Simulated Concrete Pore Solution Research Articles

Crevice corrosion of reinforcing steel in carbonated simulated concrete pore solutions contaminated by chloride

Crevice corrosion of reinforcing steel in carbonated simulated concrete pore solutions contaminated by chloride

Influence of Solution Alkalinity and Alternating Current Density on Anti-corrosion Property of CoCrFeMnNi High-Entropy Alloy in Simulated Concrete Pore Solution

Influence of Solution Alkalinity and Alternating Current Density on Anti-corrosion Property of CoCrFeMnNi High-Entropy Alloy in Simulated Concrete Pore Solution

Rust Prevention Property of a New Organic Inhibitor under Different Conditions.

The corrosion resistance properties of a new type of environmentally-friendly organic inhibitor containing amino ketone molecules are presented in this paper. To evaluate the prevention effect of the inhibitor on corrosion of reinforcement, the electrochemical characteristics of steels in the simulated concrete pore solution (SPS) were investigated under varied conditions of the relevant parameters, including concentrations of the inhibitor and NaCl, pH value, and temperature. The inhibition efficiency of the material was characterized through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and the weight loss of steels. The results reveal a significant improvement in the corrosion resistance of steels with the inhibitor. A maximum resistance value of 89.07% was achieved at an inhibitor concentration of 4%. Moreover, the new organic inhibitor exhibited good corrosion protection capability for steels under different NaCl concentrations. Its inhibition efficiency was determined to be 65.62, 80.06, and 66.30% at NaCl concentrations of 2, 3.5 and 5%, respectively. On the other hand, it was found that an alkaline environment was favorable for an enhanced corrosion prevention effect, and an optimal pH value of 11.3 was observed in this work. Besides, the inhibition efficiencies at different temperatures showed a trend of 25 > 35 > 40 > 20 > 30 °C, with a maximum value of 81.32% at 25 °C. The above results suggest that the new organic material has high potential to be used as an eco-friendly and long-term durable inhibitor for steel corrosion prevention under complex conditions.

Effects of –NH2 and –COO− functional groups on the steel passivation in concrete pore solution: Passivation performance and interfacial adsorption mechanism

The use of organic corrosion inhibitors is a common method for enhancing the corrosion resistance of steel in concrete. Whereas, the effects of common functional groups (–NH2 and –COO−) on the steel passivation are still unclear. Herein, propylamine (C3H7NH2) and calcium butyrate ((C3H7COO)2Ca) were selected as representative inhibitors containing –NH2 and –COO− groups, respectively. The passivation performance of steel affected by C3H7NH2 or (C3H7COO)2Ca in simulated concrete pore solution was explored by electrochemical method, XPS tests, and DFT simulation. Experimental results show that the (C3H7COO)2Ca has little effect on passivation performance, while the C3H7NH2 exhibits an inhibition effect. The XPS data shows that the (C3H7COO)2Ca decreases the Fe/Fen+ ratio on the steel surface, thereby enhancing the physical protectiveness of passive film. Although the C3H7NH2 causes an increase in the chemical protectiveness of passive film (Fe2+/Fe3+ ratio increase), it induces a more pronounced decrease in physical protectiveness, resulting in the poor passivation performance of steel. DFT results indicate that the C4H7O2− adsorption increases the activity of iron surface, thereby promoting the adsorption of passivation substances (OH–/CaOH+). Moreover, insoluble C4H7O2-Ca-Fe compounds form due to the electron transfer between –COO− and CaOH+. Besides, the C3H7NH2 inhibits the adsorption of OH–/CaOH+ on steel surface.

Passivation of cold-sprayed zinc-coated steel bars in simulated concrete pore solution

Hot-dip galvanized coating is proved to be effective in preventing chloride ion induced corrosion on steel bars, however, highly-toxic substances generated during the plating process seriously pollute the surrounding environment. Cold-sprayed zinc as an environment-friendly technology is an alternative to the hot-dip galvanized technology, but it has not been applied to steel bars in the alkaline environment of concrete. This study first fabricated the cold-sprayed zinc-coated steel bars, and then investigated the influences of Ca2+ concentration and pH on the passivation of zinc-coated steel bars in the simulated concrete pore solutions through electrochemical tests, microstructure examination, and element composition analysis. The experimental results show that passive film can be generated on the surface of cold-sprayed zinc-coated specimens in the simulated concrete pore solutions with pH = 12.5 and Ca2+ concentration above 0.8 g/L, but Ca2+ concentration determines the density and quality of the passive film. The passive film can resist the attack of chloride ions up to 0.2 mol/L. Compared with hot-dip galvanized coating, more large-sized and compacted crystals are generated on the surface of cold-sprayed zinc coating. Thus, it is feasible to apply cold-sprayed zinc technology to provide corrosion protection for steel bars in the concrete.

Potential application of Ginkgo biloba extract as a green corrosion inhibitor for carbon steel reinforcement in chloride-polluted simulated concrete pore solution

The present work describes the development of a green and sustainable corrosion inhibitor using the extract of Ginkgo biloba fruit (GBFE). The screening of the inhibitory performance of GBFE was done in a simulated concrete pore solution (SCPS). The results report that GBFE inhibits B450 ribbed steel bar (RSB) corrosion and represents a significant decrease in corrosion rate with the rising dose at 50 °C temperature. Electrochemical experiments manifest that GBFE can restrain reactions of the cathode and anode of RSB. The molecular adsorption of GBFE is governed by Langmuir adsorption isotherm. The main active components were classified using Fourier Transform Infrared Spectrometer (FTIR) and Mass spectrometry (MS). The morphology maps of surface analysis support the creation of an inhibitive layer of GBFE over the RSB surface. DFT and MC describe the adsorption of GBFE over the RSB.

Corrosion Behavior of Coupled Steel Bars under Different Stress Levels in Simulated Concrete Pore Solutions

Corrosion Behavior of Coupled Steel Bars under Different Stress Levels in Simulated Concrete Pore Solutions

Effect of high-energy shot peening on the corrosion behavior and chloride threshold concentration of AISI 316L stainless steel rebar in simulated concrete pore solution

The corrosion behavior and chloride threshold concentration of AISI 316L stainless steel reinforcement bar (rebar), subjected to high-energy shot peening (HESPed), are compared with its solution-annealed (SAed) counterpart in simulated concrete pore solution (CPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that HESP significantly reduces the surface grain size to the ultrafine/nanometric range and increases the density of various dislocation structures, including dislocation walls and cells. This augmented presence of grain boundaries and dislocations, acting as high diffusivity paths, contributed to the formation of a thicker surface film with higher Cr content and lower donor/acceptor density in the HESPed sample compared to the SAed. Moreover, corrosion behavior analyses in CPSs with NaCl concentrations ranging from 0.0 to 2.0 M demonstrated that HESPed samples exhibit broader passivation ranges, more positive corrosion potentials, and higher polarization resistance under equivalent chloride concentrations. Additionally, threshold chloride concentrations obtained from the potentiodynamic polarization tests show values between 0.5 and 1.0 M for the SAed and between 1.0 and 1.5 M for the HESPed samples. Based on diffusion equations, a physical model is proposed to elucidate the improved behavior resulting from the HESP treatment.

Effect of immersion time on the corrosion behaviour of X70 and X80 line pipe steels in simulated concrete pore solution

Effect of immersion time on the corrosion behaviour of X70 and X80 line pipe steels in simulated concrete pore solution

Investigation of Cr and rare earth (RE) on the corrosion resistance of HRB400 rebar in simulated concrete pore solutions containing chloride and sulfate ions

The effect of Cr and rare earth (RE) on the corrosion resistance of HRB400 in simulate concrete pore solution containing Cl− and SO42− was investigated. The results of electrochemical tests and corrosion morphology observations revealed that HRB400 corrosion rates increased with sulfate concentration, but Cr/RE addition notably reduced rates and passive current density, particularly in high sulfate conditions, suggesting a sulfate-Cr/RE interaction. The mechanism involves structural changes in the surface passivation film. Furthermore, the combination of Cr and RE effectively mitigated localized corrosion risk compared to Cr alone, highlighting their synergistic corrosion resistance enhancement.

A novel LDHs-VB3- inhibitor for rebar corrosion in simulated concrete pore solution: Synthesis, performance and mechanism

Developing novel chloride-trapping inhibitors is of great significance for enhancing the durability of marine concrete structures. In this study, a novel LDHs-VB3- inhibitor was synthesized through the ion exchange method. Then, the corrosion inhibition mechanism of LDHs-VB3- inhibitor for rebar in the whole process of release - capture - adsorption - retardation was studied using experiments and density functional theory (DFT) simulations. The chloride ion exchange test demonstrates that the LDHs-VB3- inhibitor has a chloride trapping capacity of 35.5 mg/g in the saturated Ca(OH)2 solution containing 0.14 M NaCl, implying that it could capture Cl- in concrete pore solution. According to the electrochemical tests, the critical chloride concentration of rebar in the simulated concrete solution containing LDHs-VB3- falls within a range of 0.22 M–0.28 M, which is much higher than that in the solution without LDHs-VB3- (0.10 M–0.14 M). DFT simulations indicate that LDHs-VB3- exhibits more positive binding energy and uneven binding forces in contrast to LDHs-Cl-. Consequently, VB3- could be easily replaced by Cl- and then released into the pore solution of concrete. Moreover, the released VB3- could adsorb on the α-Fe2O3 surface in a concrete environment via the interaction of surface Fe atoms with N and O atoms of VB3-. The preadsorbed VB3- could diminish the interaction of Cl- with the α-Fe2O3 surface by reducing electron transfer, thereby mitigating the risk of passive film breakdown and retarding the chloride-induced corrosion of rebars.

Electrochemical dielectric response of steel corrosion induced by chloride in simulated concrete pore solution

Electrochemical and dielectric properties of steel oxide films can have an impact on the corrosion process but are still poorly understood due to the unavailability of measurement methods. In this study, electrochemical impedance spectroscopy (EIS) was adopted to interpret steel corrosion induced by chloride in a simulated concrete pore solution. Particularly, validation of EIS data by Kramers–Kronig transforms was performed prior to further EIS interpretation. Relative dielectric permittivity of corroded steel/electrolyte interface was derived through theoretical induction and corrosion products were analyzed by X-ray photoelectron spectroscopy. Results indicated that measured EIS data in the present study depicted good causality and stability. Corrosion at the steel/electrolyte interface induced by increasing chloride led to high relative permittivity within the low frequency domain while marginal difference could be observed at the high frequency range. AC conductivity of corrosion products at steel/solution interfaces revealed a notable frequency dependence, based on which three distinct frequency regions were subdivided.

Repassivation characteristics of carbon steel in chloride-free pore solution after thermal cycles of simulated tropical marine environments

Abstract Repassivation characteristics of carbon steel experienced thermal cycles in tropical marine environments were investigated in a simulated concrete pore solution (SCPS). The results suggested that the damage of passive films on the carbon steel mainly occurred during the cooling process in thermal cycles. The damaged passive films gradually recovered in the SCPS, and the duration of repassivation extended with the amplitude of thermal cycles and cyclic number in the high-amplitude thermal cycles (20–60 °C and 20–70 °C), while it was not significantly affected by the cyclic number in the low-amplitude thermal cycles (20–40 °C and 20–50 °C).

Corrosion inhibition by fruit extracts -Inhibition of corrosion of mild steel in simulated concrete pore solution prepared in sea water by an aqueous extract of apple juice- A Case study

The inhibition efficiency of an aqueous extract of apple juice in controlling corrosion of mild steel immersed in simulated concrete pore solution (SCPS) prepared in sea water, has been evaluated by weight loss method. Langmuir adsorption isotherm has been investigated. The mechanistic aspect of corrosion inhibition has been investigated by Electrochemical impedance spectra (AC impedance spectra). The protective film has been analysed by Fluorescence spectroscopy, FTIR spectroscopy and AFM. The SCPS system offers 60% inhibition efficiency to mild steel immersed in sea water. In presence of apple juice extract the inhibition efficiency increases as the concentration of the extract increases. When 10 ml of extract is added, 85% inhibition efficiency is obtained. Electrochemical impedance spectra (AC impedance spectra) reveal that a protective film is formed on the metal surface. In the presence of inhibitor system, charge transfer resistance value increases, impedance value increases, phase angle value increases whereas double layer capacitance value decreases as expected. The FTIR spectral study reveals that the protective film consists of complexes consisting of iron-active principles of the apple juice extract. AFM study reveals that when the inhibition efficiency increases the roughness of the surface decreases or in other words the smoothness of the system increases.

Function of Cu-Sb or Al microalloying on the corrosion resistance of 9Cr steel exposed to simulated concrete pore solution

The role of Cu-Sb or Al on the passivation and Cl-induced depassivation of 9Cr steel in simulated concrete pore solution was systematically obtained via electrochemical tests and microstructure characterization. Both microalloying enhanced electrochemical passivation even if the solution pH dropped. Cu and Al participated in the formation of natural passive film, and the properties of passive film were optimized in terms of resistance, composition, and inner film thickness. However, the chloride threshold level (CTL) was not increased with Cu-Sb microalloying and even decreased with Al microalloying, which is understood from the stability of Al-containing products and the hazards of inclusions.

Synthesis and properties of biomass derived carbon/PEG composite as photothermal conversion effective phase change material for functional concrete

Mixing phase change material (PCM) into concrete is a practical strategy for functionalizing concrete as an energy-storage unit. This study aims to invent an efficient photo-thermal conversion type PCM for the manufacturing energy storage functional concrete, which meet the needs of hydration heat storage and thermal storage in service. To solve the liquid leakage problem of PCM, a novel bamboo-based hydrothermal carbon sphere (HCS) with unique mesoporous structure was prepared to pack polyethylene glycol (PEG) to make shape stable PCM. The photo-thermal material nano-Ag was successfully introduced into the composite PCM through a high-voltage electrostatic field. To understand the stability and performance of the PCM for concrete use, the structural composition and thermal storage efficiency of Ag@HCS-CNTs/PEG in simulated concrete pore solution (a highly alkaline solution containing potassium, sodium, and calcium cations) were systematically studied via multiple characterization methods. After being soaked in concrete pore solution for 7 days, the PCM shows outstanding thermal storage density (147 J/g), photo-thermal conversion efficiency (110.6%), and resistance to Na+, Mg2+, Cl− and SO42−. In addition, the biomass subtracted PCM preparation has low energy consumption and low carbon emission features. These open a window of realistic PCM application in the structural concrete, insulation porous walls and energy storage buildings.

Inhibition performance of extract reinforcement corrosion inhibitor from waste Platanus acerifolia leaves in simulated concrete pore solution

In our previous study, the ultrasound-assisted enzymatic extract of Platanus acerifolia leaves (PAL) was confirmed as an efficient corrosion inhibitor of steel. In this study, a new strategy-ultrafiltration-was proposed to further enhance the corrosion inhibition effect of this green steel corrosion inhibitor. To pinpoint the main players in the corrosion-inhibiting performance, the active compounds of the treated PAL extract were further quantitatively characterized via high performance liquid chromatography (HPLC). Electrochemical approaches were employed to investigate the anti-corrosion behavior. The adsorption film and surface morphology of the steel surface were characterized via X-ray photoelectron spectroscopy (XPS) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS), respectively. Furthermore, simulations were carried out to further explore the inhibition mechanisms of the active molecules. The results showed that ultrafiltration significantly removed the polysaccharide impurities, thereby further concentrating the inhibition constituents. Twelve flavonoids and their derivatives were quantitatively traced, among which the procyanidins was the most pronounced ingredient (220 ppm). Ultrafiltration can effectively improve the inhibition performance of the extract. In the presence of chloride ions, the inhibition efficiency of the 1.5 wt% two-step processed extract was equivalent to that of the 5 wt% primary extract. Plus, SEM-EDS observations confirmed that the two-step processed extract was able to effectively mitigate the corrosion degree. XPS and simulation analyses revealed that the flavonoids and their derivatives executed the corrosion inhibition performance by forming a protective carbon-containing organic film on the steel surface via chelation and surface physical adsorption.

Effects of a novel carbon nanomaterial on hydration, mechanics, and chloride binding of cement composites

Nanomaterials have made significant progress in the field of cementitious materials, but suffer from primary problems of high cost and poor dispersity. Carbon dots (CDs) as a novel low-cost and high-dispersity nanomaterial preliminarily demonstrate their potential for cement. Nevertheless, it lacks systematic research on their effects on cement properties. For the first time, this work comprehensively investigates the effects of CDs on the hydration, mechanics, and chloride binding of cement composites. More importantly, the relevant mechanisms are revealed in depth. Specifically, cost-efficient ($0.013/g) and well-dispersed (dispersed in simulated concrete pore solution for 7 d) CDs are directly prepared by a facile microwave approach. The CDs dramatically retard the early hydration, improve later mechanical performance, and obviously enhance chloride binding. In detail, 0.2 wt% CDs reduce the second exothermic peak value by 75%, but improve the chloride binding capacity of paste by 51%. And 0.1 wt% CDs enhance the compressive/flexural strength of mortar by 17%/21%. Crucially, related influence mechanisms are uncovered. Namely, CDs create a protective barrier to retard hydration through the complexation of their abundant surface groups with Ca2+; While CDs exert the nucleation effect to boost the formation of C–S–H and Friedel's salt, thereby playing a positive impact on chloride binding; Meanwhile, CDs with suitable dosages carry out nucleation effect to counteract their air-entraining effect, thus improving later mechanical properties of cement composites. This study is expected to provide a novel low-cost and high-dispersity CDs nanomaterial to advance the development of high-performance cementitious materials.

Influence of AgCl film resistance on stability and potential response of Ag/AgCl chloride-sense electrode in simulated concrete pore solution

The characteristics of AgCl film determine performance of Ag/AgCl electrode for chloride detection in concrete pore solution. In this study, the microstructure effect of AgCl film on the durability and sensitivity of Ag/AgCl electrode was investigated by electrochemical methods with SEM. The results indicated generally thick and dense AgCl film resulted in the improved service life and prolonged response time of Ag/AgCl electrode. Further, potential fluctuations were relevant for AgCl film thickness>32.04 µm. Based on the obtained data, the relationship between AgCl film resistance and service life/response time of Ag/AgCl electrode was established, which can accurately evaluate the performance of Ag/AgCl electrode in concrete.

Interface Bonding Properties and Mechanism of Steel Fiber and Hot Melt Adhesive via Interface Design Engineering.

Steel fiber textile, which is composed of steel fibers and glass fibers, has a support layer impregnated with hot melt adhesive (HMA). During long-term service, the bonding force between the steel fiber/HMA system interfaces is poor. In order to improve the bond strength and durability of the interface, this paper introduced sandblasting, acid-etching, and phosphating treatments on the surface of the steel fibers. Also, the effects of these three pretreatment methods on the bond strength of the steel fiber/HMA interface were investigated. The results indicate that the interfacial bond strength of composites made from steel fibers is improved via surface treatment. Under a hydrothermal and simulated concrete pore solution environment, the durability of the steel fiber/HMA interface after sandblasting and acid-etching pretreatment is not as good as that after phosphating pretreatment. The mechanical properties of the phosphating/HMA composite were maintained at 4.56 and 2.24 times compared to those of the untreated/HMA composite, respectively. This is because the pinning effect formed by the phosphating film on the surface of steel fibers at the interface of steel fiber/HMA can serve as a physical barrier against corrosion, preventing the invasion of chloride ions and water vapor and improving the durability of the interface.