• Journal of the Korean Ceramic Society
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• v.23 no.6
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• pp.1-6
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• 1986

The hydration of $C_3A$ and $C_3A-CaSO_4$.$2H_2O$ was investigated with varying concentration (0.1-1.0%) of sodium gluconate solution. gluconate solution. Sodium gluconate accelerates cation dissolution from $C_3A$ for the first several minutes but depresses the rate of heat evolution in the course of $C_3A$ hydration. The hydration of $C_3A$ in the presence of sodium gluconate was modified such that the formation of the intermediate hydrate C4AH$\chi$ crystal was much reduced and most of the product became amorphous. The retardation of $C_3A-CaSO_4$.$2H_2O$ hydration in the presence of sodium gluconate was controlled by the competitive adsorption between gluconate anion and $SO_4^{-2}$ onto $C_3A$ surface.

• Cement Symposium
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• s.34
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• pp.129-137
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• 2007

This paper presents a numerical model which can predict degree of cement mineral component, such as $C_3S$, $C_2S$, $C_3A$, $C_4AF$ and microstructure of hydrating cement as a function of water to cement ratio, cement particle size distribution, cement mineral components and temperature. In this model cement particles are parked randomly in cell space and hydration process is described using a multi-component intergrated kinetic model. The simulation result of degree of hydration of cement mineral component agrees well with experiment result. The content of cement hydration product, such as CSH and CH can be obtained as an accompanied result during hydration process. By introducing of equal-area projection method, water withdrawl mechanism and contact area among cement particles can be considered in detail. By using proposed method, pore size distribution of hydrating cement is predicted.

• Journal of the Korean Ceramic Society
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• v.30 no.11
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• pp.905-910
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• 1993

$\alpha$-tricalcium phosphate($\alpha$-TCP) powders were synthesized and their hydration properties were investigated in Tris. solution. Two kinds of $\alpha$-TCP powder samples were prepared; the one is reaction product of CaHPO4.2H2O and CaCO3, and another is that of hydroxyapatite(HAp) and $\beta$-Ca2P2O7. They were satisfied with Ca/P mole ratio 1.5 and were heated at 150$0^{\circ}C$ for 5 hours. In the hydration of $\alpha$-TCP samples the powder which was synthesized from HAp and $\beta$-Ca2P2O7 was hydrated faster than that from CaHPO4.2H2O and CaCO3. The hydration reaction of $\alpha$-TCP powder transformed rapidly into HAp accompanying setting and hardening. It was realized that the hydration reaction of $\alpha$-TCP was due to the solution-precipitation mechanism and the hydrates from the reaction were Ca-deficient HAp having funtional group HPO42-.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.3
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• pp.39-47
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• 1997

Retinol as well as RA is well known to have many beneficial effects on aged skin. But the skin irritation potential and unstable condition of the products containing them have been some problems in their cosmetic uses. So, retinol containing gel product was developed for less skin irritancy and more stability in cosmetic products. To examine the clinical effects of retinlo containing product, we used cilnicla non-invasive assessment techniques on 40 volunteers for 6 months maintaining double-blind test conditions. According to our results, the use of retinol containing product improved skin color and hydration level slightly. But there was no statistical differences. There was no erythema reaction compared to the use of RA. Especially, the skin elasticity increased above 20% and skin wrinkles of crows' feet region decreased more than 10%. Besides the instrumental analysis, a large majority of volnteers felt that their skin were improved in the case of wrunkles, elasticity, hydration and color.

• International Journal of Concrete Structures and Materials
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• v.9 no.1
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• pp.55-60
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• 2015

In this study, influence of different stone powders (SP), including limestone powders (LP), quartzite powders (QP), and granitic powders (GP), on the hydration behaviors of portland cement, for example, setting time, hydration heat, and hydration products, were discussed. The initial and the final setting time both shorten when the content of LP is 5 %, however, they are slightly delayed by the other two SPs. The LP has no obvious influence on the arrival time of the first peak in the exothermal curves, and it makes the peak value decrease; the other two SPs postpone the appearance of the first peak, and they also make the peak value decrease. For the second peak, LP shifts the peak position to the left, QP has no effect on this peak position, and GP makes the appearance of this peak delayed by 143 min. Similarly, three kinds of SPs have different influence on the hydration products of portland cement. The LP precipitates the formation of hydrated calcium carbo aluminate, the QP the formation of hydrated garnet, and the GP makes the amount of Tobermorite increase.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.84-92
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• 2014

The purpose of study is to analyze mechanism with early high portland cement and hardening accelerator. As the result, it was concluded that hardening accelerator makes accelerates appearance of $Ca(OH)_2$ through experiment using TG-DTA when it hydrates with cement. On the result of compressive strength, as increasing the amount of hardening accelerator used, early compressive strength was improved. Also, as a result of hydration heat, hardening accelerator accelerates hydration of $C_3S$ that is cement's component. On the result of XRD's analyzation, hydration product for each age could be check and it was shown that as increasing the amount of hardening accelerator used, peak point of hydration product was recorded high. As the result of SEM, appearance of C-S-H was shown as the amount of $Ca(OH)_2$'s appearance and each age according to additive contents of hardening accelerator. Therefore hardening accelerator used on this study is effective on getting early compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.321-330
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• 2020

The addition of a limestone filler(LF) to fill into the voids between cement and aggregate particles can reduce the cementitious paste volume. In previous studies, it has been found that the addition of LF to reduce the cementitious paste volume would substantially increase the compressive strength, and reduce the heat generation. This paper aim to evaluate the influence of LF contents on the hydration kinetics and compressive strength. Hydration kinetics were evaluate using heat of hydration, ignition loss and thermal analysis. The heat of hydration was measured using Isothermal Calorimetry. The degree of hydration was measured using ignition loss. Hydration product analysis was carried out by Thermal Gravimetric and Differential Thermal Analysis. The results show that the addition of LF reduces not only the initial setting time and heat of hydration peak, also degree of hydration and rate of strength development at early age increase with the addition of LF. It can be concluded the LF fills the pore between cement particles due to formation of carboaluminate, which may accelerate the setting of cement pastes.

• Journal of Veterinary Clinics
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• v.18 no.3
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• pp.206-210
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• 2001

Various commercial shampoos were frequently prescribed for dermatologic therapy in small animal practice. Skim hydration affected by the shampoos, however, was not evaluated routinely. In order to evaluate the skin hydration for the exact prescription of shampoos method to measure skin hydration of shampoos are needed. This study was undertaken to evaluate the skin hydration effect of shampoo on canine skin using Corneometer. Five healthy dogs were applied with 7 commercial shampoos: Humilac, Sebocalm, Sebolytics, Etiderm, Benzoyl peroxide, HyLyt and Zn-7 Derm. Skin hydrations were evaluated by measurement of electrical capacitance by Corneometer. A statistically significant increase in skim hydration was found 17(p<0.05) and 77 minutes(p<0.01) after application of Humilac indicating a humidifying effect of this product. A statistically significant decrease in skin hydration was found for the Benzoyl peroxide after 77 minutes(p<0.05). No statistically significant differences between the other shampoos were found. None of the products tested had any negative effect on the skin barrier function. The Corneometer was found useful for detecting skin hydration to shampoos and considered as a simple and useful tool for prescription of various shampoos routine practice.

• Smart Structures and Systems
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• v.12 no.1
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• pp.41-54
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• 2013

Concrete is known as a heterogeneous product which is composed of complex chemical composition and reaction. The development of concrete thermal effect during early age is critical on its future structural health and long term durability. When cement is mixed with water, the exothermic chemical reaction generates hydration heat, which raises the temperature within the concrete. Consequently, cracking may occur if the concrete temperature rises too high or if there is a large temperature difference between the interior and the exterior of concrete structures during early age hydration. This paper describes the contribution of novel Fabry-Perot (FP) fiber optic temperature sensors to investigate the thermal effects of concrete hydration process. Concrete specimens were manufactured under various water-to-cement (w/c) ratios from 0.40 to 0.60. During the first 24 hours of concreting, two FP fiber optic temperature sensors were inserted into concrete specimens with the protection of copper tubing to monitor the surface and core temperature change. The experimental results revealed effects of w/c ratios on surface and core temperature developments during early age hydration, as well as demonstrating that FP fiber optic sensors are capable of capturing temperature variation in the concrete with reliable performance. Temperature profiles are used for calculating the apparent activation energy ($E_a$) and the heat of hydration (H(t)) of concrete, which can help us to better understand cement hydration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.95-102
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• 2022

Recently, there has been a growing interest in reducing greenhouse gases in all industrial fields. In the construction industry, studies have been conducted for the use of high-volume fly ash concrete to replace cement with fly ash. Quantitative measurements of cement hydration and fly ash reactivity enable a clear understanding of the strength development mechanism of high-volume fly ash concrete. It is very difficult to describe the reactivity in a simple way because the hydration and pozzolanic reactions of cement paste containing fly ash are very complex and the composition of the hydration product cannot be accurately determined. This study investigated the hydration and mechanical properties of high volume fly ash (HVFA) cement according to the substitution rate of fly ash (FA). The hydration degree of cement and the reactivity of FA were evaluated through the selective dissolution method and the non-evaporable water content of the paste according to age. In addition, compressive strength was measured using HVFA mortar specimens according to age. As a result of the experiment, as the substitution rate of fly ash increased, the hydration degree of cement increased, but the reactivity of FA decreased.