• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.813-822
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• 2002

The purpose of the present study is first to refine the mathematical material models for moisture and temperature distributions in early-age concrete and then to incorporate those models into finite element procedure. The three dimensional finite element program developed in the present study can determine the degree of hydration, temperature and moisture distribution in hardening concrete. It is assumed that temperature and humidity fields are fully uncoupled and only the degree of hydration is coupled with two state variables. Mathematical formulation of degree of hydration Is based on the combination of three rate functions of reaction. The effect of moisture condition as well as temperature on the rate of reaction is considered in the degree of hydration model. In moisture transfer, diffusion coefficient is strongly dependent on the moisture content in pore system. Many existing models describe this phenomenon according to the composition of mixture, especially water to cement ratio, but do not consider the age dependency. Microstructure is changing with the hydration and thus transport coefficients at early ages are significantly higher because the pore structure in the cement matrix is more open. The moisture capacity and sink are derived from age-dependent desorption isotherm. Prediction of a moisture sink due to the hydration process, i.e. self-desiccation, is related to autogenous shrinkage, which may cause early-age cracking in high strength and high performance concrete. The realistic models and finite element program developed in this study provide fairly good results on the temperature and moisture distribution for early-age concrete and correlate very well with actual test data.

• Food Engineering Progress
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• v.13 no.1
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• pp.50-55
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• 2009

The effect of active gluten supplementation on the quality properties of rice bagel was investigated. Water hydration capacity of rice flour increased as the amount of gluten increased, whereas alkaline water retention capacity decreased. Pelshenke value and sedimentation value were incerased as the amount of gluten increased, but these values are lower than those of strong wheat flour. Peak viscosity, setback, peak height, and peak width decreased as the amount of gluten increased. When the active gluten of 23% was added to the rice flour, the specific loaf volume of bagel increased more that two times compared with the active gluten of 11%. Hardness, gumminess, and chewiness were decreased as the amount of gluten increased. Specific loaf volume of bagel showed highly positive correlation in water hydration capacity, Pelshenke value, and sedimentation value of which values were r=0.962, r =0.964, and r =0.966, respectively.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.49-56
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• 2018

The use of highly absorptive materials in cement-based materials is increasing for internal curing purpose. However, calculation of correct absorption capacity of such materials is not easy, which leads to change in the effective water-to-cement ratio of cement paste by either absorbing or releasing water. In this study, effective absorption capacity of a highly absorptive material was found using isothermal calorimetry. Moreover, the effect of specific surface area was investigated. It was found that the method was capable of finding effective water absorption capacity of activated carbon fiber. For the activated carbon fiber used in this research, the effect of specific surface area was negligible because the high BET surface area was due to micropores less than 1nm, which does not affect the rate of hydration curve. Thus, the effective absorption capacity of such materials can be found successfully using this method.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.2
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• pp.179-184
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• 2020

Elasticity and softness of the skin depend on the level of moisture present in the stratum corneum, which is known to be affected by various environmental changes, such as cold and hot winds and dry environments. However, not many studies have been conducted on changes in skin moisture and the degree of recovery due to individual skin differences. In the present study, we aimed to investigate the effect of warm air heating on skin hydration levels and develop moisturizing formulas to improve lowered skin hydration levels. In order to deliver warm air heating condition, heating dryer (40 ℃, 6 m/s, 30 cm apart from forearm) was applied into inner forearm of healthy subjects (male: 10, female: 39, age: 25 - 63) Among 49 subjects, 26 subjects showed significantly lowered skin hydration levels until 30 min after warm air heating exposure (lowered group). In addition, moisturizing cream with high water holding capacity was applied to forearm of 10 subjects in lowered group for 3 weeks and skin hydration levels after warm air heating were significantly improved at the levels of before application of warm air heating. From this study, we found out that there is a skin type that skin hydration levels are significantly decreased under warm air heating condition (dehydrated skin) and this dehydrated skin can be improved by moisturizing formulas with high water holding capacity.

• International Journal of Highway Engineering
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• v.17 no.2
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• pp.99-105
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• 2015

PURPOSES: In this study, alkali-activated blast-furnace slag (AABFS) was investigated to determine its capacity to absorb carbon dioxide and to demonstrate the feasibility of its use as an alternative to ordinary Portland cement (OPC). In addition, this study was performed to evaluate the influence of the alkali-activator concentration on the absorption capacity and physicochemical characteristics. METHODS: To determine the characteristics of the AABFS as a function of the activator concentration, blast-furnace slag was activated by using calcium hydroxide at mass ratios ranging from 6 to 24%. The AABFS pastes were used to evaluate the carbon dioxide absorption capacity and rate, while the OPC paste was tested under the same conditions for comparison. The changes in the surface morphology and chemical composition before and after the carbon dioxide absorption were analyzed by using SEM and XRF. RESULTS: At an activator concentration of 24%, the AABFS absorbed approximately 42g of carbon dioxide per mass of paste. Meanwhile, the amount of carbon dioxide absorbed onto the OPC was minimal at the same activator concentration, indicating that the AABFS actively absorbed carbon dioxide as a result of the carbonation reaction on its surface. However, the carbon dioxide absorption capacity and rate decreased as the activator concentration increased, because a high concentration of the activator promoted a hydration reaction and formed a dense internal structure, which was confirmed by SEM analysis. The results of the XRF analyses showed that the CaO ratio increased after the carbon dioxide absorption. CONCLUSIONS : The experimental results confirmed that the AABFS was capable of absorbing large amounts of carbon dioxide, suggesting that it can be used as a dry absorbent for carbon capture and sequestration and as a feasible alternative to OPC. In the formation of AABFS, the activator concentration affected the hydration reaction and changed the surface and internal structure, resulting in changes to the carbon dioxide absorption capacity and rate. Accordingly, the activator ratio should be carefully selected to enhance not only the carbon capture capacity but also the physicochemical characteristics of the geopolymer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.88-94
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• 2013

The hexavalent chromium (Cr(VI)) is well known as a hazardous ion, presumably inducing dermatic diseases and if serious cancer. The present study concerns the binding capacity of Cr(VI) ions in the cement powder and matrix for a quantitative technique of Cr(VI) ions in cement to influence human health. Both the water-soluble and acid-soluble Cr(VI) ions present in 3 types of ordinary Portland cement (OPC), pulverised fuel ash (PFA), ground granulated blast furnace slag (GGBS), and silica fume (SF) were measured using the spectrophotometer. As a result, it was found that the concentration of water-soluble Cr(VI) ion in cement ranged from 10.5 to 18.9mg/kg-cement, and in the additional materials a very low value of Cr(VI) ion was measured. Acid-soluble Cr(VI) ion was even higher than water-soluble Cr(VI) ion, ranging from 172.4 to 318.2mg/kg-cement. Nevertheless, the concentration of acid-soluble Cr(VI) ion is not proportional to addition of acid. It depends rather the variable pH of solvent involving cement paste. As enough cement hydration occurs, the binding capacity of Cr(VI) ion increases, inhibiting this ions from leaching out in the presence of hydration products such as ettringite or tri-calcium aluminate which bind Cr(VI) ion by ion-exchange.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.4
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• pp.343-349
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• 2016

Many minerals and nutrient salts are abundant in Jeju lava sea water. The objective of this study was to evaluate the skin hydration effects of Jeju lava sea water. The skin barrier serves as a protective barrier that prevents the loss of moisture. The water holding capacity and water transport of the epidermis have been proposed to be important determinants of skin hydration. Jeju lava sea water increased the mRNA expression of filaggrin and caspase-14 which is related to natural moisturizing factor (NMF) formation. Aquaporins 3 (AQP3) are proteins that facilitate the transport of water across cell membranes. Jeju lava sea water increased the mRNA expression and protein expression of AQP3. We employed a skin equivalent model to assess the efficacy of Jeju lava sea water. In a skin equivalent model, Jeju lava sea water increased the CD44 (hyaluronic acid receptor) which is related to skin hydration. From these results, we found out Jeju lava sea water maybe help to skin hydration.

• Korean Journal of Materials Research
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• v.25 no.2
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• pp.75-80
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• 2015

The carbon dioxide($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical method to reducing $CO_2$ for building materials is the addition of slag and fly ash, like pozzolan material, while another method is reducing $CO_2$ production by carbon negative cement development. The MgO-based cement was from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements could improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as main starting materials, as well as silica fume, fly ash and blast furnace slag for the mineral admixture, were carried out for industrial waste material recycling. In order to increase the hydration activity, $MgCl_2$ was also added. To improve hydration activity, $MgCO_3$ and serpentinite were fired at $700^{\circ}C$ and autoclave treatment was conducted. In the case of $MgCO_3$ as starting material, hydration activity was the highest at firing temperature of $700^{\circ}C$. This $MgCO_3$ was completely transferred to MgO after firing. This occurred after the hydration reaction with water MgO was transferred completely to $Mg(OH)_2$ as a hydration product. In the case of using only $MgCO_3$, the compressive strength was 3.5MPa at 28 days. The addition of silica fume enhanced compressive strength to 5.5 MPa. In the composition of $MgCO_3$-serpentine, the addition of pozzolanic materials such as silica fume increased the compression strength. In particular, the addition of $MgCl_2$ compressive strength was increased to 80 MPa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.1-8
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• 2019

Phase change material(PCM) has the capacity to absorb or release energy in heat when the phase changes. This study conducted to investigate the effect of strontium-based PCM on the hydration heat and mechanical properties of mortar with fly ash and blast furnace slag. The amounts of PCM were 1%, 2%, 3%, 4%, and 5% by the cementitious materials weight. The tests about mortar flow, semi-adiabatic temperature rise, compressive and flexural strength tests were carried out for twelve types of mortar mixtures. The test results indicated that the use of PCM was effective to reduce hydration heat and retard hydration of mortar with industrial by-products. In particular, the heat generation rate of mortars with fly ash was lower than that of mortars with blast furnace slag. The compressive strength of mortar with fly ash and blast furnace slag were decreased with increasing PCM ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1463-1469
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• 2013

Portland cement used as binding material in combination of ferrous iron for reductive dechlorination of chlorinated organics is already widely studied topic by several researchers. However there is no clear evidence about the component solely responsible in cement for trichloroethylene (TCE) dechlorination. Many researchers suspect that the ettringite, monosulfate phases associated with hydration of cement are responsible active agents for TCE dechlorination. This study deals with synthesizing different pure crystalline minerals like ettringite and monosulfate phases of cement hydration and check individual phase's TCE dechlorinating capacity in combination with ferrous iron. The results indicated that the synthesized minerals showed no reduction capacity for TCE. The findings in the present study is significant as it shows that ettringite and monosulfate phases which were suspected minerals by previous researchers for TCE dechlorination are not reactive. Hence it is suspected that some other mineral or mineral form in cement phase could be responsible for TCE degradation.