• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.1-7
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• 2015

The objective of this study is to develop a high-performance foamed concrete made with a new mixture proportioning as an alternative of autoclaved lightweight concrete (ALC) block. For the early-strength gain of the foamed concrete under an atmospheric curing condition, the binders and chemical agents were specially contrived as follows: 3% anhydrous gypsum was added to ordinary portland cement (OPC) in which $3CaO{\cdot}SiO_2$ content was controlled to be above 60%; and the content of polyethylene glycol alkylether in a polycarboxylate-based water-reducing agent was modified to be 28%. Using these binders and chemical agents, 11 mixes were prepared with the parameters of W/B ratio (30% to 20% in a interval of 2.5%) and unit binder content ($400kg/m^3$ to $650kg/m^3$ in a interval of $50kg/m^3$). The quality and availability of the mixed foamed concrete were examined according to the minimum requirements specified in the KS for ALC block and existed conventional foamed concrete. The measured properties satisfied the minimum requirement of KS for ALC block and proved that the developed high-performance foamed concrete had considerable potential for practical application.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.141-141
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• 2016

방식 코팅 기술은 조선해양산업은 물론 에너지, 철강 및 비철 소재, 건설 산업 등 산업 전반에서 폭넓게 적용되고 있다. 또한 산업 고도화에 따라 점차 가혹해지는 소재의 적용 환경을 고려해보면 향후 지속적으로 산업 수요가 증대될 것으로 예상할 수 있는 기술이다. 특히 아크 열용사법을 이용한 방식 코팅 기술은 미국이나 일본과 같은 선진국에서는 해양플랜트, 석유 시추시설 등 대형 해양 구조물은 물론 다리, 항만시설과 같은 철재 또는 시멘트 구조물의 방식 기술로 널리 적용되어 일반화된 기술이다. 그러나 국내에서는 아직까지도 초기 비용 상승 및 미약한 관련 기술 등의 이유로 대부분 방식도료를 사용하고 있는 실정이다. 그리하여 단기 수명에 따른 재시공 시 많은 환경오염을 유발하는 방식도료를 대체할 수 있는 아크 열용사법을 이용한 방식코팅 기술에 대한 관심과 수요가 점차 증가되고 있다. 그 일환으로 본 연구에서는 해양 구조물 강재의 방식을 위해 니켈계 용사재료를 이용하여 아크 열용사 코팅을 실시한 후 다양한 전기화학적 실험을 통해 내식성을 평가하고자 하였다. 아크 열용사 코팅은 구조용 강재 SS400강에 대하여 니켈합금 선재(1.6 Ø)를 사용하여 실시하였다. 용사 시 용사거리는 200 mm, 공기압력은 약 $7kg/cm^2$ 정도로 유지하면서 용사코팅을 실시하여 약 $200-250{\mu}m$ 두께로 코팅 층을 형성시켰다. 그리고 전기화학적 실험은 천연해수 속에서 자체 제작한 홀더(holder)를 이용하여 $3.14cm^2$의 용사코팅 층만을 노출시켜 실시하였다. 그리고 기준전극은 은/염화은 전극을, 대극은 백금전극을 사용하였다. 전기화학적 실험을 통해 부동태 특성 및 용사코팅 층 표면의 양극 용해반응 특성을 분석하기 위한 양극분극 실험은 OCP로부터 +3.0 V까지 실시하였다. 또한 부식전위 및 부식전류밀도 분석을 위한 타펠분석은 OCP를 기준으로 -0.25에서 +0.25 V까지 분극시켜 실시하였다. 그리고 주사전자현미경과 3D 분석을 통해 부식손상 표면을 관찰하였다. 그 결과 니켈합금으로 용사코팅된 강재의 내식성이 상당히 향상되었다.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.523-529
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• 2014

Large amounts of waste shells have been produced each year from shellfish raising industries located in Korean costal areas. Due to the limited space for the waste shell disposal, the related environmental problem has been a serious issue. It is believed that using the waste shells as a source of aggregate for mortar, concrete or bricks can be a good solution. In this research, possibility of utilizing waste shells as an aggregate of mortar is investigated. Waste shells of manila clam, cockle, clam, sea mussel, and oyster were properly crushed, sieved, and sorted to meet the requirements of the grading of standard fine aggregate. After that, the waste shells were used as partial and total replacement of the fine aggregate, and their absorption and 28-day compressive strengths of mortar were measured. In general, replacement of waste shells increased the absorption and decreased the strength. However, one specimen with cockle increased compressive strength as replacement ratio increased. Mortar with cockle of 50% and 100% replacement showed higher compressive strength than that of control mortar. This increase of compressive strength was found to be affected by the strong interfacial bonding properties of the cockle and a cement matrix.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.577-584
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• 2012

Carbonation resistance is one of the most influencing factors on durability of concrete. Alkali activated slag (AAS) is known to have weaker resistance for carbonation than OPC due to the low calcium contents. In this paper, the carbonation characteristic of AAS mortar which is related to the basicity (CaO/$SiO_2$) was investigated. In order to give the various basicity conditions, SM (source material) was blended with quicklime (CaO) and silicon dioxide ($SiO_2$) by adopting mechano-chemical treatment method. Experiments including flow test, compressive strength test, carbonation depth test, together with XRD, FTIR and TGA were employed to evaluate the effects of basicity of SM on the carbonation characteristics. The test results showed that the carbonation resistance effectively increased with the increase of the basicity of SM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.119-126
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• 2018

Recently, the production of circulating fluidized bed combustion ash has been increased in thermal power plants. The addition of limestone for the desulfurizing effect of circulating fluidized bed boiler ash increases the content of CaO and $SO_3$ contained in ash, which is higher than the free fly ash in general fly ash. Unlike conventional fly ash, the circulating fluidized bed combustion ash has a high reactivity when it comes into contact with water due to its hydraulic properties and high free-CaO content. The aim of this study is to investigate the possibility of non-sintered binder by using self-cementing properties of circulating fluidized bed combustion ash. The mechanical and hydration characteristics were investigated according to the content of CFBC ash. In addition, the effects of gymsum type and content on the compressive strength and micro-structure of non-sintered binder pastes.

• Journal of the Society of Disaster Information
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• v.10 no.2
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• pp.238-243
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• 2014

Recently environmental pollution is serious and therefore, This study aims at reviewing individual mixing ratio and engineering characteristics of concrete due to mixture and mixing using fine powder and fly ash of blast furnace slag having effect on aspects of environmental preservation and resources recycling and performance increase of the concrete, and verifying possibility of application in the field. Test results are as follows: 1)As mixing quantity of the admixture has increased, performance of the slump has been improved, 2)As mixing quantity of the admixture has increased, there is a trend of delayed ending time, 3)As mixing quantity of admixture has increased, it has showed lower strength at short time age, however, as the age has elapsed and mixing quantity has increased, strength improvement has increased and the admixture has effect on the long term age. In this study, the characteristics and critical value of concrete contained blast furnace slag and fly ash are defined, and will be examined about the field applications.

• Resources Recycling
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• v.23 no.4
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• pp.37-46
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• 2014

Carbon dioxide generated from construction materials and construction material industry among the fields of construction is approximately 67 million tons. It is about 30% of the carbon dioxide generated in the fields of construction. In order to reduce carbon dioxide in the fields of construction, it is necessary to control the use of fossil fuel consumed and decrease carbon emission by reducing the secondary and tertiary curing generating carbon dioxide in construction material industry. Therefore, this study manufactured mortar by having cement as the Plain and substituting three binding materials up to 50% and then adopted different curing methods to analyze congelation and strength characteristics. Test results for strength property by changing binding materials showed that specimens with blast furnace slag, CSA 15% and CAMC 5% resulted in positive effect for strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.271-279
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• 2016

This study examines the properties of high-fluidity concrete after adding copper slag as a mineral admixture. For this purpose, the replacement ratio of cement to copper slag was varied to 0, 10, 20, 30, 40, and 50%. A slump flow test, reach time slump flow of 500 mm, and a U-Box and O-lot test were conducted on the fresh concrete. The compressive strength of the hardened concrete was determined at 3, 7, 14 and 28 days. According to the test results, the workability, compaction, and compressive strength of the high-fluidity concrete increased when replacing 30% of the cement with copper slag. These parameters decreased for all material ages with more than 30% copper slag, which was the optimal mixture ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.125-132
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• 2020

The causes of concrete shrinkage are very diverse, in particular, aggregates impact the characteristics of shrinkage in concrete by constraining the shrinkage of cement paste. Meanwhile, owing to the lack of natural aggregate, various alternative aggregates are being developed, and their application in concrete also becomes more diverse. This study aimed to experimentally evaluate the drying and autogenous shrinkage in concrete that was composed of electric arc furnace slag as coarse aggregates. And, the results were compared with prediction models. From the results, the application of electric arc furnace slag can reduce the drying and autogenous shrinkage. In particular, autogenous shrinkage is greatly decreased. The predictions using GL2000 for drying shrinkage and Tazawa model for autogenous shrinkage were similar to the experimental results. However, the most prediction models do not consider the impact of aggregates, hence, the new prediction model should be developed or improved.

• Journal of the Korean Geotechnical Society
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• v.26 no.9
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• pp.59-69
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• 2010

This study is experimentally investigated for characteristics of lightweight air-trapped soils with uniform quality. Previously, EPS (Expanded PolyStyrene) blocks are often used as lightweight embankment, but many problems such as the level difference and cracks were caused by plastic (creep) deformation. So, a new material development is urgent. By means of alternatives, lightweight air-mixed soil using in-situ soils has been developed and applied to fields. In comparison with EPS block, lightweight air-mixed soil has less plastic (creep) deformation in long period, but the strength characteristics are different according to the soils where they are obtained. Therefore, the quality management of lightweight air-mixed soil is very difficult. Therefore in this study, characteristics of lightweight air-trapped soil using a manufactured sand with uniform quality are investigated. To found out the compression and tensile characteristics of lightweight air-tapped soils, unconfined compression test and splitting tensile test are conducted on the specimens prepared with different unit weight, cement-sand ratio and air-pore.