서중(暑中)환경에서 Mock-up 실험을 통한 콘크리트 품질특성에 관한 연구

임석도(Lim Suk-Do),정상진(Jung Sang-Jin),백민수(Paik Min-Su),김성덕(Kim Seong-Deok) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.8

When concrete is manufactured and used for construction in a hot-weather environment, the increase in the concrete temperature due to the high air temperature may lead to a high hydration temperature and thermal expansion that may affect the long-term strength of the concrete. In this study, a Mock-up specimen of an actual post was introduced in terms of concrete casting and maintenance in a hot-weather or summer environment. This study reviewed and evaluated the effects of hot weather on concrete hydration temperature and strength, and compared the results with those in the standard seasons (spring and fall), during which the temperature is similar to the standard curing temperature of 20℃. There was a slump loss as a flow characteristic as time passed, which indicated that transport and outside air temperature changes must be reviewed in a construction site. In hot weather, the strength of the specimen varied via the curing method, and the specimen achieved the desired strength on the 28th day. The core strength was high at the lower part of the specimen. With the passing of time, the strength in hot weather became similar to that in the standard period. As for the hydration temperature, the temperature rise was faster in the hot-weather period due to the effect of outside air. The maximum difference between the temperatures at the center and on the surface was 8-13ºC depending on the material and the desired strength. The temperature crack index was 1.1 at 24㎫ in standard period, 1.2 at 24㎫ in the hot-weather period, 1.3 at 40㎫ in the standard period, and 1.7 at 40㎫ in the hot-weather period. The probability of crack occurrence was lower when the desired strength was higher and the concrete was cast in the hot-weather period.

콘크리트充塡 鋼管構造(CFT)用 高流動 高强度 콘크리트에 관한 實驗的 硏究

강용학(Kang Yong-Hak),정근호(Jung Keun-Ho),김진호(Kim Jin-Ho),정상진(Jung Sang-Jin),최문식(Choi Mun-Sik) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.6

CFT(Concrete Filled steel Tube) is a structure of circular or squared of steel column filled with concrete. The steel tube holds the concrete inside and that makes this structure to perform superior features on stiffness, proof stress, transformation, fire resistance and also on construction itself. In this study, research has been done on the basic property of matter such as fluidity, resistance on segregation, compressive strength, setting icons of the concrete filled in the steel tube under conditions of cold and hot weather. This was compared to the data started in the index of planning and construction of steel tube structure, and mock up test has been done under air curing and adiabatic curing condition. In this study, hydration heat variations while the concrete hardening, core samples were extracted to analysis compressive strength and unit weight. With the results from the tests, it is possible to conclude that adiabatic cured mock up show better proof stress condition under cold weather condition, and air cured mock up show better proof stress condition under hot weather condition. In order to have a satisfactory quality control, special curing management according to the weather conditions is required. Especially when using the method of tremie, special care is needed on the decreasing proof stress of the concrete between two diaphragms.

시공단계 및 계절별 온도영향을 고려한 롤러다짐콘크리트댐의 온도응력 해석

차수원(Cha Soo-Won),장봉석(Jang Bong-Seok) 대한토목학회 2008 대한토목학회논문집 A Vol.28 No.6A

국내 최초로 시공되는 롤러다짐 콘크리트 댐(RCD)의 온도균열 관리방안 수립하기 위하여 RCD 공법의 시공특성인 층 (layer) 타설 방식을 고려하여, 댐체의 온도분포 및 온도응력 해석을 수행하였다. RCD 공법은 수 백 개의 시공단계로 구성 되어 있고, 실제 타설 층을 시공단계로 해석하는 것과 6층을 한 시공단계로 시공하는 경우를 비교하여 해석 단계의 단순화 기능성을 검토하였으며 , 단위시멘트량이 130 ㎏/㎥ 내외로 발열량이 매우 작은 RCD 배합의 경우에도 여름철에는 온도균열 지수가 1.0 이하로 나타나 온도관리의 필요성을 확인하였다. The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DLANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.

배합수 냉각방법 및 지연제 사용에 따른 서중 원전콘크리트의 특성

이승한(Lee, Seung-Han),정용욱(Jung, Yong-Wook),장석수(Jang, Seok-Soo),여인동(Yeo, In-Dong),최종오(Choi, Jong-Oh) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.9

온도차가 극심한 하절기와 동절기 콘크리트 타설의 경우 각종 균열의 발생, 콘크리트 품질불량, 내구성 및 강도저하 등 다양한 문제를 야기 시키고 있다. 특히 원전콘크리트의 경우 대량의 타설로 인한 4계절 연속시공이 이루 어져 서중환경에서 콘크리트 품질관리에 많은 문제점이 발생되고 있는 실정이다. 이에 본 연구에서는 서중환경에서 많이 사용되어지는 프리쿨링 공법 중 배합수 냉각방법과 지연제 사용이 원전콘크리트의 특성에 미치는 영향을 검토 하였다. 배합수 냉각방법은 냉수 5℃와 Ice Flake 50% 치환사용 하였으며, 지연제 사용에 따른 원전콘크리트의 굳지 않은 콘크리트 및 경화 후 콘크리트의 특성을 검토하였다. 굳지 않은 콘크리트 특성으로는 슬럼프, 공기량, 응결시간 및 경화 후 압축강도를 측정하였으며, 단열거푸집을 제작하여 손실되는 열을 최소화시켜 각 온도조건하에서 수화열을 측정하였다. 실험결과, 슬럼프 및 공기량 경시변화 종료시간은 20℃에서 120분, 40℃에서 40분으로 나타났으며, 관입 저항에 의한 응결시간은 배합수 냉각방법 및 지연제 사용 모두 초결과 종결을 지연시키는 것으로 나타났으나, 외기온 도가 상승할수록 지연폭은 감소하는 것으로 나타났다. 수화열은 배합수 냉각방법 모두 최고온도의 저감과 도달시간을 지연시키는 것으로 나타났으나, 지연제 사용의 경우 최고온도 저감효과는 없는 것으로 나타났다. 또한 재령별 압축강 도의 경우 3일, 7일의 초기재령에서 Plain과 비교하여 낮은 강도 값을 나타내었으나, 재령 28일에서는 설계기준강도를 모두 만족시키는 것으로 나타났다. In summer and winter, the difference between the temperature during the day and that during the night is high, which leads to various problems during concrete placement, such as cracks and defects in the concrete as well as low durability and strength. Although nuclear power plant concrete is widely used for placement in all seasons, particular attention must be paid to its quality during the summer. Therefore, we evaluated the effects of a cooling method for mixing water, which is a commonly used hot weather precooling method, and the use of a retarder, on the characteristics of Nuclear Power Plant concrete. In the cooling method for mixing water, cold water at 5 was used, with 50% of the water content consisting of ice flakes. The effects of using a retarder were evaluated by reviewing the characteristics of the cement at the unset stage and after hardening. To evaluate the characteristics of the unset cement, we measured the slump, air volumes, setting times, and pressure strengths after hardening. Furthermore, we measured the heat of hydration at different temperatures; the loss of heat was minimized using insulation. Both the slump time and the complete ageing time of the air volume were found to be 120 min at 20℃ and 40 min at 40℃. In the case when the cooling method for mixing water was used and in the case when a retarder was used, the initial and final sets by penetration resistance were delayed, and the delay decreased with increasing air temperature. For the heat of hydration, the cooling method for mixing water not only lowered the maximum temperature but also delayed its attainment. However, the use of a retarder had no effect on the maximum temperature. Moreover, in the early ages (e.g., 3 and 7 days), the pressure strength of the concrete was lower than that of plain cement. However, the strength of 28-day concrete met the standard construction specifications.

서중환경시 갱폼 거푸집 내부 철근의 온도변화

김경훈 ( Kyoung Hoon Kim ),손호정 ( Ho Jung Son ),임춘근 ( Chun Keun Lim ),한민철 ( Min Cheol Han ),한천구 ( Cheon Goo Han ) 한국건축시공학회 2012 한국건축시공학회 학술발표대회 논문집 Vol.12 No.2

This study investigates the temperature rise of reinforcement bars located in the middle of the form (for reinforcement concrete) during hot weather condition. The temperature was measured for three consecutive days before placing concrete. Test results showed that the temperature started to increase at 7:00 AM before sun rised, and peaked at around 2:00 PM. It was found that the thinner the diameter of a reinforcement bar, the higher is the speed of temperature rise and drop of the bar. The peak level of temperature for D13, D19, D25 and D32 was 54.4℃, 55.2℃, 56.4℃ and 60.2℃, respectively.

여름철 Apt현장 조건에서의 철근 및 거푸집의 온도특성

이제현 ( Lee Jea-hyeon ),문병룡 ( Moon Byeong-yong ),이상운 ( Lee Sang-un ),이정교 ( Lee Joung-gyo ),한민철 ( Han Min-cheol ),한천구 ( Han Cheon-goo ) 한국건축시공학회 2016 한국건축시공학회 학술발표대회 논문집 Vol.16 No.2

On apartment construction sites in hot weather environments, the high temperature of 30 ℃ and above and radiation from the sun cause iron and mold temperatures to rise, which lowers worker efficiency and has a negative effect on the deposited concrete. Therefore this study measured the temperature of D10 ~ D16 iron and aluminum items actually used on box frame apartment construction sites currently under construction, in order to give reference information to solve hot weather concrete problems. The temperature measurement results showed that for iron, temperatures rose to around 45 ℃, and for mold around 58.8 ℃, calling for safety measures for workers in case of possible burning and other problems.

전기발열시트 표면가열 양생공법의 현장적용 연구

김형래 ( Hyung Rae Kim ),조호규 ( Ho Kyu Cho ),김찬수 ( Chan Soo Kim ),지남용 ( Nam Yong Jee ) 한국건축시공학회 2003 한국건축시공학회 학술발표대회 논문집 Vol.3 No.1

The purpose of this study is to analyze the curing effect of planar surface heater for concreting in cold weather. Some experiments were conducted to evaluate the temperature history of concrete structures cured with heating sheets. Results are as follows ; (1) The temperature of concrete showed continuously rising trend with the heating by planar surface heater under the cold environmental condition of 3~-12℃. And after about 24 hours the maximum temperature of concrete was reached at 25~30℃. (2) The temperature of slab concrete heated by planar surface heater of 130W/㎡ was at least 25℃ higher than that of an exterior air, and the curing performance was much more effective than heating by hot wind machine. (3) Through the curing by planar surface heater for 48 hours, the concrete maturity of about 1.5 times to heating by hot wind machine was acquired.

경년변화에 따른 우리나라 서중 콘크리트 적용기간의 변천

최성용 ( Sung Yong Choi ),홍석민 ( Seak Min Hong ),이충섭 ( Chung Sub Lee ),김성일 ( Cheng Ri Jin ),한민철 ( Min Cheol Han ),한천구 ( Cheon Goo Han ) 한국건축시공학회 2008 한국건축시공학회 학술발표대회 논문집 Vol.8 No.2

This paper is to investigate the change of the period of hot weather concrete with elapse of age based on climate data. Climate data for 30 years and 5 years are used respectively. Determination of the period of hot weather concreting on architectural execution in Korea according to the specifications of AIJ, KSCE, and ACI are discussed. According to the research, the period of hot weather concreting with each specification in most regions lasts over 35 days. Compared with the period of cold weather concreting in hillside and inland area, coastal areas have shorter period in the same latitude. The period of hot weather concreting tends to decrease with high latitude. As expected, with the elapse of age, the period of hot weather concrete exhibited to decrease, especially, big city like Seoul, Busan etc had remarkably increased period by as much as a week. This is due to the global warming and industrialization effect with the elapse of age.

서중환경에서 스트론튬계 수화열저감재를 사용한 콘크리트의 수화발열특성 평가

서동균 ( Dong-kyun Suh ),김규용 ( Gyu-yong Kim ),길배수 ( Bae-su Kil ),코야마토모유키 ( Tomoyuki Koyama ),남정수 ( Jeong-soo Nam ) 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 논문집 Vol.24 No.6

초고층 건축물과 같은 대형 건축물의 부재가 대형화 되면 수화발열로 인하여 내 외부 온도차가 커져 균열이 발생한다. 잠열재인 상전이 물질을 수화열저감재로써 사용하는 방법은 다른 방법들보다 접근성, 사용성, 효율성이 높다. 이에 따라 수화열저감재로 상전이 물질을 사용한 연구들이 많이 진행되고 있다. 하지만 상전이 물질은 상전이 반응온도가 다르기 때문에 외기온도, 콘크리트 비빔온도 같은 환경요인에 영향을 받을 수 있는데 이를 고려한 연구는 미미한 수준이다. 따라서 본 논문에서는 서중환경에서 수화열저감재를 사용한 콘크리트의 수화발열특성과 품질을 평가하였다. 그 결과, 서중환경에서 스트론튬계 수화열저감재를 3wt.%, 5wt.%를 혼입했을 경우, OPC수준보다 수화발열은 8%, 21% 저감이 가능하고 발열속도는 약 75분, 85분 정도 지연할 수 있는 것으로 나타났다. 이는 온도가 높을 때 상전이 반응이 상대적으로 촉진되어 실험실환경보다 향상된 성능 나타난 것으로 판단된다. 향후 서중환경에서 다른 종류의 수화열저감재 효율과 비교하고, 장기 재령에서의 강도발현 등에 대한 세부적인 검토를 진행할 예정이다. When concrete member become large like in high rise buildings, hydration heat makes temperature difference inside and outside and cause cracks. The method of using latent heat material as heat reducer could be more accessible, usable and efficient than other methods. Therefore, many studies using PCM as heat reducer are being conducted. Since heat reducer have different reacting temperature, they may be affected by environmental factors like ambient and concrete mixing temperature but studies issuing this are insignificant. Therefore, this paper attempt to evaluate the hydration heat characteristics and quality of concrete using strontium-based PCM under hot weather conditions. As a result, when the strontium-based hydration heat reducer was mixed 3wt.% and 5wt.% in hot weather condition, hydration heat speed and heating rate could be reduced by 8%, 21%, and 75, 85 minutes compared to OPC, respectively. This is considered to be the phase change reaction is relatively promoted when the temperature is high and cause improve performance than room condition result. Later, comparing the efficiency of other types of P.C.M in hot weather condition, and conduct detailed reviews on the strength development in long-term age.

서중환경에서 표면피복 양생재 종류변화가 콘크리트의 초기 온도이력 및 균열발생에 미치는 영향에 관한 현장적용성 평가

한민철(Han, Min-Cheol),이상운(Lee, Sang-Woon) 대한건축학회 2018 大韓建築學會論文集 : 構造系 Vol.34 No.5

Concrete placed under hot weather condition suffers from larger slump loss, rapid moisture evaporation due to high air temperature. Proper measures for material, transportation and curing should be taken to prevent the quality deterioration of the concrete under hot weather condition. In Korea, Although the period of hot weather concrete in Korea occupies only 2 months, there are a lot of quality problems including plastic, drying shrinkage and cold joint. Therefore, the objective of this paper is to investigate and compare the temperature history and crack occurrence of the concrete, which was placed in the actual apartment house construction field under hot weather condition, in response to the application of surface covered curing blankets including PE film, single layer clear bubble sheet, white colored bubble sheet and aluminum metalized bubble sheet. Test results indicated that the application of white colored bubble sheet and aluminum metalized bubble sheet showed most favorable results in terms of reduction in temperature rise and crack occurrence as well as easiness in handling. But, due to light reflection by aluminum metalized bubble sheet, it is believed that white colored bubble sheet is preferable.