• 한국구조물진단유지관리공학회 논문집
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• 제10권5호
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• pp.171-178
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• 2006

고온에 노출된 고강도 콘크리트의 폭렬저감대책으로서 폴리프로필렌 섬유를 콘크리트에 혼입함으로써 취성적 파괴를 방지할 수 있는 것으로 보고 되었다. 그러나 초고강도 콘크리트 배합시 다량으로 혼입되는 PP섬유는 시공성을 저하시키는 원인이 된다. 또한 초고강도 콘크리트의 강도발현을 위하여 필수적으로 사용되는 실리카흄은 콘크리트의 수밀성을 높여 폭렬현상이 더욱 심하게 발생할 것으로 판단된다. 본 연구에서는 고강도 콘크리트에서 실리카흄이 폭렬에 미치는 영향과 초고강도 콘크리트의 시공성을 확보하기 위하여 PP섬유를 대신하여 PP분말 및 PVA의 내화성능을 실험을 통하여 관찰함으로써 초고강도 콘크리트의 내화성능확보를 위한 기초 자료를 제시하였다.

• Advances in concrete construction
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• 제9권2호
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• pp.183-193
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• 2020

The present investigation is to identify an optimum mix combination amongst 28 different types of artificial lightweight aggregates by pelletization method with aggregate properties. Artificial aggregates with different combinations were manufactured from fly ash, cement, hydrated lime, ground granulated blast furnace slag (GGBFS), silica fume, metakaolin, sodium bentonite and calcium bentonite, at a standard 17 minutes pelletization time, with 28% of water content on a weight basis. Further, the artificial aggregates were air-dried for 24 hours, followed by hardening through the cold-bonding (water curing) process for 28 days and then testing with different physical and mechanical properties. The results found the lowest impact strength value of 16.5% with a cement-hydrated lime (FCH) mix combination. Moreover, the lowest water absorption of 16.5% and highest individual pellet crushing strength of 36.7 MPa for 12 mm aggregate with a hydrated lime-GGBFS (FHG) mix combination. The results, attained from different binder materials, could be helpful for manufacturing high strength artificial aggregates.

• 한국구조물진단유지관리공학회 논문집
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• 제11권1호
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• pp.85-94
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• 2007

재유화형 폴리머는 보수용 모르타르의 개질재료로 주로 사용되고 있으며, 이러한 보수용 폴리머 시멘트 모르타르에는 폴리머 이외에 각종 혼화재료가 첨가된다. 기존의 연구들은 시멘트-폴리머 비가 모르타르에 미치는 영향에 대하여 주로 이루어졌으며, 혼화재료가 폴리머 시멘트 모르타르에 미치는 영향은 보고 되어있지 않는 실정이다. 본 연구에서는 혼화재료들(CSA계 팽창재, CSA계 속경재, 석고, 실리카 흄)의 배합비율에 따라 폴리머 시멘트 모르타르에 미치는 영향을 분석하고자 모르타르의 작업성, 응결시간, 건조수축, 압축강도, 휨 및 부착강도 등의 기초적 성질에 대하여 실험적으로 구명하였다.

• Structural Engineering and Mechanics
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• 제86권4호
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• pp.431-441
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• 2023

The aim of this paper is to present a new sustainable ternary and quaternary binder by partially replacing ordinary Portland cement (OPC) with different percentages of supplementary cementitious materials. The motivation is to reduce our dependency on OPC to reduce CO₂ emission and carbon foot print. As the main substitute for the OPC, siliceous fly ash was used. Moreover, silica fume and nanosilica were also used. During examinations the main mechanical parameters of concrete composites, i.e., compressive strength (f_cm) and splitting tensile strength (f_ctm) were assed. The microstructure of these materials was also analysed. It was found that the concrete incorporating pozzolanic materials is characterized by a well-developed structure and has high values of mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good strength parameters as well as the most favourable microstructure, whereas the worst mechanical parameters with microstructure containing microcracks at phase interfaces were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Nevertheless, all concretes made on quaternary binders had better parameters than the reference one. It can be stated that sustainable concrete incorporating pozzolanic materials could be good substitute of ordinary concretes.

• Advances in nano research
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• 제16권5호
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• pp.459-472
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• 2024

Nanotechnology is a popular field in the construction industry due to its multiple functions. It mitigates CO₂ emissions and enhances the desirable properties of concrete by replacing small amounts of cement with supplements. This study assess the sustainability impact of using two different nanoparticles partially replacing the cement with 0.3%, 0.6%, 1.0% of nano silica (NS) and 0.03%, 0.045%, 0.06% of Multi-Walled Carbon Nanotubes (MWCNT) in the green concrete mix developement. Nano-sized fragments at the atomic scale tends to modify the properties of concrete. Concrete may increase its strength, durability by adding nanocomposite materials, which will decrease the amount of nano and micropores in structural parts. The strength of the structural elements can be greatly improved and allowing them to withstand higher loads and resist deformation. It improved durability properties by 64.8% in water absorption, 56.4% in acid attack, 78.1% in sulphate attack, and 53.4% in chloride attack. There was an improvement in compressive strength of 37% and split tensile strength of 90%. SEM, FTIR, and XRD investigations have used to look at the microstructural characteristics of nanoconcrete dictated the microstructure characteristics may be made more consistent and dense by adding nanocomposite materials.

• 마이크로전자및패키징학회지
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• 제29권4호
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• pp.9-14
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• 2022

실리카 에어로겔은 매우 낮은 밀도, 고비표면적을 갖는 다공성 물질로 구조적 특성으로 인한 취약한 기계적 특성 때문에 응용이 제한되어 이를 해결하기 위한 폴리머와의 다양한 복합화 기술이 제안되어 왔다. 본 연구에서는 에어로겔의 기계적 강도를 향상시키고자 폴리이미드가 가교된 실리카 에어로겔을 합성하였다. 실리카 에어로겔을 만들기 위한 전구체로 tetraethyl orthosilicate(TEOS)가 사용되었고, 3-Aminopropyltriethoxysilane(APTES)은 폴리이미드와 가교 결합을 하기 위한 coupling agent로 사용되었다. 폴리이미드는 pyromellitic dianhydride, 3, 5-diaminobenzoic acid를 사용해 합성되었고 ${\frac{n_1}{n_2}}={\frac{n}{n+1}}$의 반응식을 사용해 폴리이미드 체인의 반복 단위 수가 10인 폴리이미드를 가교 결합하여 기계적 물성이 향상된 실리카 에어로겔을 구현하였다. 겔화 전에 다양한 중량비를 갖는 폴리이미드를 첨가하여 최대 압축 강도가 실리카 에어로겔 대비 19배 이상 증가가 관찰되어 폴리머 가교결합을 통한 실리카 에어로겔의 기계적 강도가 크게 개선될 수 있음을 확인하였다.

• 한국해양공학회지
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• 제22권5호
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• pp.94-99
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• 2008

Three types of salt resistant concrete beams reinforced with glass fiber reinforced polymer-ribbed bars (GFRP-ribbed bars) were selected, and their applicable properties were investigated with the goal of improving the problem of capacity deterioration in marine structures due to sea water corrosion. In this study, the structural behaviors were similar to RC beams in relation to the development of the strength and stiffness up to the generation of the initial crack. After the growth of this initial crack, the structural properties decreased owing to a sudden loss of bond strength. Also these beams showed the trends of brittle failure. As a result, it was confirmed that a GFS beam replaced with Fly Ash (20%) and Silica Fume (5%) has the best application as a marine structural element.

• Structural Engineering and Mechanics
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• 제62권3호
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• pp.357-364
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• 2017

This paper presents the results of a study that investigated the improvement of the mechanical properties of coarse and fine recycled asphalt pavement (RAP) produced by adding silica fume (SF) with contents of 5%, 10%, and 15% by total weight of the cement. The coarse and fine natural aggregate (NA) were replaced by RAP with replacement ratio of 20%, 40% and 60% by the total weight of NA. In addition, SF was added to NA concrete mixes as a control for comparison. Twenty eight mixes were produced and tested for compressive, splitting tensile and flexural strength at the age of 28 days. The results show that the mechanical properties decrease with as the content of RAP increases. And the decrease in the compressive strength was more in the fine RAP mixes compared to the coarse RAP mixes, while the decrease in the splitting tensile and flexural strength was almost the same in both mixes. Furthermore, using SF enhances the mechanical properties of RAP mixes where the optimum content of SF was found to be 10%, and the mechanical properties enhancement of coarse RAP were better than fine RAP mixes. Accordingly, the RAP has the potential to be used in the concrete pavements or in other low strength construction applications in order to reduce the negative impact of RAP on the environment and human health.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.747-756
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• 2020

High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 × 600 × 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.

• 한국재료학회지
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• 제14권5호
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• pp.358-362
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• 2004

$Si_3$$N_4$ ceramics have been identified as one of the promising structural ceramics. This study has been carried out to investigate of the synthetic behaviors of $Si_3$$N_4$ derived from domestic silica-stone by direct nitriding method. The silicon nitridation reaction has been studied in the temperature range of $1300～1550^{\circ}C$. Below the $1400^{\circ}C$, the nitriding rate was measured to be 16%. For the temperatures higher than the $1400^{\circ}C$, $\beta$-$Si_3$$N_4$ phase was formed mainly, and the nitriding rate showed above 98%. With the increasing of sample weight of silicon powder, the nitriding rate and $\beta$-$Si_3$$N_4$ phase increased at $1400^{\circ}C$ for 2 hours. The shape and particle size of$ Si_3$$N_4$ powder synthesized at $1400^{\circ}C$ for 2 hours showed the irregular angular-type and 10 $\mu\textrm{m}$, respectively.