber volume fraction contribute to the improvement in ductility. The failure modes of R-UHPC are determined by the ratio of reinforcement ratio and fiber volume fraction, rather than a single parameter, which also means that R-UHPC with different parameters may correspond to different methods to predict tensile load-bearing capacity. For UHPC with a fiber volume fraction low to 0.5%, incorporating steel rebars gives superior multi-crack cracking behavior and excellent capacity to restrict the maximum crack width. Increasing the fiber volume fraction from 0.5% to 1.0% at the same reinforcement ratio will yield little benefit other than an increase in tensile load-bearing capacity. [ABSTRACT FROM AUTHOR]

Treating tibial bone defects in the setting of recalcitrant native knee arthritis presents a challenging biomechanical problem for orthopaedic surgeons. A dynamic antibiotic spacer offers an effective solution to preserve patient function and manage infection. However, severe bone loss may compromise the fixation of the dynamic spacer. We describe the application of acetabular screws as rebar in a case of an Anderson Orthopaedic Research Institute type 3 defect of the medial tibial plateau. Additionally, we outline a facile method for fabricating the tibial stem component to ensure optimal fit within the intramedullary canal. Short-term follow-up (8 months) indicates successful fixation of the tibial component, absence of knee pain, and a knee range of motion up to 100 degrees.

Corrosion is the irreversible, interfacial reaction of metals in the presence of an electrochemical environment which ultimately results in the deterioration of metals. Corrosion of reinforcement is the major problem in the reinforced concrete (RC) structure. Corrosion of reinforcement is a slow process because of the protective layer of concrete. Even in a severely corrosive environment corrosion process takes time to be initiated and propagated. Since to carry out research work, some techniques are required to accelerate the corrosion process in the shortest period. To overcome this problem, in the past, many researchers use a different method to accelerate the corrosion of steel in concrete. In this paper, a review is presented of various techniques used for accelerated corrosion testing. The suitability of reviewed methods on corrosion acceleration for several research works is presented. After that few case studies review to make use of various predicted empirical models and an experimental technique for predicting corrosion rate and the assessment of the remaining life of the structure. And finally, the paper is concluded by comparing the natural method of corrosion and the accelerated method of corrosion and the future scope of accelerated corrosion. [ABSTRACT FROM AUTHOR]

The production of steel rebar is an energy-intensive process that generates CO2 emissions. In construction, waste is generated by cutting stock-length rebar to the required lengths. The reduction rate achieved in most previous studies was limited due to adherence to lap splice positions mandated by building codes and the use of stock-length rebar. A previous study demonstrated a significant reduction in rebar usage and cutting waste, approaching zero, upon optimizing the lap splice position, reducing the number of splices, and utilizing special-length rebar. However, the reference length used to determine the special-length rebar was not clearly optimized. This study proposes a special length priority optimization model to minimize wall rebar usage and waste by reducing the number of splices while simultaneously ensuring an optimal reference length. The proposed model was validated using a case study wall with a standard hook anchorage at the top of the wall reinforcement. The optimization model reduced rebar cutting waste to 0.18% and decreased rebar usage from the original design by 16.16%. [ABSTRACT FROM AUTHOR]

The durability of reinforced concrete structures exposed to aggressive environments is affected by corrosion of carbon steel reinforcement. For this reason, it is of great practical interest to look for alternative solutions guaranteeing durability through the incorporation of corrosion‐resistant materials, such as stainless steel rebars. This type of steel is specially recommended for structures with a long lifespan, located in aggressive environments, with chlorides or de‐icing salts, and for structures where repair, inspection and rehabilitation is complicated. This solution presents a challenge from the point of view of the materials themselves, the mechanical design and their durability. This article presents the material properties of stainless steel and their influence on concrete structures. Furthermore, it is explained how these properties have been taken into account in the latest draft of the second‐generation Eurocode 2. [ABSTRACT FROM AUTHOR]

The use of cementitious materials in deep sea environments, focusing on the durability challenges of low‐temperature seawater and hydraulic pressure, are presented in this paper. The authors conducted laboratory and deep‐sea field experiments, thermodynamic calculation, and evaluated the performance of different types of binders in deep sea conditions. Durability of rebar in cementitious materials was investigated. In situ construction methods using cementitious materials was demonstrated on the deep‐sea field. Testing results revealed that deep sea conditions, especially low‐temperature seawater, can accelerate the disintegration of cement hydrates, and the use of pozzolanic admixture and calcium aluminate cement can improve its resistance. Our study provides valuable insights and applicability of cementitious materials to deep sea infrastructure construction. [ABSTRACT FROM AUTHOR]

The fast economic growth, urbanization, and industrialization of Ethiopia led to the requirement for the establishment of various infrastructures and many residential building constructions consuming different types of materials. Reinforced steel bar is one of the most consumed construction materials in Ethiopia. The demand for reinforced steel bars in Ethiopia is satisfied by the local production and international market. However, most people lack trust to the use local products without justified reasons. This investigation work was done to evaluate the performance of the locally produced rebar concerning the Compulsory Ethiopian Standard (CES) to develop trust in contractors and consultants of different projects. A Compulsory Ethiopian Standard (CES) is an Ethiopian standard that has been prepared under the direction of the Technical Committee for Concrete and Concrete Products and published by the Ethiopian Standards Agency (ESA). Experimental works were done on rebar of grades B400BWR and B500BWR with different diameters collected from four different factories. The collected samples were investigated based on their yield strength, ultimate tensile strength, elongation, hardness, chemical composition, and microstructure formation of the product. The yield strength, ultimate tensile strength, and elongation of the rebar were analyzed based on the tension test results obtained from the 2000 KN Universal Testing Machine (UTM), and the chemical composition analysis was done using the Spark Emission Spectrometer Analyzer. The micro-hardness test was done using the Vickers Hardness Tester with 3kgf and 15-s dwell time at a 0.5 mm gap along the cross-section of the rebar. Microstructure analysis is done using EDX scanning electron microscope (SEM) and optical microscopy with different magnifications and resolutions on the cross-section of the rebar. From the tested samples one sample failed from B400BWR to achieve the minimum required yield strength of 400 MPa stated by CES 101, 2017. Samples of B500BWR satisfy all the requirements stated by the standard even if there is an increment up to 41 % beyond the minimum requirement.

This paper examines the random variation of the residual radius along the length of both naturally corroded and artificially corroded rebars. The rebars are washed to remove rust, and their residual area is measured by the water volume method for every 20-mm long segment of each rebar. Tests are carried out to determine the stationarity or non-stationarity of the stochastic field used to model the residual radius of the specimens. Then, the autocorrelation function, power spectrum and marginal probability distribution function of each specimen are estimated. It is found that the residual radius field of both naturally and artificially corroded rebars with mean corrosion levels below 20% is stationary, while the situation can change as the mean corrosion level increases and concrete cover spalling occurs. The residual radius field along the rebar length of stationary specimens is found to be white noise for both naturally and artificially corroded rebars. The marginal probability distribution function of the residual radius is determined to be skewed and can be fitted with a Beta distribution for naturally corroded rebars and with a Weibull distribution for artificially corroded rebars. This is the first paper studying and comparing both naturally and artificially corroded rebars. [ABSTRACT FROM AUTHOR]

Divide shear assembly in a rebar rolling mill performs the function of cutting rebars into 72 m length. It uses two shear blades mounted on rotating arms, which rotate in directions opposite to each other and cut the rebars passing in between. These blades hit the rebars at a location from two opposite sides for cutting, and their cutting edges gradually become blunt after cutting of approximately 4000–5000 tons of rebars. Replacing the blunt blades results in interruption in operation leading to increased down time and resulting decreased productivity. A thorough metallurgical root cause analysis was carried out to improve the service life of shear blades. Damages on shear cutting blades were analyzed after trimming of 4000–5000T on thermo-mechanically treated rebars. Chemical analysis revealed that the material of the shear blade was AISI D2, which is a widely used material for cutting of rebars in cold conditions. AISI D2 is a high carbon grade with high Cr content. Microstructural examination revealed large fraction of coarse carbides in tempered martensitic matrix. However, excessive number of coarse carbides imparts brittleness which can limit its applications under severe conditions. The used blade exhibited chipping off materials at the cutting edge in brittle manner. The damaged blades and subsurface damage were examined using Profilometer, SEM, XRD and other metallography techniques. After detailed metallurgical investigation new material was developed to improve the (performance) of the cold shear blades. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) with a low steel fiber volume fraction offers lower material costs than UHPC with typical steel fiber volume fractions, and has the potential to mitigate the ductility degradation of rebar-reinforced UHPC (R-UHPC). This study explores the reinforcement effect on the tensile behavior of UHPC with a low fiber volume fraction with the aim of facilitating more cost-efficient UHPC applications. The axial tensile behavior of 30 UHPC specimens with low fiber volume fractions at different reinforcement ratios was tested through direct tensile tests. The findings indicate that adopting UHPC with a low fiber volume fraction can significantly mitigate the ductility deterioration of rebar-reinforced UHPC (R-UHPC), and both increasing the reinforcement ratio and decreasing the fiber volume fraction contribute to the improvement in ductility. The failure modes of R-UHPC are determined by the ratio of reinforcement ratio and fiber volume fraction, rather than a single parameter, which also means that R-UHPC with different parameters may correspond to different methods to predict tensile load-bearing capacity. For UHPC with a fiber volume fraction low to 0.5%, incorporating steel rebars gives superior multi-crack cracking behavior and excellent capacity to restrict the maximum crack width. Increasing the fiber volume fraction from 0.5% to 1.0% at the same reinforcement ratio will yield little benefit other than an increase in tensile load-bearing capacity.

Ground-penetrating radar (GPR) has been widely applied to the detection and delineation of buried targets in the subsurface. Compared with conventional single-channel GPR, polarimetric GPR has been proven to possess an improved ability to detect and characterize an elongated object in the subsurface. This letter proves that the scattering signals from a cylinder in two orthogonal polarization channels have a phase difference of about 90° when its diameter-to-wavelength ratio is about 0.05–0.33. Consequently, a polarization-difference imaging method, which shifts the VV component by −90° and subtracts it from the HH component, is proposed for the improved detection and imaging of a subsurface elongated object. Its effectiveness is verified by numerical, laboratory, and field tests on buried rebars and pipes. The signal-to-clutter ratios of the reconstructed GPR images can be improved by up to 4.5 dB by considering the phase difference between the dual-polarization components. [ABSTRACT FROM AUTHOR]

Due to rampant building collapse in Nigeria, several works have been conducted on rebars in Nigeria without recourse to statistical analysis of the tensile and characterization. In this paper, an experimental investigation was performed to understand the mechanical properties and characteristics of reinforcement bars (rebars) produced from scraps in Nigeria. The tensile strength of twenty-two samples for each type of manufactured rebar was subjected to probability analysis using a two-parameter Weibull probability distribution model. The characterization of the rebars was performed using optical emission spectroscopy (OES), x-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and impact strength of the rebars were determined using Brinell hardness test and Charpy test, respectively. The result revealed that the carbon content of all the rebars was more than the required amount specified by international standards for a classical rebar material. The presence of flaws in the rebars has significant influence on the mechanical properties of the rebars. The two-parameter Weibull probability distribution shows that the Weibull parameters such as the Weibull modulus and the scale parameter values were very low compared to the literature. [ABSTRACT FROM AUTHOR]

Prestressed rebars are usually used to apply vertical prestress to concrete to prevent web cracking. The reduction of working stress will affect the durability of the structure. However, the existing working stress detection methods for prestressed rebars still need to be improved. To monitor the working stress of rebars, a magnetic resonance sensor was introduced to carry out experimental research. The correlation between rebar stress and the sensor's induced voltage was theoretically analyzed using the magnetoelastic effect and magnetic resonance theory. A working stress monitoring method for prestressed rebars based on magnetic resonance was proposed. Working stress monitoring experiments were carried out for 16 mm, 18 mm, and 20 mm diameter rebars. The results showed that the induced voltage peak-to-peak value and the rebar prestress were nonlinearly correlated under different working conditions. Correlations between the characteristic indicators and the rebar working stress were obtained using nonlinear and linear fit. The cubic polynomial segmented fit outperformed the gradient overall linear fit, with the goodness of fit R2 greater than 0.96. The average relative error values of working stress monitoring were less than 5% under different working conditions. This provides a new method for working stress measurement of vertical prestressed rebars. [ABSTRACT FROM AUTHOR]

In the present study, The main purpose is to focus on the applicability of using non-prestressed tendons as the main reinforcement in concrete beams. Therefore, the main reason for the analytical study is to develop a model that can predict the flexural behavior of RC beams with ordinary reinforcements and/or with non-prestressed tendons (cables). An experimental program, as well as a computational program, was designed to see the behavior of such concrete reinforced beams. To do so, 9 beam models of one concrete mix were cast. The beams were cast in accordance with ACI recommendations and all tests were conducted under the same condition. The beams tested include two types of beams with ordinary steel rebar and with cables (tendons). The beams studied in this research are classified as deep beams (L/h

The present study aims at developing a non-destructive evaluation technique based on elastic wave scattering and the finite element method for the detection and evaluation of localized damage in rebar of reinforced concrete beams. Simulation of corrosion effect was taken for a tensile bar by creating a defect in this bar while the rest of the rebar and stirrups were kept unchanged. The study is based on comparison of propagation pattern of elastic waves in the presence and in the absence of defect. The proposed method was found capable to provide non-destructive evaluation of rebar corrosion in reinforced concrete beams, thus enabling diagnosis of reinforcement concretes structures attacked by corrosion. The obtained results can be further used to locate corroded areas. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) detects a tunnel with relatively low-frequency electromagnetic waves, which can result in poorly characterized reinforced steel bar (rebar) hyperbolas and make it challenging to recognize rebar. Thus, the rebar is located by using attenuation and reflection coefficients, and the hyperbolic feature of the rebar is reconstructed for recognition. Due to differences in the electromagnetic properties of rebar and other media in the second lining, the position of rebar in the one-dimensional time wave diagram (A-scan) is determined by using the attenuation and reflection coefficients. The rebar is recognized at the peak point in the A-scan. This peak point is in the opposite phase of the incident wave. The amplitude of these peaks is smaller than the peaks of the adjacent points. Then, these negative peak points are reconstructed on the two-dimensional scanning data (B-scan). Finally, the rebar is recognized by using the hyperbolic feature of the rebar. The method is applied in the Husa Tunnel in Yunnan Province, China. Moreover, in the mileage section YK81+506–YK81+542 of the Husa Tunnel, the hyperbolic feature of the reconstructed rebar is evident, and the rebar appears in the region of 5–7 ns in the B-scan. [ABSTRACT FROM AUTHOR]

The production of steel rebar is an energy-intensive process that generates CO2 emissions. In construction, waste is generated by cutting stock-length rebar to the required lengths. The reduction rate achieved in most previous studies was limited due to adherence to lap splice positions mandated by building codes and the use of stock-length rebar. A previous study demonstrated a significant reduction in rebar usage and cutting waste, approaching zero, upon optimizing the lap splice position, reducing the number of splices, and utilizing special-length rebar. However, the reference length used to determine the special-length rebar was not clearly optimized. This study proposes a special length priority optimization model to minimize wall rebar usage and waste by reducing the number of splices while simultaneously ensuring an optimal reference length. The proposed model was validated using a case study wall with a standard hook anchorage at the top of the wall reinforcement. The optimization model reduced rebar cutting waste to 0.18% and decreased rebar usage from the original design by 16.16%.

Carbon steel rebar (ASTM A615) has been widely used in reinforced concrete (RC), but its susceptibility to chloride ions remains a critical issue. Low alloy chromium steel has been used to increase corrosion resistance and extend service life, such as in 9% Cr rebar (ASTM A1035-CS). In this work, we characterized two electrochemical systems over time: ASTM A615 and A1035-CS corrugated rebar immersed in SCPS in the presence of NaCl for 12 months. The interfacial processes evolution for the ASTM A1035-CS rebar for both general and local corrosion showed different active-passive responses from those of carbon steel. Because the 3.5% wt. NaCl exceeded the chloride threshold for passive breakdown of both materials, the ASTM A1035-CS showed a five-fold higher impedance and lower general corrosion rate. In localized conditions, the low alloy chrome content rebar showed less density localized attack than the ASTM A615 rebar. These results were attributed to the overall damage evolution involving the formation and stability of corrosion products over time. The local attack appeared to be a random spatial process due to changes in the local environment.

Incorrect rebar placement has led to serious concrete structural failures; thus, site inspectors must ensure that the rebars placed are compliant with as‐designed drawings before tunnel lining concreting. This paper aims to develop a methodology that automatically segments the semantics (e.g., main rebar and distribution rebar) and instances of curved rebars and reconstructs the tunnel lining rebars from the raw point clouds. There are five main parts in the proposed methodology: rebar mesh reshaping, rebar mesh extraction and refinement, semantic segmentation, instance labeling, and rebar mesh modeling. To validate the developed methodology, an experiment was conducted on the rebar point cloud of a high‐speed railway tunnel. The evaluation of the accuracies of segmentation was conducted by comparisons with the existing methods and manually labeled ground truth data. The results show that the rebar segmentation has high precision values with the acceptable recall values, and that the rebar models reconstructed achieve millimeter‐level (about 2 mm) accuracy. [ABSTRACT FROM AUTHOR]

Corrosion and fatigue loading would inevitably degrade bond between rebar and concrete. However, there were only a few related test results available, and confinement of rebar was different from case to case. An experimental study was conducted to investigate the combined effects of corrosion and fatigue loading on bond behaviors between strong confined rebar and concrete. A total of 72 cube specimens with 13 target corrosion levels from 0% to 30% with a step of 2.5% were made and tested. Seven specimens were tested with monotonic pull‐out load. Sixty‐five specimens were tested with fatigue loads and divided into two groups according to corrosion level with two different loaded upper limits. Bond strength, corresponding slip value, residual slip value, and residual bond stress of tested specimens with different corrosion levels and stress levels are studied. Three typical failure modes were observed during fatigue loading processes: rebar fracture, bond fatigue failure, and pull‐out splitting failure, respectively. Test results indicated the residual slip continued to accumulate under fatigue load, and corrosion further increased the residual slip value. Specimens began to show bond fatigue failure when the actual stress level was >50%. The results of this study can provide reference for service life evaluation of reinforced concrete structures in coastal area under repeated loading. [ABSTRACT FROM AUTHOR]

One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. The concrete cover protects against corrosion. This paper presents research, the primary purpose of which was to determine the effect of the addition of steel fibers to concrete on the development of corrosion of the main reinforcement. The tests were carried out on three types of reinforced concrete specimens made of ordinary concrete and concrete with different amounts of steel fibers (0.25% and 0.50%). In order to initiate corrosion processes, specimens were partially submerged in a 3% sodium chloride solution and were subjected to freeze–thaw cycles. The electrochemical polarization galvanostatic pulse method was used for analyzing the reinforcement corrosion activity. Moreover, it was verified whether the corrosion of reinforced concrete elements affects the acoustic emission wave velocity. The addition of steel micro-reinforcement fibers increases the corrosion resistance of reinforced concrete. In addition, a strong linear correlation between the AE wave velocity and the values of the corrosion current density was revealed. [ABSTRACT FROM AUTHOR]

Corrosion is an important phenomenon that occurs at concrete-rebar interface and affects the life of structures in coastal environments. Fe-600 grade steel is used in India for construction purposes especially in seismic zones. Hence, the corrosion of the rebars and its optimization is necessary to increase the lifetime of structures. In this regard, the present investigation examines the applicability of electroless Ni-P based ternary coatings as candidates for corrosion protection and obtains an optimal bath formulation. Investigation of electrochemical corrosion phenomenon (potentiodynamic polarization) was carried out in 3.5% NaCl to simulate saline coastal environment. Ni-P coatings with Cu and W inclusion were considered due to their proven corrosion resistance. The bath constituents such as nickel sulphate (Ni source), sodium hypophosphite (reducing agent and source of P) and the tungsten / copper concentration were varied to get various elemental composition following a sequential experimental design i.e. Taguchi’s L9 orthogonal array. A grey based fuzzy reasoning approach was proposed to optimize the bath and achieve enhanced corrosion resistance. The optimized coatings exhibited initiation of passivation which could prove to be beneficial for the health of the structure in the long-run. A noble corrosion potential and lower corrosion current density could be obtained in the coated rebars from the grey fuzzy methodology.

• Chemical analysis of failed concrete structures to assess the reason for rebar corrosion. • Detailed analysis of the rebar corrosion under various environmental conditions. • Study on the influence of different bacterial interactions on rebar corrosion. • Testing of the suitability of different coatings to combat rebar corrosion. • Development of coating with superior biocorrosion resistance and anticorrosion characteristics. Corrosion of the reinforcing steel bar (rebar) prevails as a serious issue, in the construction sector, leading to the deterioration of concrete infrastructures. The extent of concrete failure due to rebar corrosion depends greatly on the environmental conditions. The present paper describes a detailed analysis of the rebar corrosion under various environmental conditions and the development of different coatings to combat rebar corrosion. It also details the role of severe corrosive environment and the influence of microbial interactions on rebar corrosion. The long-term exposure (14 days) of the rebar to different bacterial suspensions such as E. coli , B. subtilis , and seawater consortium indicate that the rebar undergoes severe surface degradation in seawater consortium as compared to the other suspensions. The suitability analysis of the zinc phosphate and electroless nickel coatings to combat rebar corrosion in severe corrosive medium confirm nickel coated rebar as more corrosion resistant than zinc phosphate coated/bare rebars. The biocorrosion resistance analysis of zinc and composite zinc coated rebars in seawater consortium after long-term exposure (28 days) indicates composite zinc coated rebar as the best with the lowest bacterial survivability percentages in all the bacterial suspensions. The composite coated rebar exhibits attractive electrochemical stability even after long-term bacterial exposure in seawater consortium , and acts as a protective coating with superior biocorrosion resistance and anticorrosion characteristics. [ABSTRACT FROM AUTHOR]