• Journal of the Korean institute of surface engineering
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• v.21 no.4
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• pp.168-175
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• 1988

The nickel0zinc allot depositions have been studjen in ammonium chloridw added chloride baths to fine out the effects of ultrasonic irradiation for the electrodeposition processes. The compositions of deposited alloys, the current efficiencies, corrosion resistance and brightness in various conditions of electrodeposition were investigated, in the range of ultrasonic irradiation of 50,500 and 1,000kc/s respectively. The results obtained are as follows; 1. the ratio of nikel to zinc in the deposit increased according 시 the ammonium chloride concentration in irradiated baths. 2. The current efficiencies became also higer in the irradiated bath. 3. Ammonium ions in solution seem to retard formation of zinc hydroxide. 4. The corrsion resistance and brightness of the deposits are dependent upon nickel content of deposits which ranges 10-18%(wt)nickel in the irradiated baths and 11-15%(wt)in ninirradisted baths. 5. The corrosion resistance and brightnes of the deposited are appreciably better in the irradiated baths than in non-irradiated bath with the mole ratio of 3.4(NH+4/Ni+++Zn++).

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.585-588
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• 2008

To predict the service life of reinforced concrete structures exposed to chloride environment, quantitative measures of material properties such as the critical chloride content for corrosion in concrete and the diffusion coefficient of chloride ions of concrete and the surface chloride content of the concrete are essential. However, it should be noted that they are influenced by several factors such as concrete mix proportions, cement type, and environmental conditions, etc. Thus, the purpose of this research is to estimate more actually the critical chloride content for corrosion of the reinforcing steel in concrete by field exposure experiment. For this purpose, the prism concrete test specimens were made for water-cement(W/C) ratios of 31%, 42%, 50%, and 70%, and then the field exposure experiment for them were conducted at Youngduk of the east coast for about 3 years. During the test, corrosion monitoring by half cell potential method was carried out to detect the time to initiation of corrosion for test specimens and its chloride content was evaluated by breaking the concrete test specimens when corrosion of the reinforcing steel in concrete was perceived. It was observed from the test results that the critical chloride content for corrosion of reinforcing steel in concrete would be dependent on W/C ratio and almost irrespective of concrete cover.

• Resources Recycling
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• v.29 no.5
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• pp.28-37
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• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Journal of the Korean institute of surface engineering
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• v.20 no.3
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• pp.118-126
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• 1987

The Zn-Al composite electroplating was studied by using chloride zinc bath containing metal hydroxides $(Zn(OH)_2,\;Al(OH)_3))$ and aluminium powder. The size of Al powder codeposited in the beaker bath with Al powder of-400 mesh was under 10${\mu}m$. The Zn-Al composite was electro-deposited at 40$^{\circ}C$ in the ranges of current density of 5-50 A/$dm^2$ in the flowing electrolyte. The content of aluminium particles codeposited increased slightly with increasing flow rate of electrolyte from 0.5 m/sec to 1.0 m/sec, and decreased with increasing current density from 5 A/$dm^2$ to 50 A/$dm^2$. The content of aluminium particles codeposited by using the electrolyte containing zinc hydroxide(0.1M) was 2~4 wt%. The Al powder was codeposited mainly near the surface layer of the electrodeposits. The dissolution rate of aluminium particles in the electrolyte containing 0.1M $Zn(OH)_2$ and Boric acid was 0.41 g/l. day in comparison with 1.5 g/l. day dissolution rate in pure chloride bath.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.553-558
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• 2012

Airborne chlorides are transported to inland by sea wind to be attached to seashore concrete structure surface then penetrated into concrete structure members. Since the surface attached chloride amount are dependent on the amount of airborne chlorides, the prediction of distribution of airborne chlorides is important information in preventing chloride corrosion problems in seashore concrete structures. The prediction of surface chloride amount from airborne chlorides environment is extremely difficult than concrete directly in contact with seawater. In addition, their penetrating tendency is different from that of concrete immersed in seawater. In this study, properties of surface and penetrated chlorides under airborne chlorides environment are investigated. Concrete specimens were manufactured and exposed to marine environment for 3 years. The specimens were analyzed at the time durations of 1, 2, and 3 years to check surface chloride amount to penetrated chloride depth. The results revealed that there were certain differences according to surface roughness of concrete and with and without washing effect due to rainfalls. The evaluation results showed that penetrated chlorides depend on amount of airborne chlorides and duration of exposure. In addition, a notable tendency of having deeper chloride penetration and higher chloride content in concrete members under long-term exposure was observed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.65-72
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• 2016

Service life evaluation for RC Structures exposed to chloride attack is very important, however the previous two methods(deterministic and probabilistic method) show a big difference. The paper presents a service life simulation using deterministic and probabilistic method with time-dependent diffusion coefficient. Three different cases are considered for diffusion coefficient, concrete cover depth, and surface chloride content respectively, and then the PDF(probability of durability failure) and the related service life are obtained. Through adopting time-dependent diffusion, the discrepancy between the two methods can be reduced, which yields reasonable service life. When diffusion coefficient increases from $2.5{\times}10^{-12}m^2/sec$ to $7.5{\times}10^{-12}m^2/sec$, the service life decreases to 25.5~35.6% level, and cover depth does from 75 mm to 125 mm, it increases to 267~311% level as well. In the case of surface chloride content from $5.0kg/m^3$ to $15.0kg/m^3$, it changes to 40.9~54.5%. The effect of cover depth is higher than the others by 8~10 times and also implies it is a key parameter to service life extension.

• Polymer(Korea)
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• v.34 no.3
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• pp.198-201
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• 2010

We have worked a surface modification to release a strong agglomeration of multi-walled carbon nanotube(MWCNT) and a incorporation of hydrophilic polymer to improve compatibility between MWCNT and polymers. Carboxylated MWCNT was easily obtained by acid treatment and the carboxylate was converted to acylchloride by thionyl chloride. Then, we tried one more synthesizing routes to achieve covalent bonds with poly(ethylene oxide) having amine end groups of low molecular weight. We measured the polymer content on the surface of MWCNT by TGA and observed increased diameter of MWCNT by SEM and TEM analysis.

• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.511-520
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• 2019

The critical chloride content of rebar embedded in concrete was experimentally evaluated according to the admixture replacement ratio and admixture type. Four types of reinforced concrete were mixed OPC 100%, OPC 70% + GGBFS 30%, OPC 40% + GGBFS 60%, and OPC 40% + GGBFS 40% + FA 20%. NaCl solution was supplied to the specimens, and the open circuit potential of the embedded rebar was monitored. The specimens determined to initiate corrosion were cut at intervals of 5mm from the NaCl solution supply surface and conducted to chlorine ion profile. Corrosion initiation time of rebar embedded in concrete was delayed as the admixture replacement ratio increased. Looking at the critical chloride content of the types of reinforced concrete, it was highest in OPC 1.46kg/㎥, followed in order by S30 0.98kg/㎥, TBC 0.74kg/㎥, and S60 0.71kg/㎥.

• Computers and Concrete
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• v.19 no.5
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• pp.489-499
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• 2017

Self-Compacting Concrete (SCC) is a new technology capable to flow without segregation or any addition of energy which leads to efficient construction and cost savings. In this study, the effect of replacing the Ordinary Portland Cement (OPC) with Fly Ash (FA) on the strength, durability of the concrete was investigated experimentally, and carbon footprint and cost were also assessed. Four different replacement FA ratios (0%, 20%, 40% and 60%) were used to create four SCC mixes. Standard test methods were used to determine the workability, strength, and durability of the SCC mixes including resist chloride ion penetration, water permeability, water absorption, and initial surface absorption. The axial cube compressive strength tests were performed on the SCC mixes at 1, 7, 14, 28 and 35 days. Replacing the OPC with FA had a significant positive impact on chloride iron penetration resistance and water absorption but had a considerable negative impact on the compressive strength. The SCC mix with 60% FA had 36.7% and 15.8% enhancement in the resistance to chloride ion penetration and water absorption, respectively. Evaluation of the carbon footprint and the cost of each SCC mixes showed the $CO_2$ emissions mixes 1, 2, 3 and 4 were significantly reduced by increasing the FA content from 0% to 60%. Compared with the control mix, the cost of all mixes increased when the FA content increased, but no significant differences were seen between the estimated costs of all four mixes.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.708-717
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• 2002

Durability is a major concern in the design and construction of concrete structures which are located in the sea environments. In particular, the combined action of chlorides, sulfates, and carbonation nay influence greatly the deterioration behavior of concrete structures. The purpose of the present study is to explore the diffusion characteristics of chloride ions in concrete structures under combined deterioration conditions. The present test results indicate that the chloride penetration into concrete structures is more pronounced under combined attacks of chlorides, sulfates and carbonation. The diffusion coefficients and surface chloride contents were found to increase under combined multiple deterioration conditions. The present study provides quantitatively the penetration and diffusion characteristics of chloride ions in concrete structures under various deterioration conditions. The results of present study may be efficiently used for the realistic design of concrete structures under combined deterioration conditions.