Advances in the understanding of corrosion and performance of hot-dip galvanized rebar in concrete structures

Key parameters and mechanism of blistering of coil-coatings in humid-hot laboratory environments

Galvanostatic testing for the durability of marine concrete under fatigue loading

The main objective of this work is to study the electrochemical behavior of galvanic coupling between carbon steel, CS, and stainless steel, SS, in an alkaline environment simulating the conditions prevailing in a repaired structure in which stainless steel rebar’s will be an option. Previously research conducted in different parts of the world on this subject reach agreement with the fact that AISI 304 SS and 316 SS embedded in concrete offers high corrosion resistance in aggressive environments but only for the case of new structures, and no further explanation has been given on the behavior of SS when in contact with CS. Galvanic coupling between these two metals should increase the corrosion process of the more anodic, CS in this case, but this phenomenon does not occur in practice.Galvanic coupling was investigated by means of the electrochemical coulostatic technique. Tests performed allow determining the Tafel slopes of anodic and cathodic processes. The Tafel slope values obtained show that the process is being controlled by the reduction of oxygen, O2 in the environment where the samples were placed. On the basis of these kinetic parameters, a mechanism for the corrosion process is proposed in which the rate determining step would be O2 mass transfer process. The diffusion of O2 would take place through a formed oxide film, passivating in nature. Due to the formation of this oxide film, the cathodic oxygen reduction reaction, ORR, on stainless steel surface would be very slow. The high polarization of ORR rate would be the factor controlling the whole process, then minimizing the risk of damage by galvanic corrosion, demonstrating the feasibility of using stainless steel in the repairing of concrete structures.

Corrosion of carbon steel rebars in concrete structures significantly compromises their safety, reliability, and environmental performance. This work focuses on enhancing rebar corrosion resistance by repairing the defects of oxide scale. Here, sol-gel was employed as a carrier, by which Ce3+ and Ni2+ were transferred to the oxide scale defects based on the isoelectric point theory, and deposited at these defects with the pH variation as temperature. The repaired oxide scale showed enhanced uniform elemental distribution and improved electrochemical properties, maintaining integrity even under prolonged exposure to Cl−-rich environments. Notably, the impedance modulus at 0.01 Hz (|Z | 0.01Hz) of treated samples was six times higher than untreated ones, indicating superior performance against high electric fields. This strategy shows great potential for enhancing the durability of concrete structures.

As adhesive bonding is a preferred method of joining advanced composite structures for modern aerospace and automotive designs, the need for a quantitative nondestructive evaluation (NDE) method for adhesive bond strength has sharply increased. For many years, adhesively bonded joints have been examined with conventional NDE methods, but none have proved able to detect weak or "kissing" bonds, except where major bonding defects occur. Here, the problem of weak interfacial bonding is investigated with a novel swept-frequency ultrasonic phase measurement method. High- resolution, swept-frequency ultrasonic phase measurements are obtained at each frequency through the use of a constant- frequency pulsed phase-lock-loop instrument. The method is tested on single lap joints fabricated with polished glass adherents and adhesive cured with ultraviolet (UV) light. The cohesive and adhesive bonding properties are modified by varying the adhesive's exposure time to UV light and thereby changing the degree-of-cure. After fitting the measured phase response to a model of the ultrasonic response of the bonded joint, the stiffness constant of the adhesive/adherent interface is found. The interfacial stiffness constant is shown to have a strong linear correlation with measured mechanical tensile strength. As such, high-resolution swept-frequency phase measurements are shown to have a sensitivity to interfacial bond strength without the presence of gross bonding defects, allowing for bond strength quantification rather than a simple identification of "good" or "bad" bonding. This method has the potential to be a quality control and service life assessment method for both newly-fabricated and in-service bonded joints for the aerospace, automotive, and other industries.

Polymer cement mortar (PCM) has been widely utilized in engineering practice for the repair and strengthening of damaged concrete. However, the bond strength of PCM-concrete interface can deteriorate under high temperatures. To enhance bonding performance, a new interface treatment method needs to be explored. This study aimed to investigate the bond performance between concrete and PCM after adding a layer of epoxy bonding agent (EP) or carbon fiber-reinforced polymer (CFRP) to the interface, as well as to investigate the effect of temperature. The bond behavior was evaluated by interfacial split tensile tests. The experimental results show that the splitting tensile strength of the specimens decreased as the temperature increased. After being exposed to a temperature of 100 °C, the splitting tensile strength of specimens without interface reinforcement, EP- and CFRP-reinforced interface specimens decreased by 35.42%, 58.90%, and 63.39%, respectively. When the ambient temperature exceeds 80 °C, bonding with epoxy or CFRP does not improve the bond performance due to the decomposition of epoxy. Finally, the relationship between the splitting tensile strength of the three types of specimens and temperature was clarified, and a model was developed to predict the strength degradation under elevated temperatures. The results are useful for improving the durability and safety of concrete structures repaired with PCM.

In order to study the durability of the stainless steel bars (SSRs) in the marine environment, 52.5 Ordinary Portland cement (OPC) and CA50 concrete specimens (CAC), ordinary carbon reinforcing steel bars, and S32304 duplex SSRs were used to make two concrete blocks. Electrochemical monitoring of steel bars in concrete was carried out in two marine environments, i.e. splash zone and full immersion zone, were simulated via alternating dryingwetting cycles and immersion in the simulated sea water solution. Test results show that the durability of concrete structure can be improved by using S32304 duplex SSRs and CA50 concrete specimens.

Prediction model for equivalent exposure time in indoor dry-wet cycling tests for concrete in marine tidal zones

PurposeAdmixtures are materials that are added to concrete at some stage in its production to give concrete new properties whether in fluid or plastic conditions. The admixtures used in the construction industry are broadly classified into Mineral and Chemical admixtures. In recent years, the use of mineral and chemical admixtures in producing high performance concrete has increased significantly. The chemical reaction of cement with admixtures differs from material to material. Calcium nitrite based corrosion inhibiting admixtures have gained popularity for protection of reinforced and pre‐stressed concrete structures but calcium nitrite is not commercialized indigenously in India due to manufacturing difficulties. Hence, the objective of the present investigation was to study a novel corrosion inhibiting admixture system and to compare its effectiveness with sodium nitrite.Design/methodology/approachDi‐sodium phthalate, sodium orthophosphate and sodium nitrite‐based corrosion inhibiting admixtures were selected for the present investigation. The critical quantities of corrosion inhibiting additives were determined by accelerated laboratory tests. The following types of tests were conducted to evaluate the efficiency of the corrosion inhibiting admixtures: compressive strength of 100 × 100 × 100 mm concrete cubes after 3,7,14 and 28 days of curing, linear polarization resistance measurements, electrochemical impedance spectroscopy measurements, an accelerated 12 V controlled potential test.FindingsFrom the above tests, the inhibitor admixtured concrete not only improved in compressive strength but also increased its corrosion resistance properties. Of the inhibitors studied, di‐sodium phthalate showed superior corrosion resistance properties, compared to sodium nitrite.Originality/valueDi‐sodium phthalate may be considered a better substitute for calcium nitrite‐based corrosion inhibiting admixtures for durable concrete structures. This fulfils the objective of the investigation.

Fiber reinforced polymer parts have shown tremendous benefits in aerospace structural applications, but their qualification and certification for use in safety critical areas are currently hindered by the lack of a capable non-destructive evaluation (NDE) method or technique for the inspection of these adhesively bonded parts. Conventional NDE methods and techniques typically detect gross bond defects in a qualitative (Pass/Fail) manner. These techniques struggle to detect weak or kissing bonds. Also, there are no widely adopted NDE methods or techniques for measuring interfacial bond strength or detecting kissing bonds. Bond strength is currently ensured by process control and semi-destructive testing. Results from recent research from other authors, including but not limited to mechanical testing, have shown an excellent correlation between interfacial stiffness of an adhesively bonded joint and the adhesive bond strength of that joint. In this paper, a measurement system analysis (MSA) of a novel phase-based ultrasonic NDE Technique, developed at NASA Langley Research Center, is presented for bond strength measurements to assess at an increased level the measurement process and identify components of variation in the process.

The deterioration of concrete structures is a matter of critical concern as it threatens the durability and strength of concrete structures. Kenaf fibrous concrete composite (KFCC) can be used with advantage in new structures such as precast elements, as well as the strengthening, repair and rehabilitation of old structures to improve their durability properties. These structures are composite components, with parts as Plain concrete (PC) and others as KFCC. This study, therefore, investigated the interfacial bonding behaviour between KFCC and PC. Shear, tensile and compressive tests were carried out to measure the bond strength in shear, direct tension and compression respectively for PC to PC, PC to KFCC and KFCC to KFCC interface. Three different types of concrete grade (25, 35, and 45 MPa) were produced for the KFCC and one type of concrete grade (35 MPa) for the substrate PC. The outcome of the test showed that KFCC had an excellent interlock with the surface of the PC substrate, and thus, gives bond strength greater than the strength of PC. New concrete with the highest concrete grade of 45 MPa ensued in high compressive, tensile and shear bond strength.

I served as the guest editor of the July/August 2010 issue of the Journal of Bridge Engineering. During the last 2 years, partly because of the failure of the I-35 Bridge inMinnesota in 2007 and other incidents, there has been significant focus and healthy discussion among bridge infrastructure stakeholders, including several elected leaders, in using nondestructive methodologies in assisting bridge inspection, evaluation, and maintenance. At present, nondestructive evaluation and testing (NDE/NDT) methods, such as ground penetrating radar and infrared thermography, are being commonly used by most transportation agencies. Several federal and state agencies are funding significant resources in developing and researching nondestructive test methods for quantitative evaluation of bridge infrastructure to augment visual inspection data. This special issue presents some of the recent advances and applications of nondestructive test methods and structural health monitoring for bridge evaluation and management. A majority of bridge failures are attributed to scour damage that is hard to detect in real time and appropriate preventivemeasures that are hard to apply when scour damage is detected. Hence, scour monitoring is an important topic for transportation owners, especially during high-flood events and in coastal areas. The technical paper “VibrationBased Method and Sensor for Monitoring of Bridge Scour” by Zarafshan et al. introduces a new fiber-optic Bragg grating (FBG) scour sensor. The scour-depth detection is based on the inverse relationship between the fundamental frequency and the length of the sensor rod embedded in the riverbed. This paper describes development of the theoretical basis for the sensor, computational methodology for detection of the riverbed foundation properties, laboratory and small-scale field verification tests, and installation and remote monitoring of scour in a multispan scour critical bridge in Illinois. Cable-stayed bridges are increasingly popular in the United States because of their elegance and the advantages they offer for relatively long spans. When these unique bridges are built, several design assumptions are made and may have to be verified after their construction. A cable-stayed bridge was recently constructed by the Ohio Department of Transportation. Following recent trends, the stays at this bridge were built without the use of grout for the purposes of inspection and possible replacement in the future. The bridge incorporated measures put forth to mitigate stay motion. The technical paper “Cable-Stayed Bridges: Case Study for Ambient Vibration-Based Cable Tension Estimation” by Kangas et al. presents experiments that were performed to determine the viability of using traditional vibration techniques that assume an integral sheath to estimate cable tension with this new configuration. Acoustic emission (AE)-based techniques have been widely used for detecting breaks in suspension and cable-stayed bridges. The technical paper “Detection of the Presence of BrokenWires in Cables by Acoustic Emission Inspection” by Zejli et al. studies AE techniques to detect the presence and location of broken wires in anchorages. Structural health monitoring (SHM) is becoming popular in bridge monitoring. System configuration is very important to effectively monitor performance parameters of interest. The technical paper “Measurement System Configuration for Damage Identification of Continuously Monitored Structures” by Laory et al. discusses a systematic approach to determine the appropriate number and location of sensors to configure measurement systems in which static measurement data are interpreted for damage detection using model-free (nonphysics-based) methods. A railway truss bridge in Zangenberg, Germany, is used as a case study to illustrate the applicability of this proposed approach. The technical paper “Approach to Reduce the Limitations of Modal Identification in Damage Detection Using Limited Field Data for Nondestructive Structural Health Monitoring of a Cable-Stayed Concrete Bridge” by Ismail et al. proposes a technique to reduce the limitations of modal identification in damage detection using reduced field data for nondestructive SHM of a cable-stayed concrete bridge. Use ofmonitoring systems for bridgemaintenance is also gaining popularity. The technical note “Automated Ice Inference and Monitoring on the Veterans’Glass City Skyway Bridge” by Kumpf et al. presents an ice inference system installed on Veterans’ Glass City Skyway (VGCS) Bridge to assist the Ohio Department of Transportation in managing the response to icing events. Variation in modal properties because of the environment has to be studied before they can be correlated to possible structural damage. If variation in modal properties, caused by temperature variations to which the structure is subjected, is less than the variation caused by the damage of interest, thismethod cannot be reliably used for damage detection. Hence, the technical note “Effect of Temperature on Daily Modal Variability of a Steel-Concrete Composite Bridge” by Mosavi et al. investigated the effect of temperature variations onmodal characteristics of a two-span, steel-concrete composite bridge in North Carolina, and addresses the extent and reason of the daily changes observed in its dynamic properties. The deck is a major component of a bridge structure and is in direct contact with live traffic, subjected to inclement weather, and deicing salts are directly applied over it. Deck performance directly affects the durability and life-cycle costs of a bridge. The technical paper “In-Service Condition Assessment of Bridge Deck Using Long-Term Monitoring Data of Strain Response” by Ni et al. focuses on obtaining information of interest (such as peak stress distribution and dynamic internal forces) to structural engineers using data from the instrumented Tsing Ma Bridge. Inspection and evaluation considerations are very important from planning and design stages to preserve the structural health and durability while minimizing life-cycle costs. The technical paper “Damage Evaluation for Concrete Bridge Deck byMeans of StressWave Techniques” by Shiotani et al. focuses on detection of the fatigue damage of concrete bridge decks utilizing propagation of stress waves. This experimental study concludes that by using sparsely arrayed AE technology, global integrity of bridge decks could be carried out so that local NDE methods can be employed for further investigation of areas of interest. Use of ground penetrating radar, impact echo, and infrared thermography based techniques are widely used by bridge owners to augment visual inspection data from bridge decks for informed

With the continuous development of urbanization and industrialization in the world, concrete is widely used in various engineering constructions as an engineering material. However, the consequent problem of durability of concrete structures is also becoming increasingly prominent. As an important additional measure, a protective coating can effectively improve the durability of concrete performance. Moreover, the uniformity of the concrete surface coating will directly affect its protective effect. Therefore, we propose a nondestructive inspection and evaluation method of coating uniformity based on infrared imaging and cluster analysis for concrete surface coating uniformity detection and evaluation. Based on the obtained infrared images, a series of processing and analysis of the images were carried out using MATLAB software to obtain the characteristics of the infrared images of the concrete surface. Finally, by extracting the temperature distribution data of the pixel points on the concrete surface, an evaluation method of concrete surface coating uniformity based on a combination of cluster analysis and hierarchical analysis was established. The evaluation results show that the determination results obtained by this method are consistent with the actual situation. This study has a positive contribution to the testing of concrete surface coating uniformity and its evaluation.

The design of a gradient structural concrete component was investigated to improve the durability of concrete structures under harsh environments. On the basis of the theory of functionally graded materials with high crack resistance, low transmission, and good self-repairing capability of the cement-based material without a mesoscopic interface transition zone, the reinforcement on performance of protective layer could be achieved. Given the differences in construction situation, structural shape, inner, and outer layer among materials, the gradient structural concrete member (GSCM) and general single-layer concrete member would be prepared. The Deformation coordination capacity, chloride transport properties, and preparation method were investigated, through simulation of stress and deformation, interface bond strength test, and accelerated corrosion test. Results showed that the consistent volume deformation of GSCM did not cause failure, and the surface layer strength of GSCM improved by up to 30%. Only 0.02–0.05 mm cracks were observed without the aid of instruments, and 0.2–0.5 mm cracks were observed in general single-layer members. Moreover, the GSCM had a depth of penetration and chloride diffusion coefficient of 0 mm and 6.3×10−13 m2/s, respectively. These values indicated that the GSCM exhibited good tricyclic assemble performance and satisfied the construction requirement. Meanwhile, the values obtained for the general single components were 15 mm and 12.8×10−13 m2/s.

This paper reviews the applications and performance advantages of ultra-high-performance concrete (UHPC), engineered cementitious composite (ECC), and recycled aggregate concrete (RAC) in composite flexural members. UHPC is characterized by its ultra-high strength, high toughness, excellent durability, and microcrack self-healing capability, albeit with high costs and complex production processes. ECC demonstrates superior tensile, flexural, and compressive strength and durability, yet it exhibits a lower elastic modulus and greater drying shrinkage strain. RAC, as an eco-friendly concrete, offers cost-effectiveness and environmental benefits, although it poses certain performance challenges. The focus of this review is on how to enhance the load-bearing capacity of composite beams or slabs by modifying the interface roughness, adjusting the thickness of the ECC or UHPC layer, and altering the cross-sectional form. The integration of diverse concrete materials improves the performance of beam and slab elements while managing costs. For instance, increasing the thickness of the UHPC or ECC layer typically enhances the load-bearing capacity of composite beams or plates by approximately 10% to 40%. Increasing the roughness of the interface can significantly improve the interfacial bond strength and further augment the ultimate load-bearing capacity of composite components. Moreover, the optimized design of material mix proportions and cross-sectional shapes can also contribute to enhancing the load-bearing capacity, crack resistance, and ductility of composite components. Nevertheless, challenges persist in engineering applications, such as the scarcity of long-term monitoring data on durability, fatigue performance, and creep effects. Additionally, existing design codes inadequately address the nonlinear behavior of multi-material composite structures, necessitating further refinement of design theories.