• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.37-46
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• 2015

In this study, a blast furnace slag with the alkaliphilic microorganism (Bacillus halodurans) alkaline activator was used to cement natural soils in the field. A low-cost and massive microbial solution for cementation of field soils was produced and compared with existing microbial culture in terms of efficiency. A field soil was prepared for three different cementation areas: a cemented ground with microbial alkaline activator (Microbially-treated soil), a cemented ground with ordinary Portland cement (Cement-treated soil), and untreated ground (Non-treated soil). The testing ground was prepared at a size of 2.6 m in width, 4 m in length, and 0.2 m in depth. After 28 days, a series of unconfined compression tests on the cement-treated and microbially-treated soils were carried out. On the other hand, a torvane test was carried out for non-treated soil. The strength of field soils treated with microorganism was 1/5 times lower than those of cement-treated soil but is 6 times higher than non-treated soil. The pH measured from microbially-treated soil was about 10, which is lower than that of cement-treated soil (pH = 11). Therefore, it is more eco-friendly than Portland cemented soils. The C-S-H hydrates were found in both cement- and microbially-treated soils through SEM-EDS analyses and cement hydrates were also found around soil particles through SEM analysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.257-262
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• 2015

Recently the world wide efforts reduce occurrence of $CO_2$; global warming main reason. The aim of this study is to improve recycling rate of the fly ash (FA) and fused waste slag (FWS) from the power plant and to carbonate under supercritical condition ($40^{\circ}C$, $80kgf/cm^2$ pressure, 60 min) for $CO_2$ fixation. Specimens of mortar with various mixing ratios of FA, FWS (from 100:0 to 20:80 in 5 steps of 20 % reduction each time), distilled water and 3 M NaOH alkali activators were prepared. As a result, the proportion of weight change ratio increases with CaO content, to 12 % after carbonation under the supercritical condition. There is difference of compressive strength between the carbonated and the alkali activator mortar specimens. The stabilization of $CO_2$ fixation through carbonation which could confirm the applicability of the eco-friendly materials without loss of compressive strength.

• Resources Recycling
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• v.17 no.6
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• pp.68-78
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• 2008

Using a Pinus koraiensis and Pinus rigida which are normally being discarded in South Korea, optimal conditions of producing activated carbons have been studied to recycle as a higher value-added product. This study consists of two processes, the production process of charcoals from waste timbers by low temperature pyrolysis and the production process of activated carbons from the charcoals by chemical activation reaction. This paper deals with the production process of activated carbons from the charcoals by chemical activation reaction. As an alkali has been generally used as an activating agent, KOH and NaOH which react well with a carbon were used in this study. As a result of the experiments, it is confirmed that activated carbons made with KOH treatment had superior values in physicochemical properties to NaOH, showing that there was no remain of KOH at the surface of the charcoals while there was $3{\sim}4%$ of NaOH remaining after the experiments. Thus, it is concluded that KOH reacted more actively with a charcoal than NaOH. Moreover, it was also found that values in physicochemical properties when using a Pinus koraiensis are superior to the ones when using a Pinus rigida. The optimal mixing ratio of an activating agent to a charcoal was 400 wt.%. To improve the physicochemical properties, activated carbons were washed out by distilled water after neutralization with SM hydrochloric acid solution. When activated carbons were produced from a Pinus koraiensis in this optimal conditions, value of BET surface area was found to be approx. $2400\;m^2/g$.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.321-329
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• 2016

The use of ternary blended cement consisting of Portland cement, granulated blast-furnace slag (GGBFS) and fly ash has been on the rise to improve marine concrete structure's resistance to chloride attack. Therefore, this study attempted to investigate changes in chloride attack resistibility of concrete through NT Build 492-based chloride migration experiments and test of concrete's ability to resist chloride ion penetration under ASTM C 1202(KS F 2271) when 1.5-2.0% of alkali-sulfate activator (modified alkali sulfate type) was added to the ternary blended cement mixtures (40% ordinary Portland cement + 40% GGBFS + 20% fly ash). Then, the results found the followings: Even though the slump for the plain concrete slightly declined depending on the use of the alkali-sulfate activator, compressive strength from day 2 to day 7 improved by 17-42%. In addition, the coefficient from non-steady-state migration experiments for the plain concrete measured at day 28 decreased by 36-56% depending on the use of alkali-sulfate. Furthermore, total charge passed according to the test for electrical indication of concrete's ability to resist chloride ion penetration decreased by 33-62% at day 7 and by 31-48% at day 28. As confirmed in previous studies, reactivity in the GGBFS and fly ash improved because of alkali activation. As a result, concrete strength increased due to reduced total porosity.

• 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.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.657-665
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• 2013

The purpose of this study is the basic research of self-compacting concrete using Alkali-Activated Slag (AAS) binder in order to emphasize the durability of structures and facilitate casting the fresh concrete in field. The AAS binder emitted low carbon dioxide ($CO_2$) is eco friendly material of new concept because AAS products not only emit little $CO_2$ during production but also reuse the industrial by-products such as ground granulated blast-furnace slag (GGBS) of the steel mill. Until now, almost of domestic and foreign research are using Ordinary Portland Cement (OPC) for self-compacting concrete, and also, nonexistent research about AAS. The self-compacting concrete must get the performance of flowability, segregation resistance, filling and passing ability. Nine concrete mixes were prepared with the main parameter of unit amount of binder (400, 500, 600 $kg/m^3$) and 3 types of water-binder (W/B) ratio. The results of test were that fresh concretes were satisfied with flowability, segregation resistance, and filling ability of JSCE. But the passing ability was not meet the criteria of EFNARC because of higher viscosity of AAS paste than OPC. This high viscosity of AAS paste enables the manufacturing of self compacting concrete, segregation of which does not occur without the using of viscosity agent. It is necessary that the development of high fluidity AAS binders of higher strength and the study of better passing ability of AAS concrete mixes in order to use self compacting AAS concrete in field.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.487-494
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• 2011

In this research, the possibility of using bottom ash as a binder for the alkali-activated cement mortar is studied. Several experiments were performed to investigate the variation of the material properties according to the mix proportion. In the experimental program, the flowability and compressive strength were evaluated for various values of water/ash ratio, activator/ash ratio, sodium silicate to sodium hydroxide ratio, curing temperature, and the fineness of bottom ash as the main variables. The experimental results showed that high strength of 40 MPa or greater could be achieved in $60^{\circ}C$ high temperature curing condition with proper flowability. For $20^{\circ}C$ ambient temperature curing, the 28 days compressive strength of approximately 30MPa could be obtained although the early-age strength development was very slow. Based on the results, the range of optimized mix design of bottom-ash based alkali-activated cement mortar was suggested. In addition, using the artificial neural network analysis, the flowability and compressive strength were predicted with the difference in the mix proportion of the bottom-ash based alkali-activated cement mortar.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.119-124
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• 2004

최근 소형 다기능, 고기능 전자장비의 개발로 인하여 고밀도 전원이 필요성이 대두되고 있다. 연료전지는 높은 전력 밀도를 가짐으로 인하여 소형 전원 장비에 가능성을 가지는 것으로 여겨지고 있다. 연료전지 중 특히 고분자 전해질 연료전지는 높은 전력밀도와 낮은 작동온도 등으로 인하여 이차전지의 자리를 대체할 수 있을 것으로 보여지지만 현재까지 연료 공급장치의 문제로 인하여 실용화되지 못하고 있다. 본 연구에서는 여러 가지 수소저장 물질 중에서 알칼리 붕소 수소화물을 이용하여 연료전지에 수소를 공급하고자 하며, 수소발생에 사용되는 촉매에 대한 연구를 진행하였다. 알칼리 붕소 수소화물의 수소발생 반응에 사용되는 촉매로는 Pt, Ru, Co, Ni 등이 사용되어질 수 있다. 이중에서 가장 수소발생 능력이 높은 촉매는 Ru이며, 비귀금속 촉매 중에는 Co가 높은 활성을 나타내었다. 본 연구에서는 Ru 촉매와 Co 촉매의 특성을 비교하였으며 연료전지에 수소를 공급할 수 있는 가능성을 확인하였다. Ru와 Co 촉매의 공통적인 특징은 알칼리 붕소화물인 NaBH$_4$의 농도가 높아질수록, 온도가 높아질수록 수소의 발생속도를 높이는 현상을 보였다. 또한 안정화제인 NaOH에 대하여, Ru의 경우는 농도가 높아질수록 수소발생 속도가 낮아졌으며, Co는 그 반대의 결과를 보였다. NaBH$_4$의 분해 반응으로 발생된 수소를 연료전지에 공급하여 2W급의 휴대폰용 연료전지를 구동할 수 있었다. 이로써 알칼리 붕소수소화물로부터 발생된 수소를 이용하여 안정적으로 연료전지를 구동할 수 있는 가능성을 확인하였다. 유류 분해정도를 파악하는 지시자로써 특정 무기 오염물질을 이용할 수 있을 가능성이 있으므로 좀더 이들 관계성에 대한 연구가 진행될 필요성이 있다고 판단된다.고 과학적으로 분석할 수 있는 방법이 될 수 있을 것으로 기대된다. 의미를 되새기는 것으로 짧은 연구를 시작하겠다. 등은 활성 값이 70% 이상으로 퇴적물 독성이 상대적으로 낮았다. 이중나선 DNA 함량은 28.4 % - 49%로 대조군에 비해서 감소가 크다. 대부분의 정점이 대조군의 30% 내외로 정점 간의 차이는 크지는 않다. 그러나 다른 측정자료와 같이 정점 22에서 18%로 최소치를 나타내고, 정점 2, 12에서 20% 내외의 값을 보인다. 종합적으로 볼 때 오염물질의 유입이 크고, 광양제철 인근 정점 들이 모두 다른 정점에 비해서 낮아서, 퇴적물 독성이 높은 정점으로 조사되었다.hiwo의 광합성 능력은 낮은 농도들에서는 대조구와 유사하였으나, 5 $\mu\textrm{g}$/l의 높은 농도에서는 초기에 매우 낮은 광합성 능력을 보이다가 시간이 경과하면서 대조군보다 더 높은 경향을 나타냈다. 이러한 결과는 식물플랑크톤이 benso[a]pyrene의 낮은 농도에서 노출될 때는 이 물질을 탄소원으로 사용할 가능성이 있음을 시사한다. 본 연구의 결과들은 연안해역에 benso[a]pyrene과 같은 지속성 유기오염물질이 유입되었을 때 내정여부에 따라 식물플랑크톤 군집내 종 천이와 일차생산력에 크게 영향을 미칠 수 있음을 시사한다.TEX>5.2개)였으며, 등급별 회수율은 각각 GI(8.5%), GII(13.4%), GIII(43.9%), GIV(34.2%)로 나타

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.75-84
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• 2016

This paper presents an investigation of the mechanical properties on non-sintered cement pastes immersed in sea waters at three different temperatures. The non-sintered cement pastes were synthesized using blended binder(Class F fly ash; FA and ground granulated blast furnace slag; GGBFS) and alkali activator(sodium hydroxide and sodium silicate). Binders were prepared by mixing the FA and GGBFS in different blend weight ratios of 6:4, 7:3 and 8:2. The alkali activators were used 5wt% of blended binder, respectively. Calcium carbonate was used as an chemical additive. The compressive strength, bulk density and absorption of alkali-activated FA-GGBFS blends pastes were measured at 3 and 28 days after immersed in sea waters at three different temperatures($5^{\circ}C$, $15^{\circ}C$ and $25^{\circ}C$). The XRD and SEM tests of the pastes were conducted at 28 days. Water-soluble chloride(free chloride) and acid-soluble chloride(total chloride) contents in the pastes were also measured after 28 days immersion in sea water. The experimental results showed that increasing the content of FA in alkali-activated FA-GGBFS blends pastes immersed in sea water increases the absorption, water-soluble chloride content and acid-soluble chloride content, and reduces the compressive strength and bulk density. And it was found that there was a variation of strength change for the alkali-activated FA-GGBFS blends pastes immersed in sea waters at three different temperatures that depends on the blending ratio of FA and GGBFS.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.47-54
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• 2017

Cement industry is typical carbon-emission industry. If the industrial by-products(granulated blast-furnace slag (GGBFS), fly ash, etc.) are used a large amount, it might be able to reduce cement consumption and mitigate carbon emissions. In this case, however, decrease of early strength is relatively large. Therefore, there is a limitation in increase of the amount of substitute. Considering these circumstances, it would be a good solution to reduce carbon emissions in cement industry to improve the performances of mixed cement through proper alkali-activation in Portland blended cement using GGBFS or fly ash. Therefore, this study prepared concrete in ready-mixed concrete manufacturing facilities with an addition of a binder which used 2.0% modified alkali sulfate activator after mixing Portland cement, GGBFS and fly ash in the ratio of 4:4:2 and assessed its basic properties. The results found the followings: The use of modified alkali-sulfate activator slightly reduced slump and shortened setting time. As a result, bleeding capacity decreased while early strength improved. In addition, there is no big difference in carbonation resistance. It appears that there should be continued experiments and analyses on the related long-term aged specimens.