• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.681-686
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• 2002

In this study, a high volume fly-ash substituted concrete experiments in two curing temperature circumstances - 35${\circ}$, 20.${\circ}$, High volume fly-ash concrete is tested in fresh concrete properties and hardeded concrete properties. There is slump, air contents, concrete setting tests. 3, 7, As fresh concrete test items and 28 days water curing compressive strength is measured in the hardened concrete test. The purpose of this study is to submit a various fly-ash concrete data for application to field. The result of this study is that the best strength is developed at the plain concrete cured 20 ${\circ}$, and Mixing F43 shows the best strength among specimens which cured at 35${\circ}$,

• Journal of the Korea Concrete Institute
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• v.12 no.2
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• pp.31-42
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• 2000

This paper discusses the validity of models predicting the compressive strength of concrete subjected to various temperature histories and the shortcomings of existing rate constant model and apparent activation energy concept. Based on the discussion, a modified rate constant model is proposed. The modified rate constant model, in which apparent activation energy is a nonlinear function of curing temperature and age, accurately estimates the development of the experimental compressive strengths by a few researchers. Also, the apparent activation energy of concrete cured with high temperature decreases rapidly with age, but that of concrete cured with low temperature decreases gradually with age. Finally generalized models to predict apparent activation energy and compressive strength are proposed, which are based on the regression results.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.117-124
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• 1997

In this study, mechanical properties of type V cement concrete with different curing temperature were investigated. The tests for mechancial properties, i.e., compressive strength and modulus of elasticity, were carried out on two kinds of type V cement concrete mixes. concrete cylinders cured at 10, 23, 35 and 50℃ were tested at 1, 3, 7 and 8 days. The 'rate constant model' was used to described the combined effects of time and temperature on compressive strength development. Test results show that concrete subjected to high temperature at early age attains greater strength than concrete to low temperature but eventually attains lower later-age strength than that. With type V cement concrete, the linear and Arrhenius rate constant models both accurately describe the development of relative strength as afunction of the equivalent age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.89-92
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• 2005

Our country has experienced variations in temperature as belong to the area of the continental climate that shows four significant seasons. These occur quality of construction. As the hydration of cement processes, the strength of concrete is developed. In order to improve the quality of concrete, various conditions including temperature and humidity should be maintained appropriately and concrete itself should be cured sufficiently This paper is basic experiment for estimating influence of strength by seasonal mock-up concrete's heat of hydration and estimate relationship of compressive strength development by curing temperature. And show basic document as quality control.

• Journal of the Korean Society of Tobacco Science
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• v.17 no.1
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• pp.15-19
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• 1995

This study was made of the effects from exposure to air temperature and amount of solar radiation during the wilting period on the sunburn of burley tobacco. Tobacco stalks were cult with one hour interval from 8:00 to 16:00, and were left on the field to expose to weather, and tobacco single leaf placed under 4 temperatures regimes in indoor. Sun-burn of the leaves was occurred when the leaves were exposed to temperature higher than 33$^{\circ}C$, and to solar radiation more than 800w/$m^2$ between 11:00-15:00 in a day during the curing season. The leaf temperature was increased until 52$^{\circ}C$ under the weather condition. The tobacco leaves were also burned without solar radiation when the leaves were exposed to high temperature until 5$0^{\circ}C$ of leaf temperature. Sun-bum was increased at upper leaves and at higher moisture content of leaf.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.316-319
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• 2004

Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. The purposed of this paper is to propose the model for the stress-strain relation of recycled-PET polymer concrete at monotonic uniaxial compression and is to investigate for the stress-strain behavior characteristics of recycled-PET polymer concrete with different variables(strength, resin contents, curing conditions, addition of silane and ages). The maximum stress and strain of recycled-PET polymer concrete was found to increase with an increase in resin content, however, it decreased beyond a particular level of resin content. A ascending and descending branch of stress-strain curve represented more sharply at high temperature curing more than normal temperature curing. In addition, results show that the proposed model accurately predicts the stress-strain relation of recycled-PET polymer concrete.

• Journal of Ocean Engineering and Technology
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• v.18 no.4 s.59
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• pp.46-51
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• 2004

The surface layer in dredged and reclaimed marine clay is improved by mixing of shallow soils and hardening agents, which is made of cement, containing some other special admixtures. Tests in both laboratory and field settings are performed to investigate the improvement effect and strength properties of cement-stabilized soils. The test results show that the hardening agent sufficiently improves the soil properties of the surface layer, while increasing the load-carrying capacity. The strength of cement-stabilized soils depends, primarily, on water-to-cement ratio and curing temperature. That is, the higher curing temperature and the longer curing time, the higher the strength in cement-stabilized soils. The high ratio of water-ta-cement results in a lower strength.

• Korean Journal of Agricultural Science
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• v.8 no.2
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• pp.185-194
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• 1981

This study was carried out to determine the effect of accelerated curing on the strength of standard sand mortar and briquette ash mortar. The standard sand mortars and the briquette ash mortars made by mixture of the standard sand:cement and the briquette ash:cement at the ratio of 2 : 1, 3: 1 and 4 : 1, respectively, were cured at 4 different temperature of $20^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$. The compression and tensil strength of mortars were measured at ${\sigma}_3$, ${\sigma}_7$, ${\sigma}_28$. The results obtained are summarized as follows; 1. At each age of curing and each curing temperature, the compression and tensile strength of the mortars made by the mixture of cement and standard sand was significantly higher than that of the mortars made by the mixture of cement and briquette ash. But the increasing rate of strength in compression and tension was significantly higher at the mortars of cement and briquette ash than those of cement and standard sand. 2. The strength of mortars which showed lower strength than Korean Standard at ordinary curing temperature was significantly increased and showed higher value than Korean Standard by the accelerated curing at high temperature. The increasing rate of strength by the accelerated curing was higher at the mortars containing less amount of cement than those containing more cement. The hardening of the mortars containing less amount of cement was significantly promoted by the accelerated curing in high temperature. 3. When the briquette ash was substituted for the materials of cement mortar, decline of the mortar strength is. unavoidable. But the enhancement of the mortar strength is still expected by the experimental results that the strength of cement-briquette ash mortar showed an increase of 137.6% by the accelerated curing at $60^{\circ}C$, 164.1% at $80^{\circ}C$ C and 183.8% at $100^{\circ}C$, respectively, compared with the strength of mortar cured at $20^{\circ}C$ for 28 days. 4. As the strength of cement briquette mortar is lower than that of cement standard sand mortar, the cement briquette ash mortar is expected to be increased in strength by the accelerated curing at high temperature. The cement briquette mortar is expected to be utilized to the production of secondary mortar goods or the constructions which need low strength of mortar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.284-291
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• 2016

To evaluate the properties of inorganic composites using a great quantity of high-calcium fly ash generated in combined heat and power plants, high-calcium fly ash and F-class fly ash commonly used as concrete admixtures were substituted with binding materials to examine changes of fluidity and compressive strength depending on the substitution ratio for each curing temperature. According to the experimental result, CFA-mixed mortar showed a tendency to reduce its flow unlike FFA-mixed mortar as the substitution ratio was increased, but its flow loss showed smaller than FFA as time passed. As a result of examining compressive strength depending on mixing FA, FFA-mixed mortar had an optimum range within 50% when curing at ambient temperature, but it was found that the compressive strength is reduced when mixing CFA. When curing at high temperature, FFA did not relatively have a great effect on the substitution ratio, but CFA could expect a strength enhancement effect compared with 100% of OPC when using within 25% of binding materials.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.1
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• pp.25-41
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• 1990

The purpose of this study was to evaluate and compare the dimensional changes of relined dentures with a light-curing resin, a heat-curing resin, and a direct, hard reline resin. And also to measure the transverse strength, impact strength, surface hardness of the three resins used in relining. The surface textures of three resins also of evaluated by using scanning electron microscope. Through analyses on the data from this study, the following conclusions were obtained. 1. Impact strength of heat-curing resin was highest, and direct, hard reline resin higher, light-curing resin lowest. 2. Transverse strength of heat-curing resin was highest, and direct, hard reline resin and light-curing resin was lower and not signiicantly different. 3. Surface hardness of light-curing resin was lighest, heat-curing resin higher, and direct, hard reline resin was lowest. 4. After storage of the relined dentures for 1 day and 1 week in water at room temperature, linear shrinkage of distance between the reference points in the maxillary base relined with direct, hard reline resin was lowest, and those relined with light-curing resin and heat-curing resin were lower and were not significantly different. 5. After storage for 4 weeks in orator at room tempeature, linear shrinkage of distance between ridge crests of dentures relined with heat-curing resin was highest and that of distance between denture borders was not significantly different. 6. The dimensional changes of relined dentures during storage in water was not significant except those of distance between denture borders relined with light-curing resin at 1 day and 1 week storage in water. 7. At low magnification (x40) of SEM examination, the surface textures of three resins were similar except light-curing resin which had some defects. At high magnification (x200), the surface textures of hard, direct reline resin were smooth with little defects, but those of heat-curing resin and light-curing resin w ere irregular.