Total Chloride Ion Research Articles

Effect of Stray Current on Chloride Binding Mechanism in Concrete

In this article, simulation tests of chloride binding were made under the condition of sodium chloride as an internal admixture while loaded with stray current externally. Through the potential titration method, free chloride ion concentration Cf 、 total chloride ion concentration Ct and chloride binding rate RCl were determined. The results show that: With the increase of the strength and action time of the stray current, the number of internal free chloride ions in the cement paste increases while that of the corresponding bound chloride ions reduces significantly, leading to the decrease of chloride binding rate. The relationship between chloride binding rate and the two can be shown as follows respectively:RCl=50.754e(-I/28.258)+42.532、RCl=63.427 e(-T/8.238)+27.325.

Total shrinkage, oxygen permeability, and chloride ion penetration in concrete made with white Portland cement and blast-furnace slag

This study investigated the influence of slag content and curing time with respect to the total shrinkage, penetration of chloride ions after shrinkage, and oxygen permeability of concrete made with white Portland cement (WPC). Concretes were made with water–binder (w/b) ratios of 0.30, 0.42, or 0.55 and slag contents as a substitute for WPC of 0%, 50%, or 70% and were subjected to moist curing for 3 or 7 days. The same mixtures of gray Portland cement (GPC) were also investigated for comparison purposes. A mixture containing 50% slag in place of WPC that was activated by sodium sulfate (4% by weight of binder) was molded to analyze the influence of the activator on the total shrinkage and chloride penetration of the cement. Before being immersed in a saline solution to determine the chloride penetration, the test samples were submitted to a 91-day drying period. The results demonstrated that the partial replacement of 70% of the white Portland cement by slag reduced the total shrinkage by an average of 39% and 35% and the chloride penetration by 37% and 47% when the concrete samples were cured for periods of 3 and 7days, respectively. Mixtures composed of white Portland cement and slag (50% and 70%) had average oxygen permeabilities of 28% and 56%, respectively, which were lower than those of similar mixtures composed of gray Portland cement.

A Simple Method for Amplifying RNA Targets (SMART)

We present a novel and simple method for amplifying RNA targets (named by its acronym, SMART), and for detection, using engineered amplification probes that overcome existing limitations of current RNA-based technologies. This system amplifies and detects optimal engineered ssDNA probes that hybridize to target RNA. The amplifiable probe-target RNA complex is captured on magnetic beads using a sequence-specific capture probe and is separated from unbound probe using a novel microfluidic technique. Hybridization sequences are not constrained as they are in conventional target-amplification reactions such as nucleic acid sequence amplification (NASBA). Our engineered ssDNA probe was amplified both off-chip and in a microchip reservoir at the end of the separation microchannel using isothermal NASBA. Optimal solution conditions for ssDNA amplification were investigated. Although KCl and MgCl(2) are typically found in NASBA reactions, replacing 70 mmol/L of the 82 mmol/L total chloride ions with acetate resulted in optimal reaction conditions, particularly for low but clinically relevant probe concentrations (≤100 fmol/L). With the optimal probe design and solution conditions, we also successfully removed the initial heating step of NASBA, thus achieving a true isothermal reaction. The SMART assay using a synthetic model influenza DNA target sequence served as a fundamental demonstration of the efficacy of the capture and microfluidic separation system, thus bridging our system to a clinically relevant detection problem.

Corrosion of Steel Bars in Autoclaved Concrete Pile Containing γ-2CaO·SiO2 with an Accelerated Carbonation Curing Submerged in the Real Marine Environment

This paper presents a set of the investigation of corrosion of steel bars in autoclaved concrete pile containing γ-2CaO·SiO2 (γ-C2S) with carbonation curing. OPC, γ-C2S, and fine silica powder were used as the binders; the replacement ratio of OPC by γ-C2S was 0%, 40%, and 80% by mass. Autoclaved concrete pile after carbonation was submerged in real marine environment at Kurihama Bay for two years. After immersion, visual observation of steel bars was conducted to confirm the corrosion state of steel inside the concrete pile. Furthermore, to evaluate the corrosion of steel bars - weight loss, corrosion current density, and anodic polarization curve were measured ; various corrosion substances also were measured to evaluate the permeability of corrosion factors. In addition, cement past sample with same mixed proportion and curing condition was made for explaining the permeable characteristics of corrosion substances. As the results, the steel bars in the 80% γ-C2S replacement ratio did not corrode while steel bars in the other mixed proportions had corroded. The weight loss of steel bar in the 80% γ-C2S replacement ratio after carbonation reduced by 39% and corrosion current density reduced more than 95% compared with the 0% γ-C2S replacement ratio. Furthermore, the corrosion substances in concrete pile - carbonation depth, total chloride ion content, and oxygen diffusion rate, reduced significantly at the 80% replacement ratio of γ-C2S. Based on the overall results of this study, we suggest that, when using γ-C2S with an autoclave curing, accelerated carbonation curing is able to do to densify the concrete surface preventing the steel from corrosion for the long-term exposure.

Effect of Mineral Admixtures on Chloride Ions Content in Concrete Repair Materials

The amount of total chloride ions in concrete used as repair materials were measured under immersion conditions. The corresponding major influencing factors under natural diffusion condition were also investigated by different testing methods. The results indicated that the amount of total chloride ion significantly varies with the water to binder ratio when the water to binder ratio varies from 0.3 to 0.55. Compared with pure cement concrete, the precipitation of chloride ions in the concrete with fly ash or ground granular blast furnace slag (GGBFS) under sigle dimensions immersion was much lower. The concrete with double adding of 10% FA and 20% GGBFS acheives the lowest value of total chloride ions content.

Resistance to the Penetration of Chloride Ions of Concrete with Intensified Recycled Aggregates

In order to study on methods for and effect of improving performances of recycled concrete, this paper has adopted the recycled aggregates intensified by dipping in the chemical grout, on which basis, the recycled concrete is prepared through the double admixing technology, i.e. mixing of the high-quality mineral admixture and the high-efficient water reducer. The chloride ion permeability of the recycled concrete is researched in the laboratory. In the test, the electric flux, the total chloride ion content and the free chloride ion content at different depths of the recycled concrete have been obtained. The research has shown that dipping in the chemical grout is an effective way to intensify recycled aggregates and that recycled concrete prepared with the intensified recycled aggregates, high-quality mineral admixture and high-efficient water reducer features favorable permeability resistance.

Modeling of chloride diffusivity coupled with non-linear binding capacity in sound and cracked concrete

The objective of this research is to establish a model that can predict chloride transport phenomena in sound and cracked concrete. The chloride diffusivity is formulated based on computed micro-pore structure, which considers tortuosity and constrictivity of porous network as reduction factors in terms of complex micro-pore structure and electric interaction of chloride ions and pore wall. In the real environment, concrete structures are not always crack-free, therefore chloride transport in cracked concrete is also simulated by section large void spaces in a control volume to represent the crack and by proposing a model of chloride diffusivity through the cracked region The proposed models are implemented into a finite-element computational program DuCOM, which simulates the early-age development process of cementitious materials. The calculated concentration profiles of total chloride ions are verified through a comparison with experiments results.

Response and evolution of formation water chemical fields of the paleogene in Dongying sag

东营凹陷古近系水化学场分布与湖盆演化有着良好的对应关系,以CaCl₂水型为主的高矿化度地层水是东营凹陷古近系咸化湖盆的典型响应特征,矿化度从深到逐渐降低,体现出从咸化湖盆向微咸化湖盆及淡水湖盆演化的地球化学响应.剖面上可以划分为四种水文环境:强开放性水文流畅带(地表到1.1km)、弱开放性水文流畅带(1.1-2.0km)、水文阻滞过渡带(2.0-2.5km)和封闭性水文迟缓带(2.5km以下),水化学剖面的分带性与压力分布有着良好的对应关系.东营凹陷古近系水化学场经历了早期的沉积与淋滤的交替和新生代的埋藏封闭作用期,其中在东营运动时期古近系水化学场表现最为活跃,是深层卤水咸化地表浅层淡水从而使浅层出现高矿化度地层水的关键作用期,断裂的沟通起了重要作用,显示出断陷湖盆的典型特征.;The formation of water chemical characteristics in the Paleogene System had good response to the sedimentary conditions and its evolution in Dongying sag. The type of CaCl₂ formation water with high salinity was representative response of the brine lake of the Paleogene System in Dongying sag. The content of total salinity and chloride ion decreased from the deep depth to the lower, which was good response to the evolution of the Dongying sag from salted basin to freshwater basin. According to the vertica1 characteristics of the underground water formation, four hydrological environments can be classified: stronger formation water frequency alternation belt(0-1.1km), feeble formation water frequency alternation belt(1.1-2.0km), formation water alternate blocking belt (2.0-2.5km) and formation water alternate tardy belt (>2.5km). In every belt the total salinity, ions and ion composition ratio had different responses, and the belts corresponded to the distribution of formation pressure. The formation water chemical field experienced deposition and leaching in early time and burial in later time. In the period of Dongying Movement the formation water chemical field was active, and salted water from the Member 4 of Shahejie Formation migrated to the lower, and in the course the faults played important roles, which demonstrated the representative characteristics of faulted basin.

Photochemical treatment of 2-chlorophenol aqueous solutions using ultraviolet radiation, hydrogen peroxide and photo-Fenton reaction

In the present work, the photochemical oxidation of 2-chlorophenol aqueous solutions in a batch recycle photochemical reactor using ultraviolet irradiation and hydrogen peroxide was studied. Specifically, the effect of hydrogen peroxide initial concentration (0–10316 mg L −1) and 2-chlorophenol initial concentration (150–3000 mg L −1) was examined. The process was attended via total organic carbon (TOC), 2-chlorophenol, chloride ion, acetic acid, formic acid and pH measurements. The conversion of 2-chlorophenol observed was always much higher than the corresponding total organic carbon removal, whereas the increase in hydrogen peroxide amount in the solution led to higher values of 2-chlorophenol conversion and total organic carbon removal. Finally, the photo-Fenton reaction was applied to the oxidation of 2-chlorophenol, leading to a higher degree of mineralization of the parent compound.

Treatment of 2-chlorophenol aqueous solutions by wet oxidation

In the present work, the wet oxidation (WO) of 2-chlorophenol (2-CP) was studied in aqueous solutions, in a high-pressure agitated autoclave reactor. Specifically, the effect of temperature (160–190 °C), oxygen partial pressure (5–40 bar) and 2-CP initial concentration (250–1500 mg L −1) was examined. The process was attended via total organic carbon (TOC), 2-CP, chloride ion, acetic acid, formic acid and pH measurements. Significant rates of 2-CP disappearance and TOC removal were achieved above 170 °C. A decrease in 2-CP initial concentration below 1000 mg L −1 resulted in a dramatic decrease in the TOC removal achieved, whereas an increase in oxygen partial pressure enhanced greatly the decontamination of the 2-CP aqueous solution, especially from 10 to 20 bar. Much attention was given on the chloride ion removal from the phenolic ring in order to attend the dechlorination of 2-CP during WO. In the WO process, the majority of chloride ions were detached from organic compounds. Finally, a parallel and in series reaction scheme has been proposed for the interpretation of the experimental results.

Penetration Behavior of Chloride Ions into Concrete in Coastal Areas

Exposure test on chloride ion penetration behavior into Concrete in coastal area was implemented. The distances between concrete specimens and coast were changed in the range from 50 to 150 meters, and water-cement ratios (W/C) were 45, 55, 60 and 65 %. The total chloride ion content at each different depth from surface of concrete specimen was measured at the age of 1, 2, 3, 5, 7, 8 and 10 years. In this paper, apparent diffusion coefficient (D) and chloride ion content on surface of concrete (C0) were calculated by inverse analyses from the measured total chloride ion content, and the chloride ion penetration behavior was simulated using the calculated D and C0. As a result, the chloride ion penetrated in concrete with a W/C of 60 % at a point 50 m from the sea for 10 years was estimated approximately 0.2 kg/m3.

Effects of storage conditions on chemical and physical properties of electrolyzed oxidizing water

Electrolyzed oxidizing waters (EOWs) were generated at different water flow rates, salt concentrations and water temperatures. The EOWs were stored in closed dark-brown glass bottles at room temperature for 21 days. Another duplicated set of the EOWs were stored for 12 days with four periodical openings of the screw caps. The effects of these treatments on pH, oxidation–reduction potential (ORP), electrical conductivity, total residual chlorine, dissolved oxygen (DO), sodium ion and chloride ion concentrations of the EOWs were investigated. Results indicated that pH, ORP, conductivity and chloride ion concentration did not change much under the storage conditions. Sodium ion concentration decreased 10–13% during storage. Total residual chlorine and DO decreased 24% and 21%, respectively, in the 21-day closed storage and decreased 81% and 47%, respectively, in the 12-day semi-open storage. This indicated that exposure to the atmosphere reduced more of these compounds than prolongation of the storage time.

Simultaneous Transport of Chloride and Calcium Ions in Hydrated Cement Systems

This paper presents a new method for numerically calculating the concentration profiles of both solid calcium and total chloride ions (Cl−) in concrete in contact with 3% (0.5 mol/l) sodium chloride (NaCl) solution. Since the diffusion of ions present in the pore solution is a primary controlling factor, the application of mutual diffusion coefficients of corresponding ions that are influenced by the concentration of other coexisting ions is proposed. The method of calculation is based on the generalized form of Fick's First Law suggested by Onsager, which is composed of the Onsager phenomenological coefficient and the thermodynamic force between ions, which occurs according to the gradient of electrochemical potential in a multicomponent concentrated solution for the pore solution. In addition, the chemical equilibrium for Ca(OH)2 dissolution and C-S-H decalcification are also modeled and coupled with diffusion. Increased porosity due to dissolved Ca2+ and a chloride binding isotherm are taken into consideration. The concentration profiles of solid calcium and the presence of Friedel's salt in mortar specimens are experimentally identified by the X-ray diffraction method (XRD) and the thermal analysis (TG/DTA) as well as the total chloride profile using an acid extraction method after three years of exposure to 0.5 mol/l NaCl solution. This experimental result verifies the calculation result.

Leaching of copper(I) sulfide in calcium chloride solution

Finely grained samples of copper(I) sulphide were leached by CaCl 2·2H 2O solution with added HCl and the introduction of gaseous oxygen. The occurrence probability of chemical reactions was analysed based on literature and products, which were formed during the process, and the overall leaching reaction was defined. The effect of temperature, concentration of CaCl 2·2H 2O, HCl and total chloride ions, stirring speed, phase ratio and time, on the leaching degree of copper was studied. The quantity of copper dissolved increases with the increase of the values of all the parameters. The role of chloride ions is to disrupt the passivating sulphur layer on the particle surface, by promoting the formation of crystalline sulphur rather than a crypto-crystalline or amorphous product. It was concluded that the leaching reaction is second order, with respect to the concentration of total chloride ions. Experimental results show that the leaching mechanism is very complex. By using appropriate mathematical kinetic models, it is found that the leaching rate is diffusion-controlled.

Evaluation of a concrete cascade solar still

The quality of the distilled water produced by the Concrete Cascade Solar Still wasevaluated by the comparison with the conventional electrically powered still used for the samepurpose and the quality of the tap water intake prior to these investigations. The samples weredrawn from the following areas: the cascade solar still (over a continuous five days period) ; theelectrically powered still; and a five day storage period (in the dark) of the previouslymentioned areas. The Water Quality Indices (WQI) were 4.50, 3.76 and 29.35 for the watersamples from the cascade solar still, the electrically powered still and tap water respectively. Theheavy metals and sodium and calcium profiles also showed that the tap water had higherconcentrations of these metals. However, the microbiological assays showed that the cascadesolar still had the highest colonies forming units (1400 CFU/ml) , with respect to the electricallypowered still (22 CFU/ml) and tap water (12 CFU/ml) . The C.V. for the selected parameterswere: 0.875, 0.214, 2.060, 1.443, 2.109, 0.218, 1.888, 0.436, 1.082, 1.081 and 0.939 for theconcentrations of iron, lead, calcium, zinc and sodium, and the values of pH, conductivity,turbidity, total suspended solids, chloride ions and microbiological assays respectively.

The use of microwave digestion method for the determination of chemical forms of sodium and chloride ions in seashell structures

A new method was developed for understanding the distribution of chemical species such as mobile-sodium, total-sodium, mobile-chloride, and total-chloride ions in seashell structures. The microwave digestion method was applied for the dissolution of different chemical species of these elements. Several kinds of solutions were used to separate the various species of sodium and chloride ions. Using this method, the distribution of sodium and chloride ions in seashell structures was revealed to differ markedly. Total-sodium ion concentration seemed to be constant in the different layers. Conversely, total-chloride ion concentration was one order of magnitude less than that of total-sodium ion. Mobile-chloride ion concentration also shows that chloride ion is more mobile than sodium ion.

Statistical Approach to Ingress of Chloride Ions in Silica Fume Concrete for Bridge Decks

This paper presents the results of a study of chloride ion ingress into silica fume concretes designed for full-depth and overlay placements of highway bridge decks. Mixtures for each application were prepared over a range of silica fume contents and water-to-cementitious material ratios (w/cm). Concrete laboratory specimens were prepared for ponding of chloride solution over 180 days. Cores taken from the specimens were milled at 1 mm increments and powders analyzed for total chloride ion. Data were then fitted to Fick's second law of diffusion to obtain apparent chloride ion diffusion coefficients. Regression analyses were performed on data developed from the laboratory testing, and response surface models were developed. Analyses of variance were carried out to compare behavior of Type K cement concretes and concretes prepared with silica fume in slurry form. For any given w/cm, as silica fume content was increased, the apparent chloride ion diffusion coefficient dropped. The most sensitive region was in the lower range of silica fume contents, where the apparent chloride ion diffusion coefficient changed at a faster rate as the silica fume content was increased. At silica fume contents over 4-6%, a much greater addition was needed to effect a large change in diffusivity. A point of diminishing returns may be reached at silica fume contents over approximately 6%. At the lower w/cm values, the apparent chloride ion diffusion coefficient is relatively insensitive to increases in the silica fume content above 6%. The effects of w/cm on apparent chloride ion diffusion coefficient were much less than that of silica fume content. Use of Type K cement or type of silica fume did not have a significant effect on results.

Determination of some inorganic species in edible vegetable oils and fats by ion chromatography

A procedure has been developed for the ion chromatographic determination of total chlorine, phosphorus and sulphur and of iron, copper, nickel, zinc, cobalt, lead and cadmium in edible vegetable oils and fats. The organic matrix which strongly interferes in analytical procedures, is completely removed by saponification followed by oxidative UV photolysis. This method is simpler and requires less reagents compared with other sample pretreatment procedures. To oil and fats, ethanol and potassium hydroxide were added, and they were saponified for half an hour. Hydrogen peroxide was added and the sample was subjected to UV photolysis at 85±5°C. In less than 1 h organic constituents were completely degraded, while inorganic constituents, except nitrates, iodides and manganese, remained unaffected by UV radiation. Chlorine, phosphorus and sulphur, present in different organic compounds, can be quantified as total amounts only, without speciation. The clear sample solutions were directly injected on to an ion chromatograph equipped both with a conductivity detector, for the determination of total chloride, phosphate and sulphate ions using a carbonate–hydrogencarbonate eluent, and a post-column reactor and a variable-wavelength UV–Vis detection system, for the determination of lead and cadmium using an oxalate eluent and iron, copper, nickel, zinc and cobalt using a pyridine-2,6-dicarboxylic acid eluent. The method has been tested on spiked and unspiked samples of vegetable oils and fats and was found to be satisfactory for the determination of the previously cited elements. Ion chromatographic responses were compared to voltammetric ones and were found to be in good agreement (±3%).

Sample pretreatment by UV photolysis for the ion chromatographic analysis of plant material

Information on the elemental content of leaves, juices and extracts of vegetables, fruits and plants is of great botanical, nutritional and environmental interest. Procedures are described for the ion chromatographic determination of total chlorine, bromine, phosphorus and sulfur (carbonate-hydrogen carbonate eluent), iron, copper, nickel, zinc and cobalt (pyridine-2,6-dicarboxylic acid eluent) and lead and cadmium (H 2SO 4HClKCl eluent). Detection limits range between 20 and 100 μg/l and the calibration graphs were linear up to 1000–2500 μg/l. In order to dissolve samples prior to chromatographic analysis, oxidative UV photolysis was used; it has decisive advantages over other sample pretreatment methods, owing to the simple procedure and the minimal reagent addition requirement, resulting in minimal contamination. Depending on the type and amount of organic matter, the UV photolysis conditions can be adjusted as required. The homogenized sample is mixed with a small amount of hydrogen peroxide and/or nitric acid and subjected to UV photodegradation in a digester equipped with a high-pressure mercury lamp (500 W); the temperature of the sample was maintained at 85 ± 5°C by means of a combined air-water cooling system. Organic constituents are degraded and organic-bound metals and non-metals are set free and their quantification remains unaffected by UV radiation, except for nitrate, iodide and manganese. It follows that chlorine, bromine, phosphorus and sulphur, normally present in different organic compounds, can be quantified as total amount only, without any speciation. The clear solution is injected directly into an ion chromatograph equipped with both a conductivity detector, for the determination of total chloride, bromide, phosphate and sulphate ions, and a postcolumn membrane reactor and variable-wavelength UV-Vis detector, for the determination of lead, cadmium, iron, copper, nickel, zinc and cobalt.

Measurement and correlation of ion activity coefficients in aqueous solutions of mixed electrolyte with a common ion

Ion selective electrodes have been used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of mixtures of NaCl and KCl up to 4 molal total chloride ion concentration, and of NaCl and NaBr up to 4 molal total sodium ion concentration. The experimental results show that the activity coefficient of an ion in the presence of different counterions depends on the nature and concentration of all counterions present in the solution. The results also show that the activity coefficients of the cations in an aqueous mixture are different from those of the anions. These effects can be considered as a corollary of the ion-ion and ion-solvent interactions. A modified form of the Pitzer's model, coupled with a mixing rule which distinguishes between the activity coefficients of the anion and the cation, has been used to correlate the experimental results.