• Title/Summary/Keyword: hydration products

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Evaluating the Efficacy of Whitening Products by Using Luminescence Measurement and Revealing Correlation between Luminescence and Other Parameters (투명감 측정을 통한 제형의 미백 효능 평가와 투명감에 관여하는 요소들에 대한 분석)

  • Jeong, Choon-Bok;Kim, Han-Kon;Nam, Gae-Won
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.36 no.4
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    • pp.253-258
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    • 2010
  • Until now, evaluating the efficacy of brightening mainly depends on total reflective light measurement. For example, SHV (Saturation, Hue, Value), $L^*$ $a^*$ $b^*$ (CIELAB color space system) color space system was used and lightness and saturation changes were chosen as major parameters for evaluating brightening effect. However, those parameters were calculated from total reflective light on the skin and it is hard to evaluate perceptive efficacy such as luminescence, and glossy. In this research, we applied new method for estimating change of luminescence of skin by using 'Lumiscan' which uses polarized light for detecting surface and inside reflective light independently. We also tested 15 different parameters for finding correlations between luminescence and those parameters. As a results, our 2 different brightening products showed 5 ~ 9 % increase of luminescence at 4 and 8 weeks. And we also found that skin roughness (-28 %), melanin index (-17 %), redness (-7 %), hydration (15 %), and lightness (6 %) were related to luminescence of skin.

Properties of Strength Development of Concrete at Early Age Using High Fineness Cement and Fly Ash (고분말도 시멘트와 플라이애시를 치환한 콘크리트의 조기강도 발현 특성)

  • Ha, Jung-Soo;Kim, Han-Sic;Lee, Young-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.2
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    • pp.154-160
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    • 2018
  • Cement industries are considered key industries for reducing carbon emissions, and efforts are off the ground to reduce the use of cement in the concrete sector. As a part of this effort, research is off the ground to utilize a large amount of industrial by-products that can be used as a substitute for a part of cement. Concrete using industrial by-products has advantages such as durability, environment friendliness and economical efficiency, but there are problems such as retarding and early-age strength deterioration. Therefore, this study aimed to reduce the use of cement and solve the problem of early-age strength deterioration while using fly ash, which is an industrial by-product. Accordingly, it was confirmed that the strength was improved at all ages irrespective of curing temperature by accelerating the hydration reaction by using high fineness cement. Subsequently, high fineness cement was partially replaced with fly ash and the strength development characteristics were examined. As a result, it was possible to exhibit strength equal to or higher than ordinary portland cement even at the early age. Also, it was confirmed that even when the fly ash is replaced by 30%, it is possible to shorten the time for dismantling the forms of vertical and horizontal members.

A Study on the Compaction and Permeability According to the Mixture Ratio of Pond Ash and Bentonite for Liner Material (매립지 차수재로써 매립회-벤토나이트 혼합비에 따른 다짐 및 투수특성에 관한 연구)

  • Lee, Jungsang;Lee, Jonghwi;Lee, Jinkyu;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.1
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    • pp.31-36
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    • 2012
  • Recently, industrial by-products are exponentially growing because energy consumption is increasing due to rapid industrial development and improved living standards. The purpose of this study is to determine the proper mixing ratio to meet the liner conditions(must be less than $1{\times}10^{-7}$cm/sec), using pond ash and bentonite as liner. As the result of the compaction test, depending on the increase mixing ratio of bentonite, the maximum dry unit weight was decreased but the optimum moisture content was tended to be increased at the compaction curve. As the result of the permeability test, depending on the increase mixing ratio of bentonite, the coefficient of permeability showed tendency to be decreased in the form of index and the tendency was caused by the hydration reactions filling the void of the pond ash. When the mixing ratio of bentonite was approximately over 15%, it was satisfied with the land fill liner conditions. In other words, it is necessary to consider other mixtures containing the cement or another material in the economical aspect for application of the pond ash.

Experimental Study on Improving Compressive Strength of MWCNT Reinforced Cementitious Composites (MWCNT 보강 시멘트 복합체의 압축강도 향상에 대한 실험적 연구)

  • Kang, Su-Tae;Park, Soon-Hong
    • Journal of the Korea Concrete Institute
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    • v.26 no.1
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    • pp.63-70
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    • 2014
  • This experimental study was intended to improve the compressive strength of multi-walled CNT reinforced cementitious composites with efficiency. The variables considered are the degree of sonication, the amount of surfactant, the replacement ratio of silica fume, etc. Optical microscope informed that fiber dispersion of CNT was improved with the increase of sonication time, and the compressive strength was proved to be enhanced as the degree of sonication increased. When superplasticizer as a surfactant had SP/CNT ratio of 4~6, the best improvement in strength was obtained. Silica fume was shown to produce the highest compressive strength at 10% replacement. Microstructure of CNT composites was also analyzed; XRD and SEM results indicated that CNT addition hardly changed hydration products and microstructure, and MIP analysis found the reduction of total porosity as well as the increase of nano-pores with the size of tens of nm instead of the decrease of pore distribution in the region of around 10 ${\mu}m$ and 100 nm. The results of microstructure analysis explains that the strength improvement is closely related to physical contribution rather than chemical influence by adding CNT.

The Influence of Al2O3 on the Properties of Alkali-Activated Slag Cement (알칼리 활성화 슬래그 시멘트의 특성에 미치는 Al2O3의 영향)

  • Kim, Tae-Wan;Kang, Choong-Hyun
    • Journal of the Korea Concrete Institute
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    • v.28 no.2
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    • pp.205-212
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    • 2016
  • This research investigates the influence of ground granulated blast furnace slag (GGBFS) composition on the alkali-activated slag cement (AASC). Aluminum oxide ($Al_2O_3$) was added to GGBFS binder between 2% and 16% by weight. The alkaline activators KOH (potassium hydroxide) was used and the water to binder ratio of 0.50. The strength development results indicate that increasing the amount of $Al_2O_3$ enhanced hydration. The 2M KOH + 16% $Al_2O_3$ and 4M KOH + 16% $Al_2O_3$ specimens had the highest strength, with an average of 30.8 MPa and 45.2 MPa, after curing for 28days. The strength at 28days of 2M KOH + 16% $Al_2O_3$ was 46% higher than that of 2M KOH (without $Al_2O_3$). Also, the strength at 28days of 4M KOH + 16% $Al_2O_3$ was 44% higher than that of 4M KOH (without $Al_2O_3$). Increase the $Al_2O_3$ contents of the binder results in the strength development at all curing ages. The incorporation of AASC tended to increases the ultrasonic pulse velocity (UPV) due to the similar effects of strength, but increasing the amount of $Al_2O_3$ adversely decreases the water absorption and porosity. Higher addition of $Al_2O_3$ in the specimens increases the Al/Ca and Al/Si in the hydrated products. SEM and EDX analyses show that the formation of much denser microstructures with $Al_2O_3$ addition.

Effect of Phosphate-to-binder and Water-to-binder Ratio on Magnesia-potassium Phosphate Cement (마그네시아-인산칼륨 시멘트에 대한 인산염 비 및 물-결합재비의 영향)

  • Lee, Kyung-Ho;Yoon, Hyun-Sub;Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.29 no.3
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    • pp.275-281
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    • 2017
  • This study examined the effect of water-to-binder ratio (W/B) and phosphate-to-binder ratio (P/B) on the flow, setting time, compressive strength development, and pH variation of magnesium-potassium phosphate composites, MKPC mortars. Ten mortars mixtures were prepared with the W/B varying from 20% to 40% at each P/B of 0.3 or 0.5. The hydration products and microstructural pore distribution of the MKPC pastes were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The initial flow and setting time of MKPC mortars tended to decrease with an increase of P/B, indicating that the final setting time was shortened by approximately 24% when P/B increased from 0.3 to 0.5. The slope of the early-strength development measured in the MKPC mortars was considerably higher than that of cement concrete specified in code provisions. For obtaining a relatively good 28-day strength (above 30 MPa) and a near neutral pH (below 9.0) in MKPC mortars, the P/B and W/B need to be selected as 0.5 and 30%, respectively. The strubite-K crystal increased with the increases of P/B and W/B, which leads to the decrease of the macro-capillary pores.

Physical and Chemical Properties of Cement Mortar with Gamma-C2S

  • Lee, Sung-Hyun;Kim, Kyungnam;Mabudo, Mabudo;Song, Myong-Shin
    • Journal of the Korean Ceramic Society
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    • v.53 no.2
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    • pp.194-199
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    • 2016
  • Presently, for the cement industry, studies that seek to reduce $CO_2$, because of the development of the plastic industry and demand for reduction of energy use, have been actively conducted among them, studies attempting to use Gamma-$C_2S({\gamma}-C_2S)$ to fix $CO_2$ have been actively conducted. The ${\gamma}-C_2S$ compound has an important function in reacting to $CO_2$ and stiffening through carbonatization in the air. The ${\gamma}-C_2S$ compound, reacting to $CO_2$ in the air, generates $CaCO_2$ within the pore structure of cement materials and densifies the pore structure this leads to an improvement of the durability and to the characteristic of resistance against neutralization. Therefore, in this experiment, in order to synthesize ${\gamma}-C_2S$, limestone sludge and waste foundry sands are used these materials are plasticized for 30 or 60 minutes at $1450^{\circ}C$, and are prevented from being cooled in the temperature range of $30{\sim}1000^{\circ}C$ when they are about to be cooled. XRD analysis and XRF analysis are used to determine the effects of this process on ${\gamma}-C_2S$ synthesization, the temperature at which a thing is plasticized, and the conditions for cooling that obtain in the plasticized clinker also, in order to confirm the $CO_2$ capture function, analysis of the major hydration products is conducted through an analysis of carbonatization depth and compressive strength, and through MIP analysis and XRD Rietveld analysis. As a result of these analyses, it is found that when ${\gamma}-C_2S$ was synthesized, the clinker that was plasticized at $1450^{\circ}C$ for one hour demonstrated the highest yield rate the sample with which the ${\gamma}-C_2S$ was mixed generated $CaCO_3$ when it reacted with $CO_2$ therefore, carbonatization depth and porosity were reduced, and the compressive strength was increased.

Properties of Non-Sintered Cement Mortar using Alkali and Sulfate Mixed Stimulants Accroding to Curing Method (양생방법에 따른 알칼리 및 황산염 복합자극제를 사용한 비소성 시멘트 모르타르의 특성)

  • Park, Sung-Joon;Kim, Ji-Hoon;Hyung, Won-Gil
    • Journal of the Korea Concrete Institute
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    • v.27 no.3
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    • pp.237-244
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    • 2015
  • Entering the 20th century since the industrial revolution, the cement has been widely used in the field of construction and civil engineering due to the remarkable development of construction industry. However, result from that development, each kind of industrial by-products and waste and the carbon dioxide generated in the process of cement production cause air pollution and environmental damage so earth is getting sick now slowly. Therefore, we have to recognize importance about this. It means that the time taking specific and long-term measures have come. In this research paper, as substitution of the cement generating environmental pollution, we investigate the hydration reaction of non-Sintered Cement mortar mixed with GBFS, active stimulant of alkaline and sulphate series by using SEM and XRD, mechanical and chemical properties according to the curing method. As a result of this experiment, NSC realized outstanding strength for water curing and steam curing. It means that it has a good possibility as substitution of cement. From now on, it can be used for structure satisfying specific standard. We expect to find a substitution of outstanding cement by progressing continuous research making the best use of pros and cons according to the curing method.

The Effects of Na2CO3 on Early Strength of High Volume Slag Cement (대량치환 슬래그 시멘트의 초기강도에 미치는 Na2CO3의 영향)

  • Kim, Tae-Wan;Hahm, Hyung-Gil
    • Journal of the Korea Concrete Institute
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    • v.28 no.3
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    • pp.349-356
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    • 2016
  • This report presents the results of an investigation on the early strength development of pastes high volume slag cement (HVSC) activated with different concentration of sodium carbonate ($Na_2CO_3$). The ordinary Portland cement (OPC) was replaced by ground granulated blast furnace slag (GGBFS) from 50% to 90% by mass, the dry powders were blended before the paste mixing. The $Na_2CO_3$ was added at 0, 2, 4, 6, 8 and 10% by total binder (OPC+GGBFS) weight. A constant water-to-binder ratio (w/b)=0.45 was used for all mixtures. The research carried out the compressive strength, ultrasonic pulse velocity (UPV), water absorption and X-ray diffraction (XRD) analysis at early ages(1 and 3 days). The incase of mixtures, V5 (50% OPC + 50% GGBFS), V6 (40% OPC + 60% GGBFS) and V7 (30% OPC + 70% GGBFS) specimens with 6% $Na_2CO_3$, V8 (20% OPC + 80% GGBFS) and V9 (10% OPC + 90% GGBFS) specimens with 10% $Na_2CO_3$ showed the maximum strength development. The results of UPV and water absorption showed a similar tendency to the strength properties. The XRD analysis of specimens indicated that the hydration products formed in samples were CSH and calcite phases.

A Study on Properties of High Blaine Cement for Shotcrete (숏크리트용 고분말도 시멘트의 특성)

  • Kim, Jae-Young;Kim, Teuk-Jun;Lee, Min-Suk;Ryoo, Dong-Woo
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.633-640
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    • 2010
  • This study was performed to get basic information about properties of high blaine cement for shotcrete use. Particle size distribution, setting time and compressive strength test, analysis like as SEM, DSC thermal analysis, XRD was carried out to investigate principle properties of high blaine cement. Setting time of high blaine cement was shorter and compressive strength was higher than those of ordinary portland cement (OPC). Results of analysis showed early hydration products of high blaine cement is smaller and spread widely due to increased specific surface. From the SEM observation and analysis of DSC and XRD results, it was seen that the aluminates accelerators promoted calcium aluminium hydrates while the alkali free accelerators increased ettringite and monosulfates formation. Strength and setting time measurement of cement paste with aluminate accelerator is more effective than the alkali free accelerator in reducing the setting time and increasing early strength while alkali free accelerator is more effective in increasing the strength after 7 days.