표면 개질제 첨가량 변화에 따른 흄드 실리카의 분산성 연구

김영훈,이동욱,김윤환,손민영,문명준 한국화상학회 2018 한국화상학회지 Vol.24 No.3

본 연구는 두 종류의 표면 개질제 trimethylchlorosilane(TMCS), hexamethyldisilazane(HMDZ)를 사용하여 fumed silica의 표면 개질 과정에서 첨가량 변화에 따른 소수성 및 분산성 변화에 대한 연구를 진행하였다. 표면 개질 과정에서 사용된 개질제는 fumed silica 중량 대비 0~80wt%로 첨가하였으며, FT-IR(Fourier transform infrared spectroscopy), EA(Elemental analysis) 분석을 통해 개질제의 첨가량이 증가함에 따라 fumed silica의 소수성이 증가함을 확인하였다. 그리고 fumed silica의 소수성이 증가함에 따른 분산성 변화 분석을 위해 TEM(Transmission electron spectroscopy), PSA(Particle size analyzer)를 측정하였다. 그 결과, fumed silica의 소수성이 증가함에 따라 fumed silica의 입자간의 응집력이 약화되어 분산성이 향상되고 평균 입자 크기 또한 감소하는 것을 확인할 수 있었다. Fumed silica의 개질 안정성을 평가하기 위해 자체 실험을 진행한 결과, 소수성 개질된 fumed silica의 경우 표면 개질제 첨가량과 관계없이 일정 시간 이후에도 소수성이 유지되고 있음을 확인하였다. This study was carried out to investigate the hydrophobicity and dispersibility of fumed silica according to the addition amount of two kinds of surface modifiers, trimethylchlorosilane and hexamethyldisilazane. The surface modifiers used in surface modification process were added in an amount of 0~80wt% based on the weight of the fumed silica, Fourier transform infrared spectroscopy and Elemental analysis showed that the hydrophobicity of fumed silica is increased by increasing the addition amount of surface modifiers. To investigate the change in dispersibility of fumed silica as the hydrophobicity of fumed silica increases, Transmission electron microscopy and Particle size analysis were measured. As a result, it was confirmed that as the hydrophobicity of fumed silica increases, the cohesion between the particles of fumed silica is weakened so the dispersibility of fumed silica is improved and average particle size is decreased. In order to evaluate the modification stability of fumed silica, self-experiment was carried out. From the self-experimental result, it was confirmed that the hydrophobicity of hydrophobically modified fumed silica was maintained even after a certain time regardless of the addtion amount of the surface modifiers.

Effects of using silica fume and lime in the treatment of kaolin soft clay

Alrubaye, Ali Jamal,Hasan, Muzamir,Fattah, Mohammed Y. Techno-Press 2018 Geomechanics & engineering Vol.14 No.3

Soil stabilization can make the soils becoming more stable by using an admixture to the soil. Lime stabilization enhances the engineering properties of soil, which includes reducing soil plasticity, increasing optimum moisture content, decreasing maximum dry density and improving soil compaction. Silica fume is utilized as a pozzolanic material in the application of soil stabilization. Silica fume was once considered non-environmental friendly. In this paper, the materials required are kaolin grade S300, lime and silica fume. The focus of the study is on the determination of the physical properties of the soils tested and the consolidation of kaolin mixed with 6% silica fume and different percentages (3%, 5%, 7% and 9%) of lime. Consolidation test is carried out on the kaolin and the mixtures of soil-lime-silica fume to investigate the effect of lime stabilization with silica fume additives on the consolidation of the mixtures. Based on the results obtained, all soil samples are indicated as soils with medium plasticity. For mixtures with 0% to 9% of lime with 6% SF, the decrease in the maximum dry density is about 15.9% and the increase in the optimum moisture content is about 23.5%. Decreases in the coefficient of permeability of the mixtures occur if compared to the coefficient of permeability of kaolin soft clay itself reduce the compression index (Cc) more than L-SF soil mix due to pozzolanic reaction between lime and silica fume and the optimum percent of lime-silica fume was found to be (5%+6%) mix. The average coefficient of volume compressibility decreases with increasing the stabilizer content due to pozzolanic reaction happening within the soil which results in changes in the soil matrix. Lime content +6% silica fume mix can reduce the coefficient of consolidation from at 3%L+6%SF, thereafter there is an increase from 9%L+6%SF mix. The optimal percentage of lime silica fume combination is attained at 5.0% lime and 6.0% silica fume in order to improve the shear strength of kaolin soft clay. Microstructural development took place in the stabilized soil due to increase in lime content of tertiary clay stabilized with 7% lime and 4% silica fume together.

Improvement of bearing capacity of footing on soft clay grouted with lime-silica fume mix

Fattah, Mohammed Y.,Al-Saidi, A'amal A.,Jaber, Maher M. Techno-Press 2015 Geomechanics & engineering Vol.8 No.1

In this study, lime (L), silica fume (SF), and lime-silica fume (L-SF) mix have been used for stabilizing and considering their effects on the soft clay soil. The improvement technique adopted in this study includes improving the behaviour, of a square footing over soft clay through grouting the clay with a slurry of lime-silica fume before and after installation of the footing. A grey-colored densified silica fume is used. Three percentages are used for lime (2%, 4% and 6%) and three percentages are used for silica fume (2.5%, 5%, 10%) and the optimum percentage of silica fume is mixed with the percentages of lime. Several tests are made to investigate the soil behaviour after adding the limeand silica fume. For grouting the soft clay underneath and around the footing, a 60 ml needle was used as a liquid tank of the lime-silica fume mix. Slurried silica fume typically contains 40 to 60% silica fume by mass. Four categories were studied to stabilize soft clay before and after footing construction and for each category, the effectiveness of grouting was investigated; the effect of injection hole spacing and depth of grout was investigated too. It was found that when the soft clay underneath or around a footing is injected by a slurry of lime-silica fume, an increase in the bearing capacity in the range of (6.58-88)% is obtained. The footing bearing capacity increases with increase of depth of grouting holes around the footing area due to increase in L-SF grout. The grouting near the footing to a distance of 0.5 B is more effective than grouting at a distance of 1.0 B due to shape of shear failure of soft clay around the footing.

Fumed Silica/Ceramic Wool 무기복합재의 제조 및 열적 성질

안원술(Ahn, Won-Sool) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.6

Fumed Silica와 섬유상의 Ceramic Wool을 사용하여 경량의 무기복합재 샘플을 제조하기 위한 조건과 만들어진 샘플 의 단열특성을 살펴보았다. 정량된 Fumed Silica 미세분말과 Ceramic Wool을 혼합한 반죽을 몰드에 넣고 상온에서 안정화시 킨 후에 150℃ 오븐에서 완전히 건조하여 샘플을 제작하였다. 소량의 PVA 계면접착제를 사용하지 않는 샘플에서는 Fumed Silica 조성비가 10-70wt% 사이에서 벌크밀도가 0.6-0.8 g/cm₃이었으며, 50wt% 이상의 샘플에서는 건조 수축으로 인한 크랙 현상이 관찰되었다. 그러나 3wt%의 PVA를 사용한 샘플의 벌크밀도는 절반 정도로 크게 감소하면서도 기계적 특성과 단열 성은 향상되었다. 만들어진 샘플들은 800oC 이상의 고온에서도 열크랙 없이 안정한 열적 특성을 보여주었으며, 샘플의 단열 성은 Fumed Silica 조성비가 높아질수록 향상되는 것으로 나타났다. Fumed Silica 30wt%인 샘플의 열전도도는 500oC에서 약 0.08 W/moK의 우수한 단열 특성을 보여 주었다. This study examined the fabrication and thermal properties of fumed silica/ceramic wool inorganic composites. A predetermined quantity of fumed silica and ceramic wool was mixed uniformly into a slurry state and stabilized in the mold at room temperature, and converted to a massive foamed body through a complete drying process at 150 °C. Although the samples without polyvinyl alcohol (PVA) as an interfacial adhesive showed a bulk density of 0.6-0.8 g/cm₃ in the range, 10-70wt% fumed silica, those samples with 3wt% PVA exhibited remarkably lower bulk densities with enhanced mechanical and thermal insulation properties, without thermal cracking even above 800oC. The K-factor of the samples was lower in proportion to the fumed silica contents, showing good thermal insulation properties of ca. 0.08 W/moK at 500oC for the sample with 30wt% fumed silica.

국산 저가형 실리카퓸을 이용한 고성능 콘크리트의 물리적 특성 분석

김상도(Kim Sang Do),윤경구(Yun Kyung Ku),한승연(Ham Seung Yeon),이겨레(Lee Kyeo Re) 강원대학교 산업기술연구소 2017 産業技術硏究 Vol.37 No.1

In this study, as part of a research on the development of economical high-performance concrete with high strength and high quality, the physical properties of high-performance concrete were analyzed by substituting a certain amount of low-cost domestic silica fume exempted from the re-importation type distribution structure of the domestic production and the existing high-priced silica fume distribution structure. Performing tests to identify the physical properties of the fresh and hardened concrete and durability analogy of the concrete which use low-cost domestic silica fume and imported silica fume, the chloride ion penetration resistance test result showed that the strength difference between the low-cost silica fume and the imported silica fume is not big but the strength of the low-cost silica fume was measured higher than the imported silica fume. The chloride ion penetration resistance of all variables was measured as “very low”. Since the low-cost domestic silica fume can be used as a high-performance admixture of concrete, the results suggest that it is possible to produce a more economical high-performance concrete.

Fracture behavior of fly ash concrete containing silica fume

Peng Zhang,Ji-Xiang Gao,Xiao-Bing Dai,Tian-Hang Zhang,Juan Wang 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.2

Effect of silica fume on fresh properties, compressive strength at 28 days and fracture behavior of fly ash concrete composite were studied in this paper. Test results indicated that the fluidity and flowability of fly ash concrete composites decreased and fly ash concrete composite are more cohesive and appear to be sticky with the addition of silica fume. Addition of silica fume was very effective in improving the compressive strength at 28 days of fly ash concrete composite, and the compressive strength of fly ash concrete composite has a trend of increase with the increase of silica fume content. Results also indicated that all the fracture parameters of effective crack length, fracture toughness, fracture energy, the critical crack opening displacement and the maximum crack opening displacement of fly ash concrete composite decreased with the addition of silica fume. When the content of silica fume increased from 3% to 12%, these fracture parameters decreased gradually with the increase of silica fume content. Furthermore, silica fume had great effect on the relational curves of the three-point bending beam specimen. As the silica fume content increased from 3% to 12%, the areas surrounded by the three relational curves and the axes were becoming smaller and smaller, which indicated that the capability of concrete composite containing fly ash to resist crack propagation was becoming weaker and weaker.

흄드실리카로부터 제조된 실리카졸의 분산인자 상관성 연구

박민경,김훈,임형미,최진섭,김대성,Park, Min-Gyeong,Kim, Hun,Lim, Hyung Mi,Choi, Jinsub,Kim, Dae Sung 한국재료학회 2016 한국재료학회지 Vol.26 No.3

To study the dispersion factors of silica sol prepared from fumed silica powder, we prepared silica sol under an aqueous system using a batch type bead mill. The dispersion properties of silica sol have a close relationship to dispersion factors such as pH, milling time and speed, the size and amount of zirconia beads, the solid content of fumed silica, and the shape and diameter of the milling impellers. Especially, the silica particles in silica sol were found to show dispersion stability on a pH value above 7, due to the electrostatic repulsion between the particles having a high zeta potential value. The shape and diameter of the impellers installed in the bead mill for the dispersion of fumed silica was very important in reducing the particle size of the aggregated silica. The median particle size ($D_{50}$) of silica sol obtained after milling was also optimized according to the variation of the size and amount of the zirconia beads that were used as the grinding medium, and according to the solid content of fumed silica. The dispersion properties of silica sol were investigated using zeta potential, turbiscan, particle size analyzer, and transmission electron microscopy.

Effect of Steam Curing on Concrete Piles with Silica Fume

N. Yazdani,F. ASCE, M. Filsaime,T. Manzur 한국콘크리트학회 2010 International Journal of Concrete Structures and M Vol.4 No.1

Silica fume is a common addition to high performance concrete mix designs. The use of silica fume in concrete leads to increased water demand. For this reason, Florida Department of Transportation (FDOT) allows only a 72-hour continuous moist cure process for concrete containing silica fume. Accelerated curing has been shown to be effective in producing high-performance characteristics at early ages in silica-fume concrete. However, the heat greatly increases the moisture loss from exposed surfaces, which may cause shrinkage problems. An experimental study was undertaken to determine the feasibility of steam curing of FDOT concrete with silica fume in order to reduce precast turnaround time. Various steam curing durations were utilized with full-scale precast prestressed pile specimens. The concrete compressive strength and shrinkage were determined for various durations of steam curing. Results indicate that steam cured silica fume concrete met all FDOT requirements for the 12, 18 and 24 hours of curing periods. No shrinkage cracking was observed in any samples up to one year age. It was recommended that FDOT allow the 12 hour steam curing for concrete with silica fume.

Modeling of chloride diffusion in a hydrating concrete incorporating silica fume

Wang, Xiao-Yong,Park, Ki-Bong,Lee, Han-Seung 테크노프레스 2012 COMPUTERS AND CONCRETE Vol.10 No.5

Silica fume has long been used as a mineral admixture to improve the durability and produce high strength and high performance concrete. And in marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. In this paper, we proposed a numerical procedure to predict the chloride diffusion in a hydrating silica fume blended concrete. This numerical procedure includes two parts: a hydration model and a chloride diffusion model. The hydration model starts with mix proportions of silica fume blended concrete and considers Portland cement hydration and silica fume reaction respectively. By using the hydration model, the evolution of properties of silica fume blended concrete is predicted as a function of curing age and these properties are adopted as input parameters for the chloride penetration model. Furthermore, based on the modeling of physicochemical processes of diffusion of chloride ion into concrete, the chloride distribution in silica fume blended concrete is evaluated. The prediction results agree well with experiment results of chloride ion concentrations in the hydrating concrete incorporating silica fume.

Modeling of chloride diffusion in a hydrating concrete incorporating silica fume

왕소용,박기봉,이한승 사단법인 한국계산역학회 2012 Computers and Concrete, An International Journal Vol.10 No.5

Silica fume has long been used as a mineral admixture to improve the durability and produce high strength and high performance concrete. And in marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. In this paper, we proposed a numerical procedure to predict the chloride diffusion in a hydrating silica fume blended concrete. This numerical procedure includes two parts: a hydration model and a chloride diffusion model. The hydration model starts with mix proportions of silica fume blended concrete and considers Portland cement hydration and silica fume reaction respectively. By using the hydration model, the evolution of properties of silica fume blended concrete is predicted as a function of curing age and these properties are adopted as input parameters for the chloride penetration model. Furthermore, based on the modeling of physicochemical processes of diffusion of chloride ion into concrete, the chloride distribution in silica fume blended concrete is evaluated. The prediction results agree well with experiment results of chloride ion concentrations in the hydrating concrete incorporating silica fume.