Chloride Research Articles

Microstructural Investigations of Weld Deposits from Manganese Austenitic Alloy on X2CrNiMoN22-5-3 Duplex Stainless Steel

Duplex stainless steels are materials with high performance under mechanical stress and stress corrosion in chloride ion environments. Despite being used in many new applications such as components for offshore drilling platforms as well as in the chemical and petrochemical industry, the automotive industry, etc., they face issues of wear and hardness that limit current applications and prevent the creation of new use opportunities. To address these shortcomings, it is proposed to develop a hardfacing process by a special welding technique using a universal TIG source adapted for manual welding with a pulsed current, and a manganese austenitic alloy electrode as filler material. The opportunity to deposit layers of manganese austenitic steel through welding creates advantages related to the possibility of achieving high mechanical characteristics of this steel exclusively in the working area of the part, while the substrate material will not undergo significant changes in chemical composition. As a result of the high strain hardening rate, assisted mainly by mechanical twinning, manganese austenitic alloys having a face-centered cubic crystal lattice (f.c.c) and low stacking fault energy (SFE = 20–40 mJ/m2) at room temperature, exhibit high wear resistance and exceptional toughness. Following cold deformation, the hardness of the deposited metal increases to 465 HV5–490 HV5. The microstructural characteristics were investigated through optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Vickers hardness measurements (HV). The obtained results highlighted the feasibility of forming hard coatings on duplex stainless steel substrates.

Self-forming barrier layer for carbon dioxide corrosion protection of mild steel in NaCl solution containing hydroxychavicol isolated from Piper betle L. leaf

Hydroxychavicol compound was isolated from Piper betle L. leaf and identified via preparative high performance liquid chromatography (Prep-HPLC) and nuclear magnetic resonance (NMR) spectroscopy. Hydroxychavicol compound was demonstrated to be a potential inhibitor for mild steel corrosion in carbon dioxide-containing environments due to the formation of a barrier layer on the steel surface. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the inclusion of hydroxychavicol in the aggressive environment made steel surfaces more homogeneous and smoother with a rough mean square roughness of 7.78 nm, whereas the steel surface was severely corroded in the blank solution. Moreover, X-ray photoelectron spectroscopy (XPS) results showed an enrichment of hydroxychavicol species combined with iron oxides and hydroxides on the mild steel surface. This can lead to the creation of a protective layer on the mild steel surface, thereby enhancing corrosion protection and localized inhibition. The work suggested a novel approach to isolate corrosion inhibitors from natural products, particularly agricultural by-products for mild steel in carbon dioxide and chloride ion environment with high inhibition performance.

Performance of fly ash and CNI as corrosion prevention methods for steel reinforcement embedded in cracked HPC concrete exposed to a natural marine environment

In this study, the effectiveness of fly ash and a calcium nitrite-based corrosion inhibitor in cracked high-performance concrete was investigated. Concrete prisms were fabricated and the specimens featured artificially transverse cracks 0.25 and 0.5 mm width. These specimens were exposed to a natural marine environment for seven years and the corrosive activity was monitored annually using electrochemical techniques. At the end of the exposure period, chloride ion content at the steel-concrete interface, mass loss, pitting depth and tensile parameters on the steel reinforcement were estimated. It was found that cracking exacerbated corrosion and the prevention methods assessed or their interactions were ineffective. Ultimate strength and ductility losses of the steel reinforcement ranged between 7% and 11% and 44–60% for 0.25 mm crack, while between 11% and 14% and 48–66% for 0.50 mm crack. The results from this research are original because they contribute to elucidating the effect of the interactions between the investigated corrosion prevention methods.

Study on the Effect of Citric Acid-Modified Chitosan on the Mechanical Properties, Shrinkage Properties, and Durability of Concrete.

As an environmentally friendly natural polymer, citric acid-modified chitosan (CAMC) can effectively regulate the hydration and exothermic processes of cement-based materials. However, the influence of CAMC on the macroscopic properties of concrete and the optimal dosage are still unclear. This work systematically investigates the effects of CAMC on the mixing performance, mechanical properties, shrinkage performance, and durability of concrete. The results indicated that CAMC has a thickening effect and prolongs the setting time of concrete. CAMC has a negative impact on the early strength of concrete, but it is beneficial for the development of the subsequent strength of concrete. With the increase in CAMC content, the self-shrinkage rate of concrete samples decreased from 86.82 to 14.52 με. However, the CAMC-0.6% sample eventually expanded, with an expansion value of 78.49 με. Moreover, the long-term drying shrinkage rate was decreased from 551.46 to 401.94 με. Furthermore, low-dose CAMC can significantly reduce the diffusion coefficient of chloride ions, improve the impermeability and density of concrete, and thereby enhance the freeze-thaw cycle resistance of concrete.

Bond performance of NSM FRP–concrete interfaces with epoxy under chloride‐salt conditioned environments

AbstractConcrete in coastal areas is susceptible to structural damage caused by corrosion and expansion of reinforcement. Near‐surface mounted (NSM) fiber‐reinforced polymer (FRP) bars have become effective for strengthening damaged reinforced concrete structures. The bonding performance of NSM FRP bars in concrete is a key factor limiting their application and promotion in civil engineering. In this study, the influences of the conditioned environment, such as the chloride salt concentration, immersion time, and bond length of the FRP bar, on the bonding performance were investigated experimentally. First, material properties in a conditioned environment were studied. Subsequently, the failure mode, bond stress–slip curve, and bond strength of the NSM FRP bar in concrete were investigated. Finally, the microstructure and chemical composition of the materials were revealed using scanning electron microscopy and energy‐dispersive spectroscopy (EDS) images of the materials under environmental conditions. The transfer mechanism of NSM FRP bars in concrete with epoxy was revealed. The results showed that the failure modes of the pullout specimens can be divided into epoxy splitting failure and basalt fiber‐reinforced polymer (BFRP) pulling failure. The chloride‐salt concentration was a critical factor affecting the bond properties, and the longer the bond length, the lower the bond strength. The microstructure clearly shows that the degradation of the bonding behavior at the interface of the NSM FRP bar in concrete in a conditioned environment is attributable primarily to the resin damage of the epoxy, resulting in pit corrosion. There was no significant damage to the fibers in the FRP bar, and the degradation was primarily due to resin matrix damage and interfacial debonding. The EDS results showed that the degradation of the epoxy resin and BFRP bars was caused by CO bond and SiO bond fractures, respectively.

Corrosion Behavior of Candidate Structural Materials for Molten Salt Reactors in Flowing NaCl-MgCl2

Abstracts. A high-temperature molten salt natural convection loop was designed and manufactured for chloride-based salts. NaCl-MgCl2 salt was prepared and injected into the loop. Corrosion coupons composed of SS304, SS316L, and high-Ni alloys were also prepared as candidate structural materials for molten chloride salt reactors. After a corrosion experiment was conducted for 500 h, the salt was drained from the loop to the drain tank; inductively coupled plasma optical emission spectroscopy was used to investigate metal dissolution from the materials into the salt. The corroded materials were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy to calculate the corrosion rate. Materials exposed to NaCl-MgCl2 molten salt showed varying levels of corrosion resistance. The high-Ni alloy demonstrated the highest resistance, followed by SS316L and SS304. Furthermore, corrosion products were observed to migrate along the molten salt through natural convection, eventually depositing onto the surface of the high-Ni alloy in the cold leg of the loop.

Unraveling the molecular landscape of kAE1: a narrative review.

Kidney anion exchanger 1 (kAE1) is an isoform of the AE1 protein encoded by the SLC4A1 gene. It is a basolateral membrane protein expressed by α-intercalated cells in the connecting tubules and collecting duct of the kidney. Its main function is to exchange bicarbonate and chloride ions between the blood and urine to maintain blood pH at physiological threshold. The kAE1 protein undergoes multiple post-translational modifications such as phosphorylation and ubiquitination and interacts with many different proteins such as claudin-4 and carbonic anhydrase II. Mutations in the gene may lead to the development of distal renal tubular acidosis, characterized by the failure to acidify the urine, which may result in nephrocalcinosis and in more severe cases, renal failure. In this review, we discuss the structure and function of kAE1, its post-translational modifications, and protein-protein interactions. Finally, we discuss insights gained from the study of kAE1 mutations in humans and in mice.

Photochlorination of Anthracene in Saline Ice under Simulated Solar Light

Polycyclic aromatic hydrocarbons (PAHs) can undergo photochemical reactions in chlorine-containing environments, generating chlorinated polycyclic aromatic hydrocarbons (ClPAHs). This phenomenon has been confirmed in aqueous and soil environments, while was previously overlooked in saline ice. Thus, this study aimed to investigate the photochemical chlorination behavior of anthracene (ANT) in saline ice. Under photoexcitation, the ground state ANT generates the singlet state ANT (1ANT*), which is transformed into the triplet state ANT (3ANT*) via intersystem crossing. Simultaneously, the oxygen receives electrons and further reacts to form the hydroxyl radical (·OH). The ·OH reacts with chloride ions (Cl−) to produce chlorine radicals (·Cl). The ·Cl then reacts with 3ANT* to form monochloroanthracene (9-ClANT, 2-ClANT). The resulting monochloroanthracene further reacts with ·Cl to form dichloroanthracene (9,10-Cl2ANT). Lower temperature, higher salinity, and dissolved organic matter are facilitated to generate ClPAHs, which may show negative impacts on the ecological environment.

Understanding the effect of non-carbon-based nanoinclusions on chloride penetration resistance and chloride binding capacity of ultra-high performance cementitious composite

Ultra-high performance cementitious composite (UHPCC) with high durability has been widely employed to prevent the chloride corrosion of reinforced concrete structures exposed to the marine environment. Adding nanoinclusions is expected to fundamentally eliminate the defects (i.e., pores and microcracks) caused by the formulation principle of UHPCC, thereby reducing connected pathways for chloride diffusion. Furthermore, the diffusion resistance of chloride ions largely depends on the chloride binding capacity (CBC) of cement-based composites. Regrettably, the effects of non-carbon-based nanoinclusions on chloride penetration resistance (CPR) and CBC of UHPCC still lack comparison and analysis. This study investigated the effect of non-carbon-based nanoinclusions on the CPR and CBC as well as microstructures of UHPCC, including nano-SiO2 (NS), nano-ZrO2 (NZ), nano-TiO2 (NT), and boron nitride (BN). Correlation between pore structure parameters and CPR of composites was established based on the grey system theory. The results of rapid chloride migration (RCM) tests indicate that due to the incorporation of 1 % NS, 3 % SiO2-coated NT, 1 % NZ, and 0.5 % BN, the CPR of UHPCC is improved by 89.6 %, 66.5 %, 87.5 %, and 73.6 %, respectively. The results of the grey correlation analysis highlight the critical role of harmless and less harmful pores with a diameter below 50 nm in preventing the diffusion of chloride ions. The modifying mechanisms of nanoinclusions can be attributed to the nano-core effects, contributing to reducing chloride diffusion pathways and increasing disconnectivity and tortuosity of the pathways. Firstly, nanoinclusions can reduce pores and microcracks, improving the homogeneity of pore size distribution and inhibiting the growth of CH crystals, thus enhancing the compactness of the cement paste matrix. Secondly, nanoinclusions enriched in the interfacial transition zone (ITZ) can improve the homogeneity of ITZ by optimizing the Ca/Si ratios of C–S–H gels and improving the interfacial bond between cement paste and aggregate. Additionally, Langmuir and Freundlich isotherms can accurately describe the CBC of composites. Only NS among nanoinclusions can significantly improve the CBC of UHPCC. This can be attributed to the involvement of pozzolanic NS in cement hydration, promoting the formation of C–S–H gels for physically adsorbing chloride ions while increasing the diffusion resistance of chloride ions in the pathways.

GhCLCc-1, a Chloride Channel Gene from Upland Cotton, Positively Regulates Salt Tolerance by Modulating the Accumulation of Chloride Ions.

The ionic toxicity induced by salinization has adverse effects on the growth and development of crops. However, researches on ionic toxicity and salt tolerance in plants have focused primarily on cations such as sodium ions (Na+), with very limited studies on chloride ions (Cl-). Here, we cloned the homologous genes of Arabidopsis thaliana AtCLCc, GhCLCc-1A/D, from upland cotton (Gossypium hirsutum), which were significantly induced by NaCl or KCl treatments. Subcellular localization showed that GhCLCc-1A/D were both localized to the tonoplast. Complementation of Arabidopsis atclcc mutant with GhCLCc-1 rescued its salt-sensitive phenotype. In addition, the silencing of the GhCLCc-1 gene led to an increased accumulation of Cl- in the roots, stems, and leaves of cotton seedlings under salt treatments, resulting in compromised salt tolerance. And ectopic expression of the GhCLCc-1 gene in Arabidopsis reduced the accumulation of Cl- in transgenic lines under salt treatments, thereby enhancing salt tolerance. These findings elucidate that GhCLCc-1 positively regulates salt tolerance by modulating Cl- accumulation and could be a potential target gene for improving salt tolerance in plants.

Potential of fly ash geopolymer concrete as repairing and retrofitting solutions for marine infrastructure: A review

Corrosion in maritime infrastructure, particularly in reinforced concrete, has emerged as a significant cause for concern due to the presence of chloride ions in seawater. To address this challenge, geopolymer concrete has been proposed as a viable solution for retrofitting and restoring marine structures. This review paper explores the potential application of fly ash geopolymer concrete in marine infrastructure restoration. Fly ash's properties make it ideal for marine infrastructure restoration. Its high levels of amorphous silica and alumina enable geopolymerization, forming a strong binder resistant to chloride corrosion. Its fine, spherical particles enhance concrete workability and density, improving mechanical strength and impermeability. This geopolymer binder offers excellent resistance to corrosion from chloride ions commonly found in seawater, making fly ash geopolymer concrete highly suitable for marine applications. Overall, fly ash's chemical composition and physical traits offer resilience and sustainability in restoring marine infrastructure, ensuring long-term durability against corrosion. This review paper explores the potential application of fly ash geopolymer concrete in marine infrastructure restoration. By examining the primary forms of damage and mechanisms underlying concrete degradation in marine settings, this study highlights the durability and sustainability of geopolymer concrete compared to traditional concrete. Additionally, it discusses current solutions for repairing and retrofitting concrete in marine environments, emphasizing the promising characteristics of geopolymer concrete for integration into such structures. Through this analysis, innovative and environmentally conscious approaches are introduced for addressing corrosion-related challenges in the maritime industry, offering a resilient solution for the construction of enduring marine structures. Finally, recommendations for further research on the application of fly ash geopolymer concrete in marine infrastructure restoration are presented.

Air-Stable Cobalt(III) and Chromium(III) Complexes as Single-Component Catalysts for the Activation of Carbon Dioxide and Epoxides.

Cobalt(III) and chromium(III) salophen chloride complexes were synthesized and tested for the cycloaddition of carbon dioxide (CO2) with epoxides to obtain cyclic carbonates. The cat1, cat2, cat4, and cat5 complexes presented high catalytic activity without cocatalysts and are solvent-free at 100 °C, 8 bar, and 9 h. At these conditions, the terminal epoxides (1a-1k) were successfully converted into the corresponding cyclic carbonates with a maximum conversion of ∼99%. Moreover, cat5 was highlighted due to its capability of opening internal epoxides such as limonene oxide (1l) with a 36% conversion to limonene carbonate (2l), and from cyclohexene oxide (1m), cyclic trans-cyclohexene carbonate (2m) and poly(cyclohexene carbonate) were obtained with 15% and 85% selectivity, respectively. A study of the coupling reaction mechanism was proposed with the aid of electrospray ionization mass spectrometry (ESI-MS) analysis, confirming the single-component behavior of the complexes through their ionization due to epoxide coordination. In addition, crystallographic analysis of cat1 single crystals grown in a saturated solution of pyridine helped to demonstrate that the substitution of chloride ion by pyridine ligands to form an octahedral coordination occurs (Py-cat1), supporting the proposed mechanism. Also, a recyclability study was performed for cat5, and a total turnover number of 952 was obtained with only minor losses in catalytic activity after five cycles.

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 chlorine salt antifreeze road dust suppressants for open-pit coal mines

In addressing the significant challenge of trucking road dust emanating from open-cast coal mines, the prevalent method of conventional water sprinkling for dust removal on transport roads has proven suboptimal. This inadequacy is attributed to the pronounced mobility of truck transport roads, substantial dust loads, and extensive open dust sources. Particularly in cold mining regions, the use of water in winter exacerbates the issue by causing icy road surfaces, thereby increasing the risk of truck skidding and overturning, posing a severe hazard to both mine safety and the well-being of truck drivers. A pragmatic imperative exists to devise a solution that effectively addresses both anti-freezing and dust suppression in open-pit coal mine roads, while minimizing corrosive impact. Against the backdrop of Hebei Open-pit Coal Mine in Huolin, Inner Mongolia, this study focuses on the development of a chloride salt antifreeze-type road dust inhibitor tailored for open-pit transportation roads. The proprietary anti-freezing dust suppressant achieves a freezing point as low as −36.4 °C, exhibiting corrosion efficiency merely at 56.5% of that of water. Notably, the effective dust suppression duration surpasses that of water by a factor of 150, resulting in a 53% reduction in dust suppression costs. This innovation is specifically applicable to high-cold and arid surface coal mines in northern regions and similar mining contexts. It offers technical support for the establishment of environmentally sustainable practices in surface coal mines, representing a pivotal step toward the realization of green mining initiatives.

Undecanoic Acid and L-Phenylalanine in Vermiculite: Detection, Characterization, and UV Degradation Studies for Biosignature Identification on Mars.

Solar radiation that arrives on the surface of Mars interacts with organic molecules present in the soil. The radiation can degrade or transform the organic matter and make the search for biosignatures on the planet's surface difficult. Therefore, samples to be analyzed by instruments on board Mars probes for molecular content should be selectively chosen to have the highest organic preservation content. To support the identification of organic molecules on Mars, the behavior under UV irradiation of two organic compounds, undecanoic acid and L-phenylalanine, in the presence of vermiculite and two chloride salts, NaCl and MgCl, was studied. The degradation of the molecule's bands was monitored through IR spectroscopy. Our results show that, while vermiculite acts as a photoprotective mineral with L-phenylalanine, it catalyzes the photodegradation of undecanoic acid molecules. On the other hand, both chloride salts studied decreased the degradation of both organic species acting as photoprotectors. While these results do not allow us to conclude on the preservation capabilities of vermiculite, they show that places where chloride salts are present could be good candidates for in situ analytic experiments on Mars due to their organic preservation capacity under UV radiation.

Invertebrates from naturally brackish areas are less impacted by road salt and alternative deicers

AbstractRoad salt (NaCl) is the most common deicer used to melt snow and ice from roadways in cold climates, but its use results in runoff of sodium and chloride ions into sewers and into soil and freshwater ecosystems. Road salt causes harmful effects on wetland habitats, which host an abundance of macroinvertebrate species. Alternatives to road salt, such as beet juice, are commercially available, but their impact on invertebrates is less well studied. We examined the impact of road salt alternatives on four invertebrate species (Daphnia pulex, Eisenia fetida, Heterocypris sp., and Culicoides sp. larvae), some of which come from a naturally brackish area. Our expectation was that road salt alternatives (beet salt, molasses, pickle juice, and sand) would be less toxic to the animals than traditional road salt. This study comprised two experiments: the first exposed individuals of the four invertebrate species to road salt alternatives, and the second exposed the invertebrates to a range of road salt concentrations. Only individuals of D. pulex were negatively impacted by road salt. The other invertebrates were not significantly affected by any salt alternative, demonstrating interspecific differences in response to salt. Species found in naturally salty environments were more tolerant of both road salt and alternatives. This research shows species‐ and habitat‐specific responses to road salt alternatives, which has implications for municipalities looking to salt roads without negatively impacting freshwater ecosystems.

Design and Preparation Technology of Green Multiple Solid Waste Cementitious Materials.

For solid waste-based cementitious materials, most scholars focus their research on the hydration reaction of cementitious materials, but there is still a lack of solid waste design that comprehensively considers mechanical properties and durability. Therefore, this article focuses on exploring the mix of design and the microscopic and macroscopic properties of multi solid waste cementitious materials (MSWCMs), namely steel slag (SS), slag powder (SP), desulfurization gypsum (DG), fly ash (FA), and ordinary Portland cement (OPC). According to the orthogonal experimental results, the compressive strength of MSWCMs is optimal when the OPC content is 50% and the SS, SP, DG, and FA contents are 10%, 20%, 5%, and 15%, respectively. The MSWCMs group with an OPC content of 50% and SS, SP, DG, and FA contents of 5%, 15%, 5%, and 25% was selected as the control group. The pure OPC group was used as the blank group, and the optimal MSWCMs ratio group had a 28-day compressive strength of 50.7 megapascals, which was 14% and 7.6% higher than the control group and blank group, respectively. The drying shrinkage rate and resistance to chloride ions were also significantly improved, with maximum increases of 22.9%, 22.6%, and 8.9%, 9.8%, respectively. According to XRD, TG-DTG, and NMR testing, the improvement in macroscopic performance can be attributed to the synergistic effect between various solid wastes. This synergistic effect produces more ettringite (AFt) and C-(A)-S-H gel. This study provides a good theoretical basis for improving the comprehensive performance of MSWCMs and is conducive to reducing the use of cement, with significant economic and environmental benefits.

Effect of tissue fixatives on the corrosion of biomedical magnesium alloys

In this work, the corrosion behavior of pure Mg, Mg3Ag, Mg6Ag, and MgZnYNd alloys in different fixatives (ethyl alcohol (EA), 85 % ethyl alcohol (85 % EA), 10 % neutral buffered formalin (10 % NBF), 4 % glutaric dialdehyde (4 % GD), and 4 % paraformaldehyde (4 % PFA)) was investigated to provide a valuable reference for the selection of fixatives during the histological evaluation of Mg implants. Through the hydrogen evolution test, pH test, and corrosion morphology and product characterization, it was found that corrosion proceeded slowest in the EA and 85 % EA groups, slightly faster in 4 % GD, faster in 10 % NBF, and fastest in 4 % PFA. After corrosion, the EA group surface remained unchanged, while the 85%EA group surface developed minor cracks and warping. The 4%GD fixative formed a dense needle-like protective layer on the Mg substrate. The 10%NBF group initially grew a uniform layer, but later developed irregular pits due to accelerated corrosion. In contrast, the 4%PFA solution caused more severe corrosion attributed to chloride ions. The main corrosion products in the EA and 85%EA groups were MgO and Mg(OH)2, while the other fixatives containing diverse ions also yielded phosphates like Mg3(PO4)2 and MgHPO4. In 4 % PFA, AgCl formed on the surface of Mg6Ag alloy after corrosion. Therefore, to minimize Mg alloy corrosion without compromising staining quality, EA or 85 % EA is recommended, while 4 % PFA is not recommended due to its significant impact.

Feasibility Study of UHPC Reinforced Masonry Structure

With the increase of service life of masonry structure and the damage of masonry structure caused by external environment, the structure will be difficult to meet the design requirements. It is necessary to repair and reinforce the existing structure or replace the original structure with a new type of composite structure. ultra-high performance concrete (UHPC) is a kind of high strength, high ductility, high durability material, which has the advantages of almost impermeability, almost no carbonization, and almost zero chloride ion penetration and sulfate penetration. UHPC has been widely used in the field of concrete structure reinforcement, whether the masonry structure can be better strengthened has become the research content of this paper. Basic mechanics of UHPC materials at home and abroad By systematically combing and summarizing the research progress of performance and reinforcement design, the feasibility of UHPC reinforced masonry structure is obtained.

Durability life evaluation of marine infrastructures built by using carbonated recycled coarse aggregate concrete due to the chloride corrosive environment

Due to the harsh marine environment of chloride ion invasion and corrosion, the issues of long-term chloride transport and durability life evaluation for marine infrastructures constructed/maintained by recycled aggregate concrete (RAC) after enhancement remain poorly understood. For our studies, an accelerated carbonation modification method for recycled coarse aggregate (RCA) was adopted to prepare carbonated recycled coarse aggregate (CRCA) samples, and the macroproperties, i.e., apparent density and water absorption, of CRCA were enhanced by approximately 1.40-3.97% and 16.3-21.8%, respectively, compared with those of RCA. An in-door experiment for chloride transport into concrete specimens subjected to a simulated marine environment of alternating drying-wetting cycles was conducted. The chloride profiles and transport characteristics of carbonated recycled coarse aggregate concrete (CRCAC), recycled coarse aggregate concrete (RCAC), and natural coarse aggregate concrete (NCAC) were analysed and compared. The results indicated that the chloride penetration depths and concentrations of CRCAC were approximately 52.6-96.2% of those of RCAC, which highlighted the better chloride resistance of CRCAC. A chloride transport model for marine concrete structures with various coarse aggregate types in a corrosive marine environment was established. Taking a certain harbour wharf as an example, the durability life of this case considering the application of the CRCAC was evaluated based on the chloride transport model, and the durability life of the CRCAC structure was improved by approximately 28.10% compared with that of the RCAC. The CRCAC developed in this paper has improved mechanical performance and durability than those of RCAC, and it has the potential to replace the NCAC and further support the construction and maintenance of marine infrastructures.