Chloride Permeability Research Articles

Chloride Permeability of Alkali-Activated Slag Concretes after Exposure to High Temperatures.

The number of fires in buildings and on bridges has increased worldwide in recent years. As a structural material, the strength of alkali-activated slag (AAS) concrete after exposure to high temperatures has been given much attention. However, research of its durability is still lacking, which limits the application of this type of concrete on a larger scale. In this context, as one of the most important aspects of durability, the chloride permeability of AAS concretes after exposure to high temperatures was examined in this study. The influence of the alkali concentration (Na2O%) and the modulus (Ms) of the activator, as well as the influence of heating regimes, including the heating rate, duration of exposure to the target temperature, and cooling method, was also discussed. The results show that the chloride permeability of the AAS concretes increased with temperature elevation. Due to the interference of pore solution conductivity, the influence of the Na2O% and the Ms of the activator on the chloride permeability of the AAS concretes was not made clear by using the ASTM C 1202 charge passed method; however, after exposure to high temperatures, AAS with a lower Na2O% and lower Ms has lower porosity and may have lower chloride permeability, which needs further investigation. Faster heating for a longer duration at the target temperature and water cooling reduced the resistance of the AAS concretes to chloride permeability as a result of their increased porosity.

Selective electrodialysis: Targeting nitrate over chloride using PVDF-based AEMs

The depletion of natural resources and the escalating environmental concerns associated with pollution necessitate innovative approaches for sustainable resource management. In this study, we investigated the selective separation of nitrate from chloride in electrodialysis (ED) using a recently introduced PVDF-based anion-exchange membrane (PVDF-50) and two commercially available membranes (ACS and AMX from Neosepta). Experimental ED data show that the membrane PVDF-50 presents a higher value of nitrate over chloride selectivity compared with the two commercial membranes, the highest reported in literature.However, recognizing that completely preventing the permeation of chloride ions into the concentrate stream was not feasible, we explored the potential of a system in which anion-exchange membranes presenting different monovalent selectivity were alternated. In this approach, referred to as nitrate-selectrodialysis (NO3-SED), the different selectivity of PVDF-50 and AMX membranes was leveraged to demonstrate the possibility of increasing nitrate concentration, while simultaneously reducing chloride levels in a stream. This approach proves highly advantageous in applications where mitigating chloride contamination is a significant concern while recovering nitrate.

The acid and chloride permeability resistance of masonry cement plaster mortar incorporating high-volume fly ash content

The utilization of masonry cement mortar has been on the rise in recent years, gradually supplanting the traditional use of lime and Portland cement in plastering applications. Masonry cement mortar is favored for its enhanced workability; however, it remains vulnerable to environmental factors, and there is a dearth of information regarding the durability assessment of masonry cement plaster mortar. While incorporating fly ash in mortars is a common practice, it is often paired with Ordinary Portland Cement as the primary binding agent. This research project was devised to investigate the performance characteristics of masonry cement plaster mortar infused with varying levels of fly ash. The control specimen was systematically replaced with fly ash in 10% weight increments, up to 50%. Evaluations were conducted immediately in its fresh state, and assessments of strength and durability were extended over 360 days. Scanning Electron Microscope (SEM) and X-Ray diffraction analysis (XRD) were used as characterization techniques. The outcomes of the study were noteworthy. Mortars containing 30% or more ash exhibited a significant 15% enhancement in flow and an impressive 88% increase in compressive strength compared to plain mortar. The durability assessment revealed that masonry cement mortar incorporating 40% and 50% fly ash displayed nearly 14 times greater resistance to chloride penetration and maintained its strength when exposed to acidic solutions. This underscores the dual benefits of this material, enhancing the aesthetics of buildings and fortifying them against external chemical attacks that can compromise the integrity of concrete and bricks.

Enhancing Volumetric Stability of Metakaolin-Based Geopolymer Composites with Organic Modifiers WER and SCA

Shrinkage during hardening and curing is one of the largest challenges for the widespread application of metakaolin-based geopolymers (MKGs). To solve this problem, a silane coupling agent (SCA) and waterborne epoxy resin (WER) were used to synthesize MKG composites. The individual and synergistic effects of the SCA and WER on chemical, autogenous, and drying shrinkage were assessed, the modification mechanisms were investigated by microstructural characterization, and shrinkage resistance was evaluated by the chloride ion permeability of MKG composite coatings. The results showed that the SCA and WER significantly decreased the chemical shrinkage, autogenous shrinkage, and drying shrinkage of the MKG, with the highest reductions of 46.4%, 131.2%, and 25.2% obtained by the combination of 20 wt% WER and 1 wt% SCA. The incorporation of the organic modifiers densified the microstructure. Compared with the MKG, the total volume of mesopores and macropores in MKG-WER, MKG-SCA, and MKG-WER-SCA decreased by 11.5%, 8.7%, and 3.8%, respectively. In particular, the silanol hydrolyzed from the SCA can react with the opened epoxy ring of the WER and the aluminosilicate oligomers simultaneously to form a compact network and resist shrinkage during the hardening and continuous reaction of the geopolymer. Furthermore, the apparently lowered chloride ion diffusion coefficient of concrete (i.e., reduction of 51.4% to 59.5%) by the WER- and SCA-modified MKG coatings verified their improved shrinkage resistance. The findings in this study provide promising methods to essentially solve the shrinkage problem of MKGs at the microscale and shed light on the modification mechanism by WERs and SCAs, and they also suggest the applicability of MKG composites in protective coatings for marine concrete.

Influence of limestone powder mixing method on properties of manufactured sand concrete

For the purpose of enhancing the utilization rate of limestone powder (LP) in concrete and maximizing its activity effect. In this paper, the replacement methods for replacing fly ash (FA) with fine particles and manufactured sand (MS) with coarse particles were proposed. The content of LP replacing FA increased from 10% to 50%, and the content of LP replacing MS increased from 5% to 20%. The effects of LP replacing FA alone, replacing MS alone and particle-screened LP replacing both FA and MS on the workability, mechanical properties, durability of concrete were compared. Analysis of variance (Anova) was used to determine the importance level of the test parameters on the performance characteristics of concrete. The results suggested that LP replacing MS improved the workability and strength of concrete, and ameliorated the carbonation and chloride ion permeability resistance. However, the amount of LP substitution was very low, only 10%. Compared with LP replacing FA alone, the screened substitution improved the cohesion and water retention of concrete. The improvement in strength at 7 and 28 days was better, which was 1.6 MPa and 1.3 MPa higher than replacing FA alone. And there was no significantly adverse effect on the durability of concrete. Moreover, it was conducive to enhancing the utilization rate of LP. According to the research results, the effect of the interaction between LP content and the mixing method on the performance of concrete cannot be ignored. In addition, the screened substitution method was more environmentally friendly and economical, because it was conducive to the recycling of solid waste and landfill waste treatment.

Compressive strength and chloride permeability of cement-based materials with high-volume compound mineral admixtures

Ground granulated blast-furnace slag (GGBFS) is well known to be capable of improving the performance of cement-based materials, but few studies focus on the impact of its large dosage on concrete containing basalt powder. In this study, the compressive strength and chloride permeability of cement-based materials with compound mineral admixtures (CMAs) containing high-volume GGBFS, basalt powder and desulfurisation gypsum were investigated. The results showed that the mortar strengths at 3, 7 and 28 days decreased with increasing GGBFS content, but that at 56 and 84 days increased with the addition of 45 wt% GGBFS. This is because the activity of GGBFS at an early stage has not been stimulated and the pozzolanic effect is exerted at a later stage. Moreover, cement replacement with up to 55 wt% GGBFS caused a significant decrease in the chloride diffusion coefficient of the mortar and concrete. Furthermore, the incorporation of GGBFS led to a remarkable refinement in pore structure of the hardened paste due to pozzolanic and filler effects. Therefore, the partial replacement of cement with high CMA contents (≥70 wt%) in concrete is desirable for ocean projects requiring low chloride permeability, and significantly reduces carbon dioxide emissions.

Effect of basalt fibers and silica fume on the mechanical properties, stress-strain behavior, and durability of alkali-activated slag-fly ash concrete

Previous investigations have shown that there is limited exploration into the combined mechanism of silica fume and basalt fibers of various lengths on the performance of alkali-activated concrete. Based on this, the primary focus of this study is to elucidate the current knowledge gaps concerning the mechanical properties and durability of basalt fiber-reinforced alkali-activated concrete, with a particular emphasis on its stress-strain behavior. The effects of basalt fiber content (i.e., 0.2%, 0.4%, and 0.6% Vf), basalt fiber length (i.e., 6 and 12 mm), mixing proportions of 6 mm and 12 mm basalt fibers (i.e., 75:25, 50:50, and 25:75) and silica fume content (i.e., 3%, 6%, and 9%) on the workability, mechanical properties, stress-strain behavior, and durability of alkali-activated concrete were investigated. Based on experimental results, predictive models were proposed for the splitting tensile strength, flexural tensile strength, elastic modulus, peak strain, and stress-strain relationship of basalt fiber-reinforced alkali-activated concrete, showing excellent predictive accuracy. Additionally, the durability properties of all samples, including shrinkage, carbonation depth, and chloride ion permeability, were also tested. The results indicate that the combined effect of fibers and silica fume can enhance the mechanical properties and durability of the concrete. Finally, the reinforcement mechanism of the synergistic action of fibers and silica fume is discussed.

Improvement on durability of concrete by early age continuous loading treatment

This study investigated the effect of different pressure levels of continuous loading (2.5 MPa, 5.0 MPa, 7.5 MPa, and 10.0 MPa) on the enhancement of concrete durability and proposed the underlying mechanisms behind. To evaluate the efficiency of continuous loading, in addition to compressive strength, the durability, including chloride ion permeability, freeze-thaw resistance and carbonation resistance of the concree were determined, and the micro-scale investigation, including pore structure, microhardness, hydration product and microstructures were conducted. The results showed that, compared to reference (non-pressurized sample), the continuous loading process increased the 28d compressive strength of concrete by 10.3% to 27.4%, decreased chloride ion migration coefficient by 34% to 48.9%, increased freeze-thaw cycles by 20%, and reduced the carbonation depth by 12.3% to 36.2%. The improved performance was attributed to the enhancement of pore structure and reduction of ITZ width, which was a result of multiple factors such as increased compaction and improved movement of free water.

Effects of alkali activator on the chloride-ion permeability of one-part alkali-activated nickel slag concrete

Herein, the effects of the ionic types and content of alkali activator on the chloride-ion permeability of one-part alkali-activated nickel slag concrete were examined. The NT Build 492 method was adopted to measure the Cl− transport performance. In general, the total Cl− concentration in concrete decreases with the increase of penetration depth; however, the enrichment of Cl− concentration in the sample is not obvious. Anions have more effect on 28-d compressive strength, while cations have more effect on chlorine-ion permeability. For the same Na2O content, SiO32−-activator and Na+-activator perform better than other anions and cations, while OH– and K+ perform worse than other ions. The chloride-ion permeability coefficient (DRCM) of concrete with Na2SiO3 is the lowest and that with KOH is the highest. The DRCM of concrete prepared with KOH is 1.93 times higher than that of concrete prepared with Na2SiO3. When the activator is Na2SiO3, the DRCM of concrete decreases with the increase in Na2O content when the Na2O content is less than 7%. However, when the Na2O content exceeds 7%, the DRCM of concrete increases with the increase in Na2O content.

Preparation and Performance Study of High-Strength and Corrosion-Resistant Cement-Based Materials Applied in Coastal Acid Rain Areas.

Investigations regarding the preparation and durability of cement-based materials applied in specific coastal acid rain environments are scarce, particularly those involving the addition of four auxiliary cementitious materials (ACMs) to cement for modification. To improve the durability of concrete structures in coastal acid rain areas, a systematic study was conducted regarding the preparation of high-strength and corrosion-resistant cement-based materials using ACM systems composed of fly ash (FA), granulated blast furnace slag (GBFS), silica fume (SF), and desulfurization gypsum (DG) instead of partial cement. Through an orthogonal experimental design, the effect of the water-binder ratio, cementitious ratio, and replacement cement ratio on the compressive strength, corrosion resistance coefficient, and chloride ion permeability coefficient of the materials were analyzed and the mix proportions of the materials were evaluated and optimized using the comprehensive scoring method. The results show that implementing a FA:GBFS:SF:DG ratio of 2:6:1:1 to replace 60% of cement allows the consumption of calcium hydroxide crystals generated through cement hydration, promotes the formation of ettringite, optimizes the pore structures of cementitious materials, and improves the compressive strength, acid corrosion resistance, and chloride ion permeability of the materials. This study provides a reference for selecting concrete materials for buildings in coastal acid rain environments.

The Influence of Salt Erosion on the Mechanical Performances of Ultra-High-Performance Concrete with Secondary Aluminum Dross

Secondary aluminum dross containing a large amount of active substance can be used to prepare concrete. The mechanical strengths, the mass loss rate (MR) and the relative dynamic modulus of elasticity (RME) of ultra-high-performance concrete with secondary aluminum dross are researched. The NaCl freeze–thaw cycles (F-Cs) and dry–wet alternation (D-A) effects with NaCl and Na2SO4 are considered. The corresponding permeability of chloride ions and the carbonation depth (Dc) are obtained. The scanning electron microscope (SEM) photos are researched to reveal the variation of the mechanical mechanism. Results show that after specimens’ suffering from the action of 20 NaCl D-As, the MR of ultra-high-performance concrete is the highest. Specimens exposed to 200 NaCl F-Cs show the lowest MR and CMC. The RME of UHPC under salt actions increase in the order of 20 NaCl D-As < 20 Na2SO4 D-As < 200 NaCl F-Cs. After suffering 200 NaCl F-Cs, 20 Na2SO4 D-As and 20 NaCl D-As, the corresponding Dc values are 1.86 mm to 2.31 mm, 1.79 mm to 2.23 mm and 2.11 mm to 2.76 mm. The flexural strength decreases at the rates of 0.99%–25%, 3.92%–27.84% and 1.47%–21.59% respectively. The MR increases and the RME decreases as the cubic function changes with the amount of salt erosion. After the secondary aluminum dross is added, the CMC decreases at the rates of 0% to 11.53%, 0% to 33.17% and 0% to 8.41% during the process of the salt action. The SAD can reduce the Dc with the decreasing rates of 19.48%, 23.55% and 19.73%. The SAD can increase the compactness of ultra-high-performance concrete. Ultra-high-performance concrete suffering from 20 NaCl D-As shows the largest number and the highest width of cracks. However, when the specimens are exposed to 20 Na2SO4 D-As, the number of cracks is the lowest and the width is the narrowest.

Study on the Effect of Ultra-fine Limestone Powder on the Resistance of Cement-slag Powder System to Chloride Ion Permeability

The effect of different limestone powder fineness on the chloride ion migration coefficient of the cement paste was tested using the Rapid Chloride Migration (RCM) method. The changes in the phase composition and pore structure of the paste were studied using hydration kinetics analysis, XRD and pore structure analysis. The results showed that before the chloride ion erosion, the limestone powder mainly exhibited filling effect, microcrystalline nucleation effect, and chemical activity effect. It reacted with the hydration products of cement to form calcium aluminate carbonate, which improved the strength of the hardened paste. After chloride ion erosion, the diffraction peak of calcium aluminate carbonate weakened, and Friedel’s salt was formed. With the increase of the specific surface area of limestone powder, the chemical activity of the powder became more obvious, and the generation of Friedel’s salt increased, leading to stronger resistance to chloride ion penetration. Limestone powder can reduce the porosity of the hardened paste and optimize the pore structure. When the particle size of the powder increased from 800 to 5000 mesh, the total porosity of the hardened paste decreased from 20.7% to 14.7%, and the most probable pore size decreased from 450nm to 75nm. Limestone powder with a particle size larger than 1500 mesh can fully exert its activity and play a role in solidifying chloride ions, thus improving the resistance to chloride ion penetration of limestone powder cement-based materials.

Properties evaluation of concrete made with recycled coarse aggregate modified by graphene oxide

Previous application of graphene oxide (GO) in recycled aggregate concrete (RAC) is the direct replacement of cement or binder to achieve performance improvement. To develop a more efficient recycled aggregate (RA) modification technique and improve the properties of the corresponding RAC, this paper performed GO solution pre-spraying and pre-soaking treatment on RA. The modification efficiency of GO was evaluated by compressive strength, interfacial transition zone (ITZ) properties, and chloride ion permeability of RAC. The results show that the pre-spraying and pre-soaking methods improved the compressive strength of RAC at different ages by 20%–28.6 % and 8.3%–30.8 %, respectively. The GO-modified RAC also exhibited lower electric flux in the chloride ion permeability tests. However, no significant effect was observed on the elastic modulus of RAC. The modified RAC showed lower total porosity and harmful pore content. Meanwhile, the GO-modified ITZ between old and new mortar had denser hydration products. As a result, the elastic modulus and hardness of the ITZ increased by 27.8%–65.8 % and 9.8%–107 %, respectively, while the width of the ITZ decreased by 15.4%–30.8 %. The good filling and nucleation effect of GO were credited with the enhancement mechanism of RA by pre-spraying and pre-soaking methods.

Influence of Nanoparticles on the Mechanical and Durability Properties of Concrete: A Microstructural Analysis

This study investigates the effects on mechanical and durability properties of concrete by including nano-silica, nano- titanium dioxide, and nano-alumina. The concrete mixes included nanoparticles in a range of quantities, from 0.5% to 4% by cement weight. Several experimental tests were performed, including those for chloride permeability, workability, compressive strength, and flexural strength. Compressive strength increased to 40.5 MPa and chloride permeability decreased to 1000 Coulombs, indicating an improvement in durability, when the nano-silica content was found to be 3%. Nano-titanium dioxide and nano-alumina also shown a minor but noticeable improvement. A detailed SEM microstructural analysis demonstrates the formation of a dense and refined microstructure, lending credence to the claims of improved mechanical properties. Results show that adding nanoparticles to concrete, particularly nano-silica, increases its performance without reducing its strength or durability.

Study on Bonding Performance of Magnesium Phosphate Cement Mortar in Chloride Corrosion Environment

The effects of nano‐SiO2 and hydroxypropyl methyl cellulose (HPMC) on the physical and mechanical properties of magnesium phosphate cement (MPC)‐based mortar under salt corrosion environment were studied. The variation of strength under salt corrosion environment was compared and studied. The chloride ion permeability of modified MPC mortar was evaluated by electric flux method. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to observe the composition and morphology of the samples under salt corrosion environment. Results showed that appropriate amount of nano‐SiO2 can significantly improve the compressive strength, flexural strength, and chloride ion penetration resistance of MPC‐based mortar under 3% NaCl solution corrosion. There existed an optimal dosage. The incorporation of HPMC would significantly reduce the compressive and flexural strength and the resistance to chloride ion penetration of MPC‐based mortar. Appropriate amount of nano‐silica and HPMC could improve the bonding performance of modified MPC‐based mortar under salt corrosion environment.

Durability and FTIR Characteristics of Sustainable Bacterial Concrete with Mineral Admixtures

The objective of this study is to optimize the concentrations of bacillus megaterium (BM), alccofine (AF), and silica fume (SF) in self-healing concrete while controlling the content of manufactured sand (M-sand). This research addresses the pressing need for sustainable alternatives to traditional cement as excessive energy consumption and environmental impacts continue challenging the construction industry. A novel “binary and ternary blended cementitious system” was developed, featuring twelve distinct mix proportions. M-sand was fully utilized as an acceptable aggregate substitute, with bacterial concentrations of (10–50)·105 cells/ml incorporated to mitigate crack formation. Cement was partially replaced with AF, and the M-sand content was adjusted from 0 to 20 % in 5 % increments. This study also uniquely evaluates the durability properties of the various cementitious systems, including water absorption, concrete density, porosity, long-term strength retention, and rapid chloride permeability – at intervals of 7, 14, and 28 days post-curing. Fourier transform-infrared spectroscopy (FTIR) was employed to analyze calcite precipitation, providing insights into the biochemical mechanisms. The results indicate that while SF demonstrates superior effectiveness compared to AF, combining both enhances durability compared to alternative mixes. The findings reveal that bacterial concrete incorporating zeolites can significantly improve structural strength and be a sustainable building material. Notably, incorporating additional cementitious materials with mineral admixtures increased strength by up to 10 % through optimized bacterial concentrations. The successful precipitation of calcium carbonate confirmed the beneficial properties of the bacterial agents, which are safe and non-toxic to the environment. Overall, this study contributes valuable knowledge on reducing cement usage and carbon dioxide emissions, positioning BM, alongside AF and SF, as a promising approach for environmentally friendly concrete solutions.

The influence of recycled aggregate on the properties of geopolymeric recycled concrete: A comprehensive review

This paper offers a comprehensive review of geopolymeric recycled concrete (GRC) research, particularly focusing on mechanical properties, durability, microstructure, and the interfacial transition zone (ITZ). The study emphasizes the influence of recycled aggregate (RA) content on GRC performance. Findings indicate that higher RA content leads to a gradual reduction in GRC’s compressive, tensile, and flexural strengths, elastic modulus, and toughness. The elastic modulus is most affected, followed by compressive strength, while tensile strength experiences the least decline. Moreover, increased RA content is associated with elevated water absorption, decreased resistance to chloride ion permeability, sulfate corrosion, acid, frost, and carbonization in geopolymer concrete. The integration of RA creates more intricate ITZs in geopolymer concrete, resulting in reduced bonding strength and a looser, more porous microstructure. However, the use of geopolymers can mitigate these effects by enhancing bonding in ITZs. The paper also presents a statistical analysis of compressive strength test results from various studies and proposes a preliminary method for estimating the compressive strength of geopolymer concrete with different RA replacement rates.

Experimental Analysis on the Characteristics of Concrete by Incorporating Steel Slag as Partial Replacement of Sand

Abstract: Steel slag is a by-product obtained in the manufacture of pig iron in the blast furnace and is produced by the blend of constituents of iron ore with limestone flux. Presently in India, owing to restricted methods of use, massive amounts of iron and steel slag are deposited in the yards of every production facility, occupying significant agricultural land, and seriously polluting the entire ecosystem. Meanwhile, the application of ecological environment protection has limited the mining of gravel, leading to a shortage of natural aggregate. Numerous studies have sought to replace natural aggregate in concrete with steel slag aggregate due to its good engineering qualities. The current research work is to investigate the concrete’s characteristics for M40-grade concrete by substitution of sand with steel slag at 10%, 20% and 30% during various curing ages. Several experiments were conducted on the characteristics of the concrete, compressive strength, and durability properties (such as water absorption and rapid chloride permeability test) up to the age of 90 days

Effects of healing start time and duration on conventional and high-performance concretes incorporating SAP, crystalline admixture, and sepiolite: A comparative study

This research investigates the self-healing capability of conventional and high-performance concrete containing either a superabsorbent polymer (SAP), a crystalline admixture (CA), or water-encapsulated in sepiolite by quantifying the recovery of water tightness through the water permeability test and chloride permeability via cracks and matrix penetration on healed specimens. Specimens were pre-cracked to a crack width range of 50–450 µm at 28 days. Specimens were healed under water in four time combinations: healing starting at the concrete age of 28 days or 56 days and a healing duration of 28 or 56 days. Additionally, a healing condition of presaturation during 1 day of water immersion and storage in a humidity chamber for 27 days was studied. The results show that delayed healing reduced the self-healing efficiency, and extending the duration to 56 days enhanced healing, especially for narrow cracks (≈100 µm), and reduced chloride permeability. Specimens with SAP showed superior early-stage healing, but low delayed healing. Sepiolite enhanced healing for delayed cracks with variable effectiveness. CA improved healing for both early and delayed healing, exhibiting low chloride penetration in healed specimens.

Reducing Chloride Ion Permeation during Seawater Electrolysis Using Double-Polyamide Thin-Film Composite Membranes.

Low-cost polyamide thin-film composite membranes are being explored as alternatives to expensive cation exchange membranes for seawater electrolysis. However, transport of chloride from seawater to the anode chamber must be reduced to minimize the production of chlorine gas. A double-polyamide composite structure was created that reduced the level of chloride transport. Adding five polyamide layers on the back of a conventional polyamide composite membrane reduced the chloride ion transport by 53% and did not increase the applied voltage. Decreased chloride permeation was attributed to enhanced electrostatic and steric repulsion created by the new polyamide layers. Charge was balanced through increased sodium ion transport (52%) from the anolyte to the catholyte rather than through a change in the transport of protons and hydroxides. As a result, the Nernstian loss arising from the pH difference between the anolyte and catholyte remained relatively constant during electrolysis despite membrane modifications. This lack of a change in pH showed that transport of protons and hydroxides during electrolysis was independent of salt ion transport. Therefore, only sodium ion transport could compensate for the reduction of chloride flux to maintain the set current. Overall, these results prove the feasibility of using a double-polyamide structure to control chloride permeation during seawater electrolysis without sacrificing energy consumption.