• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.19-27
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• 2017

This study investigated to predict the compressive strength of unsaturated polyester resin based polymer concrete using the maturity method. The test results show that the development of the compressive strength increased exponentially until an age of 24 hours. After 24 hours, the development of the compressive strength just increased gradually. This test result shows that the strength of unsaturated polyester resin based polymer concrete was developed mainly at the early age. Estimated datum temperature of unsaturated polyester resin based polymer concrete was $-20.67^{\circ}C$ which was much lower than of datum temperature ($-10^{\circ}C$) of Portland cement concrete. Also, this study result shows that the existing maturity index associated with Portland cement concrete was not applicable for polymer concrete because curing time of Portland cement concrete is different clearly with curing time of polymer concrete. The cause of different curing time was that there were different curing mechanisms between Portland cement concrete and polymer concrete. In order to best apply the experimental data to a model, CurveExpert Professional, the commercial software, was used to determine the predictive model regarding the compressive strength of unsaturated polyester resin based polymer concrete. As a result, Gompertz Relation or Weibull Model was an appropriate model as a predictive model. The proposed model can be used to predict the compressive strength, especially, it is more useful when the maturity is in the range between $40^{\circ}C{\cdot}h^{0.4}$ and $900^{\circ}C{\cdot}h^{0.4}$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.110-119
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• 2012

Fiber reinforced polymer (FRP) reinforcing rebar with non-corrosive property is suggested as an alternative replacement to steel reinforcing rebar due to its enhanced durability and non-corrosive characteristics. Currently, a limited number of glass fiber reinforced polymer rebar (GFRP) are sold commercially due to their high cost, relatively low performances, and brittle failure characteristics. Therefore, the performance enhancements and cost reduction of GFRP rebar are needed to increase its applications in construction fields. The intent of this study is to develop high performance GFRP rebar by improving its tensile and shear properties. Also, in order to reduce manufacturing costs, factors such as material composition and manufacturing process were evaluated to improve manufacturing efficiency. Finally a GFRP rebar with enhanced material properties and less expensive than the GFRP rebar currently sold in the market was manufactured and evaluated for its application possibility in construction fields.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.212-219
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• 2016

The sprayable waterproofing membrane is installed between shotcrete to provide crack bridging and hence prevent flow of liquid water as a waterproofing system. Because of its material characteristics, the sprayable membrane can be constructed at more complex structure than sheet membrane. The main component of the sprayable waterproofing membrane is a polymer-based material, therefore, moisture can migrate through sprayable waterproofing membrane materials by capillary and vapor diffusion mechanisms. The moisture transport mechanisms can have an influence on the degree of saturation and may influence the pore pressure and risk of freeze-thaw damage on concrete linings and membrane. In this study, long-term hygrothermal behavior was simulated with considering moisture transport and long-term effects on saturation of tunnel linings. From the simulation, due to water absorption and vapor transport properties of sprayable membrane, change of relative humidity and water content in tunnel lining can be evaluated.

• Journal of Navigation and Port Research
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• v.44 no.4
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• pp.305-311
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• 2020

Rising sea levels along the coast from global warming causes the increase of wave energy along the coast. This rise in sea levels results in relatively deep water levels, which would incur the loss of sand that had not occurred in the past from erosion in coastal areas. Generally, it has been challenging to protect against coastal erosion, and the slope, cross-sectional shape, and materials are selected for the site conditions depending on the change in external forces. However, the application of counter measures based on insufficient understanding of the phenomenon is causing various damage, indicating the need for technological development and converging technologies to improve credibility. In this study, we developed eco-friendly permeable biopolymer concrete blocks to control the coastal erosion by using the Bio-Coast, an effective porous structure that mitigates the destructive erosion caused by the rising sea levels. The hexagonal design of Bio-Coast was derived from the honeycomb, columnar joints, and clover, which are durable and stable structures in nature, and the design was changed to apply bumps on the Bio-Coast filling in the form of a clover to reduce wave overtopping and run-up. Applying the field condition of beaches on the east coast of Korea, the block weight and size were decided and the prototype blocks were manufactured and are ready for field placement. In particular, it is intended to protect coastal areas from destructive erosion by natural and artificial external forces, and to extend the design to river,s lakes, and natural walking trails, to improve the efficiency of quality control and process control through the use of blocks.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.549-556
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• 2003

Various researches on the application of polymer dispersions to the cement mortar and concrete have been practised in many countries like America, Japan and Germany and so on because of high performance and good modification effect of these. In this study, SBR, Polymer dispersion that widely used in situ is employed that the self-flowability may be induced in the cemen mortar. In order to comprehend and investigate the modification of cement mortar with self-flowability by SBR and properties and fracture mode of adhesive strength in tension of that, experimental parameter was set as SBR solid-Cement ratio(S/C) and Cement:Fine aggregate(C:F) and the experiments such as Unit weight, Flow, Consistency change, Crack resistance and Segregation that inform on the general properties have been done. In addition of that, Adhesion in tension is measured with a view to comprehending the properties and fracture mode in tensile load. Consistency change of cement mortar modified by SBR did grow better as the ratio of SBR solid-Cement increased and was much superior to that of resin based flooring such as polyurethane and epoxy which recorded the loss of consistency in 90min. after mixing. Adhesive strength in tension increased with continuity in the curing age and showed the maximum in case of C:F=1:1 and S/C=20%. As the increase of curing age, the fracture mainly happened in the concrete substrate and the interface between the specimen and concrete substrate.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.85-95
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• 2015

PURPOSES : Recently, bonded concrete overlay has been used as an alternative solution in concrete pavement rehabilitation since its material properties are similar to those of the existing concrete pavements. Deteriorated concrete pavements need rapid rehabilitation in order to prevent traffic jams on Korean expressways. Moreover, speedy and effective repair methods are required. Therefore, the use of bonded concrete overlay with ultra-rapid hardening cement has increased in an effort to reopen promptly the expressways in Korea. However, mobile mixer is required for ultra-rapid hardening cement concrete mixing in the construction site. The use of mobile mixer causes various disadvantages aforementioned such as limitation of the construction supply, open-air storage of mixing materials, increase in construction cost, and etc. In this study, therefore, hydration accelerator in-situ mixing on polymer modified concrete produced in concrete plant is attempted in order to avoid the disadvantages of existing bonded concrete overlay method using ultra-rapid hardening cement. METHODS : Bonded concrete overlay materials using ultra-rapid hardening cement should be meet all the requirements including structural characteristics, compatibility, durability for field application. Therefore, This study aimed to evaluate the application of hydration accelerator in-situ mixing on polymer modified concrete by evaluating structural characteristics, compatibility, durability and economic efficiency for bonded concrete overlay. RESULTS : Test results of structural characteristics showed that the compressive, flexural strength and bond strength were exceed 21MPa, 3.15MPa and 1.4MPa, respectively, which are the target strengths of four hours age for the purpose of prompt traffic reopening. In addition, tests of compatibility, such as drying shrinkage, coefficient of thermal expansion and modulus of elasticity, and durability (chloride ions penetration resistance, freezing-thawing resistance, scaling resistance, abrasion resistance and crack resistance), showed that the hydration accelerator in-situ mixing on polymer modified concrete were satisfied the required criteria. CONCLUSIONS : It was known that the hydration accelerator in-situ mixing on polymer modified concrete overlay method was applicable for bonded concrete overlay and was a good alternative method to substitute the existing bonded concrete overlay method since structural characteristics, compatibility, durability were satisfied the criteria and its economic efficiency was excellent compare to the existing bonded concrete overlay methods.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.289-298
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• 2023

In this study, the development of a self-healing concrete waterproofing agent was examined, focusing on its manufacturing and waterproofing properties. The optimal ratio using microcapsules for the concrete waterproofing agent was determined through assessments of flow, compressive strength, and permeability conducted during the mortar stage. These findings aimed to provide fundamental data for evaluating the self-healing properties of the concrete waterproofing agent designed for use in concrete structures. The self-healing concrete waterproofing agent was comprised of three types of inorganic materials commonly used for repair purposes. From experimental results, a composition ratio with a high potassium silicate content, referred to as SIM-2, was found suitable. A surfactant mixing ratio of 0.03 % was identified to enhance the dispersibility of the concrete waterproofing agent, while a mixing ratio of 0.2 % distilled water was deemed suitable for viscosity adjustment. For the magnetic self-healing concrete waterproofing agent's healing agent, using microcapsules in the range of 0.5 % to 0.7 % met the KS F 4949 and KS F 4926 standards.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.669-683
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• 2017

The objective of this study is to propose a modification of the previously proposed drainage system for catching the partial leakage of underground concrete structures. Two techniques were proposed for applying the drainage system only to the leaking parts. One was for conveying leaking groundwater to the collection point in the drainage system and the other was for conveying the collected groundwater to the primary drainage system of the underground concrete structure. Four waterproofing materials for conveying leaking groundwater to the catchment point of the drainage system, Durkflex made of porous rubber material, KE-45 silicone adhesive with super strong adhesion, Hotty-gel made of polymeric materials and general silicone adhesive were evaluated for waterproofing performance. Hotty-gel only showed perfect waterproof performance and the other three waterproof materials leaked. The modified drainage system with Hotty-gel and drainage pipe with fixed saddle to convey the leaking groundwater from the catchment point to the primary drainage system were tested on the concrete retaining wall. The waterproof performance and the drainage performance were evaluated by injecting 1,000 ml of water in the back of the modified drainage system at the 7-day, 14-day, 21-day, 28-day, 2-month and 3-month. There was no problem in waterproof performance and drainage performance of the modified drainage system during 3 months. In order to evaluate the construction period and construction cost of the modified drainage system, it was compared with the existing leaching repair method in surface cleaning stage, leakage treatment stage, and protective barrier stage. Total construction period and construction cost were compared in considering the contents of work, repair material, construction equipment, working time, and total number of workers. As a result of comparing and analyzing in each construction stage, it was concluded that the modified drainage system could save construction period and construction cost compared to the existing leaching repair method.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.102-109
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• 2011

In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, watertightness and durability properties of URHM on temperature condition of construction field were performed. Test result, seepage quantity and water absorption coefficient regarding watertightness of URHM were as in the following : series II > series I. Seepage quantity for the standard condition were smaller than low temperatures. all specimens were satisfied below 20g as standards of seepage quantity on KS F 4042. Because of the decrease of unit cement content by to replacement of blast furnace slag, the neutrlization resistance for durability properties was reduced. The result of alkali resistance and acide resistance, compressive strengths for specimens soaked in calcium hydroxide solution of seriesI were lower than compressive strengths for specimens not soaked. On the other hand, the case of series II show that the deterioration of compressive strengths for specimens was not almost showed. Compressive strengths of specimens soaked were similar with specimens not soaked except series II-C in $5^{\circ}C$. Therefore, specimens using both blast furnace slag and bottom ash were good in alkali resistance and acide resistance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.91-98
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• 2011

Recently, the usage of elastic paving using EPDM Chip instead of pedestrian sidewalk blocks or permeable concrete used mostly for pedestrian walk, trails and in parks has been increassed as it can absorb impact during walking and produce wide range of colors and designs. However, the properties of EPDM Chip including elasticity and durability are decreased when exposed to ultraviolet ray and scenic paving functions through various colors are lowered due to the yellowing phenomenon. In this study, ultraviolet ray accelerated weathering test has been conducted to analyze the color changes in EPDM Chip and polyurethane resin, which are the main ingredients of elastic paving, when exposed to ultraviolet ray. The color differences are quantitatively analyzed through the color value coordination of the colored space by using the color difference scheme. The experimental results show that the color changes in BL polyurethane resin which is used most frequently at present was larger than that of EPDM Chip. Moreover, the total color difference, ${\Delta}E$, of BC polyurethane resin are 3.162 on the $14^{th}$ day of commencement of acceleration, which is 6 times greater color change resistance against ultraviolet ray than that of BL polyurethane resin with total color difference of 20.639. Therefore, the usage of BC polyurethane resin, which is manufactured to have chain-type molecular structure by using the isocyanate as the HMDI at the time of producing polymer, as binder in elastic paving with EPDM Chip is found to be a highly efficient method of restraining the color changes due to the ultraviolet ray.