Chloride Extraction Efficiency Research Articles

Novel application of electrochemical chloride extraction fixing polymer-modified conductive repair mortar as anode

Electrochemical chloride extraction (ECE) technique provides an effective technique to remove the chloride ions from concrete and realize reinforcements performance recovery. In this study, a novel type of polymer-modified conductive repair mortar (PCRM) was developed as the anode of ECE system, while the impacts of electrochemical parameters, anode types and reinforcements layout on the chlorides extraction efficiency were investigated, in addition, an innovative method is also proposed to further enhance the ECE efficiency. The results highlight that PCRM can be successfully fabricated with proper initial/final setting time, which presents the similar extraction efficiency compared with PC-based repair mortar and stainless-steel mesh anode. Furthermore, reinforcement cages provide target concrete with lower extraction efficiency inside the cage, and the efficiency can be remarkably increased by pulse current. Most importantly, the chloride extraction efficiency of PCRM anode is increased from 45.1% to 59.6% (electrochemical parameters), 53.7% (reinforcements layout), 60.2% (pulse current), respectively.

The efficiency of chloride extraction using un-galvanized steel anode

Electro-chemical Chloride Extraction (ECE) is considered one of the most effective techniques used to extract chloride ions from reinforced concrete structures. The effectiveness of using ECE depends on some important factors such as anode type, current intensity, extraction duration, type of rebar, and chemical properties of concrete. On the other hand, ECE may cause some detrimental effects on some mechanical properties of concrete and steel such as a reduction in bond and compressive strengths of concrete, and embrittlement (i.e. reduction in ductility) ductility of reinforcing steel. The major aim of this research work was to investigate the effectiveness of ECE using locally available un-galvanized steel mesh with conductive cement paste anode as a new type of anode on a reinforced concrete slab as a structural element. The slab behavior before and after ECE was studied by determining compressive strength, water absorption rate, concrete chloride content, and steel corrosion potential. The slab behavior was studied taking into consideration the established steel arrangement with spacing 20 cm between re-bars. The effect of initial chloride content on chloride extraction efficiency was investigated. Effectiveness of ECE with small initial chloride content 0.4% and 0.8% was compared with that of high initial chloride content 2.5% to know whether the initial chloride content is an important factor in ECE effectiveness or not.

Efficiency of ECE Applied on RC Slab using Locally Available Un-Galvanized Steel with Conductive Cement Paste Anode

Electro-chemical Chloride Extraction (ECE) is considered one of the most effective technique used to extract chloride ions from reinforced concrete structures. Effectiveness of using ECE depends on some important factors such as anode type, current intensity, extraction duration, type of rebar and chemical properties of concrete. On the other hand, ECE may cause some detrimental effects on some mechanical properties of concrete and steel such as a reduction in bond and compressive strengths of concrete, and embrittlement (i.e. reduction in ductility) ductility of reinforcing steel. The major aim of this research work was to investigate the effectiveness of ECE using locally available un-galvanized steel mesh with conductive cement paste anode as a new type of anode on a reinforced concrete slab as a structural element. The slab behavior before and after ECE was studied by determining compressive strength, water absorption rate, concrete chloride content and steel corrosion potential. The slab behavior was studied taken into consideration the established steel arrangement with spacing 20 cm between re-bars. Another aim of this research work was to investigate the effect of initial chloride content on chloride extraction efficiency by applying optimum current intensity and duration (3 A/m2 and 6 weeks) on cylinders with pure chloride content 0.4% and 0.8% (by weight of cement). Effectiveness of ECE with small initial chloride content 0.4% and 0.8% was compared with that of high initial chloride content (2.5%) in order to know if the initial chloride content is an important factor on ECE effectiveness or not.

Effect of Imidazoline Inhibitor on the Rehabilitation of Reinforced Concrete with Electromigration Method.

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of the steel bar under the action of an electric field. During the migration process, a higher ionization capacity of the inhibitor with a symmetrical molecular structure was introduced. A new imidazoline inhibitor was, therefore, employed in this study due to its great ionization capacity. The effect of imidazoline and triethylenetetramine inhibitor on chloride migration, corrosion potential, and strength of concrete were explored. The research results showed that the effect of chloride extraction and electrochemical chloride extraction made no significant difference on the surface of the concrete, where chloride extraction efficiency was more than 70%, and the chloride extraction efficiency was more than 90% around the location of the steel. while a dry-wet cycle test, the potential of concrete increased by about 200 mV by mixing imidazoline inhibitor. The imidazoline inhibitor was found to be effective at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete’s strength.

Experimental Study on Reinforcement and Chloride Extraction of Concrete Column with MPC-CFRP Composite Anode

In this research, Magnesium Phosphate Cement (MPC) was innovatively used to bond with Carbon Fiber Reinforced Plastic (CFRP) in order to form the MPC-CFRP as a composite material, adopted both for chloride ions extraction and reinforcement of concrete columns. First of all, a series of tests were conducted to evaluate the feasibility of the MPC-CFRP as anode of Electrochemical Chloride Extraction (ECE) system, including chloride ions concentration, Scanning Electron Microscope (SEM) and tensile strength. Then, the MPC-CFRP was used to wrap around reinforced concrete column for the sake of reinforcement and extraction of chloride ions. The test results indicated that the chloride extraction efficiency and the tensile resistance of the MPC-CFRP electrode were superior to the control group. The ECE process can decrease the interface bonding strength between the concrete and the steel rebar while the compression resistance of the columns could be increased remarkably. Therefore, the MPCCFRP composite material is capable of achieving the dual functions of strengthening and repairing the reinforced concrete construction.

Effect of ultrasound on electrochemical chloride extraction from mortar

In this paper, the effect of auxiliary ultrasound on electrochemical chloride extraction (ECE) was studied. The chloride removal efficiency was investigated by examining the chloride content with ultrasound-assisted ECE and changing the introducing time of ultrasound. The experimental results showed that removal of chloride ions was noted to be more effective in ECE treatment assisted with ultrasound treatment (UT). In addition, the lower w/c ratio led to more distinct effect of ultrasonic cavitation on chloride removal. Electrochemical behaviors measured with different treatment revealed that UT treatment was effective on moderating the corrosion condition. Microstructural analyses revealed a significant alteration in composition and morphology of cementitious phases with UT treatment. Pull-out tests indicated that ultrasound had a certain negative impact on the bond strength. Although the effect of introducing ultrasound in the first 2 weeks or the last 2 weeks on the extraction efficiency was not obvious, intermittent ultrasound could not only ensure the chloride extraction efficiency, but also reduce the adverse effect of ultrasound on the bond strength.

Research of electrochemical chloride extraction and reinforcement of concrete column using MPC-bonded carbon fiber reinforced plastic sheet & mesh

Magnesium phosphate cement (MPC) is used as an adhesive that bonds carbon fiber reinforced plastic sheet (CFRP sheet-Cs) and mesh (CFRP mesh-Cm) in formation of the MPC-CFRP composite material. This type of MPC-CFRP composite material can serve as both an anode, Cs and Cm electrodes, for extracting chloride ions and a reinforcement material for concrete columns, and it contributes to bearing capacity improvement and electrochemical chloride extraction (ECE) of concrete structures. Compared with the traditional Ti-RuO2 anode (T electrode), the MPC-CFRP composite material is used to strengthen concrete columns and extract chloride ions. Current density, i=4, 8A/m2, and power-on time, t=14, 28, 42d, are considered to illuminate the effect of the ECE system on the axial compressive strength, chloride ion concentration and bond strength of the rebar-concrete interface of concrete columns. Cs and Cm electrodes can be used as anodes of the ECE system to migrate chloride ions near the rebar effectively toward the concrete surface. The increase of power-on time and current density improves the chloride extraction efficiency. Cs electrode has similar chloride extraction efficiency as T electrode under the same experimental condition superior to Cm electrode. The bond strength of the rebar-concrete interface degrades after ECE and the degradation increases as the current density and power-on time increases. Cs and Cm electrodes significantly improves the bearing capacity and ultimate displacement of concrete columns. However, the strengthening effect decreases as the current density and power-on time increases. The mechanical properties of the strengthened concrete columns are still superior than those of the un-strengthened. Cs and Cm electrodes can achieve the dual effects of reinforcing and repairing reinforced concrete structures. The estimated equations of ECE efficiency and ultimate load of concrete columns agree with the test data.

Electrochemical chloride removal in reinforced concrete structures: Improvement of effectiveness by simultaneous migration of silicate ion

For rehabilitating the chloride contaminated concrete structure to extend its service life, an electrochemical chloride extraction (ECE) treatment with simultaneous migration of silicate ion was proposed. The electrochemical technique is capable of alienating the chloride ions from the reinforcement and simultaneous injecting SiO32− into the mortar to interact with Ca(OH)2, resulting in mortar desalination and densification. By a comparative experiment, the chloride extraction efficiency and corrosion properties of steel reinforcement in sodium chloride solution after the electrochemical treatment were investigated by chloride potentiometric titration, corrosion potential (Ecorr) and corrosion current density (Icorr) determined by electrochemical impendence spectroscopy (EIS). The microstructure of mortar after the electrochemical treatment was observed using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), differential thermo-gravimetric analysis (DTG) and X-ray diffraction (XRD). About 40–55% of initial chloride was removed from the mortar using a current density of 2A/m2. The electrochemical treatment can effectively prolong the initiation time of secondary corrosion for the steel reinforcement, due to the mortar densification by electro-migration of silicate ion.

Extraction of Sodium Chloride from Water and Solubility of Water in Hydrophobic Trialkylammonium Alkanoate-Based Ionic Liquids

The sodium chloride extraction from aqueous solutions by using hydrophobic trialkylammonium alkanoate ionic liquids (ILs) is studied experimentally. The water solubility in these ILs is also determined. It is found that trialkylammonium alkanoate ILs show sodium chloride extraction efficiencies up to 0.101 g NaCl extracted/g NaCl start. This efficiency cannot be explained by the low water uptake (up to 0.02 gwater/gIL) in the IL. Instead, the sodium chloride extraction must be attributed to other factors, such as steric hindrance considerations. Steric hindrance considerations also explain the dependence of sodium chloride extraction efficiency on the IL structure. Kinetic experiments were performed to ensure a state of chemical equilibrium.

Chloride transference during electrochemical chloride extraction process

Chemical titration method and lab-made chloride probes were jointly adopted to investigate the effects of water-to-cement (W/C) ratio and the impressed current density on chloride transport for cement-based materials during electrochemical chloride extraction (ECE) process. The dissolution of bound chlorides and the effect of current density on dissolution were analyzed. The variations of chloride concentration at different depths and the chloride transference process were monitored. Test results show that W/C ratios adopted have slight influence on chloride extraction, while chloride extraction efficiency is mainly determined by the impressed current density. During ECE process a portion of bound chloride ions dissolved and the amount of bound chlorides released is directly proportional to current density.

Chloride extraction from archaeological iron: comparative treatment efficiencies

AbstractThis paper compares the chloride extraction efficiency of the following aqueous washing methods: alkaline sulphite, Soxhlet hot wash, repeated boiling and pressurized water. Absolute extraction efficiencies are determined by digestion of the objects following treatment. Alkaline sulphite is shown to be a more efficient chloride extractor than the other three treatments examined, either separately or combined. Its mean chloride extraction rate is 87% as compared to 72% for the combined treatments.