The rebar corrosion induced by chloride attack is a major factor threatening the durability of reinforced concrete structures in marine environments. This study examines the concrete matrix and rebar/concrete interface from eccentrically arranged reinforced concrete members incorporating two triethanolamine (TEA) derivatives, namely triethanolamine phosphate (TP) and triethanolamine dodecylbenzene sulfonate (TDS), after electrically accelerated corrosion. The chloride-contaminated concrete matrix was analyzed for microstructure, chemical composition, and pore characteristics, while the extracted rebar/concrete interfaces were evaluated through electrochemical tests, 3D profile scanning, and Vickers hardness measurements. Results show that TEA derivatives have a marked influence on the hydration products and microstructure characteristics of the cementitious materials. TDS exhibits an air-entraining effect, leading to the generation of irregular CH clusters and large-scale hydration pores that facilitate chloride penetration and accelerate steel corrosion. In contrast, TP refines CH morphology, promotes the formation of Friedel's salt, and densifies the cement matrix, thereby enhancing chloride binding and inhibiting localized anodic dissolution. Consequently, specimens with TP exhibit a significantly thinner rust layer (~15 μm) and a mechanically compact interface, ensuring superior corrosion resistance. These findings highlight the potential of phosphate-based TEA derivatives as effective corrosion inhibitors for reinforced concrete exposed to chloride-rich environments.

WNK kinases are chloride- and osmotic-stress-regulated protein kinases recently shown to be controlled by potassium. Prior studies demonstrated the direct binding of chloride and osmotic stress-related water in WNK kinase regulation. Here, we probe potassium binding and regulation of WNK kinases via crystallography coupled with mutagenic analysis of WNK kinase autophosphorylation and activity. Crystals of unphosphorylated WNK1 grown in cesium formate, a surrogate for potassium, yielded nonsulfur scattering peaks at 5.75 keV. Mutations were introduced into amino acids flanking the anomalous diffraction peaks. Mutations in WNK1/E388 and the corresponding WNK3/E314, probing a peak close to WNK1/I384, led to reduced inhibition by potassium while maintaining kinase autophosphorylation and substrate phosphorylation activity. Other peaks probed by mutagenesis either did not bear out as potassium regulatory sites or were not validated due to the inactivity of the mutants synthesized. Previously synthesized chloride- and water-binding mutants demonstrate correlated sensitivity to chloride and potassium. Potassium, chloride, and water are all WNK inhibitors that share a common mechanism binding the same low-activity asymmetric dimer of WNK1 kinase domains.

This study investigates the effect of replacing natural aggregates with siderite (10%, 20%, 30%, and 100%) in heavyweight concretes designed for radiation shielding. Both fine (0-4mm) and coarse (4-16mm) siderite aggregates were used, while the binder composition (cement + GGBFS) and water-to-binder ratio (w/b ≈ 0.40) were kept constant. Mechanical, durability, and radiation shielding properties were evaluated through compressive strength, abrasion resistance, ultrasonic pulse velocity, freeze-thaw resistance, high-temperature exposure, chloride migration, and gamma-ray attenuation tests at 1173 and 1333keV. The results indicate that siderite incorporation generally improves compressive strength, density, and durability-related performance. These improvements may be associated with a more compact internal structure, as reflected by reduced water absorption potential (indirectly inferred from transport-related behavior), lower chloride migration, and higher ultrasonic pulse velocity values. A strong inverse relationship between compressive strength and chloride migration (R² = 0.97-0.87) confirms improved transport resistance, where GGBFS likely contributes to chemical chloride binding, while siderite mainly enhances physical aggregate packing. Gamma-ray shielding performance also improves with increasing siderite content, with coarse aggregate systems showing superior attenuation compared to fine ones. Overall, siderite-modified concretes demonstrate strong potential for durable and radiation-shielding structural applications.

Physical adsorption and chemical binding of chloride in the laminate and interlayer of recrystallized hydrotalcite

Abstract Enhancing the durability of cement paste through the incorporation of appropriate additives represents a promising approach to improving the sustainability of cement production. In particular, the inclusion of layered double hydroxides (LDHs) in cementitious systems has been shown to enhance their corrosion resistance to Cl − and SO 4 2− anions. However, LDHs, due to their anionic exchange capability, significantly affect the initial kinetics. In this work, two types of nanometric LDHs, MgAl-NO 3 and MgAl-HCOO, were added to cement paste in different proportions (1, 3, and 5 wt% of the binder) to investigate early hydration kinetics and to quantitatively evaluate the effect of anion exchange on cement hydration products and clinker phase consumption by in situ X-Ray diffraction (XRD). In addition, the chloride binding capacity of selected LDHs was tested by means of XRD and thermogravimetric analyses. The results show that, in the early hydration stage, LDHs can capture SO 4 2 ⁻ ions, thereby inhibiting early ettringite precipitation and enhancing the production of hydration products (portlandite) after the first 24 h. LDHs containing formate decrease the availability of Ca 2 ⁺ in solution, thereby limiting the precipitation of calcium-rich phases, slowing down the dissolution of alite (C 3 S). Geochemical modelling supports these findings. Finally, both MgAl-NO 3 and MgAl-HCOO improved the chloride binding capacity of the cement paste due to their excellent anion exchangeability.

Mechanistic effects of ferrite phases structure on hydration and chloride binding: Experimental and theoretical insights

Temperature-dependent reactive-transport simulation of chloride binding in cementitious materials with kinetic Friedel salt formation

Carbon dots (CDs) have demonstrated promising application prospects in the field of corrosion protection due to their small size, excellent dispersibility, abundant and tunable surface functional groups, low cost, environmental friendliness, and unique fluorescence properties. However, existing reviews have predominantly focused on the synthesis and photoluminescence properties of CDs, lacking systematic integration and in-depth mechanistic analysis of their diverse applications in corrosion protection. This review systematically summarizes the recent research progress and underlying mechanisms of CDs in five key areas: corrosion inhibitors, anticorrosive coatings, photogenerated cathodic protection, chloride binding, and corrosion monitoring. As corrosion inhibitors, CDs form compact protective films on metal surfaces through synergistic physical and chemical adsorption. In anticorrosive coatings, CDs not only enhance the physical barrier effect but also impart intelligent functionalities such as self-healing and corrosion monitoring. In the field of photogenerated cathodic protection, CDs broaden the light absorption range of semiconductors and facilitate the separation of photogenerated carriers. As chloride binding promoters, CDs promote the formation of cement hydration products, thereby improving the durability of reinforced concrete structures. As sensing platforms, CDs enable early visual detection of corrosion through their specific fluorescence response to ions such as Fe3+. Despite significant progress, challenges remain in scalable preparation, practical application performance in complex environments, and multifunctional integration. This review systematically outlines the research advancements of CDs in corrosion protection, providing a practical reference for subsequent studies and engineering applications. Future research should focus on scalable synthesis, machine learning-assisted design, and the development of integrated multifunctional protection systems to promote the practical application of CDs in the field of corrosion protection.

Chloride binding and its sulfate-induced release in fly ash-blended cement pastes: Experimental study and thermodynamic analysis

Enhancing chemical binding of internal chlorides in ultra-high performance seawater and sea sand concrete through the synergistic effect of metakaolin and alkali-rich white mud

Alkali-activated materials (AAMs) are promising low-carbon alternatives to Portland cement, but their wider application is limited by poor volumetric stability, high shrinkage, and slow reaction kinetics, particularly in near-neutral salt-activated systems. Reactive magnesium oxide (MgO) has emerged as a multifunctional component that can address these limitations by acting as a partial precursor replacement, a composite activator, or a primary activator. This review provides a comprehensive overview of MgO's role in AAMs, focusing on hydration mechanisms, fresh properties, mechanical performance, volumetric stability, and durability. MgO influences AAM behavior through several mechanisms. Its hydration produces expansive brucite, which compensates for shrinkage, while in near-neutral systems MgO increases pore solution alkalinity, accelerating precursor dissolution and reaction kinetics. The formation of secondary phases, such as hydrotalcite-like compounds and hydrated magnesium carbonates, further refines pore structure, enhances durability, and contributes to self-healing. The impact of MgO is highly system-dependent. MgO generally reduces workability and accelerates setting, but significantly mitigates autogenous and drying shrinkage. Optimal dosages vary with activator type: approximately 4-7.5% is effective in sodium silicate-activated slag, whereas higher dosages (~ 5-10%) are typically required in Na2CO3-activated systems. Strength development is non-monotonic and activator-specific, with moderate dosages enhancing strength in Na2CO3-activated systems but potentially reducing strength in NaOH-activated slag due to excessive expansion. When optimally dosed, MgO improves durability by enhancing chloride binding and carbonation resistance. Overall, MgO performance depends on its reactivity, particle size, activator chemistry, and precursor composition. This review synthesizes these interactions to guide the design of durable, high-performance, and sustainable AAM binders.

In this work, three symmetric squaramide derivatives were synthesized, and their anion-binding properties were systematically investigated. The binding properties of squaramides I-III with anions were determined by spectroscopic titration in DMSO-d 6 using tetrabutyl ammonium salts. During titration with ammonium salts, the shift values of the protons of NH groups in the squaramide structure were recorded in 1H NMR. The variations in the chemical shifts of NH protons in the squaramides were analyzed with the DynaFit and BindFit programs to obtain the corresponding association constants. The greatest chemical shift was obtained from TBA-Cl with squaramide I titration, and it has the highest binding capacity with squaramide I and Cl- anion. Therefore, it was found that both the number of CF3 groups on the aromatic ring and the number of CH2 groups between the aromatic ring and the amide moiety in the structure of squaramide influence the strength of the anion binding ability. The stoichiometry of complexation between squaramides I-III and Cl- was also investigated using Job's plots.

The growing demand for sustainable construction has increased interest in using recycled concrete aggregates (RCA) in concrete production. Existing studies have focused on the mechanical and durability properties of recycled aggregate concrete (RAC), but the applicability of standard durability tests to RAC remains insufficiently examined. The electrical resistivity (ER) test provides a rapid and practical assessment of concrete durability. Previous studies have shown a strong correlation between ER and chloride migration, making ER a reliable indicator of concrete’s resistance to chloride ion penetration. However, this relationship may not apply to RAC. This study evaluates the performance of RAC with and without amorphous rice husk ash (RHA) by examining electrical resistivity and non-steady-state migration coefficients to assess the applicability of ER in durability evaluation of RAC. The RHA was derived from an abundant agricultural waste in the Philippines. Concrete mixes were prepared with 0% and 10% RHA as cement replacement and with RCA replacing up to 100% of the coarse aggregate. The use of RCA decreased ER due to the higher porosity of the old mortar, whereas high RCA replacement reduced the non-steady-state migration coefficient, possibly due to chloride binding within the adhered mortar. Incorporating RHA improved both resistivity and chloride resistance through pozzolanic reaction and pore refinement. Unlike in conventional concrete, a weak correlation was observed between ER and chloride migration, suggesting that ER alone is not a reliable predictor of chloride ingress in RAC. The findings emphasize the need for direct migration testing for accurate durability assessment of RAC.

Recent advances in multifunctional nanocomposites for high-performance and durable concrete in harsh environments

Effect of CO2 injection concentration during mixing on chloride migration and binding behaviors of cement paste

Green and sustainable leaf-derived carbon dots toward greatly facilitating chloride binding of cement

AFm phase chloride binding: Kinetic advantages of monocarbonate over monosulfate and the role of calcium availability

Effect of hydroxysodalite on the alkali-activated slag of seawater mixture: Early hydration behavior, chloride binding capacity, and microstructural characteristics

Coiled coils, owing to their simple yet versatile architecture, serve as valuable model systems for both experimental and computational studies in protein science. Whereas the sequence-structure relationships that govern their oligomeric state and stability have been thoroughly investigated, important gaps remain, most notably regarding the role of central chloride ions coordinated by asparagine triads observed in several trimeric coiled-coil (TCC) crystal structures. To investigate the thermodynamics of chloride binding at this site, we performed extensive molecular simulations using metadynamics and alchemical free-energy calculations, both enhanced with replica exchange, to determine the chloride binding free energy (ΔGbind) in three TCCs of similar length but different stability (PDB IDs: 2wpy, 4dzk, 1mof). Despite the nearly identical local coordination environment, the computed ΔGbind values strongly depend on the overall protein structure, with variations in superhelical radius R0 upon ion removal systematically accompanying the observed binding thermodynamics. In particular, both the metastable TCC 2wpy─a variant of the GCN4 leucine-zipper domain previously shown to be unstable in the absence of chloride─and the synthetic design 4dzk exhibit highly unfavorable binding, suggesting that current biomolecular force fields may not fully capture either the stabilizing role of chloride or the conformational ensemble of the unbound state. By contrast, the calculated ΔGbind in 1mof, a fragment of the MoMuLV retroviral transmembrane protein, is favorable and is associated with the presence of an additional C-terminal leash domain that modulates the binding-site environment. These results identify TCCs as critical benchmarks for improving the description of anion-protein interactions and the balance between bound and unbound states in future force-field developments.

Concrete durability is a critical factor influencing the longevity, safety, and sustainability of infrastructure, particularly under aggressive environmental conditions. Conventional ordinary Portland cement (OPC) concrete is susceptible to deterioration mechanisms such as chloride-induced reinforcement corrosion, sulphate attack, carbonation, and acid degradation, which compromise structural integrity and service life. The partial replacement of OPC with supplementary cementitious materials (SCMs) has emerged as an effective strategy to enhance durability while reducing the environmental footprint of concrete. This review critically examines the performance of major SCMs, including fly ash, ground granulated blast furnace slag (GGBS), silica fume, metakaolin, rice husk ash (RHA), and limestone calcined clay cement (LC3), in aggressive environments. The review highlights how SCMs influence microstructural properties, such as pore refinement, chloride binding, and formation of secondary hydration products, thereby improving resistance to chloride ingress, sulphate attack, carbonation, and acid exposure. While SCMs generally enhance durability, certain limitations, such as increased carbonation depth in high-volume fly ash and slag systems, are discussed. Furthermore, factors influencing performance such as SCM type, replacement level, curing conditions, and exposure environment are analysed.