• Advances in concrete construction
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• v.13 no.4
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• pp.315-325
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• 2022

Reinforced concrete structures are exposed throughout their lifetime to the phenomenon of carbonation, which considerably influences their durability by causing corrosion of the reinforcements. The fight against this phenomenon is usually ensured by anti-carbonation coatings which have the possibility of limiting the permeability to carbon dioxide or with coatings which absorb the CO₂ present in the air. A coating with good crack-bridging (sealing) capacity will prevent water from entering through existing cracks in concrete. Despite the beneficial effect of these coatings, their durability decreases considerably over time with temperature and humidity. In order to use coatings made from local materials, not presenting any danger, available in abundance in our country, very economical and easy to operate is the main objective of this work. This paper aim is to contribute to the formulation of a corrected dune sand-based mortar as an anti-carbonation coating for concrete. The results obtained show that the cement mortar based on dune sand formulated has a very satisfactory compressive strength, a very low water porosity compared to ordinary cement mortar and that this mortar allows an improvement in the protection of the concrete against the carbonation of 60% compared to ordinary cement mortar based on alluvial sand. Moreover, the formulated cement mortars based on dune sand have good adhesion to the concrete support, their adhesion strengths are greater than 1.5MPa recommended by the standards.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.30-35
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• 2003

In this study, sand cast AZ91E and zirconium grain refined MEZ are representative of two typical groups of magnesium alloys: those containing aluminium and those containing no aluminium but with zirconium as a grain refiner. The corrosion performance of these two alloys was evaluated and compared in 5%wt NaCI solution through measurements of weight loss and polarisation curves and examination of microstructure. Corrosion damage of AZ91E was deeper and more localised than that of MEZ, while MEZ had a lower rate of cathodic hydrogen evolution and a higher rate of anodic dissolution than AZ91E. These differences in behaviour can be related to the differences in microstructure and chemical composition between the two alloys.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.45-52
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• 1999

It is difficult to keep the balance of supply and demand for natural aggregates in recent years, because natural resources have become to be almost exhausted. Crushed stone is already used for coarse aggregate instead of river gravel at present. Now, crushed sand or sea sand should be used for fine aggregate, because natural sand also has been exhausted with a few exceptions around Nakdong River. The sea sand has a lot of problems which are the corrosion of reinforcement bars, the investment of facility for cleansing salt and the cost increase due to the insufficiency of industrial water. Therefore, it is necessary to produce and to utilize the crushed sand very actively, but some material properties which are related to water absorption, strength and chemical durability, prevent from determining the generalized criteria because its rocks make much differences in its physical and chemical characteristics. In this paper, fundamental physical properties of crushed sand, which comes from Daegu Subway construction fields, have been investigated for the usability on basic material of concrete. The optimum replacement ratio and the strength estimation method of crushed sand replacing natural sand also have been presented here through the compressive strength test of ready-mixed concrete cylinders.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.177-180
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• 2006

Reinforced concrete has been widely used as a semi-permanent construction materials. However, sea sand, deicing salt, and marine condition might induce the corrosion of embedded reinforcement due to the penetration of chlorides in concrete structures. This reinforcement corrosion causes serious problems on safety and serviceability of structures during lifetime. Also, reinforcement corrosion may cause the collapse of structures in worst case, so that the corrosion problem is more and more intensely growing. The purpose of this paper is to provide the fundamental data for the mechanical effect of corrosion through evaluation on bond characteristics of reinforced concrete using corroded bars.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.265-272
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• 2017

Inhibition of pitting corrosion of the copper sprinkler tubes by removing dissolved oxygen in water with sodium sulfite was studied on the wet sprinkler systems operated in 258 household sites. First, air in the sprinkler tubing was removed by vacuum pumping. The tube was then filled with sodium sulfite dissolved in water. Sodium sulfite was very effective in maintaining a very low dissolved oxygen concentration in water in the sprinkler tube for the observation period of six months. Water leakage from the copper sprinkler tube was reduced significantly by using sodium sulfite. Both pitting corrosion process and pitting corrosion inhibition mechanism were investigated by examining microscopical and structural aspects of corrosion pits formed in failed copper sprinkler tube. Pitting corrosion was caused by pressurized air as well as sediments such as sand particles in copper tubes through oxygen concentration cells. It was confirmed microscopically that growth of corrosion pits was stopped by reducing dissolved oxygen concentration to a very level by using sodium sulfite.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.21-25
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• 2001

This article is concerned with the application of the fractal geometry to interfacial electrochemistry. Especially, we dealt with diffusion kinetics at the fractal electrodes. This article first explained the basic concepts of the Sacral geometry which has proven to be fruitful for modelling rough and irregular surfaces. Finally this article examined the electrochemical responses to various signals under diffusion-limited reactions during diffusion towards the fractal interfaces: The generalised forms, including the fractal dimension of the electrode surfaces, of Cottrell, Sand and Randles-Sevcik equations were theoretically derived and explained in chronoamperomety, chronopotentiometry and linear sweep/cyclic voltammetry, respectively.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.27-36
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• 2004

The corrosion rate measurement procedure for the permanent ground anchors using polarization resistance measurements and electrochemical impedance spectroscopy is presented in this paper. The polarization resistance measurements were used to determine the correlation between corrosion rate in the steel and soil characteristics. The electrochemical impedance spectroscopy was used to predict the time dependent corrosion reaction and evaluate the different type of coating systems and the effect of cement grouting on the corrosion attack under various conditions. The results indicate that a low pH soil is a good indicator of a corrosive soil. The low pH soil condition (<5) in both clay and sand has a significant effect on the corrosion reaction of steel members in permanent found anchors. In the case of neutral and alkaline conditions beyond pH 6 in clay and sand, no consistent acceleration of corrosion was measured and the corrosion rate was constant regardless of variations of soil pH levels. Laboratory test data for porcelain clay indicate that the change of soil pH level has a small influence on the corrosion reaction in the steel member. The use of cement footing in the bonded length is sufficient to decrease the corrosion rate to a level close to 0.003∼0.01mm/y at the end of the given period. With epoxy and fusion bonded epoxy coating, the steel specimens remained unaffected and retained the original condition. It is suggested that epoxy and fusion bonded epoxy coating can provide effective protection against corrosion for a long time even in aggressive environment.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.153-159
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• 2002

This experimental study is aimed to increasing the velocity in the sewerage and also development of easy removal method for a corrosion and sand in the flow pipe. And the result by the increasing the out flow per unit time, diameter of sewerage pipe is becoming small size, cut down the construction fee and the same time reducing the tubulent flow pattern in the flow pipe. As a result of detected experimental velocity signal from the probe in the test wall surface, reducing the pump power and increasing the out flow unit time. Apparent water velocity decreases as the value of void ratio increases depends on the varies center of pipe.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.107-115
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• 1993

최근 건설공사의 급증으로 인한 하천골재의 고갈로 콘크리트용 대체골재로서 해사\ulcorner선사 등이 대구되고 있다. 그러나 해사는 세척하지 않고 그대로 콘크리트에 사용할 경우 콘크리트중의 철근부식 촉진에 따른 콘크리트의 균열발생 등 조기 노후화현상으로 내구성에 많은 문제점을 내포하고 있고, 산사는 국내 연구실적이 전혀 없는 상태에서 지역적으로 무분별하게 사용되고 있어 이들에 관한 제반 공학적 특성 및 활영방안 연구가 시급한 실정이다. 따라서 본 연구는 산사\ulcorner해사를 사용한 콘크리트의 압축강도 특성 및 해사의 염분함량과 콘크리트의 물-시멘트비에 따른 철근부식량과의 관계를 구명하였다.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.52-58
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• 2004

The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973～1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000～2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973～1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.