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This study aims to numerically investigate the behaviour of corroded circular reinforced concrete (RC) columns strengthened by carbon-fabric-reinforced cementitious matrix (C-FRCM) composites. Three-dimensional finite element (FE) models of the corroded circular RC columns with and without strengthening were set up and validated against previous experimental results. Based on the validated FE models, the parametric studies were carried out to investigate the effects of axial compression ratio, degree of corrosion and layer of carbon fabrics on the behaviour of corroded RC columns under cyclic loading. It shows that the lateral load resistance increased when the axial compression ratio ranged from 0.3 to 0.4, but decreased when the axial compression ratio ranged from 0.4 to 0.6; also the ductility of the corroded RC columns reduced with increasing axial compression ratio. The ultimate capacity of corroded RC columns decreased gradually with the increasing degree of corrosion. Based on the results of parametric studies, equations were developed to estimate the ultimate capacity and displacement of the corroded RC columns repaired by the C-FRCM. The proposed equations can well estimate the ultimate lateral load resisting capacity and ultimate displacement of the corroded circular RC columns strengthened by C-FRCM.

Parents of children with complicated congenital heart disease (CHD) have different needs after surgery. Little literature reports the impact factors for psychological needs of parents of children with complicated CHD.To investigate the status quo of the needs of parents of children after surgery for complex CHD, and analyze the influencing factors, in order to provide a theoretical basis for formulating corresponding nursing countermeasures.A modified Chinese version of the Critical Care Family Needs Inventory (M-CCFNI) was used to select 200 parents of children with complex CHD after surgery within 72 h after admission to the intensive care unit in our hospital to conduct an online questionnaire survey. The aim was to understand the needs of parents in relation to the following five aspects: The support from medical staff, comfort of the parents themselves, the acquisition of information, their closeness to the children, and assurance of the child's condition.Parents of children with complex CHD had a higher degree of demand, especially in terms of condition assurance, acquisition of information, and closeness to the children. The age, education level, and residence of the parents were related to the five dimensions of the needs of parents of children with complex CHD who had undergone surgery.In practice, nurses should formulate corresponding nursing strategies based on the different cultural and social backgrounds of parents of children after complex CHD surgery to meet their different needs, and improve satisfaction. These findings provide a theoretical basis for constructing a family participatory nursing model for children in the intensive care unit in the future.

This paper studies the interface bonding performance of carbon-fabric-reinforced cementitious matrix (C-FRCM) composites with the impressed current cathodic protection (ICCP) technique. Single shear tests and pull-out tests on the C-FRCM composites are launched. Three current densities of 0, 100 and 150 mA/m2 in the ICCP technique are considered. The resistance–slip relationships for all the composites are presented. It is found that the maximum resistance of the specimens in the pull-out tests decreases significantly with the increase of current density in the ICCP technique. Moreover, numerical analyses are conducted to obtain a simplified interface bonding stress–slip relationship of the specimens in the pull-out tests.

Magnesium (Mg) based alloys are promising candidates for many applications, but their untreated surfaces usually have low strength and hardness. In this study, a single point diamond turning (SPDT) technique was applied to refine the grain size and improve the mechanical properties of the surface layers of Mg-Li alloys. By refining grains in the topmost layer to the nanometer scale (∼ 60 nm), the surface hardness was found to be enhanced by approximately 60%. The atomic plastic deformation process during the SPDT was then studied by the real-time atomistic molecular dynamics (MD) simulations. A series of MD simulations with different combinations of parameters, including rake angle, cutting speed and cutting depth, were conducted to understand their influences on the microstructural evolution and associated plastic deformation mechanisms on the surface layer of the workpieces. The MD simulation results suggest that using increased rake angle, cutting speed and cutting depth can help to achieve better grain refinement. These simulation results, which provide atomic-level details of the deformation mechanism, can assist the parameter design for the SPDT techniques to achieve the high-performance heterogeneous nanostructured materials.

N-doped porous carbon (NC) was synthesized from sugar cane bagasse, which is a sustainable and widely available biomass waste.

Innovative approaches are under research to study the resistance of chloride ion penetration in concrete containing chloride ions, to minimize the impact of chloride ion penetration test errors in coastal reinforced concrete (RC), which is helpful to the design of coastal RC structures. In this study, the diffusion depth, free ion concentration and diffusion coefficient of chloride, iodide ions with different curing ages and GGBFS content were measured by the Rapid Chloride Migration Test (RCM) and Rapid Iodide Migration tests (RIM). The SEM-EDS and MIP were used to analyze the microstructures, pore size distribution and the hydrated products. The results show that the performance of GGBFS concrete against the diffusion of corrosive ions is affected by the curing age and the content of GGBFS. With the increase of GGBFS content, especially concrete with 60% GGBFS, the influence of chloride, iodide ion penetrating into concrete gradually becomes smaller. The long-age curing system is more conducive to the concrete resistance to the migration and diffusion of chloride, iodine ions. Compared with the ordinary concrete, the total porosity of concrete mixed with GGBFS is lower, the internal microstructures have fewer cracks and defects, the density is better, and the diffusion coefficient of chloride and iodide ions is also lower. In addition, using the concept of corrosive ion adjustment coefficient (conversion coefficient of diffusion between chloride ion and iodide ion) and applying the data regression analysis (DRA), it is found that there is a good quadratic parabolic function relationship between the GGBFS content and the ions adjustment coefficient.

An experimental study on nine circular reinforced concrete (RC) columns is presented in this paper, wherein one column specimen was adopted as the reference group, the other eight specimens were subjected to accelerated corrosion. After the accelerated corrosion for 180 days, two of the corroded columns were protected by impressed current cathodic protection (ICCP), while the other six corroded columns were further repaired by structural strengthening (SS). A combination of ICCP and SS, namely ICCP-SS, is adopted in this study, which adopts the carbon-fabric reinforced cementitious matrix (C-FRCM) as anode and strengthening material. Finally, specimens were cyclically loaded in a horizontal direction under different axial loads. The results indicated load-carrying and energy dissipation capacities of specimens were deteriorated due to corrosion. This phenomenon is severer under higher axial load. The dual function of ICCP-SS technique does not only improve load-carrying and energy dissipation capacities of RC columns, but also reduce the on-going corrosion of steel re-bars. These benefits can be attributed to the confinement effect to the column base provided by the C-FRCM composites and the ICCP effect using carbon fabric mesh in the C-FRCM composites as anode.

This paper describes an experimental investigation on column tests of carbon fiber-reinforced cementitious matrix (C-FRCM) jacket confined hollow section reinforced concrete (RC) columns. The experimental program consists of twenty columns on two series of confined specimens and two series of unconfined specimens. Test specimens comprise of columns having solid section and hollow section with different hollow ratios. The material properties of C-FRCM were measured through tensile coupon tests. The load carrying capacities, load-end shortening responses, load–strain curves and failure modes of RC column specimens are presented and discussed in this paper. It is shown that the hoop strain of columns under compression decreases with the increase of the hollow ratio, which means the reduction of confinement effect. The effect of hollow ratio on the compressive strength of confined concrete was discussed and an equation was proposed. It is shown that the predictions from the proposed equation agree with the test results generally well.

Hydrogen embrittlement (HE) substantially deteriorates the mechanical properties of metals. The HE behavior of nanograined (NG) materials with a high fraction of grain boundaries (GBs) may significantly differ from those of their coarse-grained counterparts. Herein, molecular dynamics (MD) simulations were performed to investigate the HE behavior and mechanism of NG α-Fe under creep loading. The effects of temperature, sustained stress, and grain size on the creep mechanism was examined based on the Mukherjee-Bird-Dorn (MBD) equation. The deformation mechanisms were found to be highly dependent on temperature, applied stress, and grain size. Hydrogen charging was found to have an inhibitory effect on the GB-related deformation mechanism. As the grain size increased, the HE mechanism transitioned from H-induced inhibition of GB-related deformation to H-enhanced GB decohesion. The current results might provide theoretical guidance for designing NG structural materials with low HE sensitivity and better mechanical performance.

Nanograined materials have much denser grain boundary (GB) networks than their coarse-grained counterparts, thereby the hydrogen (H) diffusion and trapping behaviors in nanograined materials, which are strongly influenced by GBs, may differ greatly from those in coarse-grained materials. In the present research, the grain-size dependent hydrogen diffusion coefficient in nanograined Fe is studied by theoretical analysis and molecular dynamics (MD) simulations. A theoretical model based on thermodynamics is developed. The GB-related material parameters required by the model are then obtained by fitting the MD simulation results. Finally, the grain-size dependent diffusion coefficients are compared with model predictions to evaluate the validity of the model. It is found that the trapping effect of triple junctions that usually ignored in coarse-grained materials becomes increasing important as grain size and temperature decrease. Due to the strong trapping effect of GBs in nanograined Fe, H diffusion is slowed down by the GBs.

Self-restraint stress produced in early age is a matter of interest associated with cracking of concrete. Mesoscopic modelling nowadays is one of the effective approaches to investigate internal stresses, deformation, damage of concrete at much smaller scale. However, grid discretization and mesoscopic properties calibration are still challenging issues that prevent fast pre-processing and require extremely dense meshes for accurate solutions. In this paper, a thermo-mechanical model required only regular-element discretization is proposed by developing a diffuse meshing technique to analyze the evolution of self-restraint stress. Cross-scale numerical validations are carried out to calibrate the mesoscopic parameters, along with verifying the feasibility of the proposed model. Furthermore, the effect of simplified aggregate mesostructure on the thermo-mechanical behavior of concrete is evaluated through comparisons with the results obtained by considering complex-shaped aggregate using the proposed diffuse element model. The results show the thermo-mechanical mismatch between different components is the main reason for producing the self-restraint stress, and aggregate meso-structure have nonnegligible influence on the global response or local behavior.

Non-precious TiO2 nanofibers (NFs) Schiff base phenylalanine (SBP) composite was designed via facile methodology; electrospinning and Schiff base loading. The as-fabricated TiO2 NFs/SBP material was investigated in terms of Field emission-scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), Transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques. These physicochemical characterizations indicate the successful design of a nanocomposite of TiO2 NFs/SBP. The corrosion protection of C-steel in acidic chloride environments by the designed TiO2 NFs/SBP material was examined using electrochemical tools (open circuit potential (OCP) vs. time, linear polarization resistance (LPR) corrosion rate, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS)) and surface morphology investigations (FESEM/EDX and FT-IR). The findings showed that the protection capacity (EPDP%) of the individual SBP and TiO2 NFs are 85.6 and 64.8%, respectively, while the EPDP% value for TiO2 NFs/SBP composite is 97.9% at the same conditions. The as-prepared TiO2 NFs/SBP material acts as a good mixed-type inhibitor and its adsorption at the steel/HCl interface followed Langmuir's isotherm model. FESEM/EDX and FT-IR inspections established the formation of the adsorbed layer of the TiO2 NFs/SBP molecule on the electrode surface. The outcomes display that the TiO2 NFs/SBP composite could be used as an efficient inhibitor with excellent anti-corrosion features for C-steel in the acidic pickling solution.

Although hydrogen-induced fracture at grain boundaries has been widely studied and several mechanisms have been proposed, few studies of nanograined materials have been conducted, especially for grain sizes below the critical size for the inverse Hall-Petch relation. In this research work, molecular dynamics (MD) simulations are performed to investigate the hydrogen segregation and hydrogen embrittlement mechanism in polycrystalline Fe models. When the same concentration of H atoms is added, the H segregation ratio in the model with the smallest grain size is the highest observed herein, showing the high hydrogen trapping ability of small-grain Fe, while the H concentration at the grain boundaries (GBs) is, on the contrary, the lowest. Uniaxial tensile test simulations demonstrate that as the grain size decreases, the models show an increased resistance to hydrogen embrittlement, and for small-grain models (d

The nanoscratch test has been identified as one of the important tools for evaluating the mechanical and tribological properties of materials. This paper reviews the current researches on the nanoscratch test using to characterise the mechanical properties of three typical materials, including thin film, polymer composite and concrete, from the perspectives of the Berkovich indenter, parameter selection, mode selection, and analysis of resulting data. In addition, to provide a deep understanding on the test from different magnitude, a comparison between the microscratch test and nanoscratch test on the evaluation of tribological performance is also provided in this paper. The characterisation by nanoscratch test of two structural samples, in terms of layered film structures (thin film and coating sample) and single layer block structure (polymer composite sample and concrete samples) are also described in this paper, which aims to provides a deep understand on the evaluation the adhesion, tribological and interfacial properties of the typical materials samples by nanoscratch test. Finally, the coefficient of friction and critical load are discussed, which are two important parameters in tribological properties and adhesion properties.

In fabric-reinforced cementitious matrix (FRCM) systems, one technique to increase the strengthening efficiency is to utilize the deformability of dry fiber bundles and anchor them at thei...

A new generalized method for evaluating the bond slip relationship of the interface between concrete and the externally bonded reinforcement is presented. The method is based on the relationship between the applied force and the displacement of the reinforcement at the loaded end. As no prior assumption on the detailed configuration of the bond slip relationship needs to be made using the generalized method, the obtained bond slip relationship can be regarded as a generalized relationship. The method was then used to evaluate the bond slip relationship of an investigated FRP-concrete interface reported in the existing literature, and the obtained relationship compared with several available bond slip models. It can be found that various bond slip relationships differ vastly even for the same FRP-interface, especially for the maximum bond stress and the corresponding slip as well as the the slip corresponding to the insignificant bond stress. In addition, the bond slip relationship obtained using the generalized method leads to the good prediction of the experimental results in terms of the global force versus displacement curve and strain distribution along the interface.

Microcapsules encapsulated within epoxy as a curing agent have been successfully applied in self-healing materials, in which the healing performance significantly depends on the binding behaviour of the epoxy curing agent with the cement matrix. In this paper, the binding energy was investigated by molecular dynamics simulation, which could overcome the shortcomings of traditional microscopic experimental methods. In addition to the construction of different molecular models of epoxy, curing agents, and dilutants, seven models were established to investigate the effects of chain length, curing agent, and epoxy resin chain direction on the interfacial binding energy. The results showed that an increase of chain length exhibited had limited effect on the binding energy, while the curing agent and the direction of the epoxy significantly affected the interfacial binding energy. Among different factors, the curing agent tetrethylenepentamine exhibited the highest value of interfacial binding energy by an increment of 31.03 kcal/mol, indicating a better binding ability of the microcapsule core and the cement matrix. This study provides a microscopic insight into the interface behaviour between the microcapsule core and the cement matrix.

This paper presents a detailed investigation into the flexural strength and behaviour of cold-formed steel oval hollow section beams. A series of four-point bending tests were conducted as part of the experimental programme. Following this, a total of 12 tested beams were simulated by a non-linear finite element analysis. Upon validation of the newly developed numerical model, a total of 36 numerical results were generated through a parametric study to assess the structural response of the oval hollow section beams over a wider range of cross-section dimensions. The experimental and numerical data were used to evaluate the applicability of five existing design methods for cold formed steel structural members, including Eurocode 3, the North American Specification, the Australian/New Zealand Standards, the direct strength method and the continuous strength method. In general, the results indicate that all the three design standards produce unconservative predictions, while the direct strength method and the continuous strength method yield relatively accurate and consistent predictions.

Chloride ions in marine environment can cause corrosion of steel reinforcement in reinforced concrete (RC) structures and result in structure deterioration. This study investigates a dual-functional intervention method, i.e. impressed current cathodic protection – structural strengthening (ICCP-SS) method, using carbon fibre reinforced polymer (CFRP) as both the anode material for impressed current cathodic protection and strengthening material for structural strengthening system. The effectiveness of the ICCP-SS method on the improvement of durability of RC structures is considered in a long-term timeframe. An experimental programme comprising nine simply supported beams is presented in this paper. The beams experienced 360-day accelerated corrosion and 180-day cathodic protection, followed by four-point bending tests. Flexural behaviour and capacities of the degraded beams repaired by using ICCP technology, structural strengthening technology and ICCP-SS technology were obtained. After the tests, the steel reinforcement bars inside concrete were taken out and cleaned to measure the section reduction due to corrosion. Results showed that the ICCP-SS technology can prevent the corrosion of the steel reinforcement effectively and increase the capacities of the beams at the same time. Finally, the appropriateness of existing design approaches for the intervened beams was also discussed in the paper. The ICCP-SS intervention method is found to be beneficial for the durability of RC structures in marine environment.

The popularity of reinforced concrete (RC) structures leads to increasing demand for sands, cement, aggregates and other raw materials. In the recent decades, river sand has been used to replace sea-in order to solve the resource shortages in many countries. However, sea-sand concrete might cause corrosion of steel re-bars and result in structure deterioration. Impressed current cathodic protection (ICCP) is an efficient method to prevent corrosion of re-bars, while bonding carbon fibre mesh to the RC structures can help improve the loading capacity of the deteriorated structures. This study proposes a new dual-functional intervention method, the impressed current cathodic protection – structural strengthening (ICCP-SS) method, to retrofit the deteriorated sea-sand RC structures by using the carbon – fabric reinforced cementitious matrix (C-FRCM). The C-FRCM composite, comprised of carbon fabric mesh and inorganic cementitious matrix, is both the anodic material for ICCP and the structural strengthening material. This paper presents an experimental program consisting of 11 simply supported beams, 9 of which were casted by simulated sea-sand and subjected to accelerated corrosion for 130 days. The specimens casted with simulated sea-sand were afterwards externally bonded with C-FRCM composite, exposed to ICCP for another 130 days, and finally tested. In this study, the loading capacity and deflection at midspan of the beams, as well as the open circuit potential (OCP) of re-bars were measured to assess the effectiveness of the intervention method. The proposed method has been shown to be effective in retarding the corrosion of steel re-bars and improving the loading capacity of the corroded specimens. In addition, this paper compares the experimental results with the capacity predictions set out in ACI 440.2R-08 for FRP strengthening system and ACI 549.4R-13 for FRCM strengthening system, which have been found to be rather conservative for the flexural design of retrofitted beams.

Aluminium alloys have high strength-to-weight ratios and great durability; thus, they have been extensively used in structural applications. Channel sections have a smooth and aesthetically pleasing line shape, good integrity, and are easy to connect. An experimental program using 28 specimens and a numerical study that generated 100 results were conducted on aluminium alloy columns of plain and lipped channel sections. The nominal length of columns ranged from 300 mm to 3000 mm. The generated 128 results were evaluated with respect to the existing design specifications from America, Australia/New Zealand, Europe and China. Furthermore, the direct strength method (DSM) and the continuous strength method (CSM) were also used to predict results for comparison. The results showed that the design specifications produced conservative compression strengths of aluminium alloy columns of both plain and lipped channel sections. The CSM provided more accurate and consistent design strengths. In addition, the reliability levels of the four international design codes, DSM and CSM for channel sections of aluminium alloy columns were also evaluated.

A novel method is developed to reclaim carbon fibres from carbon fabric-reinforced cementitious composites. The method takes advantage of an electrically driven chemical reaction in the presence of an aqueous electrolyte solution and an electrical current. This paper presents an experimental programme to investigate the effects of the applied current density, the sodium chloride and nitric acid concentrations in the solution and the temperatures. Both tensile strengths and interfacial shear strengths of the reclaimed carbon fibres were evaluated. Microstructural analyses on the morphologies of the reclaimed carbon fibres were also performed. The proposed method is simple, environmentally friendly and efficient. This method has no size limits on the recycled composites, which indicates the suitability of this approach for large-scale industrial applications. The reclaimed carbon fibres are found to be intact and believed to have great commercial value since the recycling process did not damage their strengths or reduce their dimensions.

The study conducts an experiment on flexural behavior of H-shaped high-strength steel beams with perforated web subjected to both gradient and constant bending. A total of 12 specimens including narrow flange and wide flange H-section beams were tested, which were made of high-strength steel Q550D and TQ700MCD, respectively. The effects of the ratio of web depth to flange width (h/b), the ratio of flange width to thickness (b/tf), the ratio of web depth to thickness (h/tw), the ratio of hole diameter to web depth (d/h) and the number of holes in the web on the flexural behavior of H-shaped steel members with high strength were investigated. Test results consist of the failure mode, bending moment-midspan deflection curves as well as the strain distributions at the midspan and the perforated sections of H-shaped high-strength steel beams. It was found that the ultimate flexural strengths and the corresponding curvatures of the specimens under gradient bending are all greater than those of the specimens under constant bending. The flexural strengths of H-shaped high-strength steel members with or without holes in the web gained in the experiments were made the comparison with those determined from current designing guidelines of perforated or imperforated steel members. The comparison reveals that American National Standard (AISC 360-16) and North American Specification (NAS) are quite conservative; Eurocode 3 (EC3) is somewhat unconservative; Australian Standard (AS) and Chinese Coding (CC) are somewhat conservative. Furthermore, Direct Strength Method (DSM) is quite conservative, Steel Design Guide Series 2 and Continuous Strength Method (CSM) are somewhat conservative for the flexural behavior of H-shaped high-strength steel beams with perforated web.

This paper presents an investigation on the bond behavior of the carbon fabric-cementitious matrix interface within the fabric reinforced cementitious matrix (FRCM) composite. The embedded carbon yarn shows a complicated bond behavior due to stochastic and incomplete impregnation of the matrix and can be subdivided into the outer (impregnated) and inner (non-impregnated) parts. Pullout tests were carried out on the carbon FRCM composite aiming at examining the effect of matrix impregnation on the bond behavior between fabric and matrix. The test results show that pullout specimens with a 30 mm embedded length failed due to pure slippage of the carbon yarn, while the failure became the slippage and partial rupture of the carbon yarn for the specimens with longer lengths. The impregnated filaments are estimated as about 30% of the total filaments within an embedded carbon yarn according to image processing and analysis results. Different bond slip relationships were assumed and evaluated for the outer and inner parts within an embedded carbon yarn based on pullout test results. The accuracy of the evaluated bond slip relationships was validated through a good agreement between experimental results and finite element modeling.

This paper presents a generalized evaluation method for determining the bond slip relationship of an external reinforcement bonded to concrete based on the experimental global force versus...

This paper experimentally studies the effects of fly ash on the diffusion, bonding, and micro-properties of chloride penetration in concrete in a water soaking environment based on the natural diffusion law. Different fly ash replacement ratio of cement in normal concrete was investigated. The effect of fly ash on chloride transportation, diffusion, coefficient, free chloride content, and binding chloride content were quantified, and the concrete porosity and microstructure were also reported through mercury intrusion perimetry and scanning electron microscopy, respectively. It was concluded from the test results that fly ash particles and hydration products (filling and pozzolanic effects) led to the densification of microstructures in concrete. The addition of fly ash greatly reduced the deposition of chloride ions. The chloride ion diffusion coefficient considerably decreased with increasing fly ash replacement, and fly ash benefits the binding of chloride in concrete. Additionally, a new equation is proposed to predict chloride binding capacity based on the test results.

Microcapsule based self-healing concrete can automatically repair damage and improve the durability of concrete structures, the performance of which depends on the binding behavior between the microcapsule wall and cement matrix. However, conventional experimental methods could not provide detailed information on a microscopic level. In this paper, through molecular dynamics simulation, three composite models of Tobermorite (Tobermorite 9 &Aring, Tobermorite 11 &Aring, Tobermorite 14 &Aring, ), a mineral similar to Calcium-Silicate&ndash, Hydrate (C&ndash, S&ndash, H) gel, with the linear urea&ndash, formaldehyde (UF), the shell of the microcapsule, were established to investigate the mechanical properties and interface binding behaviour of the Tobermorite/UF composite. The results showed that the Young&rsquo, s modulus, shear modulus and bulk modulus of Tobermorite/UF were lower than that of &lsquo, pure&rsquo, Tobermorite, whereas the tensile strength and failure strain of Tobermorite/UF were higher than that of &lsquo, Tobermorite. Moreover, through radial distribution function (RDF) analysis, the connection between Tobermorite and UF found a strong interaction between Ca, N, and O, whereas Si from Tobermorite and N from UF did not contribute to the interface binding strength. Finally, high binding energy between the Tobermorite and UF was observed. The research results should provide insights into the interface behavior between the microcapsule wall and the cement matrix.

Chloride-induced steel corrosion is the most concerning issue for the durability of concrete structures. Concrete and steel samples were obtained from a 30-year-old reinforced concrete bridge. The chloride content was measured by a potentiometric titration method and the microstructure of concrete was obtained by scanning electron microscopy and mercury intrusion porosimetry. The rust phases of the steel were detected by X-ray diffraction and Raman analysis. It was found that the convection depth for chloride transport in cracked concrete was significantly larger than that in uncracked concrete. The concrete in a pier column facing upstream had greater porosity due to the water impact and calcium leaching. The coefficients of variability of chloride diffusivity of concrete for the bridge deck and the pier column were significantly different. Rust phases including lepidocrocite, goethite, akaganeite, magnetite, and maghemite were detected using Raman spectroscopy and X-ray diffraction. The major phases of steel rust in the atmospheric zone were lepidocrocite and goethite, while they were lepidocrocite and maghemite in the tidal zone. The results of this study would provide information concerning the chloride-induced steel corrosion under a marine environment in order to predict long-term behaviors of a reinforced concrete structure.

Preserving the integrity of carbon fibers when recycling carbon-fiber-reinforced plastics (CFRPs) has been unfeasible due to the harsh reaction conditions required to remove epoxy resin matrixes, which adversely affect the properties of carbon fibers. We establish a practicable and environmentally friendly reclamation strategy for carbon fibers. Carbon fibers are recycled from waste CFRPs by an electrochemical catalytic reaction with the assistance of phosphotungstic acid (PA), which promotes the depolymerization of diglycidyl ether of bisphenol A/ethylenediamine (DGEBA/EDA) epoxy resin. The removal rate, mechanical strength, and microstructure of the recycled carbon fibers are analyzed to explore the mechanism of the electrochemical treatment. The influence of three factors&mdash, current density, PA concentration, and reaction time&mdash, are studied via an orthogonal method. Range analysis and variance analysis are conducted to investigate the significance of the factors. The optimal conditions are determined accordingly. The underlying CFRP degradation mechanism is also investigated.