• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.141-148
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• 2017

This study is experimentally investigated the effects of various steam curing parameters on the early-age compressive strength development of high strength concrete (over 40 MPa) in the precast plant production. High strength concrete are used only ordinary portland cement (type I) and water-cement ratio selected 3cases (25%, 35% and 45%). Also, steam curing parameters are as followings ; (1) Preset period 2cases (3 hours and 6 hours) (2) Maximum curing temperature 3cases ($45^{\circ}C$, $55^{\circ}C$ and $65^{\circ}C$) (3) Maintenance time of curing temperature 3cases (4 hours, 6 hours and 8 hours) (4) Maximum rate of heating and cooling $15^{\circ}C$/hr. Initial setting time and adiabatic temperature rising ratio of these concrete according to water-cement ratio are tested before main tests and examined the compressive strength development for the steam curing parameters. Also compressive strength are compared with optimum steam curing condition and standard curing at test ages. As test results, the optimum steam curing conditions for high strength concrete(over 40 MPa) are as followings. (1) Preset period ; over initial setting time of concrete (2) Maximum curing temperature ; bellow $55^{\circ}C$ (3) Maintenance time of curing temperature ; bellow 6hours. Also strength development of steam curing concrete show in the reversed strength at 28 days. It is to propose an efficient steam curing condition for high strength concrete in the precast method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.35-38
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• 2003

The purpose of this study is to investigate the manufacture of light weight concrete panel using the artificial light-weight aggregate as a part of the substitution of foamed styrene and polyurethane because of narrow allocable temperature Bone in use. The experimental parameter of this study is 40, 60 and 8$0^{\circ}C$ of curing temperature at 100% relative humidity and the type of admixture such as cement, 6mm glass fiber and St/BA emulsion. Testing item is compressive and flexural strength and strength of specimen cured at standard condition is compared to that of specimen cured at 40, 60 and 8$0^{\circ}C$ of curing temperature at 100% relative humidity. As a result or this, it was revealed that the maximum or strength is developed in 6$0^{\circ}C$ or cure temperature at 100% relative humidity in case of the most of the specimen. Specimens modified by St/BA emulsion show the highest development of strength dependent on the curing tmeperature. So, it seems to be effective that evaporation curing method shoud be considered to curing the specimen as the panel core.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.255-256
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• 2011

This study investigates the effect of a curing condition on the temperature history and strength development of concrete under -10℃. Combination of various curing methods was applied, i.e. a conventional form was combined with compressed insulation, heat panel and heat cable. Results showed that the concrete cured by a single use of a conventional form resulted in serious deterioration of early strength development. However, other concretes cured by the proposed curing methods maintained the temperature of the concretes between 5 and 20℃, and thus resulted in no frost damage.

• Journal of the Korea Institute of Building Construction
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• v.3 no.4
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• pp.87-94
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• 2003

This study is to investigate the temperature hysteresis and development of compressive strength due to the curing conditions and to evaluate the optimum curing condition of test specimens showing the same development of strength to that of real structures in cold weather. The results of temperature curve with curing conditions in mock-up tests showed the trend of decrease plain concrete with insulation form, plain concrete with heating, concrete with accelerator for freeze protection, and control concrete in turn. The strength development of plain concrete of inside and outside of shelter showed the very slow strength gains due to early freezing, but that of concrete with accelerator for freeze protection showed the gradual increase of strength with time. From this, it is clear that accelerator for freeze protection has the effects of refusing the freezing temperature and accelerating the hardening under low temperature. Strength test results of small specimens embedded in members and located in insulation boxes at the site are similar to that of cores drilled from the members at the same ages, thus it is clear that these curing methods are effective for evaluating in-place concrete strength

• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.141-148
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• 1996

The pulished works on Accelerated Curing Effect were generally performed around from 1960 to 1970th century for 18 to 24 hours - total curing periods. It is not possible to define the effect of temperature rise because those results were obtaine mainly by using the manually operated steam-curing tank. Thus, it may not be available to apply those data immediately on the domestic PC wall production line. The testing specimens were made from the standard mix proportion according to those of domestic PC factories to establish a basic data for the Accelerated Curing Effect. The experimental tests were conducted according to the conditions of each sub-curing periods. By comparing the results of compression tests on de-molded and 28-day water-curing specimens, we find that the most effective curing condition to obtain more than the required design strength after 28 day of water curing may be as follows: the presteaming period does not affect seriously and less than$30^{circ}C/hr$- the rate of temperature rise andless than $82^{circ}C$ - maximum temperature are necessary. It seems that post-curing procedure is very important factor to increase the effect of accelerated curing.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.107-111
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• 1996

The testing specimens were made from the standard mix proportion according to those of domestic PC factories to establish a basic data for the Accelerated Curing Effect. The experimental tests were conducted according to the conditions of each sub-curing periods. By comparing the results of compression tests on de-molded and 28-day water-curing specimens, we find that the most effective curing condition to obtain more than the required design strength after 28 days of water curing may be as follwings; the presteaming period does not affect seriously and less than $30^{\circ}C$/hr-the rate of temperature rise and less than $82^{\circ}C$ - maximum temperature are necessary. It seems that post-curing procedure is very important factor to increase the effect of accelerated curing.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.976-981
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• 2012

In this study, hardness, microstructure and temperature of glass transition are measured respectively by using SEM (Scanning electron microscope) and DSC (Differential scanning calorimeter) to analyze the effects on material properties by after-curing in the epoxy resin. As the result of hardness test according to the after-curing conditions, the higher the temperature of after-curing, hardness and heat resistance are, the higher hardness is. As a result of microstructure for each specimen by SEM, it could be confirmed that the specimen with after-curing has more dense fracture surface. It is also found that temperatures of glass transitions by DSC are comparatively higher in the specimens with after-curing, and the differences between after-curing conditions are negligible.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.124-129
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• 2001

The research on anticorrosive of valve for ship, waterworks, and drainage system is very important. The purpose of this paper is to develop the metal/polyurethan adhesive technique at insider of the value to prevent corrosion in the value. It is performed to the bending strength test by using metal /polyurethan in the metals (SB41, Al6061). It is investigated to the effects of bending strength on curing temperature, preheating time and curing time, and to the fracture mechanism of metal/polyurethan adhensived specimen. As a results, we find that the bending strength is the highest at curing temperature of 11$0^{\circ}C$ and the curing time is 60 minutes in metal/polyurethan adhesive specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.785-788
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• 2006

This paper investigates the temperature history of slab mock-up specimens with various surface curing sheets, in order to determine a favorable surface curing method in hot weather condition. Test showed that insulating double bubble sheets+aluminum foil simultaneously on the upper section of a specimen prevented an increase of sudden temperature and a decrease of vaporization when placed during the hot weather condition. It also secured the high strength in early age. Therefore it is found that using the double bubble sheets+aluminum foil on concrete surface declined the plastic and drying shrinkage and inclined the early strength, thus improving the concrete quality.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.458-463
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• 1996

Fresh ginger harvested in Seosan, Choongchengnam-do, was used to investigate the pretreatment effect before long-term storage. Wounded ginger were cured at the temperature of 25, 30, $35^{\circ}C$ and the RH 83 and 93% for 1, 3, 5, 7 days, respectively Then the cured ginger were stored in the laboratory scale storage room ($12^{\circ}C,$ 95% RH) in order to find out the optimum curing condition. At a constant temperature and a RH. the longer ginger were cured, the more their weight was decreased; at a constant temperature and a curing period, the higher RH was, the less weight was lost. During the curing process, sprouting rate was accelerated at temperature higher than $30^{\circ}C$ and humidity higher than 90%; mold growing was observed at any temperature and humidity, but especially at $35^{\circ}C$ the rate was relatively faster when the curing time was increased. Hardness of wound surface cured at 93% RH was relatively higher than those cured at 83% RH at all temperatures. The weight loss of store ginger after curing was $2.0{\sim}8.2$ after 30 days and $7.2{\sim}14.2%$ after 60 days storage. Compared with all results through a screening procedure, the condition of 3-days curing at $25^{\circ}C$ and 93% RH showed th best result for minimizing quality changes during storage.