• Title/Summary/Keyword: 양생 콘크리트

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An Influence of W/B and Curing Temperature on Autogenous Expansion of MgO Concrete (물-결합재비(W/B)와 양생온도가 MgO혼입 콘크리트의 자기팽창 변화에 미치는 영향)

  • Jang, Bong-Seok;Kwon, Yong-Gil;Lee, Kwang-Myong;Choi, Seul-Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.293-294
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    • 2010
  • In this study, it was analyzed that autogenous expansion of MgO concrete was affected by W/B and curing temperature. Autogenous expansion test was performed for MgO concrete, which is mixed MgO of 0%, 5% of cement weight. With autogenous expansion based on long-term time variation was measured, it was observed an influence with W/B and curing temperature.

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Effect of Curing Conditions on the Strength of Fly-Ash Based Geopolymer (양생조건이 플라이애쉬 기반 지오폴리머 강도에 미치는 영향)

  • Cho, Young-Keun;Moon, Gyu-Don;La, Jung-Min;Jung, Sang-Hwa
    • Journal of the Korea Concrete Institute
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    • v.26 no.4
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    • pp.449-456
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    • 2014
  • Material properties of geopolymer, whose the reaction is very complicated, have been influenced by chemical compositions and particle size distributions of fly ash, concentrations and types of alkali-activators and curing conditions such as temperatures and time. In this research, experiments with several variables such as curing temperatures, preset prior to the high temperature curing and high temperatures have been conducted in order to evaluate to investigate effects on the compressive strengths of geopolymer caused by curing condition. Experiment results were evaluated with compressive strengths and micro-structures such as SEM and MIP of geopolymer pastes. As a result, as higher curing temperature or longer preset time were applied to the pastes, higher compressive strengths were observed. However, compressive strengths of geopolymer pastes declined due to increases in macropores (>50 nm) under high temperatures elapsed after 24 hours. In this sense, it can be considered that strengths and microstructures of geopolymers depends on curing temperature and time.

The Effect of Curing Temperature on the Relationship between Shear Wave Velocity and Concrete Compressive Strength Using the Same Cement Paste (동일 시멘트 페이스트 사용시 양생온도가 전단파 속도와 압축강도 상관관계에 미치는 영향)

  • An, Ji-Hwan;Jeon, Sung-Il;Kwon, Soo-Ahn;Nam, Jeong-Hee
    • International Journal of Highway Engineering
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    • v.11 no.2
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    • pp.67-74
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    • 2009
  • The strength of concrete is one of the most important parameters in evaluating the properties of concrete. Compressive strength of concrete has been widely used because of its convenience of experiments and generality. Compressive strength of concrete varies according to materials and curing conditions. Even with the same materials, the strength varies according to the curing conditions. Therefore, if we want to know the strength of concrete from the construction field, we have to put it in exactly the same curing condition with the construction field. But it is impossible to make the exactly same curing conditions in the laboratory. Also damages occur in order to measure the strength of concrete, because the core hat to be made into the pavement. To overcome these limits, many studies of nondestructive method have already been researched. It was already proven that shear wave velocity was very closely related to the compressive strength. In this study, three different curing temperatures with the same mixture paste were used, and compressive strength and shear wave velocity, according to the aging were measured. The relationship between these two parameters was examined. As results, curing temperature affected the compressive strength and the shear wave velocity, but did not affect the relation between them.

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Durability of Polymers for Cement Modifier in Autoclave Cure (오토클래이브양생에 의한 시멘트 혼화용 폴리머의 내구성)

  • Joo, Myung-Ki;Lee, Youn-Su
    • Journal of the Korea Concrete Institute
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    • v.15 no.6
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    • pp.888-893
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    • 2003
  • The purpose of this study is to make clear the durability of the polymer films formed in the autoclaved polymer-modified mortars and concretes. The polymer films prepared with polymer dispersions such as a styrene-butadiene rubber (SBR) latex, a poly (ethylene-vinyl acetate)(EVA) emulsion and a polyacrylic ester (PAE) emulsion for polymeric admixtures are exposed to autoclaving at 18$0^{\circ}C$ in temperature and 1.01 MPa in vapor pressure, and subjected to tensile test and infrared spectroscopy. The durability of the polymer films is evaluated from the application of autoclaving to the polymer films under saturated Ca(OH)$_2$ solution immersion causes no degradation for SBR films and a significant degradation due to the saponification of the polymers for EVA and PAE films. Accordingly, in the application of autoclaving to polymer-modified mortars and concretes, it is suggested that SBR-modified mortars and concretes are hardly degraded but EVA- and PAE-modified mortars and concretes are markedly degraded by the saponification of the polymers.

Compressive Strength Development Model for Concrete Cured by Microwave Heating Form (마이크로웨이브 발열거푸집으로 양생된 콘크리트의 압축강도발현 모델)

  • Koh, Tae-Hoon;Moon, Do-Young;Bae, Jung-Myung;Yoo, Jung-Hoon
    • Journal of the Korea Concrete Institute
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    • v.27 no.6
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    • pp.669-676
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    • 2015
  • Time dependent model for prediction of compressive strength development of concrete cured by microwave heating form was presented in this study. The presented model is similar to the equation which is given in ACI 209R-92 but the constants which is dependent on cement type and curing method in the presented model are modified by the regression analysis of the experimental data. Laboratory scale concrete specimens were cast and cured by the microwave heating form and drilled cores extracted from the specimens were fractured in compression. The measured core strengths are converted to standard core and in-situ strengths. These in-situ strengths are used for the regression.

Temperature History of the Concrete Corresponding to Various Curing Sheets in the Low Temperature (저온환경에서의 양생시트 변화에 따른 콘크리트의 온도이력 특성)

  • Baek, Dae-Hyun;Hong, Seak-Min;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.781-784
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    • 2008
  • In this paper, insulating effect and strength development of concrete under low temperature are reported varying curing sheets. According to test results, in temperature -5$^{\circ}$C concrete subject to exposure and air cap condition, result in a frost damage at early age by a fall of below zero temperature. Mean while, the combination of PE film and non-woven fabric maintained around 3 $^{\circ}$C within first 24 hours since placement. For double bubble sheets, concrete temperature maintained above 7$^{\circ}$C due to its excellent heat insulating capability. As a result of core strength test, strength of specimens cured with viny + non-woven fabric and double bubble sheets had higher strength than strength of other specimens due to good heat insulation effect at early age.

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Maturity-Based Model for Concrete Compressive Strength with Different Supplementary Cementitious Materials (혼화재 치환율을 고려한 성숙도 기반의 콘크리트 압축강도 평가 모델)

  • Mun, Jae-Sung;Yang, Keun-Hyeok;Jeon, Yong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.6
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    • pp.82-89
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    • 2014
  • The purpose of this study is to propose a simple model to evaluate the compressive strength development of concrete with various supplementary cementitious materials (SCMs) and cured under different temperatures. For the generalization of the model, the ACI 209 parabola equation was modified based on the maturity function and then experimental constants A and B and 28-day compressive strength were determined from the regression analysis using a total of 265 data-sets compiled from the available literature. To verify the proposed model, concrete specimens classified into 3 Groups were prepared according to the SCM level as a partial replacement of cement and curing temperature. The analysis of existing data clearly revealed that the 28-day compressive strength decreases when the curing temperature is higher and/or lower than the reference curing temperature ($20^{\circ}C$). Furthermore, test results showed that the compressive strength development of concrete cured under $20^{\circ}C$ until an early age of 3 days was marginally affected by the curing temperature afterward. The proposed model accurately predicts the compressive strength development of concrete tested, indicating that the mean and standard deviation of the ratios between predictions and experiments are 1.00 and 0.08, respectively.

Strength Properties of Concrete According to Types of High Early Strength Cement and Curing Method (조강형 시멘트의 종류 및 양생방법에 따른 콘크리트의 강도특성)

  • Chang, Chun-Ho;Lee, Wang-Sup;Jung, Yong-Wook;Chung, Youn-In
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.76-84
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    • 2017
  • This study selected a method which uses high early strength cement as a way to reduce the curing time and curing energy source of concrete secondary products and reviewed the improvement in the initial strength of concrete secondary products setting the target strength of the concrete capable of removing the form to 15MPa and the curing time to 6 hours. As a result of the test, the only specimen which achieved the form removal strength of 15 MPa only through atmospheric curing within the target curing time of 6hours was ACC-100, and the specimens of TRC-100 and TRC-50 satisfied the values of 6 hours and 15MPa through steam curing. However, we could see that it was difficult to secure workability in the case of the specimen of ACC-100 due to its high rapid setting property and a retarder such as anhydrous citric acid was required to be used to improve the workability. When we look into the pattern following changes in the water to binder ratio, while, in the case of stream curing, OPC-100, TRC-100, and TRC-50 were all found to satisfy achievement of the form removal strength within 6hours as the water to binder ratio decreased, in the case of atmospheric curing, TRC-100, and TRC-50 achieved 15MPa within 12hours.

Evaluation of Compressive Strength and Freeze-thaw Resistance Properties of Concrete using Superabsorbent Polymer (고 흡수성 폴리머를 혼입한 콘크리트의 압축 강도 및 동결융해 저항성 평가)

  • Kim, Il-Sun;Choi, So-Yeong;Yang, Eun-Ik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.5
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    • pp.86-94
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    • 2020
  • When the Superabsorbent Polymer (SAP) is added into concrete, the slump decreases rapidly, deteriorating the workability, the internal curing effect can be obtained through the water absorption and discharge process, and the internal voids of the concrete are increased. In this study, the effects of internal curing and voids were evaluated by evaluating the compressive strength, freeze-thaw resistance, and chloride penetration resistance of SAP-adding concrete that secured workability using a water reducing agent. Also, the internal curing effect of SAP was evaluated by dividing the curing conditions of concrete into water curing and sealed curing. From the result, as the SAP adding ratio increased, the amount of water reducing agent increased, and as for the compressive strength, the SAP adding ratio of 1.5% showed the greatest compressive strength. In particular, in the case of sealed curing showed higher compressive strength than the water curing. It is considered that the compressive strength increased due to the reduction of the effective water-cement ratio and the internal curing effect. Adding 1.0~1.5% of SAP improved the freeze-thaw resistance similar to the case of adding the AE agent, and the addition of more than 1.0% of SAP improved the chloride penetration resistance. The optimal adding ratio of SAP is 1.5%, and the adding ratio of 2.0% or more adversely affects the compressive strength and freeze-thaw resistance.

Resistance of Chloride Penetration into High Strength Concrete Containing Mineral Admixtures according to Curing Conditions (광물질혼화재 혼합 고강도콘크리트의 양생조건에 따른 염화물이온 침투저항성)

  • Moon, Han-Young;Kim, Byoung-Kwon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.2
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    • pp.185-194
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    • 2004
  • In recent years, construction company makes inroads into the world construction market, and receives the order of extra-large concrete structure under marine environment in south-east asia specially. At this point of time, to enhance the quality of concrete, we research the High Strength Concrete (HSC) containing mineral admixtures. In this study, therefore, HSC with various combination of ordinary portland cement(OPC), blast-furnace slag(SG), silica fume(SF), and expansion admixture(SS) are cured 23 and $35^{\circ}C$ considering the site weather, and are cured in water for 3, 7 or 56 days respectively. Test results show that the HSC cured at $35^{\circ}C$ gains higher early-age strength but eventually gains lower later-age strength compare with the HSC cured at $23^{\circ}C$. Especially, HSC with combination of OPC+SG+SF+SS or OPC+SG+SF show very excellent resistance of chloride penetration. The permeability of HSC was therefore enhanced as because of containing the proper content of SG, SF, and SS and making dense micro-structure of HSC.