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

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.5
• /
• pp.63-71
• /
• 2010

This paper is about a research of steam curing which is one of the curing methods for accelerating the early-age strength of pre-cast concrete. With cylinder mold and mock-up specimen, the research was executed to study the best cycle of steam curing temperature through quantifying cycle of steam curing and maximum temperature, while the required strength is developed under the early-age. Moreover, causes and measurements for the high temperature of concrete, which is due to the steam curing, and the crack, which occurs when removing steel form, are stated. Ultimately, the economical method of producing, which satisfies early-age strength development and quality assurance while manufacturing PC structure, is stated.

• Proceedings of the KAIS Fall Conference
• /
• 2011.05b
• /
• pp.913-916
• /
• 2011

본 연구는 중년의 건강지각과 양생 이행간의 관계를 파악하여 중년의 건강증진에 도움이 되고자 본 연구를 시도하였다. 방법 : 부산광역시 K 대학 사회교육원 및 K대학 야간 재학생 및 사회교육원에 수강중인 250명 가운데 일부 자료가 누락된 56명을 제외한 총 194명을 대상으로 분석하였다. 자료 분석은 spss win 18.0 을 사용하여 다음과 같이 분석하였다. 일반적 특성은 빈도와 백분율, 건강지각 정도와 양생 이행정도는 평균과 표준편차로, 일반적 특성에 따른 건강지각과 양생 이행 정도는 t-test와 ANOVA, Scheffe' test, 건강지각과 양생 이행 정도의 상관관계는 Pearson's correlation으로 분석하였다. 결과 :중년여성의 일반적 특성에 따른 건강지각은 연령에서 통계적으로 유의한 차이가 있었다. 중년여성의 일반적 특성에 따른 양생은 결혼여부, 직업 상태와 음주 경험에 통계적으로 유의한 차이가 있었다. 건강지각과 양생 간의 상관관계에서는 유의한 상관관계가 없었다. 결론 : 본 연구의 추후 효과를 규명하기 위한 반복연구와 건강지각과 양생의 간호중재프로그램의 효과 검증하는 연구가 필요하다.

• Journal of the Korea Concrete Institute
• /
• v.15 no.4
• /
• pp.541-548
• /
• 2003

This study is to investigate the temperature curve 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 reducing 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 evaluation in-place concrete strength.

• 한국노년학
• /
• v.32 no.4
• /
• pp.1137-1146
• /
• 2012

The purpose of this study was to investigate differences on empowerment and YANGSAENG - traditional oriental health promotion - depression and non-depression for the elderly. This Study was a descriptive survey using convenience sampling. Elders(N=215), who agreed to participate in this study completed a self-report questionnaire from October to November of 2010. The collected data were analyzed with the SPSS 17.0 program, which was used for frequency, percentage, mean, standard deviation, t-test and Pearson correlation coefficients. The major findings of this study were as follows. 1) The mean(${\pm}$standard deviation) scores of each measure in this study were 6.61(${\pm}3.53$) for depression, 77.44(${\pm}11.87$) for empowerment, and 109.88(${\pm}18.19$) for YANGSAENG. 37.7% participants belong to the depression group. 2) There were significant differences between depression and non-depression on empowerment(t=6.62, p<.001), YANGSAENG(t=5.31, p<.001). 3) Specifically, among 8 subcategories of YANGSAENG, there were significant differences on Morality Yangsaeng(t=5.93, p<.001), Mind Yangsaeng(t=5.95, p.<001), Diet Yangsaeng(t=3.229, p=.002), Activity and Rest(t=2.21, p=.028), Exercise Yangsaeng(t=4.21, p.<001) and Sleep Yangsaeng(t=4.18, p<.001). 4) Lower depression scores were significantly related to having higher empowerment score(r=-.495, p<.001) and a higher YANGSAENG score(r=-.359, p<.001). Higher empowerment was significantly related to having higher YANGSAENG(r=.351, p<.001). In conclusion, Developing nursing intervention for the depression of the elderly needs more empowerment and more health promotion.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.3
• /
• pp.267-275
• /
• 2018

This study is to investigate the effect of various temperature and humidity conditions on the strength and efflorescence of alkali activated slag cement(AAS) using the red mud. As a result of examining the strength and efflorescence characteristics of AAS mixed with red mud according to the curing conditions, The compressive strength and flexural strength were the highest at 28 days, but the absorption rate, efflorescence area and soluble $Na^+$ elution were lowest in standard wet curing compared to the air curing, high temperature curing and low temperature curing.

• International Journal of Highway Engineering
• /
• v.7 no.2 s.24
• /
• pp.45-55
• /
• 2005

It is known that the Q/C(Quality Control) in the early age of portland cement concrete(PCC) pavement gives a huge effect on long term pavement performance. Thus, many studies regarding the construction of PCC pavement have focused on how to assure construction quality at the early age stage. Curing is one of the most important factor in Q/C of PCC pavement. Membrane curing that protects the evaporation of moisture by placing an impermeable layer on the slab surface is the most common practice for curing the PCC pavement. In order to improve the membrane curing practice, the rate of curing compound should be optimized. However, the optimum rate of curing compound considering Korean weather and environmental conditions has not been specified in the pavement construction specifications. In this study, a proper application rate was recommended in terms of minimizing evaporation with several full-scale tests where various rates of curing compound have been applied. Four test sites on the expressway were enlisted during the summer of 2002 and 2003. Application rates tested were in the range of $0. The rate of evaporation, the temperature pattern of the slab and the pulse velocity of concrete surface have been monitored at each test construction. The result from this study showed that the rate of current construction was approximately $160ml/m^2$ and that approximately $400ml/m^2$ of curing application was recommended as the proper rate for minimizing the moisture evaporation.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.1
• /
• pp.33-40
• /
• 2018

Currently, in South Korea, because of reducing the construction period or treating wasted water, there are some cases of missing wet curing for concrete structure even though for high strength concrete. This air curing conditions is considered to cause increased possibility of compressive strength decrease, and increasing drying or autogenous shrinkages. As a solution of shrinkage of concrete, The authors' research team conducted the research on improving durability of concrete with decreasing autogenous shrinkage by adding the oil or fat to induce the saponification. Therefore, in this research, the influence of curing method on compressive strength, shrinkage on evaporation rate of high strength mortar including high volume supplementary cementitious materials (SCMs) was evaluated depending on various curing methods such as air curing, drying after painting emulsified refined cooking oil (ERCO), and drying after 7 and 28 days' wet curing. The experimental result showed the air curing method caused approximately 50% of decreased compressive strength and 1.9 times of increased shrinkage rather than the 28-day-wet curing method, thus it was known that the wet curing significantly influences on performance of high strength mortar using high volume SCMs. However, the ERCO painting curing caused decreased performance of concrete rather than drying after 7 days curing while it caused improved performance of concrete than entire period air curing.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.2
• /
• pp.175-181
• /
• 2017

The purpose of this study is evaluating the characteristics of tensile strength of UHPC and examining tensile performance of notched specimens by direct tensile test. For test variables, 120, 150, and 180MPa of target design standard strength were aimed at. With general water curing and $90^{\circ}C$ high temperature steam as curing conditions, the properties were reviewed. Overall, it was represented that the specimens of notch-type direct tensile strength concrete was effective in inducing central cracks compared with existing direct tension specimens. Through this, it was judged that data construction with high reliability was possible. Above all, in a graph of direct tensile strength and strain, in the case of steam curing at high temperature, there was great difference of initial tensile strength compared with water curing. As passing of ages, an aspect that the difference gradually decreased was shown. Maximum tensile strength was found to increase steadily with increasing age for all target design strengths in water curing, in the case of steam curing, the tendency to increase significantly due to the initial strength development effect at 7 days of age. The initial crack strength increases with age in case of underwater curing, in the case of steam curing, it was higher than that of water curing in 7 days, while the strength of 28 days was lowered. In this part, it is considered necessary to examine the arrangement condition of the steel fiber.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.2
• /
• pp.50-59
• /
• 2020

Superabsorbent Polymer (SAP) expands inside concrete by absorbing water and contracts as it discharges water. Through this process, concrete can achieve the internal curing effect, but the space occupied by the expanded SAP remains as a void. In this study, the effects of SAP internal curing and voids were evaluated by evaluating the fundamental properties and chloride penetration resistance of SAP mixed concrete. Also, to evaluate the internal curing effect by SAP, the tests were carried out under water and sealed curing conditions, respectively. From the result, the compressive strength of water curing did not differ significantly according to the mixing ratio of SAP. In the case of sealed curing, however, the compressive strength tended to increase as the mixing ratio of SAP increased. The internal curing effect of sealed curing was considered to have influenced the increase in compressive strength. In the case of the chloride diffusion coefficient, the diffusion coefficient tended to decrease as the mixing ratio of SAP increased. In particular, as the sealed curing is applied, the chloride penetration resistance is further improved due to internal curing effect. If the curing conditions are different, it is considered inappropriate to estimate the chloride penetration resistance by the surface electrical resistivity.