• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.331-339
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• 2017

The purpose of this study is to evaluate the effect of curing age and thickness of coating material on the bond strength of polymer cement slurry(PCS)-coated rebar that can replace epoxy-coated rebar. The test specimens were prepared with two types of cement, two types of polymer dispersion as St/BA and EVA, two polymer-cement ratios, two coating thicknesses and three curing ages, and tested for bond strength test to cement concrete. The flexural behavior of RC beam that is made by optimum conditions such as polymer-cement ratio of 80%, coating thickness of $100{\mu}m$ and curing age of 7 days of PCS recommended from the bond strength test is also conducted. From the test results, The maximum bond strength of PCS-coated rebar at curing age of 7-day and coating thickness of $100{\mu}m$ was about 1.52 and 1.58 times respectively, the strength of plain and epoxy-coated rebar. The ultimate loads of RC beam using PCS-coated rebar were range of 81.1% to 102.3% of that of plain rebar, and 98.4% to 124.1% of that of epoxy-coated rebar. It is apparent that PCS-coated rebar with EVA, curing age at 7-day and $100{\mu}m$ can replace epoxy-coated rebar in construction field.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.633-640
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• 2015

Polymer cement slurry (PCS) is made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the bond strength of coated rebar by polymer cement slurry made of EVA and ultra high-early strength cement. The test pieces are prepared with EVA polymer dispersion and ultra high-early strength cement having four types of polymer-cement ratios, four types of coating thicknesses and four curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day, and coating thicknesses of $75{\mu}m$ and $100{\mu}m$. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, and coating thickness of $100{\mu}m$ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with polymer-cement ratio of 80% or 100% and coating thickness of $100{\mu}m$ at curing age of 1-day can replace epoxy-coated rebar.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.635-642
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• 2008

In recent years, epoxy-coated reinforcing bars have been widely used in order to prevent the corrosion of ordinary reinforcing bar. However, they have a bad balance between performance and cost. Especially, they have a brittleness properties, low bond strength to cement concrete and no good bend-ability in the field. The purpose of this study is to evaluate the tensile properties and adhesion of hybrid-type anti-corrosion polymer cement slurry (PCS). PCSs are prepared with four types polymer dispersions using fly ash and silica fume, and tested for proper coating thickness, tensile properties, adhesion to steel plate and bend-ability. From the test results, the viscosity of PCS is effected by polymer dispersion types, and is a little decreased by using fly ash. The coating thickness of PCS has a proper thickness at polymer-binder ratio of 100%. It is apparent that the coating thickness has various values according to viscosity of PCS, water-binder ratio and polymer-binder rato. PCS has a good various anticorrosion properties and physical properties such as tensile strength, adhesion and bend-ability. It is also recommended that proper coating thickness to reinforcing bar is in the ranges of 150 to $250{\mu}m$ for bond strength, adhesion and bend-ability. It is also expected that the coated reinforcing bar using PCS is widely used instead of epoxy coated reinforcing bar in the industrial field.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.73-80
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• 2013

Polymer cement slurry (PCS) made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the mix design conditions at early curing age of PCS-coating material effected on improvement in bond strength of coated rebar. The test pieces are prepared with two types of polymer dispersions such as St/BA and EVA, four polymer-cement ratios, two types of cement, four coating thicknesses and three curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day or less, and coating thicknesses of $75{\mu}m$ and $100{\mu}m$. The maximum bond strength of PCS-coated rebar at curing age of 3-hour is almost same as that of curing age of 1-day and 7-day. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and St/BA at polymer-cement ratio of 80%, and coating thickness of $100{\mu}m$ is about 1.52 and 1.58 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with curing age at 3-hour and coating thickness of $100{\mu}m$ can replace epoxy-coated rebar.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1473-1482
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• 2013

A disc-type rotary atomizer affords advantages such as superior paint transfer efficiency, uniformity of paint pattern and particle size, and less consumption of compressed air compared to a spray-gun-type atomizer. Furthermore, it can be applied to all types of painting materials, and it is suitable for large-scale processes such as car painting. The painting quality, which is closely related to the atomizer performance, is determined by the uniformity and droplet size in accordance with the design of the bell disc surface. This study establishes the basics of how to design a surface by modeling the operating bell disc's RPM, diameter, surface angle, and film thickness considering dye characteristics such as the viscosity, density, and surface affinity.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.227-228
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• 2014

마그네슘은 금속 재료중 화학적 활성이 높아 내식성 향상을 위해 표면처리 공정이 반드시 필요하다. 플라즈마 전해 산화를 통한 산화 피막 생성 후 좀더 높은 내식성 향상을 위해 전착 도장법을 사용할 수 있다. 본 논문에서는 전원 인가 방식에 따라 pulse 전원을 on/off 비율에 따른 피막 두께 변화를 측정 하였고 전착 도장을 시행 하여 cross cut test를 통한 부착성 시험을 진행해 on/off 비율 1:4 조건에 250V 전압을 인가 하였을 때 부착성이 가장 우수함을 확인 하였다. 또한 플라즈마 전해 산화 후 탕세 공정을 통해 전착 도장의 내열탕 시험 후 표면 blister의 개선 효과를 얻을 수 있었다.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.433-439
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• 2012

Anticorrosive paint is the most widely used in shipbuilding and the dry film thickness is very important in terms of productivity and assurance of anticorrosive performance. However, it is difficult to achieve the recommended target film thickness because the dry film thickness depends on labor's skill in practice and is affected by a number of parameters, such as spray pressure, paint flow rate, tip size, spray distance, SVR(Solid Volume Ratio), etc. Present paper derives an empirical equation through the correlation analysis of parameters selected by spray experiments of anti corrosive painting in order to predict the coated status. Comparing the calculated results with practical data, we show that the empirical equation can successfully expect DFT(Dry Film Thickness).

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.68-75
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• 2008

This paper investigates the correlation between surface roughness and gloss of aluminium sheet painted waterborne paint. One customer criterion of automotive quality is the as-painted appearance of the final products. Especially, the current emphasis on control of surface roughness of sanded aluminium sheet has been prompted by the automotive industry's concern with the as-painted appearance. because the influence of such characteristics on paintability, and painted appearance is important in defining outer panel requirements for automobile. This paper is dedicated primarily to the issue of painted appearance and reviews for improvement of roughness. The conclusions are obtained as follows ; 1) Painted aluminium sheet appearance is strongly affected by surface roughness of base-metal and influenced by sand paper and sanding method. 2) The painted appearance of aluminium sheets was determined and related to surface roughness parameters, combination of sand paper.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.117-124
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• 2003

Reinforced concrete structures under sever conditions such as marine structures, bridges and structures constructed with aggregates(dredged from sea), can be deteriorated from corrosion of the reinforcing bars. The purpose of this study is to evaluate the anti-corrosive performance of coated steel using polymer cement slurry. Polymer cement slurry with various polymer dispersions and corrosion inhibiting agent were coated to the surface of bars, and tested for accelerated corrosion tests. Tests include immersion in NaCl 10% solution, chloride ion spray, autoclave cure, autoclave cure after carbonation, penetration of NaCl 10 % solution, carbonation after penetration of NaCl 10% solution. Test results, show that the anti-corrosive performace is considerably improved by using polymer cement slurry at surface of steel. And this trend is marked by adding of corrosion inhibiting agent. This difference of the anti-corrosive properties is hardly recognized according to types of polymer dispersions. The coated steel using polymer cement slurry will be improved to a great extent compared to those of plain steel when increasing content of chloride ion in cement concrete.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.637-645
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• 2008

It is very hard to control the quality of coating work in shipbuilding process, because it is highly affected by several parameters such as space between object and nozzle tip, spray velocity, pressure, tip size, etc.. Even so a coating work in shipbuilding is done by workers' experience and skill as yet. It causes not only an excessive use of paints but also a decrease of productivity. In order to solve this problem, we developed a formula that predicts the film thickness and determined the proper coating pattern. Also we had done a series of experiments to verify the results of this study.