• Computers and Concrete
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• 제20권6호
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• pp.689-704
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• 2017

The paper presents experimental and numerical investigations of prefabricated composite structural building reinforced concrete slabs with the insulating material for a residential building construction. The building slabs were composed of concrete and expanded polystyrene. In experiments, the slabs in the full-scale 1:1 were subjected to vertical concentrated loads and failed along a diagonal shear crack. The experiments were numerically evaluated using the finite element method based on two different constitutive continuum models for concrete. First, an elasto-plastic model with the Drucker-Prager criterion defined in compression and with the Rankine criterion defined in tension was used. Second, a coupled elasto-plastic-damage formulation based on the strain equivalence hypothesis was used. In order to describe strain localization in concrete, both models were enhanced in the softening regime by a characteristic length of micro-structure by means of a non-local theory. Attention was paid to the formation of critical diagonal shear crack which was a failure precursor.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.105-106
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• 2016

The study of the sandwich wall with the increasing interest in building energy consumption have been actively conducted. This study designed exposed sandwich wall in the light of energy saving design standard and thermal bridge of share connection. The heat insulating performance was analyzed U-fator using calculation program provided in passive houses association and KS F 2277 (method of measuring thermal insulation of construction component materials).

• Computers and Concrete
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• 제23권3호
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• pp.217-233
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• 2019

This paper describes the numerical modelling of an interior slab-column connection to investigate the punching shear resistance of reinforced concrete (RC) slabs under fire conditions. Parameters of the study were the fire direction, flexural reinforcement ratio, load levels, shear reinforcement and compressive strength of concrete. Moreover, the efficiency of the insulating material, gypsum, in reducing the heat transferred to the slab was assessed. Validation studies were conducted comparing the simulation results to experiments from the literature and common codes of practice. Temperature dependencies of both concrete and reinforcing steel bars were considered in thermo-mechanical analyses. Results showed that there is a slight difference in temperature endurance of various models with respect to concrete with different compressive strengths. It was also concluded that compared to a slab without gypsum, 10-mm and 20-mm thick gypsum reduce the maximum heat transferred to the slab by 45.8% and 70%, respectively. Finally, it was observed that increasing the flexural reinforcement ratio changes the failure mode from flexural punching to brittle punching in most cases.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.51-52
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• 2011

This study is to propose a curing method for a concrete wall structure under severe cold climate. The curing methods of using heated cable, heated panel and insulated form were applied. Results showed that the concrete cured by the heated cable resulted in the highest temperature history and the highest strength development at 28 days. Further, it is believed that the curing methods of the heated panel and insulated form are also recommendable for the resistance of the early frost damage on the concrete in practice.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.269-270
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• 2012

This study discussed the applicability of double layered bubble sheet(BS) to the concrete for retaining wall to verify the insulation effect as well as prevention of condensation. The BS was applied to the surface of retaining wall, which is contacted with ground. Temperature profile was monitored since placement of concrete. As expected, the application of BS helps the concrete keeping favorable heat insulating, preventing condensation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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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.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.523-534
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• 2012

The objective of this study was to experimentally investigate the effect of heat curing methods on the temperature history and strength development of slab concrete exposed to $-10^{\circ}C$. The goal was to determine proper heat curing methods for the protection of nuclear power plant structures against early-age frost damage under adverse (cold) conditions. Two types of methods were studied: heat insulation alone and in combination with a heating cable. For heat curing with heat insulation alone, either sawdust or a double layer bubble sheet (2-BS) was applied. For curing with a combination of heat insulation and a heating cable, an embedded heating cable was used with either a sawdust cover, a 2-BS cover, or a quadruple layer bubble sheet (4-BS) cover. Seven different slab specimens with dimensions of $1200{\times}600{\times}200$ mm and a design strength of 27 MPa were fabricated and cured at $-10^{\circ}C$ for 7 d. The application of sawdust and 2-BS allowed the concrete temperature to fall below $0^{\circ}C$ within 40 h after exposure to $-10^{\circ}C$, and then, the temperature dropped to $-10^{\circ}C$ and remained there for 7 d owing to insufficient thermal resistance. However, the combination of a heating cable plus sawdust or 2-BS maintained the concrete temperature around $5^{\circ}C$ for 7 d. Moreover, the combination of the heating cable and 4-BS maintained the concrete temperature around $10^{\circ}C$ for 7 d. This was due to the continuous heat supply from the heating cable and the prevention of heat loss by the 4-BS. For maturity development, which is an index of early-age frost damage, the application of heat insulation materials alone did not allow the concrete to meet the minimum maturity required to protect against early-age frost damage after 7 d, owing to poor thermal resistance. However, the combination of the heating cable and the heat insulating materials allowed the concrete to attain the minimum maturity level after just 3 d. In the case of strength development, the heat insulation materials alone were insufficient to achieve the minimum 7-d strength required to prevent early-age frost damage. However, the combination of a heating cable and heat insulating materials met both the minimum 7-d strength and the 28-d design strength owing to the heat supply and thermal resistance. Therefore, it is believed that by combining a heating cable and 4-BS, concrete exposed to $-10^{\circ}C$ can be effectively protected from early-age frost damage and can attain the required 28-d compressive strength.

• 한국건설순환자원학회논문집
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• 제1권3호
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• pp.225-232
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• 2013

규석, 시멘트, 생석회 및 소량의 무수석고에 알루미늄 분말과 물을 첨가 혼합하여 오토클레이브 중에서 고온 고압 증기양생으로 미네랄 하이드레이트 소재를 제조하였다. 수열 합성된 미네랄 하이드레이트 소재는 균일한 세포조직을 갖는 다공질 경량 기포 콘크리트이다. 미네랄 하이드레이트 소재의 대표적인 특성으로는 다수의 기공으로 인해 뛰어난 경량성 및 단열성능을 들 수 있다. 제조된 미네랄 하이드레이트 소재의 특성은 각각 밀도 $0.26g/cm^3$, 압축강도 0.4MPa, 열전도율 0.064W/mK로 나타났다. 본 연구에서는 상기의 소재 특성을 증진시키기 위하여 "기포제의 종류 및 함량, 규석 및 시멘트의 입도 조건, 기능성 첨가제 종류 및 함량"에 따른 특성 평가 및 분석을 실시하였다. 그 결과 소재의 열적 특성을 개선할 수 있었으며, 특히 기능성 첨가제인 폴리디메틸실록산 혼화제를 첨가할 경우 밀도 및 열전도율을 개선하는 동시에 탁월한 강도 증진 효과를 나타내었다.

• 한국화재소방학회논문지
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• 제25권6호
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• pp.8-13
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• 2011

고강도 콘크리트는 구조적인 장점에도 불구하고 화재 시 폭렬과 함께 취성적인 파괴를 나타내는 단점으로 인하여 실구조물에 적용 시 주의하여 사용하여야 한다. 신축되는 고강도 콘크리트구조물의 폭렬제어를 위하여 많은 연구가 진행되어 왔으나, 사용 중인 고강도콘크리트 구조물의 폭렬제어방안에 대한 연구가 부족한 실정이다. 본 연구에서는 사용 중인 고강도 콘크리트 구조물의 내화성능을 향상시키기 위한 내화 마감재로서 미세공극과 유기섬유를 활용한 공극구조의 개선으로 단열성을 확보한 신개념의 무기질 내화 모르타르를 개발하고자 한다. 잔골재 종류, PP섬유 혼입량 및 마감두께를 변수로 하는 내화모르타르에 대한 재료시험 및 실구조물에 대한 내화시험을 통하여 내화성능을 평가하였다. 재료시험결과 다공질의 경량골재를 사용한 모르타르의 열전도율은 일반 잔골재에 비하여 크게 낮아졌으며, 기둥부재 내화시험결과 경량 잔골재의 사용으로 내화시간이 20분, 마감두께를 10 mm에서 20 mm로 증가시킬 경우 10분 그리고 PP섬유를 0.6 % 혼입함으로써 4분 증가하였다.

• 한국건축시공학회지
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• 제7권1호
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• pp.107-113
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• 2007

This study investigates the filed application in Daebul Free Trade Zone applying both a flowing method using drying shrinkage-reducing superplasticizer(SRS) and an insulating curing method using double layer bubble sheet. Test results showed that fresh concrete satisfied target slump and air content. A structure adding SRS significantly decreased the total bleeding capacity and accelerated the setting time. As for the crack occurrence, the structure applying the flowing method and double bubble sheets simultaneously exhibited the most favorable crack endurance, while conventional concrete showed more than 1mm size of crack in overall. In addition, a structure applying the flowing concrete method partially presented the micro crack. For the area proportion of crack occurrence, the structure using the double bubble sheets indicated 9.8%, while others applying flowing concrete method was 28%, compared with that of conventional one. For the compressive strength of specimens, standard curing specimens indicated $3{\sim}33%$ higher value than that of specimens cured besides the field construction. The specimens containing SRS improved the strength of $2{\sim}6MPa$, which is $10{\sim}22%$ higher than that of conventional concrete.