Article

Improvement in the anti-corrosion property of marine concrete using layered double hydroxides and polyvinylpyrrolidone

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Abstract

Chloride induce corrosion destroys the structure of marine concrete, thereby shortening its actual service life. In this study, Fe-based layered double hydroxides (LDHs), including CaFe-NO3 and CaFeAl-NO3 LDHs, and polyvinylpyrrolidone (PVP), were added to increase the anti-corrosion property of mortar. Electrochemical tests and chloride penetration resistances of the samples were conducted, and the corresponding micro-mechanisms were investigated. The samples that were immersed short-term (5 d) exhibited similar electrochemical characteristics and corrosion tendencies compared to the 7 d samples. With increasing immersion time, all the samples were corroded, whereas the LDHs-PVP composites still exhibited higher resistances and impedance, larger arc radius, and a lower corrosion current density and corrosion rate than the other samples due to the synergistic effect via the formation of a passive film by PVP, the increased compactness and adaptability by Fe-based LDHs, and promotion of uniform dispersion of LDHs in slurry by PVP. Further, the work function of the LDHs-PVP composites was lower than that of the control, indicating that the addition of LDHs and PVP decelerated the corrosion reaction of steel. Thus, the LDHs-PVP composites exhibited high anti-corrosion property; the rapid chloride migration coefficient and total charge passed decreased by 17.5% and 4.9% compared to those of the control, respectively, highlighting the potential of this composite as effective inhibitors for marine concrete corrosion.

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... This chloride ions containing hydration products could release the bound chlorides to form Kuzel's salt [7] or AFt to some extent [35] when it is exposed to chloride-free solution. The chloride ions binding ability and adsorption dynamics in different types of LDHs are also attractive for designing chloride ion sequestration additives in marine concrete [45]. Therefore, understanding the difference in crystal structures of the aluminate containing hydration products and their change under external pressures could be very important to explain the variations in mechanical properties and microstructure development of cement paste, corresponded to the replacement of clinker or cement by SCMs. ...
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The main focus of this study was to investigate the effect of silica fume (SF) and nano-silica (NS) on hydration behavior and mechanism of high sulfate resistance Portland cement (HSRPC), and were analyzed in terms of chemical shrinkage, setting time, compressive strength, rheology, pore structure, hydration heat, and hydration products. Experimental results showed that 5 wt% SF deepened the secondary hydration reaction of HSRPC, because calcium hydroxide (CH) produced by HSRPC hydrating effectively stimulated the pozzolanic activity of SF at later ages. Compared with HSRPC, the 28 d total porosity and CH content of HSRPC with 5 wt% SF respectively reduced by 6.1% and 4.4%. The corresponding compressive strength increased by 14.4%. 0.1–0.3 wt% NS moved up the acceleration period of the hydration and reduced setting time. Meanwhile, NS with high pozzolanic activity evidently increased chemical shrinkage and compressive strength at early ages. Compared with HSRPC, the 28 d total porosity of HSRPC with 5 wt% SF and 0.3 wt% NS reduced by 16.3%. The CH content in TG-DTG curve was reduced by 24.7%, which was consistent with the reduction of CH characteristic peak value. Therefore, in the later hydrating process, the synergistic effect of SF and NS significantly promoted the second hydration reaction.
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Sulfur-rich copolymer is considered as a promising cathode in lithium-sulfur battery due to its superior chemical confinement for polysulfides on the molecular level, but the sulfur-rich copolymer with low cost and physiological inert is reported rarely. Here, a novel sulfur-polyvinylpyrrolidone (PVPS) copolymer is synthesized by one-step thermal polymerization. The break and recombination of C=O lead to the formation of PVPS, which is proved by various characterizations. Due to the strong chemical confinement of C-S bond, the excellent polysulfides adsorption ability of PVP with abundant polar bonds (such as C-O and C-N) and the improved charge transfer of PVPS, 20PVPS combining with PVP-modified separator as “residence” of polysulfides delivers the high reversible capacity of 1079 and 729 mAh g⁻¹ at 0.1 and 2 C and a slow capacity fading rate of 0.093% over 500 cycles at 1 C. These findings provide a reference for the synthesis of low-cost, biocompatible and high-performance sulfur-rich copolymer in lithium-sulfur battery.
Article
In this work, the influence of sodium nitrite (NaNO2) and sodium nitrate (NaNO3) corrosion inhibitors on the composition, structure, and chloride binding behaviors of layered double hydroxides (LDHs) formed in ternary ordinary Portland cement-metakaolin-dolomite (OPC-MK-DM) systems is studied. The results show that the nitrite and nitrate anions are preferably intercalated in the CaAl LDHs (AFm phases), but not in the MgAl LDHs (hydrotalcite-type phases) due to its limited formation in these ternary cementitious systems cured at ambient temperature. The autogenously formed nitrate- and nitrite-AFm phases are decomposed upon chloride exposure accompanied by Friedel's salts formation, potentially releasing corrosion inhibitive ions to the pore solution in a progressive manner. The NaNO2 and NaNO3 incorporation in ternary OPC-MK-DM binders marginally lowers chloride binding capacity but reduces its penetration resistance mainly due to pore coarsening. Nevertheless, a strong linear correlation can be established between the water-soluble and total chloride contents in ternary OPC-MK-DM systems, regardless of OPC replacement level and corrosion inhibitor incorporation.
Article
Chloride-induced reinforcement corrosion in marine concrete structures adversely impacts its durability, which leads to the decrease of the actual service life of concrete. Three kinds of layered double hydroxides (LDHs), CaFe–NO3 LDHs (LDHs-CF), CaAl–NO3 LDHs (LDHs-CA) and CaFeAl–NO3 LDHs (LDHs-CFA), were synthesized to bind chloride. The results showed that all of the synthetized LDHs could effectively adsorb chloride from simulated concrete pore solutions (SCPSs) and artificial seawater (ASW) through the surface adsorption and ion exchange. The maximum chloride adsorption capacity of the LDHs-CFA was 3.18 mmol g⁻¹. The adsorption process could be described by the Langmuir isotherm and pseudo-second-order kinetic models. For the chloride desorption experiments, the chloride desorption rate of the LDHs-CF (29.20%) and LDHs-CFA (39.31%) were lower than that of the LDHs-CA (47.45%), because the presence of Fe³⁺ in LDHs suppressed the concentration of dissolved metals, and a crystal transformation occurred to form 3CaO·Fe2O3·0.5CaSO4·0.5CaCl2·10H2O, exhibiting excellent stability for LDHs-CF and LDHs-CFA. In conclusion, LDHs show excellent chloride binding behaviour, which makes it promising to achieve the goal of high efficiency and stability of chloride binding for marine concrete by LDHs.
Article
This paper aims to examine the corrosion protection of reinforcing steel in concrete due to carbonation alone and the coupled action of chloride penetration and carbonation by MgAl-NO2 layered double hydroxides (LDHs), which was synthesized by calcination rehydration method. The results reveal that MgAl-NO2 LDHs have a better inhibition effect on the steel corrosion by carbonation alone than the coupled action of chloride penetration and carbonation. The inhibition mechanism for carbonation alone is mainly attributed to the alkalinity increase and NO2- release. The Cl- uptake additionally contributes to the corrosion inhibition for the coupled action of chloride penetration and carbonation.
Article
Corrosion of steel rebars in concrete can reduce the durability of concrete structures in coastal environments. The corrosion rate of these concrete structures can be reduced by using suitable concrete additives and coating on rebars. This paper investigates the corrosion resistance of steel rebars by the addition of pozzolanic materials including fly ash, silica fume, polypropylene fibers, and industrial 2-dimethylaminoethanol (FerroGard 901) inhibitors to the concrete mixture. Three different types of rebars including mild steel rebar st37, and two stainless steel reinforcements, AISI 304 and AISI 316, were used. Various types of primer and coating including alkyd based primer, hot-dip galvanized coatings, alkyd top coating, zinc-rich epoxy primer, polyamide epoxy primer, polyamide epoxy top coating, polyurethane coatings, double layer of epoxy primer and alkyd top coating, and double layer of alkyd primer and alkyd top coating were applied on steel rebars to investigate the effect of coating type on the corrosion resistance of steel rebars in concrete. Polarization tests, electrochemical impedance spectroscopy, compressive strength and color adhesion tests were conducted. The best reinforced concrete mix design for corrosion resistance was the one including the rebar with zinc-rich epoxy primer and 25% fly ash, 10% silica fume, and 3% FerroGard 901 inhibitors by cementitious material weight. Polyurethane was the best coating due to the highest strength and the lowest corrosion rate. Alkyd primer was the weakest coating, although it was the most economical coating system.
Article
The objective of this study is to clarify optimal conditions for suppressing the expansion of ASR-deteriorated concrete by pressure-injecting a lithium nitrite solution. To investigate the ASR-mitigating effect of lithium nitrite, concrete mixtures with two types of reactive aggregates were impregnated with lithium nitrite by pressurized injection at three steps of ASR. The effects of different timings on the penetration of lithium nitrite driven by the pressure gradient and on the suppression of expansion were examined through tests. The expansion rate started to decrease immediately after injecting a lithium nitrite solution into the concrete in the propagation period (PP) with severe ASR cracking and an expansion strain of 2000 micro. With a lithium-sodium molar ratio of 0.6 or more, further expansion was substantially stopped. On the other hand, expansion continued even after application of lithium nitrite when the solution was injected into the concrete in the early propagation period (EPP) with slight ASR cracking and an expansion strain of 400 micro, and the final strain eventually exceeded that of the concrete that had been subjected to the lithium injection in the PP. It is assumed that the lithium nitrite solution migrates through ASR cracks first because of the pressure gradient and then diffuses into the bulk mortar. The degree of expansion could also be affected by at which stage of ASR the lithium ions reach the reactive aggregates and the ASR gel.
Article
Waste foundry sand (WFS) is a solid waste generated from the metal casting industries around the world. The problem of WFS disposal and utilization are burgeoning universally. WFS is termed as a hazardous material due to the presence of organic and inorganic materials that are capable of contaminating the environment and can cause serious health issues. The study aims to re-utilize WFS in large volumes in concrete as a fine aggregate. The major impediment in the production of self-compacting concrete (SCC) is the robustness of concrete mixture. To study the effect of WFS on the robustness of SCC, six different mixtures were prepared having WFS up to 50% at regular intervals of 10% employing metakaolin as a substitute for cement at a constant ratio. It was revealed that the incorporation of WFS improved the robustness behavior of SCC, despite the change of ±10 l/m3 water dosage in SCC mixtures, all the mixes were observed falling in the same classes. Incorporation of 40% WFS increased compressive strength by 17.2% relative to control concrete at 56 days curing ages. The findings of the study suggest that WFS can be used in large volumes for the development of SCC without compromising its properties.
Article
The effects of chloride salts on concrete durability have been financially and logistically overwhelming. Current test methods for quantifying diffusivity of chlorides in concrete are time consuming and demanding. A comprehensive electrical resistivity model has been developed to quantify the chloride diffusion coefficient of concrete. The model employs the modified Nernst-Einstein equation along with an ionic concentration sub-model, a pore solution conductivity sub-model, and a binder hydration sub-model. The sub-models, which account for the concentrations of Na⁺, K⁺, Ca²⁺, and OH⁻ ions in the pore solution derived from the binder degree of hydration, binder chemical composition, and alkalis binding to the cement hydration products, are included to accurately quantify the conductivity of the pore solution. Moreover, an experimental program was developed to verify and validate the accuracy and completeness of the electrical resistivity model. The experimental variables are volume fraction of coarse aggregate, water to binder ratio, total binder content, and silica fume (SF) and ground granulated blast furnace slag (GGBFS) as supplementary cementing materials (SCMs). The model results are found statistically equal to experimentally quantified chloride diffusion coefficient values and possess high accuracy and precision for a wide range of concrete mixture, binder composition and age.
Article
This paper presents a review of the deterioration of concrete under seawater attack with particular interests in field exposure. The research reported in the literature has shown that salinity of seawater in different areas varies considerably but the type of ions and their proportion are similar. Because of this variation, laboratory studies should use specific artificial seawater to simulate on field environments. The phase changes induced by chloride, magnesium and sulfate ions contained in seawater are reviewed. The interaction between hydrates and chloride ion can lead to the formation Friedel's and Kuzel's salts. Magnesium ion can replace the calcium in Portlandite, and lowers the alkalinity of pore solution and eventually destabilizes C-S-H gel. The expansive ettringite is inhibited at the presence of chloride ions. At the tidal zone, the phase change mainly occurs on the surface of concrete, which weakens the structure and leads to spalling and delamination under the physical attack of the wave. Based on the existing deterioration mechanisms, the protocols to enhance the durability performance of marine concrete are also reviewed, such as using supplementary cementitious materials (SCMs) to mitigate rate of chloride penetration and, more promisingly, to use alternative binder systems. This paper also proposes a concept of designing a more durable concrete cover system by enhancing the chemical stability of cement hydrates, rapid self-healing and intelligent alkalinity control.
Article
The mesoporous silica-polymer hybrid was prepared as an adsorbent for divalent heavy metals (Pb(II), Ni(II), and Cu (II)) from rice husk and polyvinylpyrrolidone (PVP) through three successive steps. The first is the preparation of the mesoporous silica (SBA-15), the second is grafting 3-aminopropyltrimethoxysilane on SBA-15, and the following step is the formation of Schiff base (PVP-SBA-15) between amine end-capped silica and PVP moieties. The materials were characterized by different techniques, including FTIR, low and wide-angle XRD, N2-adsorption, and HR-TEM. The NH2-SBA-15 displayed a moderate affinity toward heavy element ions under study. Grafting of PVP moieties introduces a high affinity toward heavy metal ions, and the adsorption is a well-fitted Langmuir adsorption model. A series of experiment adsorption equilibrium reported with SBA-15, NH2-SBA-15, and PVP-SBA-15, which showed an adsorption capacity of 128 mg/g (Cu (II)), 175 mg/g (Pb (II)) and 72 mg/g for Ni(II). Kinetic studies have shown that the best way to describe the adsorption process of heavy metals is pseudo-first-order. The value of ΔG°, ΔH°, and ΔS° demonstrated that the adsorption of heavy metals on the PVP–SBA-15 was endothermic in nature and spontaneous. These results exhibited that PVP–SBA-15 material has considerable competence in eliminating heavy metals from wastewater.
Article
The effects of limestone replacement fraction, limestone specific surface area and water-to-binder (W/B) ratio on the threshold chloride concentration (TCC) for steel corrosion were evaluated. XRD and SEM analyses were conducted to examine the crystalline phases and microstructure of limestone-blended cement paste, respectively. The influence of pH value of concrete pore solution on the chloride binding capability was also investigated. The results demonstrate that the chloride threshold decreases as the limestone content or the W/B ratio increases, while limestone fineness shows negligible effect. XRD analyses indicate that addition of limestone inhibits the transformation from ettringite (AFt) to monosulfate (AFm), which exhibits superior chemical binding capability for chloride ions. SEM analyses suggest that addition of 15 wt% limestone contribute to a denser microstructure. Reduction in the pH value of pore solution compromises the chloride binding capability of concrete.
Article
Taking into consideration the wide use of self-compacting concrete in engineering practice and the need to better understand its mechanical work, while at the same time attempting to use additives with a smaller grain size as a component of concrete, the paper presents the results of the authors' own research, conducted using the acoustic emission method, on the failure process of self-compacting compressed concrete both with and without the addition of 2.0% and 4.0% of SiO 2 and TiO 2 nanoparticles with regards to cement weight. The levels of crack initiation stresses σ i and critical stresses σ cr , which distinguish the individual stages of the investigated process, were determined. The obtained results were used to calculate the fatigue strength of all the concretes that were tested in the paper. Based on the achieved results, it can be concluded that the durability and safety of structures made of self-compacting concrete with the addition of SiO 2 and TiO 2 nanoparticles that are subjected to repeatedly variable loads will be higher when compared to structures made of concrete without these additives.
Article
Layered double hydroxide (LDH) with NO2- intercalation was successfully prepared via acidification oscillation and ion exchange. The nano-fillers were incorporated into the resin to prepare anti-corrosion coatings with the thickness of ca. 50 ± 5 μm. The electrochemical and self-repairing properties of the LDH-doped coatings were studied by EIS and LEIS. Results indicated that the addition of LDH loaded with nitrite induced obvious increased in the impedance of coating (from 4.64 × 108 Ω cm2 to 2.14 × 1010 Ω cm2) and improved the anticorrosion performance of the coating. In addition, the localized corrosion of coatings could be largely inhibited, and the released nitrite ions from LDH interlayers exhibited active anticorrosion functions. When LDH nanosheets were added to the coatings, the lamella structures improved the barrier performances of the coatings. At the same time, the excellent ion exchanges ability of LDH could be used as storage stations for chloride ions, and the release of nitrite ions could play an active anti-corrosion role. Both of them cooperated to synergistically improve the anti-corrosion performance of the coating.
Article
An experimental study is carried out in this paper to evaluate the corrosion performance of mild steel reinforcing bars (MS), high strength steel reinforcing bars (HS), epoxy-coated steel reinforcing bars (EC), and high-chromium steel reinforcing bars (HC) under harsh environmental conditions. Reinforcing bars (rebar) of 16 mm diameter and 310 mm length were embedded in cylindrical concrete samples of 60 mm diameter and 350 mm length, and subjected to a Southern Exposure test for sixteen months. The open circuit potential (OCP) was monitored during the exposure period until corrosion initiation. The linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and Tafel plot techniques were employed to assess the corrosion rates on the rebar surfaces. The macrocell corrosion current was monitored by connecting the corroding rebar with an external stainless steel bar of the same size. The polarization resistance of the HC was found to be 1.5 times higher than that of the MS. The EIS technique showed that EC, even with damaged epoxy coating, has the highest resistance to chloride attack. The macrocell current of HC rebar was 48% less than that of MS during the active corrosion state. The LPR, EIS and Tafel plots analysis provided the current densities, which were close to each other; indicating the validity of these techniques to study the problem at hand. The corrosion rates from electro-chemical methods were compared against the ones calculated by gravimetric methods. The quantitative results from this research may be used in service life prediction of concrete structures with different types of rebar. Extensive analysis of the results indicates that the corrosion resistance of the evaluated steels was in the following decreasing order: EC, HC, MS, and HS.
Article
An experimental study is carried out in this paper to evaluate the corrosion performance of mild steel reinforcing bars (MS), high strength steel reinforcing bars (HS), epoxy-coated steel reinforcing bars (EC), and high-chromium steel reinforcing bars (HC) under harsh environmental conditions. Reinforcing bars (rebar) of 16 mm diameter and 310 mm length were embedded in cylindrical concrete samples of 60 mm diameter and 350 mm length, and subjected to a Southern Exposure test for sixteen months. The open circuit potential (OCP) was monitored during the exposure period until corrosion initiation. The linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and Tafel plot techniques were employed to assess the corrosion rates on the rebar surfaces. The macrocell corrosion current was monitored by connecting the corroding rebar with an external stainless steel bar of the same size. The polarization resistance of the HC was found to be 1.5 times higher than that of the MS. The EIS technique showed that EC, even with damaged epoxy coating, has the highest resistance to chloride attack. The macrocell current of HC rebar was 48% less than that of MS during the active corrosion state. The LPR, EIS and Tafel plots analysis provided the current densities, which were close to each other; indicating the validity of these techniques to study the problem at hand. The corrosion rates from electrochemical methods were compared against the ones calculated by gravimetric methods. The quantitative results from this research may be used in service life prediction of concrete structures with different types of rebar. Extensive analysis of the results indicates that the corrosion resistance of the evaluated steels was in the following decreasing order: EC, HC, MS, and HS.
Article
The corrosion behaviour of microporous nickel-chromium systems was studied by means of conventional electrochemical techniques and localized ones using two chloride based electrolytes with and without cupric ions in their composition. The conscious combination of different methodologies using these techniques has provided valuable information about the corrosion process. Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) measurements were performed in bulk solution, whilst Scanning Kelvin Probe (SKP) measurement were carried out using two methodologies: i) electrolyte droplets monitoring (measuring simultaneously potential and droplet height with time), and ii) potential maps of dried surfaces that previously were exposed to droplets. Further characterization was done based on the morphology of the attack and composition on the surface by Optical Microscopy (OM), Field Emission- Scanning Electron Microscope (FE-SEM) and X-ray Photoelectron Spectroscopy (XPS) together with the analysis of electrolyte composition with time by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Results have shown the harmful effect of Cu²⁺ cations in the corrosion resistance and a different morphological impact on the surface. Such negative effect has revealed a new time constant at high frequency in the impedance diagrams as well as an abrupt potential decrease (due to a change in the cathodic reaction involved: Cu²⁺ + e⁻ ↔ Cu⁺ takes place) using SKP droplet test. Apparently, Cu⁺ species were stabilized in bulk solution by the formation of chloride complexes, as was confirmed by the precipitation of a white CuCl compound during droplet evaporation, pointing out the key role of Cu⁺ in the corrosion process.
Article
Using supplementary cementitious materials (SCMs) in concrete is considered as one of the possible solutions to making green concrete. Previous research often analyzed the environmental impact of concrete without considering the influences of compressive strength and durability simultaneously. Such a practice will lead to less rational life cycle assessment (LCA) results, since the service life of concrete could be shortened when durability is poor, especially if concrete is exposed to marine dry-wet environment where chloride ion is intensive. Moreover, Fick's second law of diffusion was always used to determine the chloride diffusion coefficient of concrete, without considering the influences of convection zone and peak value of chloride concentration. Therefore, this paper proposed an integrated functional unit combining durability (resistance to chloride ion diffusion), compressive strength and volume to evaluate the environmental impact of concrete containing SCMs. The chloride diffusion coefficient was calculated by re-scaling the ‘‘zero’’ of penetration axis to calibrate Fick's second law of diffusion. In addition, three other functional units (volume, combining volume and compressive strength, combing volume and durability) were also proposed and compared. Results indicate that the selection of functional unit has a significant influence on the LCA results of the studied concrete. Despite the variation with different functional units, concrete containing silica fume or silica fume as well as fly ash shows a consistently superior environmental performance over the ordinary concrete.
Article
The present study explores the hypothesis that a polymer can affect the thermal stability of a drug in solid polymer-drug dispersions. The hypothesis is tested in a systematic fashion by combining isoconversional kinetic analysis with thermogravimetric measurements on several solid dispersions. Experimental systems involve three drugs: indomethacin (IMC), felodipine (FD), and nifedipine (ND) and their solid dispersions with polyvinylpyrrolidone (PVP). It is found that PVP stabilizes IMC but destabilizes FD and ND. Isoconversional kinetic analysis provides insights into the origin of the observed effects. The enhanced thermal stability of IMC in the PVP matrix is associated with an increase in the activation energy of the respective degradation process. A detrimental effect of the PVP matrix on the stability of FD and ND has been linked to a decrease in the activation energy and an increase in the preexponential factor respectively. The molecular underpinnings of the observed effects are discussed. It is concluded that the effects in question are of relevance for drug performance and need to be taken into account in preformulation studies.
Article
Whereas steel bar corrosion is the main cause for durability deterioration of existing reinforced concrete structures, it is important to understand the steel bar corrosion in concrete and predict the corrosion process in a sufficient way. In this paper, the corrosion process of rebar in ordinary concrete and three types of fly ash concrete specimens casted with 15%, 30% and 45% fly ash replacement ratios by mass under constant climate conditions were investigated. Meanwhile, the advanced digital video microscope measure system was used to study the microstructure of the steel/concrete interface at the different stages of corrosion. The effects of fly ash replacement were analyzed in terms of the electrical resistivity of concrete and the corrosion rate in the corrosion process of steel bars in fly ash concrete. The results showed that the resistivity of concrete increased with an increase in fly ash replacement, and the corrosion rate declined with the fly ash replacement increases. In addition, in fly ash concrete, the corrosion rate of plain bars were obviously smaller than that of ribbed bars.
Article
Ca/Al-Layered Double Hydroxide (Ca/Al-LDH), was a kind of important anionic clays with broad applications owing to its properties of exchangeable anion and adjustable particle size. In this study, Ca/Al-LDH had been successfully prepared by co-precipitation method, and it was found that the particle size, crystallinity and morphology of Ca/Al-LDH could be tuned via changing ethanol/water ratio of solution. More interestingly, with the increase of the Ca/Al-LDH's dosage, the different crystal structure of Ca/Al-LDH had promoting effect on the development of the early strength of the cement slurries, however, the change trend of the strength growth rate of various kinds of cement slurries were quite different. Meanwhile, experimental results disclosed that the crystallinity and particle size of Ca/Al-LDH determined its interaction with cement hydration particles. That was likely to lead to a change in tricalcium silicate (C3S) and tricalcium aluminate (C3A) hydration process of accelerating or retarding under the different Ca/Al-LDH content, thus enabling the early strength development of slurry to exhibit different trends. And this finding could provide further interpretation for the effect of hydrotalcite-like materials on cement hydration process and offer a theoretical exploration for its practical application in the future.
Article
Corrosion-induced CaCO3 scaling is extremely widespread at metal/water interface. However, the anti-scale and anti-corrosion behaviour of existing inhibitors have mostly been investigated separately without considering their interaction. Herein, the roles of corrosion inhibition in mitigating interfacial scaling were evaluated on carbon steel and stainless steel by introducing NaNO2 to enhance their corrosion resistance. Results reveal that corrosion-induced pH increase at micro cathodes dominates the interfacial scaling processes by inducing rapid nucleation. A temperature elevation promotes interfacial scaling mainly through aggravating steel corrosion. Once the micro cathodic processes are inhibited, CaCO3 scaling can be evidently retarded even at elevated temperatures.
Article
In this study the effect of a hybrid organic/inorganic pigment based on zinc acetate-Cichorium intybus L. leaf extract on the corrosion protection properties of an epoxy ester coating were studied. Results of electrochemical impedance spectroscopy (EIS) revealed that the mild steel corrosion was significantly inhibited in the chloride solution in the presence of hybrid pigment extract. Results exhibited that with the increase in immersion time up to 24 h the corrosion inhibition efficiency significantly increased and reached the maximum value of 94%. Results obtained from the scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) techniques confirmed the deposition of inhibitive films on the mild steel surface. Results showed that in the presence of hybrid pigment not only the barrier but also the active inhibition properties of the epoxy ester coating were effectively enhanced. The low frequency impedance value of the epoxy ester coating was increased in the presence of hybrid pigment, indicating the role of pigment on the coating barrier action enhancement. The increase in charge transfer resistance of the epoxy ester coating with artificial scratch depicted the active inhibition role of the hybrid pigment.