• Journal of Industrial Technology
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• v.16
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• pp.39-44
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• 1996

The waste basalt might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Experiments were performed with the variables of W/C ratio, S/A, Crushed stone/Basalt ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that the W/C ratio is the most important factor to the concrete strength. The substitute of waste basalt up to 100% has little influence, saying that it can substitute the coarse aggregate without damaging the concrete properties.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.58-63
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• 1996

The waste foundry sand might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Exprements were performed with the variables of W/C ratio, S/A, Sand/Waste foundry sand ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that the W/C ratio is the most important factor to the concrete strength. The substitute of waste foundry sand up to 30% has little influence, saying that it can substitute the fine aggregate without damaging the concrete properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.737-742
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• 2002

The chief factors for the penetration and diffusion of chloride ions in concrete are water-cement ratio(w/c), aging, thickness of cover concrete, chloride ions concentration of given environment, wet and dry conditions and etc. In this study, effect of w/c and aging on the characteristics of chloride ions diffusion in concrete were researched when environmental factors for the penetration and diffusion of chloride ions were constant. For this purpose, the voltages passing through the diffusion cell were measured by using accelerated test method using potential difference, and then diffusion coefficients of chloride ions by using Andrade's method were estimated for 44%, 49.5% and 55% of w/c, respectively. As a result, correlation among diffusion coefficients of chloride ions, w/c and aging were concluded through multiple regression model.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.277-283
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• 1998

In this study we changed W/C into 45, 50, 55, 60%, mixed sea sand which is often used as a replacing aggregate according to the lack of recourse with river sand in the ratio of 5:5 and producted antiwashout underwater concrete. We measured slump flow, air value, pH and suspension in the fresh concrete. After testing each W/C through unit weight and compressive strength of specimen which is produced and cured in the air and salt water it was founded that if sea sand was properly used after salt manufacturing, there will be no bad influence to antiwashout underwater concrete. The characteristic of them showed excellent, when W/C was 50%.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1189-1194
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• 2000

The purpose of this investigation is to establish which consequence is happen about initial curing concrete's compressive strength of 7days, 28days which changes W/C ratio by the change of vibrating speed and vibrated time. An experimental parameter is fixed 4 degrees of W/C ratio(45%, 50%, 55%, 60%), 3 degrees of vibrated time(3hr, 6hr, 12hr) and different vibrating speed(0.25kine, 0.5kine, 1kine). As the result, compressive strength of 7days was increased when vibrating speed and vibrated time is 1kine, 12h and also compressive strength of 28days was increased when vibrating speed and vibrated time is 0.25kine and 3hr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.109-110
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• 2005

We have suggested sputtered W-C-N thin film for preventing thermal budget between semiconductor and metal. These results show that the W-C-N thin film has good thermal stability and low resistivity. In this study we newly suggested sputtered W-B-C-N thin diffusion barrier. In order to improve the characteristics, we examined the impurity behaviors as a function of nitrogen gas flow ratio. This thin film is able to prevent the interdiffusion during high temperature (700 to $1000^{\circ}C$) annealing process and has low resistivity ($\sim$200$\mu{\Omega}-cm$). Through the analysis of X-Ray diffraction, resistivity and XPS, we studied structure behavior of W-B-C-N diffusion barrier.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.5
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• pp.810-816
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• 1996

This study was conducted to measure the hydration characteristics at $20^{\circ}C$ and investigated the effect of water to rice ratio(v/w) on the texture properties of cooked rice of ten different varieties based on maturity. Water absorptions during soaking were completed between 30min and 35min at $20^{\circ}C$. The ranges of equilibrium moisture content were between 0.3247g $H_2O/g$ dry matter and 0.3577g H201g dry matter. During the cooking process, the water content of cooked rice increased 6~7% with increased the ratio of water to rice from 1.4 to 1.6(v/w). The hardness(H) of cooked rice decreased, while the stickiness(-H) and -H/H ratio increased with increased ratio of water to rice.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.139-165
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• 1991

The properties of a investment material can be described by the consistency at the slurry state, the setting time, the compressive strength and the thermal expansion during the casting. In this study the effect of the production parameters which are included the ratio of quartz and cristobalite, the content of binder, the water powder ratio and the content and concentration of additives on the properties of the gypsum-bonded investments has been investigated with help of the consistency test, the vicat needle test, the compressive strength test, the thermal expansion test, x-ray diffraction and DTA thermal differential test. The experimental results showed that the constitution of a investment with W/P ratio of 0.34, 30% of gypsum, 0.8% aluminium sulfate, 2% magnesium sulfate, 0.6% sodium phosphate was adapted for the properties of the KDA Spec. No. 13 type I investment. The important experimental results are summarized as follows. 1. The consistency of the investment decreased with increasing amount of aluminium sulfate and decreasing amount of sodium phosphate. An addition of magnesium sulfate up to 2% an increase of the consistency was shown. But 3% magnesium sulfate in investment showed a decrease of consistency. The consistency did not vary significantly with a variation of the content of gypsum and cristobalite and the W/P ratio. 2. Aluminium sulfata and the magnesium sulfate promoted the hardening and the aluminium phoshpate delayed the hardening. The setting time increased with amount of gypsum. The effect of the matrix on the setting time was insignificant. With the W/P ratio of 0.34 the setting time was 14 min. 3. The compressive strength decreased with the amount of aluminium sulfate up to 0.25% and increased with the amount of aluminium sulfate greater than 3%. The compressive strength decreased as decreasing the amount of magnesium sulfate and gypsum and as increasing the W/P ratio. The effect fo the refractory on the compressive strength was also not significant. With the W/P ratio of 0.34 the compressive strength was $34Kg/mm^2$. 4. The 1st thermal expansion was found at the temperature near $250^{\circ}C$ and the steady state or the contraction stage was found at the temperature between $250^{\circ}C$ and $500^{\circ}C$. After this stage the 2nd thermal expansion took place at the temperature near $500^{\circ}C$. The amount of thermal expansion increased with decreasing the content of magnesium sulfate, aluminium sulfate and gypsum and the W/P ratio. And the amount of thermal expansion increased as the content of sodium phosphate ad cristobalite. With the W/P ratio of 0.34 the amount of total expansion was 1.2%.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.67-72
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• 2002

The purpose of this study is to investigate on the measurement of stress due to autogenous shrinkage of high strength concrete according to the W/C ratio at early age. The main parameters are as follows W/C ratio is 25, 30, 40%. The size of specimen is 10$\times$10$\times$150cm and the autogenous shrinkage strain is measured by the bonded strain gauge at the inside of the specimens. From the test, it is suggested that the autogenous shrinkage stress increased as W/C ratio decreased.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.143-150
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• 1997

The maturity concept was adopted to predict the strength of concrete, which was subjected to same temperature conditions and variable curing conditions. Penetration test and compressive test were conducted to measure the initial and final setting time and the compressible strength of concrete specimen, respectively. Also, the temperature and time were recorded at some intervals of time for calculating the maturity. The initial and final setting were delayed as the w/c ratio increased and curing temperature decreased. The activating energy decreased as the w/c ratio increased. The relationships at the relative strength and the maturity were proposed at different w/c ratio for the same temperature curing condition, and these were applied for the variable curing conditions. The results indicated that the difference between the strength of the proposed and the specimen was big at 1 days's age but quite similar after 3 day's age.