• 한국건축시공학회지
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• 제22권5호
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• pp.507-518
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• 2022

본 연구의 목적은 부착 유형에 따른 준불연 복합단열판의 전단성능을 평가하여 외단열시스템의 구조설계법을 개발을 위한 기초자료를 확보하고자 한다. 준불연 복합단열판을 콘크리트와 동시 타설한 방법, 접착 모르타르를 활용하여 전면도포방식와 점·테두리 접착방법 등을 적용하여 전단성능을 실험적으로 평가하였다. 전단성능평가 결과, 동시 타설방법과 전면도포방식의 전단내력은 거의 유사하였고 점·테두리 접착방식은 약 80% 정도 수준이었다. 또한, 동시 타설방법은 접착 모르타르를 사용하는 방법에 비하여 외단열 시스템으로 적용할 경우 구조적·시공적으로 유리할 것으로 판단된다.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.301-313
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• 2017

This paper presents the fibre-matrix interfacial properties of hooked end steel fibres embedded in ultra-high performance mortars with various water/binder (W/B) ratios. The principle objective was to improve bond behaviour in terms of bond strength by reducing the (W/B) ratio to a minimum. Results show that a decrease in W/B ratio has a significant effect on the bond-slip behaviour of both types of 3D fibres, especially when the W/B ratio was reduced from 0.25 to 0.15. Furthermore, the optimization in maximizing pullout load and total pullout work is found to be more prominent for the 3D fibres with a larger diameter than for fibres with a smaller diameter. On the contrary, increasing the embedded length of the 3D fibres did not result in an improvement on the maximum pullout load, but increase in the total pullout work.

• 한국건축시공학회지
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• 제11권5호
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• pp.442-451
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• 2011

Blast furnace slag is recycled as a high value-added material, while steel slag is difficult to recycle or is recycled as a low-grade filler material due to its expansive characteristics. Its property is caused by the high content of free lime and instable steel oxides. Recently, an innovative and rapid cooling method for melting steel slag has been developed in Korea, which reduces free lime content to a minimum level and increases the stability of steel oxides. However, researches on the long-term stability are not sufficient so far. Therefore, this study, focusing on the electric arc furnace oxidizing slag in the steel slag, aims to investigate the properties of the steel slag aggregate, its long-term volume stability and the engineering strength of mortar, and using it as a fine aggregate. This study result indicated that it was possible for it to be used as concrete aggregate because the volume change of the steel slag appeared to be stable.

• 한국구조물진단유지관리공학회 논문집
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• 제23권3호
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• pp.83-91
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• 2019

본 연구는 화재 피해를 입은 콘크리트 구조물을 디지털 카메라 및 이미지 프로세싱 소프트웨어를 활용하여 손상도 평가를 하기 위한 기초 연구이다. 이를 위해 W/C=0.5(일반 강도) 및 0.3(고강도)의 모르타르 및 페이스트 시료를 전기로에 넣어 $100^{\circ}C$에서 $1000^{\circ}C$까지 화재피해를 모사한 후, 압축강도 및 색도 분석을 분석하였다. 여기서 페이스트는 분말형태로 가공하여 CIELAB 색도를 측정하였고, 디지털 카메라로 시료를 촬영한 후 색상 강도 분석(color-intensity analyzer) 소프트웨어로 RGB 색도를 측정하였다. 그 결과 가열 온도 $400^{\circ}C$ 까지는 압축강도 잔존율이 W/C=0.5는 87.2 %, W/C=0.3은 86.7 % 수준의 강도 손상을 보였다. 그러나 $500^{\circ}C$ 이상에서는 급격한 강도 저하가 나타났으며, W/C=0.5는 55.2 %, W/C=0.3은 51.9 %의 압축강도 잔존율이 나타났다. $700^{\circ}C$ 이상에서는 W/C=0.5는 26.3 %, W/C=0.3은 27.8 %으로써 구조물의 내구성을 확보할 수 없는 수준이었다. $L^*a^*b$ 분석 결과 $700^{\circ}C$ 이후부터 $b^*$가 급격히 높아지는 결과가 나타났다. 이는 $700^{\circ}C$이후에서 노란색의 강도가 강해지는 것으로 분석된다. 또한, RGB 분석 결과 $700^{\circ}C$ 이후부터 R 및 G의 히스토그램 첨도 및 빈도가 높아지는 것을 확인하였다. 이는 R 및 G의 픽셀(화소)이 많아지는 것으로 분석된다. 따라서 화재 피해를 입은 콘크리트의 색도 분석은 노란색($b^*$ 혹은 R+G)의 변화를 확인하는 것으로 손상 정도를 예상하는 것이 가능할 것으로 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.67-71
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• 2008

Blast Furnace slag a pigiron waste that is produced more than 800 thousand tons per year, and micronized double quenching blast furnace slag improves flexibility of concrete, and even shows improvement effect of long-term intensity. However, the concrete that used micronized double quenching blast furnace slag is restricted in its use because of many problems to assure early intensity. Even micronized blast furnace slag can assure its early intensity of concrete when maximizing, and is considered that can be applied in high strength of blast furnace slag as an alternation material for Silica-fume that depends on overall import. Hereby this paper is revised activity index and fluidity of mortar that used Nano Slag that is produced by rotten Nano crush equipment to propose its size, and possible utility of Nano Slag that was produced by blast furnace slag made in Korea as an alternation material, with the conclusion as following. 1. To measure micronized Nano slag, it is judged that it should be in progress with BET method that is based on micronized Silica-fume for concrete. 2. As a result, the test based on KS L ISO 679 is shown to satisfy the basic additive size of KS F 2563 and of KS F 2567, and to determine new combination of stipulations. 3. The strength development of Nano Slag was shown excellent in the daily initial installment of 1, 3, 7 days against the basic additive. This is judged that contains CaO controlling initial strength against Silica-fume, and contributes to higher fineness than the basic blast furnace slag 1 type.

• 대한치과기공학회지
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• 제34권2호
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• pp.75-81
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• 2012

Purpose: All ceramic crown, made from zirconia instead of metal for core material, is recognized the best esthetical prosthesis. Recently, high-priced zirconia blocks and expensive CAD/CAM machines come into use for making zirconia core. In this study, slip casting process is adapted to evaluate the possibility of the recycling the remained parts of zirconia block after machining. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Passed powders were ball milled under various conditions to obtain the optimum zirconia slip for casting. Solid casting method was used for casting the specimens with plaster mold. Formed specimens were dried and biscuit fired at $1,000^{\circ}C$ for 1 hour. Biscuit fired specimens were finished with exact shape of square pillar. Finished specimens were fired from $1,200^{\circ}C$ to $1,550^{\circ}C$ at $50^{\circ}C$ intervals for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM. Results: Above examinations indicated that the optimum firing temperture was $1,500^{\circ}C$, and when fired at this temperature for 1 hour, apparent porosity was 0% and flexural strength was 680MPa. SEM photomicrographs showed uniform 200~300nm grain size, which is equal with microcture of sintered commercial zirconia block. when compare 24% linear shrinkage of cast specimen with 20% linear shrinkage of CAD/CAM machined block, it was estimated that the size controlling of cast core was not so difficult. Conclusion: According to the all of this experimental results, the cast zirconia core produced from the remained parts of zirconia block was possible to use for all ceramic denture.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.677-680
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• 2008

저발열형 고로슬래그 시멘트의 초기강도 발현 특성을 향상시키기 위하여 낮은 분말도의 고로슬래그 분말과 보통 포틀랜드시멘트를 혼합 분쇄하여 입자 표면을 개질하였다. 사전 분쇄한 고로슬래그 분말의 비표면적은 $2535cm^2/g$(BS2), $3245cm^2/g$(BS3)의 2가지를 사용하였으며, 고로슬래그 분말과 시멘트를 진동밀에 투입하여 10분부터 30분까지 혼합 분쇄하여 표면을 개질하였다. 시멘트에 대한 고로슬래그 분말의 혼합비는 60$^{\sim}$80%의 3수준으로 변화시켰으며 혼합분쇄 후 비표면적의 변화, 입도분표, 시멘트의 수화열, 몰탈의 압축강도를 측정하였다. 시판 삼성분계 저발열 시멘트(LHC)와 비교시험 결과, 7일 압축강도발현의 100%이상과 72시간 누적수화열 170J/g 이하의 값을 만족하는 배합 및 혼합분쇄 시간을 찾을 수 있었으며 저분말도 고로슬래그를 다량으로 활용한 저발열 슬래그시멘트의 가능성을 확인하였다.

• 자원리싸이클링
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• 제24권4호
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• pp.3-11
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• 2015

도시 쓰레기 소각재 내 미연소 섬유분(Unburned fabric)이 시멘트 복합재료의 기초 물성에 미치는 부정적 영향에 대해 실험적으로 검증하였다. 먼저, 섬유분을 많이 포함하고 있는 0.6 mm 이하 소각재 미분의 물리적, 화학적 특성을 확인하였다. 그 후, 소각재 미분이 혼입된 모르타르형 시멘트 복합재료의 유동성과 강도를 측정하고, 이 결과를 소각재 미분의 물리적, 화학적 특성과 연계하여 분석하였다. 실험 결과, 시멘트 복합재료의 유동성은 미연소 섬유분에 의해 크게 감소한 반면, 복합재료의 강도는 섬유분 보다 소각재 자체에 의해 감소함을 알 수 있었다. 따라서, 시멘트 복합재료의 성능을 고려 할 때, 복합재료 내 소각재의 혼입률과 함께 소각재 미분에 대한 혼입률도 제한되어야 함을 확인하였다.

• 한국세라믹학회지
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• 제49권5호
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• pp.438-441
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• 2012

Abalone shell is a high strength and light weighted ceramic composite material, which is composed of $CaCO_3$ platelet and protein. Microstructure of abalone shell has a matrix structure that is similar to the bricks and mortar. The technology inspired from nature which consumes low energy at low temperature is called bioinspired technology. In this study, to make high strength and light weighted ceramic composite materials using bioinspired technology, porous green body was prepared with $Al_2O_3$ platelet. PMMA was infiltrated into the porous green body, then warm pressed to eliminate pores present in the composite. The microstructure of the composite was observed with FESEM, and the mechanical/thermal properties were measured.

• Structural Monitoring and Maintenance
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• 제7권3호
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• pp.215-231
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• 2020

In a reinforced concrete building different shapes of column are adopted depending on the structural orientation and the architectural aspect. When there is an increase in loading due to changes in usage or revision in the design codes these columns need to be strengthened for enhanced performance during their service life. Strengthening materials such as carbon fiber and glass fiber polymer has been successfully used however, due to high cost application other alternative materials need to be explore. Galvanized steel wire mesh (GSWM) is one of the suitable materials locally available. High tensile strength, low weight, corrosion resistance, easy installation, minimum change in dimensions of the sections and cost effectives are the advantages of GSWM. Therefore, in this paper, four different shapes of column such as circular, square, rectangular and L were wrapped with different layers GSWM and jacketed with mortar. All the specimens were tested under axial compression. The objective of the study is to investigate the effectiveness of GSWM as a confining material for strengthening of column having varying shape. Test results shows that the axial strength enhanced with wrapping of GSWM jacket and a circular column presented the highest load carrying capacity and ductility as compared to the others. From the study of 22 column specimens, it is found that axial load is increased upto 20% and 19% when circular and square column are strengthened with one wrap of GSWM respectively, while a rectangular and L column required a wraps of two and three layers respectively in order to achieved the same load capacity as that of a circular column. Based on the present study, it is concluded that GSWM can be effectively used for strengthening of different shapes of concrete columns economically.