• 대한토목학회논문집
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• 제29권5A호
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• pp.503-510
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• 2009

본 연구의 목적은 LMC로 덧씌우기 또는 보수 된 형태의 RC 보의 정적 거동 특성을 파악하는데 있다. 따라서, LMC로 덧씌우기 및 보수된 RC 보를 상대습도 60%, 온도 $20^{\circ}C$의 조건에서 양생을 실시하여 제작하였으며, 제작된 시험체를 4점 휨 실험을 수행하여 균열양상, 파괴거동 및 극한강도 등의 거동을 고찰하였다. 실험결과 전단철근이 보강된 보수형태의 RC보의 경우 100%이상의 내하력을 회복하여 보수 효과가 뛰어난 것을 알 수 있었고, LMC로 압축부에 덧씌우기 된 시험체의 경우 덧씌우기 두께가 증가함에 따라 내하력이 크게 증진되었다. 그러나, 전단철근이 보강되지 않은 보수형태의 시험체와 인장부 덧씌우기된 시험체는 부착계면 파괴양상을 보여주어 보수 및 보강 효과가 거의 없는 것으로 나타났다. 또한 부착계면의 거동특성을 파악하기 위하여 전단흐름 개념을 도입하여 LMC로 압축 덧씌우기된 시험체를 대상으로 하중증가에 따른 전단흐름량을 계산하여 부착계면 특성을 수치적으로 나타내었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.175-176
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• 2022

By studying the characteristics of matrix insulated through heat generated through oxidation of iron powder, the basic research results on the possibility of buffering and applicability of Cold weather concrete as a curing method are presented. In order to prevent freezing due to a sharp decrease in temperature in the initial stage of curing, iron powder (Fe), powder activated carbon, which is a small amount of porous carbonaceous adsorbent, and salt (NaCl) as an oxidizing agent are replaced with iron powder admixture. As the curing temperature increases, the strength tends to increase, and when replacing the admixture at the same curing temperature, the strength slightly decreases. This is determined as a result of generating iron oxide through an oxidation reaction of iron powder, activated carbon, and NaCl generating a large amount of pores in the matrix. In addition, the internal temperature tends to increase as the mixing substitution rate increases, and it is judged that the oxidation heat of the iron powder mixture affects the increase of the internal temperature during curing. The higher the replacement rate of the iron powder mixture, the slightly lower the strength, but it is determined that freezing and melting that may occur in the early stage of curing can be prevented due to an increase in the initial internal temperature.

• 한국건설순환자원학회논문집
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• 제11권3호
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• pp.276-281
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• 2023

기존 보통포틀랜드시멘트를 사용하여 제작한 수로관은 시멘트의 수화생성물이 산에 취약한 특성으로 인하여 열화가 빠르게 진행되고 내구성이 저하되는 문제점이 발생되고 있다. 따라서 본 연구에서는 다양한 산업에서 발생되는 산업부산물인 고로슬래그와 플라이 애시를 이용하여 수로관을 제작하고 그 특성을 분석하였다. 실험결과 굳지 않은 콘크리트에서 슬럼프는 플라이애시의 볼베어링작용으로 인해 증가되는 경향을 나타내었고, 공기량은 미연탄분으로 인해 감소되어 내동해성에 대한 대책이 필요할 것으로 나타났다. 또한 압축강도는 증기양생을 통해 초기강도가 증가되었고, 슬래그 50 %이상의 배합에서는 OPC와 동등이상의 결과가 나타났다. 내산성결과는 질량감소율이 5 % 미만으로 나타나 내구성에 우수한 성능을 나타내었고, 벤치플룸의 휨파괴하중도 KS기준을 모두 상회하여 상용화가 가능할 것으로 판단된다.

• 한국건축시공학회지
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• 제23권6호
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• pp.673-682
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• 2023

본 연구에서는 모르타르 조건하에서 초지연제 혼입률, 양생온도 및 강도수준 변화에 따른 응결지연 특성을 고찰하고자 하였으며, 세티메타를 이용하여 공사현장의 다양한 외기조건 및 재료배합 조건하에서 초지연제를 사용한 콘크리트의 응결시간을 효율적으로 추정할 수 있는 객관적 방법을 제시하고자 하였다. 그 결과, 비선형 회귀모델의 추정식 및 세티메타을 이용하여 초지연 모르타르의 응결시간을 추정할 수 있을 것으로 사료되며, 초결은 45 ST, 종결은 80 ST 전후로 관리하는 것이 바람직할 것으로 판단된다. 또한, 이를 통해 초지연 콘크리트의 응결시관과 관련한 효율적인 품질관리가 가능할 것으로 사료된다.

• 한국건축시공학회지
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• 제6권3호
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• pp.107-114
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• 2006

In this study, the experiment was carried out to investigate and analyze the engineering properties of concrete using fine aggregate of PS bal slagl. The main experimental variables were water/cement ratio 30, 40, 50(%), water content $170kg/m^3$, replacement ratio of slag fine aggregate 0, 25, 50, 75(%) in experiment I and water/cement ratio 30, 40, 50(%), water content 165, 170, 175($kg/m^3$), replacement ratio of fine aggregate of PS ball 0, 50 in experiment II. According to the test results, the principle conclusions are summarized as follows (1) The workability of slag fine aggregate-mixed concrete tends to improve, as the replacement rate increases. (2) The air content of slag fine aggregate-mixed concrete tends to decrease, as the replacement rate increases. (3) The unit volume weight of slag fine aggregate-mixed concrete tends to significantly increase, as the replacement rate increases. (4) The compressive strength of slag fine aggregate-mixed concrete tends to show more increasing propensity, in case the curing period is relatively long, as the replacement rate increases.

• 한국건축시공학회지
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• 제7권1호
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• pp.71-77
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• 2007

This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• 화약ㆍ발파
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• 제16권4호
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• pp.18-28
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• 1998

Effects of blasting vibrations on curing concrete have not been well studied. As a result, unreasonable and strong blasting vibration constraints have been placed on blasting when it occur in the vicinity of curing concrete. To study the effects of blasting on curing concrete blocks of $33.3{\times}27.7{\times}16.2cm$ were molded and placed on the quarry. Several sets of concrete blocks were subjected separately to peak vibrations of 0.25, 0.5, 1.0, 5.0 and 10cm/sec. The impulses of blasting vibrations were applied with thirty-minute intervals. Along with unvibrated concrete blocks, the vibrated concrete samples cored with 60.3mm in diameter were measured for elastic moduli, sonic velocity and uniaxial compressive strength. Test results can be summarized as follows; 1. The blasting vibrations between 6 and 8 hours after pour generally lowered on the uniaxial compressive strength of the concrete. 2. A low blasting vibration of 0.25cm/sec did not affect the uniaxial compressive strength. As the magnitude of the blasting vibration increases, compressive strength of concrete is decreased. 3. Physical properties of the P-wave velocity, Young’s modulus, and Poisson's ratio showed a weakly decreasing trend in the concrete blocks vibrated between 6 and 8 hours after pour.

• 한국도로학회논문집
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• 제16권3호
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• pp.51-57
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• 2014

PURPOSES : This study is to suggest tunnel length to spray curing compound, based on the field tests. METHODS : At first field test, length from the entrance of tunnel to wet wall was checked by visual survey. The second and third test, various sensors were installed in concrete or in tunnel, such as RH sensor, temperature sensor, portable weather station and etc.. And also, test for bleeding and retaining water of concrete were conducted to evaluate environmental effect on concrete pavement. RESULTS : The result of the field experiment for tunnel length to spray curing compound indicates that length changes depending on tunnel length, season, and location. Environmental condition of a short tunnel was not much different between location near entrance and at center of tunnel. However, in case of a medium and long tunnel, effect of outside environmental condition decreased, when location moved into tunnel center of it. CONCLUSIONS : From the testing results, it can be proposed that optimum tunnel length to spray curing compound is 60m for a medium and long tunnel, and whole length for a short tunnel.

• 한국도로학회논문집
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• 제19권3호
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• pp.11-18
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• 2017

PURPOSES : This study investigates the effect on concrete pavement accordance with the curing methods in cool weather and supports the best method in the field. METHODS : Two field tests evaluated the curing methods of concrete pavement in cool weather. Firstly, five curing methods were tested, including normal curing compound, black curing compound, bubble sheet, curing mat, and curing mat covered with vinyl. Concrete maturity was compared from temperature data. Secondly, normal curing compound and curing mat with vinyl, which showed the best performance, were compared in terms of maturity and join condition index. RESULTS:From the field tests, it is an evident that curing mat with vinyl accelerated the concrete strength. Therefore, it is possible to conduct saw-cut works in cool weather, which minimizes damage on concrete at joint. CONCLUSIONS : For concrete pavement in cool weather, using curing mat with vinyl as the curing method could overcome the strength delay. Therefore, strength and durability problems on concrete at joint due to cool weather would be fewer in the future.

• 한국건축시공학회지
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• 제4권2호
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• pp.113-118
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• 2004

This study is a basic experiment on quality management of the compression strength of high strength concrete, aiming. at quality management of high strength mass concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Different from ordinary concrete, high strength concrete generally shows the temperature high rising caused by hydration heat inside the concrete. It is known that, in mass concrete, thermal stress occurs due to the difference in temperature between the inside and the outside, which causes a significant difference in compression strength between structure beams and managerial test pieces. It is also reported that there is a large difference between the compression strength of cylindrical managerial test pieces of standard underwater curing and the strength of structure beam concrete. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created thermal insulation curing box and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.