• KCI Concrete Journal
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• v.13 no.2
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• pp.58-66
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• 2001

Recently, polymer-modified mortar has been studied for proposed use on industrial floors as top coat with thin thickness, typically 5~15mm. The purpose of this study is to evaluate basic properties of self-leveling materials using polymer dispersions as kinds of SBR, PAE, St/BA with thin coat (under 3mm). Superplasticizer and thickener have been included in the mixes to reduce bleeding and drying shrinkage as well as to facilitate the workability required. The self-leveling materials using four types of polymer dispersion are prepared with polymer-cement ratio which respectively range from 50% and 75%, and tested for basic characteristics such as unit weight, air content, flow, consistency change and adhesion in tension. From the test results, the self-leveling materials using PAE emulsion at curing age of 28days are almost equal to those of conventional floor using urethane and epoxy resin. The adhesion in tension of self-leveling mortars using SBR latex and PAE emulsion at curing age of 3days is over 17 kgf/cm$^2$(1.67MPa). Consistency change is strongly dependent on the type of polymer dispersion. It is concluded that the self-leveling materials using polymer dispersions can be used in the same manner as conventional floor using thermosetting resin in practical applications, in the selection of polymer dispersions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.125-131
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• 2005

Recently, to improve condition car park, using surface finishing material for variety color and property epoxy resin, urethane, cement mixed resin mortar or polymeric resin, and so on. However, it is frequent noise and wear out of tier and waterproofing materials, when the car slip or stop in car park, To minimize these cases, It is necessary that reduction of repair cost through performance long term durability of surface finishing material, improvement inside condition such as reduce dirty and car accident and ensurance the expected life of concrete slab in car park. Especially, we have not any tech for quality control, construction tech, production technology for car park surface materials, that's why park slab is not safety and suffer a loss. For this problems, this paper is to test surface finishing materials and as that result, suggest quality standard in the car park.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.133-136
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• 2005

The accidents attributed to the forklift have increased as the number of the forklift increases. It is significant that most of the accidents were fatal. This study investigated slip distance of forklift depending upon the floor materials and their conditions in industrial site. For doing this, an experiment was conducted, in which the floor materials and their conditions were adopted as independent variables and the slip distance as dependent variable. Six floor materials included asphalt concrete, two color hardener mortar, epoxy paint and deluxe tile. Two types of floor conditions, wet and dry, were used in the experiment. The results showed that the slip distance was shorter on the asphalt and concrete floors than on other floors, and that the distance on the wet floor was six times longer than that on the dry condition. Based on this result, it is recommended that as in the advanced countries, the regulation or standard on the floor conditions such as friction coefficient be established for reducing forklift relevant accidents.

• Structural Engineering and Mechanics
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• v.39 no.4
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• pp.499-520
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• 2011

The effectiveness of a technique for the repair of reinforced concrete members in combination with a technique for the repair of masonry walls of infilled frames, damaged due to cyclic loading, is experimentally investigated. Three single - story, one - bay, 1/3 - scale frame specimens are tested under cyclic horizontal loading, up to a drift level of 4%. One bare frame and two infilled frames with weak and strong infills, respectively, have been tasted. Specimens have spirals as shear reinforcement. The applied repair technique is mainly based on the use of thin epoxy resin infused under pressure into the crack system of the damaged RC joint bodies, the use of a polymer modified cement mortar with or without a fiberglass reinforcing mesh for the damaged infill masonry walls and the use of CFRP plates to the surfaces of the damaged structural RC members, as external reinforcement. Specimens after repair, were retested in the same way. Conclusions concerning the effectiveness of the applied repair technique, based on maximum cycles load, loading stiffness, and hysteretic energy absorption capabilities of the tested specimens, are drawn and commented upon.

• Economic and Environmental Geology
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• v.35 no.4
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• pp.355-368
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• 2002

The multi-storied Daewonsa stone pagoda (Treasure No. 1112) in the Sancheong, Korea was studied on the basis of deterioration and geological safety diagnosis. The stone pagoda is composed mainly of granitic gneiss, partly fine-grained granitic gneiss, leucocratic gneiss, biotite granite and ceramics. Each rock of the pagoda is highly exfoliated and fractured along the edges. Some fractures in the main body and roof stones are treated by cement mortar. This pagoda is strongly covered with yellowish to reddish brown tarnish due to the amorphous precipitates of iron hydroxides. Dark grey crust by manganese hydroxides occur Partly, and some Part coated with white grey gypsum and calcite aggregates from the reaction of cement mortar and rain. As the main body, roof and upper part of the pagoda, the rocks are developed into the radial and linear cracks. Surface of this pagoda shows partly yellowish brown, blue and green patchs because of contamination by algae, lichen, moss and bracken. Besides, wall-rocks of the Daewonsa temple and rock aggregates in the Daewonsa valley are changed reddish brown color with the same as those of the pagoda color. It suggests that the rocks around the Daewonsa temple are highly in iron and manganese concentrations compared with the normal granitic gneiss which color change is natural phenomena owing to the oxidation reaction by rain or surface water with rocks. Therefore, for the attenuation of secondary contamination, whitening and reddishness, the possible conservation treatments are needed. Consisting rocks of the pagoda would be epoxy to reinforce the fracture systems for the structural stability on the basements.

• Journal of Adhesion and Interface
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• v.13 no.2
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• pp.58-63
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• 2012

CFRP chip is the byproduct from carbon fiber reinforced plastic (CFRP) processing. CFRP chip is not simply a waste mainly composed of fine carbon fiber and epoxy resin. CFRP chip keeps matrix to maximize their reinforcing effect. To obtain a uniform length of carbon fiber in CFRP chip, chip was chopped ina mortar. CFRP chip should be purified to get better interface adhesion. Epoxy resin on the carbon fiber was removed by $H_2O_2$ surface etching treatment. Optimal dispersion and fabrication conditions of CFRP chip embedded in phenolic resin were determined by thermal stability for fire retardant applications. CFRP chip-phenolic composite exhibits better mechanical and thermal properties than neat phenolic resin. Surface condition of CFRP chip-phenolic composite was evaluated by static contact angle measurement. Contact angle of CFRP chip-phenolic composite was greater than neat phenolic due to heterogeneous condition of fine carbon fibers. From the evaluation for fire retardant (ASTM D635-06) test, thermal stability of CFRP chip-phenolic composite was found to be improved with higher concentration of CFRP chip.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.675-682
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• 2011

Recently, in retrofit of RC structures using FRP (Fiber Reinforced Polymer), researches about Near-Surface-Mounted Rertofit (NSMR) method have been widely performed. In NSMR, FRP bar is normally inserted in the slit formed in the cover concrete and then bonded by using epoxy mortar. In this paper, the bond characteristic of NSMR using FRP plate instead of bar was studied experimentally. Fracture behavior is observed from bond test using the parameters of embedment length, shear key, and FRP plate layer. In addition, an equation to predict the splitting strength of NSMR using FRP is proposed using the test result. The results showed that when the longer embedment length and more layers of FRP are used, the higher bond strength is achieved. There was a good co-relationship between the test and calculated results using the proposed equation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.245-251
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• 1999

Carbon fibre reinforced plastic(CFRP) plate is one of the alternative materials for strengthening of reinforced and prestressed concrete members due to excellent strength and light weight. In this paper, the behavior of slabs strengthened with CFRP plate is observed and analyzed from the test results. Especially specimens with thick plate is tested when large moment and large shear force appear in same position. The failure mode is a peeling-off of the CFRP plate due to flexural-shear crack. This is observed near the loading points with thick plates. Because of this failure mode, thickness of CFRP plates does not influence on the failure loads. Depending on the loading pattern, it is necessary to consider different design criteria for reinforced concrete members with external reinforcement. When large moment and large shear force appear in same location, maximum thickness may limit to 0.6mm and ratio between moment of strengthened slab and moment of unstrengthened slab is proposed 1.5-2.0.

• Korean Journal of Construction Engineering and Management
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• v.5 no.6 s.22
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• pp.212-217
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• 2004

Carbon fiber reinforced plastic(CFRP) plate Is one of the alterative materials for soengthening of reinforced and prestressed connote members due to excellent strength and light weight In this paper, the behavior of beams strengthened with CFRP plate and CFS(Carbon fiber sheet) is observed and analyzed from the test results. Especially specimens with thick plate is tested when large moment and large shear lone appear in same position. The main failure mode is a peeling-off of the CFRP plate near the loading points due to flexural-shear crack, Because of this failure mode, failure load is not linearly proportional to the thickness of CFRP plates. When beam is wrapped with CFS around oかy loading point it does not influence on the failure loads. Depending on the loading pattern, it is necessary to consider different design criteria for reinforced concrete members with external reinforcement. When line moment and large shear force appear in same location, maximum thickness may limit to 0.6mm and ratio between moment of strengthened beam and moment of unstrengthened beam is proposed 1.5-2.0. In order to use the plate of thicker than 6mm, CFS may be extended to the location which moment of strengthened beam is 1.5 times than moment of unstrengthened beam.

• Journal of Conservation Science
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• v.26 no.4
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• pp.349-360
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• 2010

The Yeongsheon Sinwoldong three-storied stone pagoda (Treasure No. 465) composed mainly of drusy alkali-granite. The major rock-forming minerals are biotite, quartz, amphiboles, orthoclase and plagioclase. Yellowish brown and black discoloration are formed at the eight sculpture Buddha of the stylobate. A broken rock fragments in the roof material were repaired using epoxy resin and cement mortar in the past. As a result of the infrared thermography analysis from the pagoda, cracks and exfoliation were not serious. Also, P-XRF analysis showed that concentration of Fe (mean 5,599ppm) and S (mean 3,270ppm) were so high in yellowish discoloration parts. Black discoloration area was detected highly Mn (mean 2,155ppm) concentration around the eight sculpture Buddha of the stylobate. The main reason for these are inorganic contaminants from disengaged rock ingredient and organic contaminants from withered plant body. Degree of physical weathering is relatively high in the southern and northern side. The eastern and western side had similar with weathering condition. The northern and eastern side were serious discoloration and biological weathering relatively. Therefore, we suggest that the pagoda need to do cleaning of biological contaminant and conservation treatment to weakened materials of rock and long term monitoring.