• 한국안전학회지
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• 제28권1호
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• pp.52-56
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• 2013

The purpose of this study is to evaluate the influence of form-oil on steam-cured concrete surface condition. Based, viscosity(high, medium, low) and flash point($26^{\circ}C$, $70^{\circ}C$) of form oil were considered as test variables. The digital image process method was applied for the extraction of air-void area from concrete surface. Test result showed that oil-based form oil reduced air-void by approximately 46% compared to water-based form oil, and the higher the viscosity was, the smaller air-void rate was. In addition, it was conformed that flash point of form oil had a considerable influence on the surface condition of steam-cured concrete.

• 한국건설순환자원학회논문집
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• 제3권1호
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• pp.1-6
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• 2015

최근 $CO_2$ 감축을 위해 고로슬래그 미분말과 같은 혼화재의 치환율을 높이기 위한 연구가 활발히 이루어지고 있다. 프리캐스트 콘크리트의 경우 증기양생을 실시하기 때문에 혼화재의 치환율을 높여도 초기 강도 확보에 유리한 것으로 알려져 있다. 하지만 다양한 증기양생이력에 따른 압축강도 특성에 대한 연구가 요구된다. 따라서 본 연구에서는 고로슬래그 다량치환(질량비 60%) 시멘트 콘크리트의 증기양생 이력에 따른 콘크리트 압축강도 특성을 규명하기 위해 물-결합재비(W/B) 32, 35%, 단위수량 135, $150,165kg/m^3$ 수준으로 콘크리트를 제조하였다. 그리고 공시체의 최고온도(50, $60^{\circ}C$) 및 최고온도유지시간(5, 6, 7hr)을 변수로 증기양생을 실시하였다. 실험결과, 증기양생을 통해 높은 초기강도를 얻을 수 있었지만 28일 압축강도에서 강도가 저하되는 현상을 확인할 수 있었다. 따라서 고로슬래그 다량치환 시멘트 콘크리트의 프리캐스트 콘크리트 부재에의 적용을 위해서는 탈형강도 및 요구강도를 확보할 수 있는 증기양생 이력에 대한 추가적인 연구가 필요하다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.170-176
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• 1997

The published works on steam curing effect have been generally concentrated on the subject, "compressive strength". However a practical test for durable steam curing concrete products has not been performed in domestic. In this study, the maximum temperature of steam is considered as a major variable to investigate the freezing and thawing resistance of the steam curing concrete. All of the specimen were cured for 24 hours which included presteaming 4 hour. Finally we found that the most effective curing condition is the case of one-day and 14-day specimens after the 24 hours steam curing at $74^{\cire}C$ degree curing temperature. It is also found that the durability of one-day samples are much weaker than those of 14-day samples. Consequently, we can conclude that the samples that produced immediately after a steam curing are more possible to deteriorate from the freezing and thawing environment.vironment.

• International Journal of Concrete Structures and Materials
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• 제4권1호
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• pp.9-15
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• 2010

Silica fume is a common addition to high performance concrete mix designs. The use of silica fume in concrete leads to increased water demand. For this reason, Florida Department of Transportation (FDOT) allows only a 72-hour continuous moist cure process for concrete containing silica fume. Accelerated curing has been shown to be effective in producing high-performance characteristics at early ages in silica-fume concrete. However, the heat greatly increases the moisture loss from exposed surfaces, which may cause shrinkage problems. An experimental study was undertaken to determine the feasibility of steam curing of FDOT concrete with silica fume in order to reduce precast turnaround time. Various steam curing durations were utilized with full-scale precast prestressed pile specimens. The concrete compressive strength and shrinkage were determined for various durations of steam curing. Results indicate that steam cured silica fume concrete met all FDOT requirements for the 12, 18 and 24 hours of curing periods. No shrinkage cracking was observed in any samples up to one year age. It was recommended that FDOT allow the 12 hour steam curing for concrete with silica fume.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.441-444
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• 2006

Extrusion molding concrete panel is cured two times, that is the steam curing at atmospheric pressure and a high-pressure steam curing(autoclaving). Steam curing at atmospheric pressure is done before autoclaving and to acquire the proper strength for treat in process. Though this curing is the important factor on the quality of product and the speed in manufacturing process, it was not evaluated properly so far. Because of ignorance about curing, some engineers even think that the dry curing is better than the steam curing. This study is to investigate the properties of specimen according to variation of curing conditions in the coring chamber such as laboratory scale, pilot plant, and commercial plant. As estimating, in case of steam curing at atmospheric pressure to make extrusion molding concrete panel, moisture curing is better than dry curing and the desirable maximum temperature in curing chamber is about $50^{\circ}C$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.695-702
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• 1998

The purpose of this study is to investigate the mechanical properties of precast concrete cured by accelerated curing methods such as, steam curing method and warm water curing method varing maximum temperature of curing along to the period of curing. Some specimens are cured by accelerated curing method(warm water curing method) and then deposited in the storehouse. The others are deposited in the storehouse directly. All of these are cured until being tested to compare these two group's mechanical characteristics for each period 3days, 7days, 28days. The goal of this comparison is to estimate the efficiency of accelerated curing method in the case of precast concrete stocked in the field or warehouse for a long term and to make guide line for factory manager to make a economical products of concrete of a good quality. We can conclude some guide lines 1) It is not efficient to cure concrete with accelerated method at higher than 80℃. 2) The continuing of curing period more than 36hr makes damage to concrete in using accelerated curing method. 3) The strength revelation of concrete cured by accelerated curing methods, added rice husk ash more delayed than OPC concrete done but the strength of maximum value is higher than OPC concrete. 4) It is not efficient to use accelerated curing method in the case of storing the products for more than 7days in the aspect of mechanical properties.

• 한국구조물진단유지관리공학회 논문집
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• 제14권5호
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• pp.63-71
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• 2010

본 논문은 프리캐스트 콘크리트 구조물의 조기강도를 촉진시키기 위한 양생공법 중에서 증기양생에 대한 연구내용으로서, 콘크리트 원주형 공시체와 목업체의 실험을 통하여 초기재령에서 요구되는 강도가 발현될 수 있는 증기양생주기와 최고온도를 정량화하여 최적 증기양생온도주기를 고찰하였다. 또한 고온의 증기양생으로 인하여 발생된 콘크리트의 높은 온도와 거푸집 제거시에 발생되는 균열의 발생원인과 대책에 대하여 기술하였으며, 궁극적으로는 PC 부재를 생산하는 과정에서의 조기강도발현과 품질확보를 동시에 만족하면서 경제성 있는 제작방법을 제시하였다.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.391-401
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• 2017

In this study, the effects of water-to-binder (W/B) ratio and replacement ratio of blast furnace slag (BFS) on the compressive strength of concrete were first investigated to determine an optimized mixture. Then, using the optimized high-strength concrete (HSC) mixture, hooked steel fibers with various aspect ratios and volume fractions were used as additives and the resulting mechanical properties under compression and flexure were evaluated. Test results indicated that replacement ratios of BFS from 50 to 60% were optimal in maximizing the compressive strength of steam-cured HSCs with various W/B ratios. The use of hooked steel fibers with the aspect ratio of 80 led to better mechanical performance under both compression and flexure than those with the aspect ratio of 65. By increasing the fiber aspect ratio from 65 to 80, the hooked steel fiber volume content could be reduced by 0.25% without any significant deterioration of energy absorption capacity. Lastly, complete material models of steel-fiber-reinforced HSCs were proposed for structural design from Lee's model and the RILEM TC 162-TDF recommendations.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.27-28
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• 2022

In this study, the mechanical properties of resource-recycling concrete containing concrete sludge waste as main materials was compared depending on whether supercritical CO2 curing was applied for the realization of CCU technology. After supercritical CO2 curing, the compressive strength of the steam-cured specimen was lowered, but it was confirmed that the compressive strength of the underwater-cured specimen was improved.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.267-268
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• 2009

Precast Concrete 모의부재를 제조할 때 사용시멘트 및 가열양생조건이 각각 다른 콘크리트부재의 온도이력특성을 총괄적으로 검토했다.