• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.52-60
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• 2005

Purpose. The intent of this study was to evaluate the effects of curing conditions on self-curing denture base resins to find out proper condition in self-curing resin polymerization. Materials and methods, In this study, 3 commercial self-curing denture base resins are used Vertex SC, Tokuso Rebase and Jet Denture Repair Acrylic. After mixing the self curing resin, it was placed in a stainless steel mold(3$\times$6$\times$60mm). The mold containing the resin was placed under the following conditions: in air at 23$^{\circ}C$; or in water at 23$^{\circ}C$; or in water at 23$^{\circ}C$ under pressure(20psi); or in water at 37$^{\circ}C$ under pressure(20psi) or in water at 50$^{\circ}C$ under pressure(20psi) , or in water at 65$^{\circ}C$ under pressure(20psi), respectively. Also heat-curing denture base resin is polymerized according to manufactures' instructions as control. Fracture toughness was measured by a single edge notched beam(SENB) method. Notch about 3mm deep was carved at the center of the long axis of the specimen using a dental diamond disk driven by a dental micro engine. The flexural test was carried out at a crosshead speed 0.5mm/min and fracture surface were observed under measuring microscope. Results and conclusion . The results obtained were summarized as follows : 1. The fracture toughness value of self-curing denture base resins were relatively lower than that of heat-curing denture base resin. 2. In Vertex SC and Jet Denture Repair Acrylic, higher fracture toughness value was observed in the curing environment with pressure but in Tokuso Rebase, low fracture toughness value was observed but there was no statistical difference. 3. Higher fracture toughness value was observed in the curing environment with water than air but there was no statistical difference. 4. Raising the temperature in water showed the increase of fracture toughness.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.529-535
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• 2007

Calcium oxide has been used as a demolition agent in fracturing rocks and old concrete structures, etc. With the agent, demolition work can be done in safety without a noise, vibration and any other pollution, since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the slurry into boreholes. But application of the non-explosive demolition agent is a time-consuming job, especially in winter. Essentially, this problem is related to the reaction rate of calcium oxide with water. This study examines the influence of additives such as cement and anhydrite on expansion pressure of calcium oxide at different curing temperatures. The expansion pressure of calcium oxide began to increase steadily with the rise of the curing temperature. When mixing calcium oxide alone with water, blown-out shot occurred. But as additives were added to calcium oxide, the reaction of calcium oxide delayed and the expansion pressure showed gradual increment. Especially, anhydrite showed a superior delaying effect than cement on the reaction of calcium oxide.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.114-115
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• 2021

In this study, the effects of thermal activation on the compressive strength and water absorption of fly ash-cement systems were studied. The results show that the increase in curing temperature improves the early-age compressive strength and reduces its water absorption.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.167-170
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• 1998

As construction technology advances, most of concrete structures are becoming larger and taller. Therefore, high strength and high quality concrete is necessary for them. Nowadays, the proposal of using belite rich cement is investigated to satisfy high flowing, low heat, and high strength. In this study, the height difference, the falling time and the maximum temperature of concrete using BRC were lower than that of concrete using OPC. Furthermore the compressive strength of concrete using BRC with and without compacting was not different. And the compressive strength of core specimens was higher than that of specimens in water curing. Compared to OPC, there was a good relationship between the curing temperature and the development of strength in BRC.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.496-501
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• 2007

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the PIC ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.51-57
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• 2014

PURPOSES : This study is to suggest tunnel length to spray curing compound, based on the field tests. METHODS : At first field test, length from the entrance of tunnel to wet wall was checked by visual survey. The second and third test, various sensors were installed in concrete or in tunnel, such as RH sensor, temperature sensor, portable weather station and etc.. And also, test for bleeding and retaining water of concrete were conducted to evaluate environmental effect on concrete pavement. RESULTS : The result of the field experiment for tunnel length to spray curing compound indicates that length changes depending on tunnel length, season, and location. Environmental condition of a short tunnel was not much different between location near entrance and at center of tunnel. However, in case of a medium and long tunnel, effect of outside environmental condition decreased, when location moved into tunnel center of it. CONCLUSIONS : From the testing results, it can be proposed that optimum tunnel length to spray curing compound is 60m for a medium and long tunnel, and whole length for a short tunnel.

• Computers and Concrete
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• v.5 no.2
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• pp.89-100
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• 2008

This research examines the engineering properties and color intensities of mortar containing different amounts of fly ash (0, 5, 10 and 20%) mixed at different water-to-binder ratios (w/b = 0.23, 0.47 and 0.59) and exposed at different temperatures (T = 25, 100, 200, 400, 600 and $800^{\circ}C$). Results show that there is greater mass loss on ignition with high w/b and higher temperatures. In addition, the color channel image analyzer (Windows software written in Delphi) is utilized to study the relationship between the curing temperature and intensity of three primary colors, red, green and blue (RGB), of the fly ash mortar specimens. The results show that the RGB intensities on the specimen surface increases from that at $25^{\circ}C$. The mortar specimen becomes white with increase in w/b but without the addition of fly ash. Moreover, for mortar specimens with greater content of fly ash, red on the specimen surface has the greatest increase in intensity at elevated temperature. Observation the variations in color on the specimen surface may help estimate the highest elevated temperatures that concrete structures can withstand.

• Textile Coloration and Finishing
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• v.21 no.4
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• pp.39-45
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• 2009

PVA films were crosslinked with dimethylol dihydroxy ethylene urea (DMDHEU) and three polycarboxylic acids of butanetetracarboxylic acid (BTCA), citric acid and malic acid Different factors influencing the crosslinking treatment with BTCA were investigated including BTCA and sodium hypophosphite (SHP) concentration, curing temperature and time. The cured films was extracted with boiling water and gel fraction was calculated based on weight change of the PVA films. The gel fraction of PVA films increased with increasing curing temperature and time. And the resistance to water and thermal stability of the crosslinked PVA films improved with the BTCA crosslinking treatment. While crosslinking with citric acid gave the highest gel fraction among the crosslinkers, crosslinking with malic acid showed the highest absorbancy in 0.9% saline solution, which was attributed to lower crosslink density and high number-average molecular weight between crosslinks. The superabsorbent PVA films could be prepared by adjusting the crosslinking condition of PVA with polycarboxilic acids.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.305-311
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• 2016

This study examined the long-term inelastic characteristics, including unrestrained shrinkage and creep, of low-heat cement concrete under different ambient curing temperatures. To achieve the designed compressive strength of 42MPa, water-to-binder ratios were selected to be 27.5, 30, and 32.5% for curing temperatures of 5, 20, and $40^{\circ}C$, respectively. Test results showed that the shrinkage strains of concrete mixtures tended to decrease with the decrease in curing temperature because of the delayed evaporation of internal capillary and gel waters. Meanwhile, creep strains were higher in concrete specimens under lower curing temperature due to the occurrence of the transition temperature creep. The design models of KCI provision gave better accuracy in comparison with test results than those of ACI 209, although a correction factor for low-heat cement needs to be established in the KCI provision.

• Computers and Concrete
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• v.6 no.4
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• pp.269-280
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• 2009

In this paper an experimental study of the influence of hot springs curing upon concrete properties was carried out. The primary variables of the investigation include water-to-binder ratio (W/B), pozzolanic material content and curing condition. Three types of hot springs, in the range $40-90^{\circ}C$, derived from different regions in Taiwan were adopted for laboratory testing of concrete curing. In addition, to compare with the laboratory results, compressive strength and durability of practical concrete were conducted in a tunnel construction site. The experimental results indicate that when concrete comprising pozzolanic materials was cured by a hot spring with high temperature, its compressive strength increased rapidly in the early ages due to high temperature and chloride ions. In the later ages, the trend of strength development decreased obviously and the strength was even lower than that of the standard cured one. The results of durability test show that concrete containing 30-40% Portland cement replacement by pozzolanic materials and with W/B lower than 0.5 was cured in a hot spring environment, then it had sufficient durability to prevent steel corrosion. Similar to the laboratory results, the cast-inplace concrete in a hot spring had a compressive strength growing rapidly at the earlier age and slowly at the later age. The results of electric resistance and permeability tests also show that concrete in a hot spring had higher durability than those cured in air. In addition, there was no neutralization reaction being observed after the 360-day neutralization test. This study demonstrates that the concrete with enough compressive strength and durability is suitable for the cast-in-place structure being used in hot spring areas.