Ingress Of Ions Research Articles

Experimental investigation on the residual strength of concrete under the multi-factor coupling action of chloride penetration, freeze-thaw, and fatigue effect

With the ongoing process of globalization and the rapid expansion of the global economy, the proliferation of coastal constructions and infrastructures has witnessed a notable surge. These structures often encounter a confluence of environmental stressors in practical engineering, including cyclic fatigue loading, chloride salt erosion, and freeze-thaw cycles. These synergistic factors accelerate concrete’s failure, resulting in accelerated deterioration and significantly reduced durability. A comprehensive understanding of the damage characteristics of concrete materials in offshore environments, under the multi-factor coupled action of freeze-thaw phenomena, along with an assessment of their residual strength, is crucial for the development of relevant structural analysis and lifetime prediction models. To address this, twenty-seven dedicated specimens were designed and fabricated for this investigation. They were employed to scrutinize the residual strength of concrete under the combined influences of fatigue, freeze-thaw, and chloride penetration. Nine distinct multi-factor coupling actions were meticulously devised and characterized by different parameters. Following the multi-factor coupling action, tests were conducted to assess the residual flexural and compressive strengths, as well as the chloride ion content near the specimen edges. The findings revealed a substantial negative correlation between the residual flexural and compressive strengths with both the number of freeze-thaw cycles and fatigue loading iterations. In contrast, chloride ion concentration and the stress level of fatigue loading (stress ratio: 0.1–0.3) exhibited a comparatively marginal influence. Despite the relatively short test duration, it was evident that both freeze-thaw cycles and fatigue loading exerted a discernible promotional effect on chloride ion ingress in the concrete of the specimens.

Insight into the dynamic evolution of competitive interaction between chloride and sulphate ions in cement-based systems: Effects on chloride diffusion and binding

The dual attack of chloride and sulphate ions is accompanied by the dynamic competitive interaction, yielding a non-negligible influence on their penetrations. Treating this interaction as a steady behaviour will underestimate the ionic ingress and then, overestimate the lifespan of concrete structures. In this study, the evolution of competitive interaction and the associated effect on the chloride diffusion and binding capacity have been investigated by comparing the exclusive chloride and the combined chloride-sulphate attacks. The experimental results disclose that the competitive interaction displayed a dynamic feature. Specifically, the competitive-induced depressions on chloride diffusion and binding capacity evolved first and then appeared to decay after reaching a threshold. Moreover, this competitive interaction was positively related to the w/c ratio and the environmental SO2-4/Cl- ratio. As the slag dosage increased from 0 % to 50 %, the competitive interaction-induced depression upon the free chloride content decreased steadily. However, the inhibition efficiency of the binding capacity decreased first as the slag dosage increased to 20 % and then, evolved significantly with the further increase through 20 % to 50 %. Furthermore, multifactor models are established with good applicability, to respectively predict the effect of this competitive interaction on the diffusion and binding of chloride ions.

Wireless, battery-free, and real-time monitoring of water permeation across thin-film encapsulation

Long-term bioelectronic implants require stable, hermetic encapsulation. Water and ion ingress are challenging to quantify, especially in miniaturized microsystems and over time. We propose a wireless and battery-free flexible platform leveraging backscatter communication and magnesium (Mg)-based microsensors. Water permeation through the encapsulation induces corrosion of the Mg resistive sensor thereby shifting the oscillation frequency of the sensing circuit. Experimental in vitro and in-tissue characterization provides information on the operation of the platform and demonstrates the robustness and accuracy of this promising method, revealing its significance for in-situ real-time monitoring of implanted bioelectronics.

Effect of ZnAl-NO2 LDH on chloride entrapment and protection of iron reinforcement in mortar samples

Layered double hydroxides (LDHs) have gained attention in the concrete research field, appearing as prospective additives for controlling chloride attack, and as micro or nano deliverers of corrosion inhibitors. This work reports the effect of ZnAl-NO2 LDH on the evolution of chloride concentration in the pore solution and on the corrosion resistance of iron in mortar samples exposed to 3.5 % NaCl solution. To this end, Ag/AgCl sensors were used to monitor the ingress of chloride ions into mortar, while the electrochemical state of the iron was evaluated by electrochemical impedance spectroscopy. Furthermore, the mortars were analyzed by XRD and TGA, and the total amount of chloride was measured with a commercial sensor. Mortars with LDH showed a slower increase of chloride ions in the pore solution and the preservation of the passive state of the Fe. The presence of LDHs did not cause a significant structural change in the mortars, which was evidenced by the similar distribution of the high frequency resistance as a function of depth in the samples with and without the additive. Finally, the amount of bound chloride in the cementitious material was higher in the LDH-containing mortars. In conclusion, ZnAl-NO2 LDH exhibited a positive effect on the protection of reinforcement embedded in mortar samples when subjected to chloride ingress.

Modeling electrochemical chloride extraction in surface carbonated concrete

This paper investigated the Electrochemical Chloride Extraction (ECE) process in concrete with carbonated surface layers. First, the ECE model for surface carbonated concrete was proposed based on pore size distribution function. Subsequently, to validate the model, concrete cube specimens exposed to natural coastal environments were modified and designed for ECE tests. Based on the validated ECE model, parametric studies were conducted. Parametric studies show that increasing the thickness of the surface carbonation layer up to 20 mm leads to a 57% increase in extraction duration, whereas the thickness of the partially carbonated zone has a relatively minor impact on the ECE process. The parametric study shows that the surface carbonated zone will pose hindrances to the extraction of chloride ions. Due to the simultaneous presence of concrete carbonation and chloride ion ingress in the actual marine atmospheric environment, considering the actual carbonation depth is of significant importance for predicting chloride ion migration during Electrochemical Chloride Extraction.

Influence of superabsorbent polymers on the chloride ingress of mortar measured by chloride diffusion and a quasi-steady-state migration test

The ingress of chloride ions is a serious threat for concrete structures. Superabsorbent polymers (SAPs) are interesting additions to cementitious systems due to their property of absorbing water during mixing and releasing it at a later time to provide internal curing, thereby reducing shrinkage and promoting durability. In addition, SAPs can improve the regain in impermeability of cracks by swelling and blocking the crack and promoting autogenous healing. The current study investigates the influence of the addition of SAPs without additional mixing water to the chloride ingress in cracked mortar via diffusion and quasi-steady-state migration testing. Filtration tests showed that the charge-screening effect in a NaCl solution is more dominant than for cement filtrate solution during swelling of SAPs. After wet/dry cycling for a month, subsequent chloride diffusion tests with 2 and 6 weeks of exposure showed that the addition of SAPs improved the performance with respect to a reference mix with the same total water-to-cement ratio. A reference mix with the same effective water-to-cement ratio as the SAP mix had a comparable performance to the SAP mix. One set of chloride diffusion experiments showed that the SAP mix was the only one successfully preventing chloride ingress into the deepest zone of the crack. The superior performance of the series with SAPs was also confirmed by migration testing where cracked and healed specimens obtained a migration coefficient which was only 12 % higher than uncracked specimens.

Research on chloride ion permeability resistance of concretes bonded with CFRP sheets under dry-wet cycles

Considering the widespread application of carbon fibre-reinforced polymer (CFRP) as a protective material for reinforced concrete (RC) structures, this study focuses on the ability of CFRP laminates with different numbers of layers bonded to the concrete surface to reduce the ingress of chloride ions. Variations in the free chloride concentration distribution in concrete before and after CFRP bonding were explored systematically. Nonlinear fitting was applied to the experimental data to establish a calculation model for the diffusion of free chloride ions in concrete with CFRP bonded to the surface, which was subsequently validated. Based on the proposed model, the reduction in the surface chloride concentration of concrete after bonding different numbers of CFRP layers was quantified as the reduction value. Moreover, recommendations for the durable design of RC structures bonded with CFRP in wet-dry cyclic environments are provided. The results indicate that the surface chloride concentration in concrete increases continuously with increasing wet-dry cycles, eventually reaching a steady state. Compared with the concrete specimens without CFRP bonding, the bonding of one, two, or three layers of CFRP led to reductions in the stable surface chloride concentration of concrete by 70.8%, 82.6%, and 84.9%, respectively. And no obvious convection zone was observed in the concrete after CFRP bonding. The validation results of the proposed calculation model demonstrated its high accuracy, making it suitable for durable design and service life prediction.

Sonication assisted superior anti-corrosion properties of cathodically deposited novel nickel-graphene oxide-zinc oxide coating

This study details the sonication-assisted synthesis and characterization of a cathodically deposited novel nickel-graphene oxide -zinc oxide (Ni-GO-ZnO) composite coating achieved through electrodeposition and its comparison with anodically deposited GO. This coating was comprehensively characterized using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM) coupled with Energy-dispersive X-ray spectroscopy (EDAX). Subsequently, its corrosion resistance for MS1010 mild steel in 3.5 wt % (NaCl) was evaluated via weight loss, contact angle, electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization, and surface analysis techniques. These observations suggest that graphene oxide-zinc oxide (GO-ZnO) adsorbs nickel onto the MS surface effectively and reduces defects, which helps in blocking active corrosion sites. Tafel plots and EIS revealed that the Ni-GO-ZnO coating exhibited the lowest current density (39.95 µAcm²) and the highest charge transfer resistance (1211 Ωcm²). This was further validated by long-term immersion testing, where the Ni-GO-ZnO coating exhibited significantly less weight loss (1.33 mils/Y) compared to the deposited GO coating (2.2 mils/Y). The mechanism of formation of deposited GO and Ni-GO-ZnO coating on the metallic surface is proposed. The enhanced corrosion resistance of the Ni-GO-ZnO coating is attributed to its ability to 1) form a more compact metallic layer and 2) Minimize the active surface area vulnerable to corrosion attack. 3) Diminishes the presence of holes and cracks for corrosive ion ingress.4) Functionally impedes the ingress of chloride ions, primarily liable for steel degradation. The synergistic effect of the GO-ZnO constituents within the nickel matrix significantly enhances the long-term durability and integrity of the protective layer, a phenomenon hitherto unexplored. The empirical outcomes advocate for the advanced application of GO-ZnO-nickel coatings in safeguarding infrastructural materials against corrosive degradation.

Rapid chloride penetration test: An evaluation of corrosion resistance in ultra-high performance concrete

Six Ultra-High Performance Concrete (UHPC) mixtures were tested to determine their chloride ion ingress potential using the rapid chloride penetration test (RCPT). The UHPC mixtures showed low to negligible chloride ion penetrability, depending on their water to cementitious materials (w/cm) ratio and curing regimen. Electrical resistivity and conductivity of the mixtures were determined based on the recorded electric current during the RCPT test. The electrical resistivity varied from 49 to 1419 Ω-meter, while conductivity ranged from 0.0007 to 0.0013 milli-Siemens/meter, indicating a moderate to very low expected corrosion rate for the mixtures. The chloride diffusion coefficient was calculated using the Nernst-Plank Equation, making corrections for Joule effect and temperature adjustment due to the temperature increase of the electrode solution during the RCPT test. The chloride ion diffusion coefficients of the UHPC mixtures ranged from 0.53–3.01 × 10−15 m2/s. These results suggest that UHPC mixtures with a w/cm ratio as high as 0.30 can exhibit excellent corrosion resistance.

Investigation of ion transport in hardened cement paste by LA‐ICP‐MS

AbstractThis study examined the impact of two different transport mechanisms and water/cement (w/c) ratios on the ingress depth of damaging ions into hardened cement paste (hcp). In addition, the effect of sample preparation, i.e. drying before and after exposure, is considered within this study. We applied Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) as an analytical method to determine the ion ingress depth. The results show that post‐drying of the samples (after exposure) significantly affects the ion ingress depth in hcp as determined by LA‐ICP‐MS. Our results confirmed, as previous studies, that ions ingress the hcp faster due to capillary suction than diffusion. This work shows that although LA‐ICP‐MS is not commonly applied in the analysis of construction material, it has a vast potential to examine the profile ingress of damaging ions.

ЛУЖНЕ АЛЮМОСИЛІКАТНЕ ПОКРИТТЯ ДЛЯ ЗАХИСТУ БЕТОНУ ВІД ТРАНСПОРТУ CL--ІОНІВ ПРИ ПЕРІОДИЧНИХ ЦИКЛАХ ЗВОЛОЖУВАННЯ І ВИСУШУВАННЯ

To ensure the durability of constructions is current world tendency of building industry. It’s well known that the periodical effect of chlorine-containing aqueous environment and carbonation under the action of atmospheric carbonic gas causes the most risk of the corrosion of steel reinforcement. The carbonation contributes toward releasing the bound Cl--ions adsorbed on hydration products. The advanced transport of Cl--ions ensures the corrosion of steel reinforcement. Thus, the mean to prevent the transport of aggressive ions in concrete from aggressive environment with combination of exposure classes XD3 and XC4 is actual for investigations. The coatings based on alkaline aluminosilicate binders were proposed for protection of reinforced concrete against the ingress of aggressive ions because of their well-known capability to ones bind in the zeolite-like phases. The aim of this research was to determine the effectiveness of coating based on alkaline aluminosilicate binder of the composition (0.2K2O+0.8Na2O)•4.5SiO2•Al2O3•nH2O as protection of reinforced concrete from transport of Cl-, CO32--ions under periodical cycles of wetting/drying. The evaluation of protective properties of proposed coating in real operating conditions under cyclic drying-wetting in chlorine-containing aqueous environment was determined using the author’s methodology. Total protection of concrete after 90 cycles of drying-wetting in a 5 % solution of NaCl in the absence of traces of Cl--ions transport can be ensured by 3 mm of the coating. High protective properties of the coating were confirmed by the retention of its adhesion as well as high corrosion resistance of coated concrete under the action of specified aggressive environment. High protective properties of the coating are caused by binding Cl and CO32- ions in the water-resistant zeolite-like matrices.

Cementitious materials with biological additive for enhanced durability in marine environment

AbstractConcrete structures suffer from cracking that leads to deterioration and shortening of service life. This is very critical for underwater structures, i.e., immersed bridge piles, immersed tunnel or submerged floating tunnels, which are consistently susceptible to ingress of harmful ions (chloride, sulphate and carbonate ions). Autonomous healing of concrete cracks can be beneficial to assure durability performance during the service life. In this context the paper presents a preliminary experimental activity carried out to study the self‐healing capacity of cementitious composites in marine environment. Four series of paste samples are prepared to evaluate the autonomous healing capabilities, achieved through biotic and abiotic additions. The experimental campaign is articulated in four phases, such as: specimen preparation; tests in compression; immersion in water; crack healing evaluation. The specimen performances are examined and compared in terms of mechanical strength and crack width healing over time. Results highlight the efficiency of the technology for crack healing.

(Invited) Grahame Symposium: Separating and Moving Charges through Functional Metal-Organic Frameworks

In line with the longstanding physical electrochemistry interests and numerous innovative contributions of Grahame Award recipient Dr. Keith Stevenson, this presentation will focus on a physical electrochemistry problem: how to separate redox-hopping based hole-transport within porous, electrocatalytic metal-organic framework coatings from transport of charge-compensating ions through the same coatings. In principle, either process, or both, could define transport rates. For electrocatalysis, the general goal is to achieve the fastest transport possible. Wall-jet electrochemistry – the approach used here – offers a useful way of assessing redox-hopping rates without complications from ion ingress or egress. The wall-jet approach turns out to be especially useful when samples cannot be made compatible with RDE or IDE assemblies.

The effect of silver diamine fluoride on the microleakage of glass ionomer restoration in primary teeth at different time intervals

Silver diamine fluoride (SDF) has shown effectiveness in hardening tooth structure and killing bacteria. Therefore, it can be used to prevent and arrest dental caries. Riva Star (SDF) treatment alone will stop cavities but will not reverse the cavitation. The Silver Modified Atraumatic Procedure, often known as Smart, is the optimum technique for regaining the tooth's structure and function. Glass ionomer was introduced in (1972) as a new material that has become one of the most widely used materials in restorative dentistry. By releasing fluoride ions, this material has a therapeutic impact on the surrounding tooth structure. Microleakage is the ingress of bacteria, its byproducts, toxins, chemicals, oral fluids, and ions between the margins of the restoration and the cavity walls. Dental restoration lifetime is significantly influenced by microleakage at the toothrestoration contact. Material and method: In this study, we used 32 primary molars, class V cavities prepared on the buccal surface of all teeth. The teeth were divided into 2 groups: Group 1: 16 teeth treated with 38%SDF 8 of them restored directly with GIC filling and the other 8 restored after 14 days; Group 2: 16 teeth as control group left untreated with 38% SDF,8 teeth restored directly and 8 restored after 14 days. Samples were thermocycled, immersed in 2% methylene blue and then sectioned in a buccolingual direction. Dye penetration was measured with a digital camera connected to a stereo microscope. Result: results of this study showed a significant difference in microleakage between two-time intervals in which microleakage in GIC filling decreased at 14-day intervals than that of first-day interval in the experimental group, while in the control group, microleakage at 14 days intervals was higher than first-day interval, but it was not significant. Conclusion: Pretreatment of the primary teeth with SDF can decrease the microleakage of GIC restoration. If placed after 14 days, the microleakage would be lesser than that if the restoration was placed directly after SDF treatment. Therefore, it is recommended that SDF treatment be done, followed by a permanent restoration after 14 days, so the null hypothesis cannot be accepted. Keywords: Microleakage, Silver diamine fluoride, Glass ionomer filling, noninvasive dentistry

Photocatalytic Activity and Mechanical Properties of Cement Slurries Containing Titanium Dioxide

The effect of titanium dioxide (TiO2) on the mechanical properties of cement slurries including their benefits on air purification and abatement of pollutants is not well documented. Cementitious-based slurries are typically applied in thin layers as decorative coatings for existing facades, protection against an ingress of aggressive ions, or rainproof covers to minimize water penetration. Different parameters including the TiO2 concentration, dispersion time during batching, and applied thickness on top of existing mortar blocks are investigated in this paper. Tested properties included the flow, colorimetry, compressive/flexural strengths, bond to existing substrates, water absorption, and photocatalytic activity evaluated using an ISO 22197-1:2007 reactor. The results showed that the mechanical properties remarkably improved with TiO2 additions, up to 8% of the cement mass. This was attributed to two concomitant phenomena including a micro-filler effect that enhances the packing density and nucleation sites to promote strength development. The removal of nitrogen oxides from the atmosphere reached 92% when the TiO2 was added at a rate of 5% of the cement mass. Such data can be of particular interest to consultants and environmental activists searching for innovative materials capable of maintaining better ambient air quality in urban and modern cities.

Unidirectional penetration approach for characterizing sulfate attack mechanisms on cement mortars and pastes

Degradation of cementitious materials by sulfate ions is commonly classified into chemical and physical sulfate attack. So-called “physical” attack dominates in many field situations, but laboratory testing focuses on “chemical” attack under full-immersion. This paper presents a new setup which looks at sulfate ion ingress under unidirectional capillary action, as a first approach to field conditions. Here, a high concentration of sulfate ions and w/c and Portland cement were used to accelerate degradation to see if the approach is feasible. The radial expansion and appearance of mortar and paste samples were tracked over time. Periodically, profiles of sulfate ingress and phase assemblage were studied in the SEM and by X-ray diffraction. The results show that physical and chemical sulfate attack occur in different areas of the same sample. The approach shows potential to uncover the mechanisms involved in sulfate attack including both “chemical” and “physical” aspects of the degradation process.

Multifunctional Concrete with Graphene-Based Nanomaterials and Superabsorbent Polymer

This study reports on the development of a multifunctional concrete using graphene nanoplatelet (GnP) and sodium polyacrylate (SP) superabsorbent polymer. A combination of concrete functionalities was convened to improve, i.e., high strength and durability along with smart properties such as self-healing and self-sensing. GnP (0.05% by weight of cement) and SP (0.11% by weight of cement) were dispersed in concrete. Compared to the control concrete mix (no GnP and SP), the compressive strength increased 14% by GnP and decreased 9% by SP, and their combination resulted in a 6% enhancement in strength. The durability performance of concrete samples under coupled degradation mechanisms of freeze-thaw and chloride ion ingress suggested that SP in concrete has a better performance than GnP in concrete. SP in concrete shows self-sealing abilities resulting in less chloride ion penetration. However, the combined effect of both GnP and SP in concrete resulted in the maximum reduction in chloride ion penetration depth under freeze-thaw, a 42% reduction compared to the control mix. Microstructural analysis was conducted and found to resist the effects of freeze-thaw and reduce chloride ion penetration in modified concrete compared to the control concrete mix. GnP developed self-sensing abilities in concrete, resulting in about 12.7% fractional change of electrical resistance under 10 KN of cyclic compressive loading. The synergic impact of GnP and SP possesses a new prospect for developing highly efficient multifunctional concrete.

An electrochemical model to characterize the chloride ion ingress in multi-phase concrete with the effect of ionic solution

The chloride (C1-) ion ingress is one of the primary causes for concrete structure deterioration. Herein, an electrochemical model is developed to simulate the C1- ion corrosion in a concrete structure with the effect of the surrounding solution, where the dissolution and precipitation reactions are fully considered between the hydrated products and the mobile ions, and the three phases are involved, including cement paste, aggregates, and interfacial transition zone. The governing equations are achieved by the conservation law of mass and the Maxwell equation, and the constitutive relations are derived by the second law of thermodynamics. Furthermore, the verified model is employed to investigate electrochemical behavior of the concrete structure. The results reveal that the spatial and temporal evolutions of the ion concentrations and the hydrated products are significantly affected by the surrounding solution, the ion diffusion constant and the electric potential applied. Furthermore, an abrupt variation is found for the ion concentration at the concrete-solution interface, showing the critical role of the surrounding solution domain. The present model may provide theoretical guidance in the design and optimization of the concrete structure durability.

Chloride Penetration of Recycled Fine Aggregate Concrete under Drying-Wetting Cycles.

Recycled fine aggregate (RFA) produced from concrete waste is commonly used in the construction industry; however, its use for structural concrete members has not been extensively studied. Moreover, its durability in a drying-wetting cycle environment still needs to be examined. In this study, the intrusion process of chloride in concrete under the drying-wetting cycles is experimentally characterized. Chloride penetration tests are carried out on concrete with the incorporation of different RFA replacement rates and mineral admixtures (i.e., fly ash and silica fume). The results show that the chloride penetration of recycled fine aggregate concrete (RFAC) is dependent upon the performance of the concrete itself, while the deterioration of chloride ion erosion resistance is due to the combined action of the replacement rate of RFA and the drying-wetting cycles. The incorporation of RFA degrades the properties of RFAC owing to its drawbacks in the degradation of interfacial properties of RFAC. Exposure to the drying-wetting cycle environment causes the content of free chloride ions in RFAC to increase initially before decreasing with the erosion depth, thereby showing an obvious convection zone and diffusion zone. The incorporation of the mineral admixture can effectively improve the compactness of the concrete microstructure and make concrete less susceptible to chloride ions ingress. RFAC mixed with 15% fly ash and 10% silica fume has a comparable resistance to chloride penetration as a natural aggregate concrete, which is a feasible method for the application of RFA.

Numerical study of interactive ingress of calcium leaching, chloride transport and multi-ions coupling in concrete

In circumstances with wastewater and seawater, the behavior of multi-ions including calcium, chloride and others in concrete attracts attention. The present study investigated the multiple mechanisms that could happen under the special field situation above, including calcium leaching, chloride transport and multi-ion coupling. To realize the interactive ingress of multi ions, the simulation method for the processing of the individual mechanisms and the mutual influences is adopted. The distributions of the diversified ions are analyzed with the influence of the interfacial transition zone. The time-spatial distribution of porosity and its evolution mechanisms are investigated by considering the interaction with calcium ions in both pore solution and solid phase. The results indicate that calcium leaching would dominantly speed up chloride transport due to the coarsened pore structure, while the multi ions electrochemical coupling effect would facilitate calcium leaching in the early stage but subtly delay calcium leaching in the later stage.