• Computers and Concrete
• /
• 제13권1호
• /
• pp.97-115
• /
• 2014

Silica fume is a by-product of induction arc furnaces and has long been used as a mineral admixture to produce high-strength, high-performance concrete. Due to the pozzolanic reaction between calcium hydroxide and silica fume, compared with that of Portland cement, the hydration of concrete containing silica fume is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing silica fume. The heat evolution rate of silica fume concrete is determined from the contribution of cement hydration and the pozzolanic reaction. Furthermore, the temperature distribution and temperature history in hardening blended concrete are evaluated based on the degree of hydration of the cement and the mineral admixtures. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and mineral admixture substitution ratios.

• 한국농공학회논문집
• /
• 제54권5호
• /
• pp.9-16
• /
• 2012

In this study, the effect of metakaoline and silica fume on the bond performances of structural polyvinyl alcohol (PVA) fiber in cement mortar, including bond strength, interface toughness, and microstructure analysis are presented. Metakaoline and silica fume contents ranging from 0 % to 15 % are used in the mix proportions. Pullout tests are conducted to measure the bond performance of PVA fiber from cement mortar. Test results showed the incorporation of metakaoline and silica fume can effectively enhance the PVA fiber-cement mortar interfacial properties. Bond strength and interface toughness increased with metakaoline and silica fume content up to 10 % in cement mortar and decreased when the metakaoline and silica fume content reached 15 %. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
• /
• pp.229-232
• /
• 1999

This study provided the engineering properties of the recycled aggregate concrete with fly-ash and silica-fume. There are considered recycled aggregate substitution ratio, and fly-ash silica-fume mix ratio as the experimental variable. From the experimental result, we could know that the recycled aggregate concrete mixed silica-fume is superior on the compressive strength but, is poor on the construction property than fly-ash. The optimal mix ratio of the fly-ash and silica-fume is 10% in all.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2007년도 추계 학술논문 발표대회
• /
• pp.37-40
• /
• 2007

This study investigates the effect of the pre-mix cement to the physical properties of the concrete according to the various combinations of the binders and the silica fume types. The results are summarized as following. For the properties of the fresh, the fluidity in the case that OPC+cilica fume-blast-furnace slag is appropriate compared to OPC+cilica fume+fly ash. Expecially, it is favorable when pre-mix is used. The fluidity time of the A, B depending on silica fume types is favorable, but it is decreased on C. The air content depending on silica fume types is low when the fly ash is used. Specially, the air content in the case that pre-mix is used is low caused by the dispersion of the silica fume. For the properties of the hardened concrete, the compressive and flexible strength when the blast-furnace slag is pre-mixed are high, and they exceed OPC. The strength depending on the silica fume types is high on B, and the strength of the others is similar.

• Geomechanics and Engineering
• /
• 제14권3호
• /
• pp.247-255
• /
• 2018

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.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
• /
• pp.489-492
• /
• 2008

물/결합재비가 0.4이면서 5%의 실리카퓸이 혼입된 3가지 매스콘크리트 배합과 실리카퓸이 혼입되지 않은 1가지 매스콘크리트 배합에 대해 단열온도상승실험과 자기수축실험을 실시하여 실리카퓸이 매스콘크리트의 수화발열특성과 자기수축에 미치는 영향을 규명하고, 그 결과를 통해 실리카퓸의 매스콘크리트에 대한 적용 가능성을 검토하였다. 실험결과, 매스콘크리트 배합의 경우에는 실리카퓸을 혼입하여도 수화반응속도가 거의 증가하지 않으면서 최종단열온도상승량이 5$^{\circ}$C 정도 감소하는 것으로 나타났으며, 콘크리트의 극한자기수축량은 실리카퓸의 혼입여부에 상관없이 거의 동일한 것으로 나타났다. 따라서 실무에서 매스콘크리트 구조물의 시공에 실리카퓸을 적용하면 내구성뿐만 아니라 수화열 균열제어에도 이점이 있을 것으로 판단된다.

• Advances in concrete construction
• /
• 제7권1호
• /
• pp.31-37
• /
• 2019

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with $T_{500}$ time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the $T_{500}$ and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and $800^{\circ}C$. Reductions in hardened properties up to $200^{\circ}C$ were found to be very close to normal vibrated concrete (NVC). For 400 and $600^{\circ}C$ reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching $800^{\circ}C$.

• Advances in concrete construction
• /
• 제8권1호
• /
• pp.47-54
• /
• 2019

Portland cement pervious concrete has been expected to have good water permeability, mechanical properties and abrasion resistance at the same time when Portland cement pervious concrete is applied to the actual vehicle pavement. In this study, the coarse aggregate and cement were replaced by the fine aggregate and the silica fume to improve actual road performance Portland cement pervious concrete. The Mechanical properties, the water permeability and the abrasion resistance of Portland cement pervious concrete were investigated. The results show that the compressive strength, the flexural strength and the abrasion resistance are increased when the fine aggregate and the silica fume are added to Portland cement pervious concrete separately. However, the porosity and the water permeability are decreased simultaneously. With assistance of silica fume and fine aggregate simultaneously, Portland cement pervious concrete could achieve a higher strength. The compressive strength, the flexural strength and the abrasion resistance of Portland cement pervious concrete mixed with 5% fine aggregates and 8% silica fume are increased by 93.1%, 65% and 65.2%, respectively. The porosity and the water permeability are decreased by 22.4% and 85% when Portland cement pervious concrete is mixed with 5% fine aggregate and 8% silica fume. Therefore, the replacement ratio of the fine aggregates and the silica fume should be considered comprehensively and determined on the premise of ensuring the water permeability coefficient.

• Computers and Concrete
• /
• 제26권5호
• /
• pp.385-395
• /
• 2020

The influence of combination of nano silica and silica fume, as partial cement replacement materials, on the properties of concrete has been studied through the measurement of compressive strength. The compressive strength of concrete in terms of mean, standard deviation and with-in-test coefficient of variation related to the variation in the nominated parameters have also been developed. The compressive strength data developed experimentally has been analyzed using normal-probability distribution and partial safety factors of composite concretes have been evaluated by using first order second moment approach with Hasofer Lind's method. The use of Nano silica and silica fume in concrete decreases the partial safety factor of concrete i.e., increase the reliability of concrete. The experimental results show that the properties of concrete having nano silica and silica fume in combination were better than that of a plain concrete. The SEM test results showing the level of Ca(OH)₂ in plain concrete and consumption level Ca(OH)₂ of concrete containing nano silica & silica fume have also been presented.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2007년도 춘계학술논문 발표대회
• /
• pp.51-54
• /
• 2007

This study investigates the properties of paste and mortar from different types and forms of silica fume on cement binder for ultra high strength. Although most Silica Fumes distributed in the market fulfill the KS quality standard, each type showed different levels of loss of ignition. When evaluating cement binder for ultra high strength in a form of paste. Flow, viscosity and moving freely time show great difference depending on the Silica Fume's form and type of primary particle's dispersibility. The evaluation of Silica Fume's dispersibility can be possible with the paste test since there is a high correlation of flow quality between paste and mortar. The compressive strength when using Silica Fume was correlated to the SiO2 content. Synthetically, selecting Silica Fume with the most the ideal primary particle is the key to optimizing the formation for cement binder for ultra high strength.