• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.2
• /
• pp.112-119
• /
• 2023

In this study, the variations in CO₂ uptake according to the type and amount of alkali-based activator (Ca(OH)₂, CSA) of geopolymer paste were evaluated. As the amount of activator added to the geopolymer paste increased, the fluidity of the paste is decreased and the compressive strength increased. According to the type of activator, it was confirmed that the addition of Ca(OH)₂ had a greater effect on improving the compressive strength than CSA. As a result of changes in chemical properties according to carbonation curing, the amount of C-S-H and C-A-S-H gels produced before carbonation increased as the amount of activator increased, and amount of CaCO₃ produced after carbonation increased. The reactivity of the blast furnace slag and zeolite increased due to the addition of the activator, and the reactivity tended to increase as the amount of addition increased. As a result of CO₂ uptake, 10.3 wt% when Ca(OH)₂ 10 % was added and 8.77 wt% when CSA 10 % was added was confirmed. It increased by 421 % and 388 % respectively, compared to the case where no activator was added.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.1011-1018
• /
• 2005

The influence of liquid shotcrete accelerators(alkali aluminate, two types of alkali-free) was investigated. Comparing to the existing alkali aluminate accelerator, new alkali-free accelerator, AF2, shortened initial and final setting of cement system, and after curing for 1 day compressive strength was analogous with others. On the other hand, compressive strength of specimen cured for 12 hour was the highest by the addition of alkali aluminate accelerator, but final strength was the lowest by that. But compressive strengths of AF1, AF2 were similar to Plain up to 28day. Further from XRD(X-Ray Diffractometer) and DSC(Differential Scanning Calorimeter) analyses, we confirmed that setting promoted by alkali aluminate was mainly because of Ca(OH)2(calcium hydroxide), but the accelerating behavior of alkali-free was influenced by the needle-like ettringite$(6CaO{\cdot}Al_2O_3{\cdot}3SO_3{\cdot}32H_2O)$ crystal.

• Applied Chemistry for Engineering
• /
• v.21 no.3
• /
• pp.301-305
• /
• 2010

In this study, the alkaline degreasing agent was developed for electroplating pretreatment process, and the efficiency and the durability was predicted. The alkaline deeping degreasing agent was prepared by blending sodium hydroxide (NaOH), sodium carbonate ($Na_2CO_3$), sodium silicate ($Na_2SiO_3$), and sodium lauric sulfate (SLS). The performance tests of the degreasing agent were evaluated in the $40{\sim}50^{\circ}C$ of the degreasing temperature and 30~40 min of the degreasing time. The efficiency and durability of the prepared degreasing agent were tested by the waterdrop formation test and Hull-cell plating test. The optimum ratio of alkaline degreasing agent was NaOH (30 g/L) + SLS (6.0 g/L) + $Na_2SiO_3$ (2.0 g/L) + $Na_2CO_3$ (40 g/L). Also, the optimum degreasing conditions were $50^{\circ}C$ of the degreasing temperature and 35 min of the degreasing time.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.323-324
• /
• 2010

The purpose of this study was to investigate alkali-silica reaction of accelerating agents in shotcrete. The test was performed with accelerating agents (aluminate, alkali-free, cement based mineral admixture) in the Type I cement. As a test result, using the nonreactive aggregates, detrimental expansion due to alkali-silica reaction doesn't occurred regardless of equivalent alkali contents of accelerating agent.

• The Korean Journal of Mycology
• /
• v.18 no.3
• /
• pp.137-144
• /
• 1990

To examine effects on complement and reticuloendothelial system, alkali extract was isolated from cultured mycelium of Ganoderma lucidum IY107. It was shown to strongly activate both classical and alternative pathways of complement as compared with krestin. Activated complement C3, 3rd peak, was observed by crossed immunoelectrophoresis. It was also shown to activate reticuloendotherial system of ICR mice in the carbon clearance test and to increase hemolytic plaque forming cells of the spleen. Carbohydrate and protein contents of the alkali extract were 10% and 49%, respectively. The carbohydrate consisted of four monosaccharides and the protein contained 16 amino acids.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.151-151
• /
• 2016

수소는 친환경 에너지원으로 주목 받고 있으며 미래 화석연료의 고갈에 대비할 수 있는 물질이다. 수전해는 natural gas steam reforming 또는 coal gasification 같은 방법에 비해 공해 물질의 방출이 없어 미래지향적인 기술로 간주된다. 저온형 수전해는 크게 알칼리 수전해와 고분자 전해질막 수전해로 구분되며 각각의 기술은 장단점을 가지고 있다. 알칼리 수전해는 비백금계 물질을 촉매로 사용할 수 있는 이점이 있으나 알칼리 용액으로 인한 부식, 높은 과전압에 의한 효율저하 그리고 간헐적인 사용에 적합하지 않다. 고분자 전해질막 수전해는 간헐적인 사용이 용이하고 높은 에너지 밀도를 가지지만 산성분위기로 인한 백금계 촉매를 사용해야 하므로 수소 생산 비용이 증가하게 된다. 본 연구에서는 알칼리 수전해와 고분자 전해질막 수전해 방식의 이점을 최대한 이용하고 단점을 극복하기 위한 방법으로 음이온 교환막(anion exchange membrane, AEM)을 적용한 셀 구조를 소개한다. 본문에서는 AEM 수전해 단위 셀의 구성요소들인 AEM 종류, 가스 확산층의 밀도와 운전조건인 알칼리 수용액 농도, 온도의 조건을 다르게 하여 최상의 구성 요소 조건 및 운전조건을 알아보았다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.1
• /
• pp.15-21
• /
• 2023

To prepare zinc oxide powder, three types of sodium-based alkali precipitants such as NaOH, Na₂CO₃, NaOH/NaHCO₃ were compared to the differences in the manufacturing process of zinc oxide powder from zinc precipitate products like intermediates with the consideration of thermodynamic reaction. The prepared zinc precipitate products by the reaction with the sodium-based alkali precipitant were confirmed to respectively hydroxy zinc chloride (Zn₅(OH)₈Cl₂·H₂O) and zinc carbonate hydroxide (Zn₅(OH)₆(CO₃)₂·H₂O) from XRD analysis. Zinc oxide particles were compared in heat treatment at 800℃ according to sodium-based alkali precipitants. The mixed NaOH and NaHCO₃ of alkali precipitant reaction was contributed to synthesize the more uniform zinc oxide particles.

• Journal of the Korea Concrete Institute
• /
• v.16 no.1 s.79
• /
• pp.70-78
• /
• 2004

Although set accelerating agents are used generally in New Austrian Tunneling Method, the standards for test methods and quality of set accelerating agents are not prescribed domestically. In this study, the proprieties of the various standards and the characteristics of set accelerating agents for shotcrete were evaluated. The alkali contents of set accelerating agents based on silicate, aluminate and cement were higher than those of alkali-free ones. From the result, it is thought that the quality control of aggregate should be enhanced and that the number of test cycle of alkali-aggregate reaction should be increased. The setting times of cement paste with set accelerating agents based on silicate and alkali-free ones were different largely with mixing methods. Compressive strength of mortar with set accelerating agents based on silicate, aluminate and cement at one day satisfied the specifications of Korea Concrete Institute. However, the strength ratio compared to control mix at 28 days showed as $50{\~}65\%$ except for the alkali-free set accelerating agents. As a results of setting time and strength test, the establishment of domestic standards that can reflect the characteristics of materials and construction methods of tunnels and that can increase quality of set accelerating agents is required immediately.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.521-522
• /
• 2009

This study is concerned with elevating the penetration depth after carbonation and porosity change of concrete structures by applying alkali silicate hydrophilic impregnants including lithium and potassium silicates.

• Applied Biological Chemistry
• /
• v.34 no.4
• /
• pp.360-365
• /
• 1991

Rheological properties of Shinsunchalbyeo(Japonica) and $Hangangchalbyeo(J{\times}Indica)$ waxy-rice starches gelatinized with thermal or alkali solutions were investigated with rotational viscometer(Brabender Viscotron). The two starches showed Bingham pseudoplastics behavior in $4{\sim}8%$ thermal or alkali gelatinized starch solutions. The shear stress of Hangangchalbyeo starch solution gelatinized with thermal or alkali showed higher values than that of Shinsunchalbyeo starch and the difference of the two varieties gelatinized with alkali showed higher values than that gelatinized with thermal. Consistency index and yield stress values of Hangangchalbyeo starch showed higher than that of Shinsunchalbyeo starch in the two gelatinized methods and the difference of the two varieties gelatinized with alkali showed higher values. And it was higher that the deffendence of consistency index on starch concentration and initial starch concentration of yield stress in the alkali gelatinized samples than those of in the thermal gelatinized ones.