• Title/Summary/Keyword: Hydration model

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Estimation of Early-Age Cracking of Reinforced Concrete Walls (철근콘크리트 벽체의 초기 균열 거동에 대한 연구)

  • Kwak Hyo-Gyoung;Ha Soo-Jun
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.898-905
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    • 2006
  • In the present paper, for a quantitative assessment of early-age cracking in an RC wall, an improved analytical model is proposed. First of all, a three-dimensional finite element model for the analysis of stresses due to hydration heat and differential drying shrinkage is introduced. A discrete steel element derived using the equivalent nodal force concept is used to simulate reinforcing steels, embedded in a concrete matrix. In advance, to quantitatively calculate the cracking potential, an analytical model that can estimate the post-cracking behavior in an RC tension member is proposed Subsequent comparisons. of analytical results with test results verify that the combined use of both the finite element model for the stress analysis as well as the analytical model for the estimation of the post-cracking behavior in an RC tension member make it possible to accurately predict the cracking ,behavior of RC walls.

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Thermodynamic Modelling of Blast Furnace Slag Blended Cement Composites (고로슬래그가 치환된 시멘트복합체의 열역학적 모델링)

  • Yang, Young-Tak;Cha, Soo-Won
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.4
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    • pp.488-495
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    • 2017
  • In this study, we conducted the kinetic hydration modeling of OPC and the final product according to the substitution ratio of GGBS by using the geochemical code, GEMS, in order to calculate the thermodynamic equilibrium. The thermodynamic data was used by GEMS's 3rd party database, Cemdata18, and the cement hydration model, the Parrot & Killoh model was applied to simulate the hydration process. In OPC modeling, ion concentration of pore solution and hydration products by mass and volume were observed according to time. In the GGBS modeling, as the substitution rate increases, the amount of C-S-H, which contributes the long-term strength, increases, but the amount of Portlandite decreases, which leads to carbonation and steel corrosion. Therefore, it is necessary to establish prevention of some deterioration.

Modeling of the Setting Characteristics of Early-age Concrete (초기재령 콘크리트의 응결특성 모델링)

  • 조호진;송하원;변근주
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.391-396
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    • 2002
  • The so called setting is defined as the onset of rigidity in fresh concrete. In the analysis of the early-age concrete behavior, we consider fresh concrete as a structural element immediately after mixing. But for the activation of real structural behavior of fresh concrete, it takes some time after the beginning of hydration reaction. So, the very early age deformations due to hydration heat and shrinkage which occur before the setting do not produce restraint stresses. In this paper, we propose a setting characteristic model based on the so called percolation theory. From the analysis using the model, the influence of curing temperature is investigated and analytical results are compared with experimental results. From the comparison, the validity of proposed model is verified. This model is also applied to evaluate stress development in a temperature-stress test machine (TSTM) specimen and then the effect of setting time on the stress development is discussed.

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Predicting Compressive Strength of Fly Ash Mortar Considering Fly Ash Fineness (플라이 애시 미세도를 고려한 플라이 애시 모르타르의 압축 강도 예측)

  • Sun, Yang;Lee, Han-seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.90-91
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    • 2020
  • Utilization of upgraded fine fly ash in cement-based materials has been proved by many researchers as an effective method to improve compressive strength of cement based materials at early ages. The addition of fine fly ash has introduced dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect into cement-fly ash system. In this study, an integrated reaction model is adpoted to quantify the contributions from cement hydration and pozzolanic reaction to compressive strength. A modified model related to the physical filling effect is utilized to calculate the compressive strength increment considering the gradual dissolution of fly ash particles. Via combination of these two parts, a numerical model has been proposed to predict the compressive strength development of fine fly ash mortar considering fly ash fineness. The reliability of the model is validated through good agreement with the experimental results from previous articles.

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A Study on the Hydration Reaction Model of Expansive Additive of Ettringite-Gypsum Type (에트링가이트-석탄 복합계 팽장재의 수화반응 모델에 관한 연구)

  • Park Sun Gyu;Takahumi Noguchi;Kim Moo-Han
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.581-586
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    • 2005
  • High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

Modified-stoichiometric Model for Describing Hydration of Alkali-Activated Slag (알칼리 활성 슬래그의 수화에 대한 개선된 화학양론적 모델)

  • Abate, Selamu Yihune;Park, Solmoi;Song, Keum-Il;Lee, Bang-Yeon;Kim, Hyeong-Ki
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.1
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    • pp.1-12
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    • 2021
  • The present study proposes the modified-stoichiometric model for describing hydration of sodium silicate-based alkaliactivated slag(AAS), and compares the results with the thermodynamic modelling-based calculations. The proposed model is based on Chen and Brouwers(2007a) model with updated database as reported in recent studies. In addition, the calculated results for AAS are compared to those for hydrated portland cement. The maximum difference between the proposed model and the thermodynamic calculation for AAS was at most 20%, and the effects of water-to-binder ratio and activator dosages were identically described by both approaches. In particular, the amount of non-evaporable water was within 10% difference, and was in excellent agreement with the experimental results. Nevertheless, notable deviation was observed for the chemical shrinkage, which is largely dependent on the volume of hydrates and pores.

Skin Hydration and Collagen Synthesis of AF-343 in HS68 Cell Line and NC/Nga Mice by Filaggrin Expression and Suppression of Matrix Metallopreteinase

  • Cho, Jae-We;Jeong, Yeon-Su;Han, Ji-Won;Chun, Young-Jin;Kim, Hyun-Kyu;Kim, Min-Young;Kim, Beom-Joon;Park, Ki-Moon;Kim, Jong-Keun;Kim, Jae-Hyun;Cho, Soo-Muk
    • Toxicological Research
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    • v.27 no.4
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    • pp.225-229
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    • 2011
  • Extract of Taraxacum platycarpum (AF-343) has been reported to have several biological properties such as skin hydration and anti-inflammatory effects. Although clinical evidences of skin hydration and antiinflammatory effect were proven in clinical trial, precise mechanism of skin hydration was not fully understood yet. In this study, we have focused skin hydration mechanism related filaggrin, collagen, and matrix metalloproteinase (MMP) in vitro and animal study. Herein, skin hydration mechanism of AF-343 is due to recovery of filaggrin in mice model and increased production of collagen with suppression of matrix MMP in vitro fibroblast cell line.

Reasonable Evaluation of Thermal Stress in the Hydration Heat Analysis (범용구조해석 프로그램의 수화열응력 산정기법 연구)

  • 전세진
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.789-794
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    • 2002
  • The relationship is investigated between material modeling of concrete and the evaluation procedure of thermal stress by the hydration heat. In this respect, some important points are suggested to which special attention should be paid to reasonably evaluate the thermal stress using the widely-used structural analysis programs. This study indicates that proper material model should be used to draw incremental stress evaluation that takes into account the change of elastic modulus with time. Some correction techniques are also presented when using the program that don't have proper built-in procedure for the calculation of the thermal stress.

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Conformational Role of Proline in $\alpha$-Helices

  • Kang, Young-Kee;Kim, Mee-Kyoung
    • Proceedings of the Korean Biophysical Society Conference
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    • 1998.06a
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    • pp.22-22
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    • 1998
  • Conformational energy calculations have been carried out for proline-containing alanine-based pentadecapeptides with the sequence Ac-(Ala)/sun n/-Pro-(Ala)$_{m}$-NHMe (n + m = 14), in order to figure out the positional preference of proline in $\alpha$-helices. The conformational energy was computed a sum of the potential energy (ECEPP/3) and the hydration free energy computed by the hydration shell model.(omitted)d)

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A study of the Bent of Hydration Analysis Underground Pier Footing by Constrution Stages (시공단계를 고려한 교각기초의 수화열해석)

  • Park Weon-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.6 no.3
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    • pp.223-230
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    • 2005
  • Lately, massive concrete structures are increasingly built. Mass concrete structures are cast in many stages with construction joints. Individually constructed segment exhibit different heat source properpies and time dependent properties. As such construction stages must be incorporated in a heat of hydration analysis model to truly reflect a real construction process. Thermal stress analysis is conducted to find the way of controlling the thermal crack of pier footing mat in this paper. The footing mat model fur the analysis is $12m\times14m$ area and 3m height. This study show the process of construction stage and analyzes the results for a foundation structure constructed in 2 stage pours.

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