• 한국농공학회지
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• 제26권3호
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• pp.46-58
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• 1984

This study was carried out to investigate the compressive strength and the other effects varying to seasons and curing days on the wet curing conditions of the plain concrete. The results obtained are summarized as follows; 1. The longer the wet curing days and the higher the temperature, the greater the compressive strength was expected. 2.。$_2$8, compressive strength of concrete at 28 days under the dry curing conditions showed a range in 64-76% of that under the wet curing conditions. 3. The seasonal variations in the compressive strength under the wet curing showed in order of summer>spring=autumn>winter, and that under the dry curing were in order of spring ≒autumn> summer> winter. 4. In order to obtain 90% of the design compressive strength, 7 days in spring or autumn and 2 weeks of the wet curing in summer were required. 5. The compressive strength of concrete under the wet curing by using wet straw bag cover was almost the same as that of water curing method. 6. Under the wet curing conditions, the higher the temperature, the greater the effect of the curing of concrete was obtained, however, the compressive strength of concrete was decreased under relatively higher (over 15$^{\circ}$ C) and lower temperature (below 4$^{\circ}$C). 7. Freezing damage was occured when temperature was below 0$^{\circ}$ C and humidity was relatively high. 8. A considerable differnce between estimation of $^{\circ}$$_2$8 from $^{\circ}$7 and measured one was appeared in case of the dry curing conditions. Oregon formula was appeared to be acceptable under the wet curing conditions. 9. In relationship between $^{\circ}$$_2$8 and $^{\circ}$7~, $^{\circ}$28=1. 52 $^{\circ}$7 under the wet curing conditions except winter season, and $^{\circ}$$_2$8 =(1.39-1, 48)$^{\circ}$7 under the dry curing conditions were shown.

• International Journal of Concrete Structures and Materials
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• 제9권4호
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• pp.487-498
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• 2015

A proper initial curing is a very simple and inexpensive alternative to improve concrete cover quality and accordingly extend the service life of reinforced concrete structures exposed to aggressive species. A current study investigates the effect of wet curing duration on chloride penetration in plain and blended cement concretes which subjected to tidal exposure condition in south of Iran for 5 years. The results show that wet curing extension preserves concrete against high rate of chloride penetration at early ages and decreases the difference between initial and long-term diffusion coefficients due to improvement of concrete cover quality. But, as the length of exposure period to marine environment increased the effects of initial wet curing became less pronounced. Furthermore, a relationship is developed between wet curing time and diffusion coefficient at early ages and the effect of curing length on time-to-corrosion initiation of concrete is addressed.

• 한국연초학회지
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• 제20권1호
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• pp.13-18
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• 1998

In the flue curing process, the wet bulb temperature is usually controlled at a constant level. To improve the quality of flue cured leaves, we studied the effect of the cyclic change of wet bulb temperature at the yellowing stage of flue curing on physical properties of cured leaves. The wet bulb temperature was automatically controlled between preset high (38℃) and low point (35℃) every one hour cyclically. As a result, the acceleration of the increase in the physical properties of cured leaves were observed. The leaves cured by this method were more or less orange in color, better bodied, and less brittle compared with the leaves produced by conventional curing. However, the leaves cured by this method had a little sharpness and harshness. As to the physical properties, there was decreased in occurrence of flat leaves than that of conventional ones. On the other hand, in case of cyclic curing method, increase of price per kg reached to 2-3% compared with those of conventional ones.

• 한국농공학회지
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• 제22권3호
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• pp.60-74
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• 1980

Soil-cement mixtures involve problems in it's durability in grain size distribution and mineral composition of the used soils as well as in cement content, compaction energy, molding water content, and curing. As an attempt to solve the problems associated with durability of weathered granite soil with cement treated was investigated by conducting tests such as unconfined compression test, it's moisture, immers, wet-dry and freeze-thaw curing, mesurement of loss of weight with wet-dry and freeze-thaw by KS F criteria and CBR test with moisture curing on the five soil samples different in weathering and mineral composition. The experimental results are summarized as follows; The unconfined compressive strength was higher in moisture curing rather than in the immers and wet-dry, while it was lowest in freeze-thaw. Decreasing ratio of unconfined compressive strength in soil-cement mixtures were lowest in optimum moisture content or in the dry side rather than optimum moisture content with freeze-thaw. The highly significant ceofficient was obtained between the cement content and loss of weight with freeze-thaw and wet-dry. It was possible to obtain the durability of soil-cement mixtures, as the materials of base for roads, containing above 4 % of cement content, above 3Okg/cm$_2$ of unconfined compressive trength with seven days moisture curing or 12 cycle of freeze-thaw after it, above 100% of relative unconfined compressive strength, 80% of index of resistance, below 14% of loss of weight with 12 cycle of wet-dry and above 1. 80g/cm$_2$ of dry density.

• 한국연초학회지
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• 제20권1호
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• pp.19-25
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• 1998

The bulk curing experiment to the improve the quality of flue-cured leaves were carried out to evaluate relationship between cyclic curing and conventional curing method. We studied the effect of the cyclic change of wet bulb temperature at the yellowing stage of flue curing on chemical properties of cured leaves. The wet bulb temperature was automatically controlled between preset high($38^{\circ}C$) and low point ($35^{\circ}C$) everyone hour cyclically during 12 hours after starting luring. As a result, the acceleration of the increase in the chemical properties of cured leaves were observed. As to the chemical properties, there was decreased in citric acid, increased in malic acid of the nonvolatile organic acids and all higher fatty acids content of leaves cured by this method compared with in that of conventional curing method, while a major chemical compounds in relation to aromatic essence of cigarette smoke in essential oil components of lured leaves was mostly higher in this method than those of conventional ones, and it was evaluated that there was decreased in CO, TPM, Tar, and $CO_2$ content of the cigarette smoke comparing to the conventional luring method.

• 한국건축시공학회지
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• 제18권1호
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• pp.33-40
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• 2018

우리나라의 많은 건설 공사에서는 건축물이 고층화 되면서, 공기단축 및 물의 처리 곤란 등의 이유로 고강도 콘크리트일지라도 습윤양생을 실시하지 않고 공사를 진행하는 경우가 존재한다. 이와 같이 건조 상태로 양생하게 되면 압축강도 감소, 건조수축 및 자기수축 등 수축변화가 크게 증가할 것으로 예상된다. 또한 본 연구팀에서는 기존의 연구로서 유지류를 콘크리트에 혼합할 경우 비누화 반응을 이용하여 콘크리트의 자기수축 저감 및 내구성 향상에 대한 연구를 진행한바 있다. 그러므로 본 연구에서는 양생방법을 비양생 건조, 유화처리정제식용유(ERCO) 도포 후 건조, 7일 수중양생 후 건조 및 28일 수중양생 후 건조 등 양생 방법 변화에 따른 혼화재 다량치환 모르타르의 압축강도 특성, 수분증발에 따른 수축변화 특성에 대하여 분석하였다. 실험결과는 양생방법으로 비양생 건조를 실시하게 되면 28일 수중양생을 실시하였을 경우보다 약 50% 전후의 강도저하와 1.9배의 수축 길이변화율 증가로 나타나, 혼화재 다량치환 고강도 모르타르에 있어 습윤양생이 매우 중요하게 영향을 미치는 것을 알 수 있었다. 단, ERCO 도포의 경우는 강도 및 수축변화측면에서 무양생인 건조보다는 우수하지만 7일 수중양생 후 건조보다는 성능이 저하하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.317-327
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• 2017

The addition of different types of polymers such as SBR, VAE, Acrylic, etc. in concrete and mortar leads to an increase in compressive, tensile and bond strength and decrease in permeability of polymer modified mortar (PMM) and concrete (PMC). The improvement in properties such as bond strength and impermeability makes PMM/PMC suitable for use as repair/retrofitting and water proofing material. In the present study effect of addition of fluoropolymer on the strength and permeability properties of mortar has been studied. In the cement mortar different percentages viz. 10, 20 and 30 percent of fluoropolymer by weight of cement was added. It has been observed that on addition of fluoropolymer in mortar the workability of mortar increases. In the present study all specimens were cast keeping the workability constant, i.e., flow value $105{\pm}5mm$, by changing the amount of water content in the mortar suitably. The specimens were cured for two different curing conditions. Firstly, these were cured wet for one day and then cured dry for 27 days. Secondly, specimens were cured wet for 7 days and then cured dry for 21 days. It has been observed that compressive strength and split tensile strength of specimens cured wet for 7 days and then cured dry for 21 days is 7-13 percent and 12-15 percent, respectively, higher than specimens cured one day dry and 27 days wet. The sorptivity of fluoropolymer modified mortar decreases by 88.56% and 91% for curing condtion one and two, respectively. However, It has been observed that on addition of 10 percent fluoropolymer both compressive and tensile strength decreases, but with the increase in percentage addition from 10 to 20 and 30 percent both the strengths starts increasing and becomes equal to that of the control specimen at 30 percent for both the curing conditions. It is further observed that percentage decrease in strength for second curing condition is relatively less as compared to the first curing condition. However, for both the curing conditions chloride ion permeability of polymer modified mortar becomes very low.

• 한국도로학회논문집
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• 제20권2호
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• pp.27-34
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• 2018

PURPOSES : It is necessary to prevent premature failure of concrete pavements caused by durability problems. The purpose of this study was to find factors affecting the durability of concrete pavements, and suggest improvement methods for existing concrete mix design. METHODS : Factors influencing durability were derived from laboratory test data for common field failure conditions and main properties of concrete cores taken from the field. The improvement of concrete properties was investigated by evaluating the performance of existing and proposed mix proportion designs and curing methods. RESULTS : The compressive strength and the absorbing performance of the low Blaine cement and the high-strength mixture were better than those of the Type I cement. Wet curing showed better compressive strength, elastic modulus, coefficient of thermal expansion, and absorption performance than air curing or compound curing. As a result of comparing concrete cores collected in the field, the sections with good durability showed good performance in terms of resistance to chloride ion penetration, absorption, and initial absorption rate. CONCLUSIONS : The absorption performance was considered as a possible foactor affecting durability of cement concrete pavements as a result of field core tests. In order to improve the durability of the pavement concrete, it is necessary to improve the existing mixtures and curing methods.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.305-312
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• 2002

To estimate the effects of lime and cement on the surplus soil, the engineering properties of the marine deposited clay and the fresh water clay were analyzed. The specimen were prepared under several curing conditions, namely, underwater curing, wet condition curing and underwater curing after heating. Unconfined compression strength were estimated after 7, 14, 28 and 60 days, respectively. The strength were steeply increased with time until first 14 days. Specially the increase of the strength of the heated soil were large.

• KCI Concrete Journal
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• 제12권1호
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• pp.79-89
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• 2000

This research developed an accelerated curing processe for cellulose fiber reinforced cement composites using vigorous reaction between carbon dioxide and cement paste. A wet-processed cellulose fiber reinforced cement system was considered. Carbonation curing was used to complement conventional accelerated curing. The parametric study followed by optimization investigation indicated that the carbonation curing can enhance the productivity and energy efficiency of manufacturing cellulose fiber reinforced cement composites. This also adds environmental benefits to the technical and economical advantages of the technology.