• 한국안전학회지
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• 제12권2호
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• pp.133-139
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• 1997

Conventional concrete mixing method is to put all of the materials simultaneously into a mixer and mix for a required time. However, recently concrete researchers have reported that mixing sequence iufluences the properties of concrete. This study discusses the influence of mixing sequence and partitioning addition of mixing water. Concrete, by method of partitioning addition of mixing water, was found to have substantially stronger strength than conventional concrete with the same water-cement ratio. This means that a higher strength concrete could be obtained by using “Sand Enveloped with Cement”(S.E.C) mixing technique. Both a high bond strength between cement paste and aggregate, and elimination of bleeding both contribute to improving the strength of S. E. C concrete.

• 한국해양공학회지
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• 제4권1호
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• pp.71-80
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• 1990

We experimented the physical property of the porous concrete by changing the water cement ratio, when the aggregate ratios are 1:5 and 1:7 separately. And then we received the results as follows. The bigger, the coarse grading of the porous concrete is, the more sensitive to the water cement ratio, the porous concrete becomes. And if we think over its compressive strength, the coarse aggregate which has 5-15mm width is most appropriate. So we concluded that when its compressive strength, permeability coefficient and its unit weight are $50kg/cm^{2}3cm/sec$ and $1900kg/m^{3}$ respectively, the water cement ratio which has 35-37% width is most appropriate, too. And its compressive strength and unit weight show that they are about a quarter and three quarters respectively about the conventional concrete.

• Advances in concrete construction
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• 제4권3호
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• pp.221-230
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• 2016

This paper presents a preliminary study on the influence of laterite soil replacing conventional fine aggregates on the strength properties of GGBS-blended-concrete. For this purpose, GGBS-blended-concrete samples with 40% GGBS, 60% Portland cement (PC), and locally available laterite soil was used. Laterite soils at 0, 25, 50 and 75% by weight were used in trails to replace the conventional fine aggregates. A control mix using only PC, river sand, course aggregates and water served as bench mark in comparing the performance of the composite concrete mix. Test blocks including 60 cubes for compression test; 20 cylinders for split tensile test; and 20 beams for flexural strength test were prepared in the laboratory. Results showed decreasing trends in strength parameters with increasing laterite content in GGBS-blended-concrete. 25% and 50% laterite replacement showed convincing strength (with small decrease) after 28 day curing, which is about 87-90% and 72-85% respectively in comparison to that achieved by the control mix.

• Structural Monitoring and Maintenance
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• 제1권3호
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• pp.323-338
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• 2014

In this study a new innovative method of earthquake-resistant strengthening of reinforced concrete structures is presented for the first time. Strengthening according to this new method consists of the construction of steel fiber ultra-high-strength concrete jackets without conventional reinforcement which is usually applied in the construction of conventional reinforced concrete jackets. An innovative solution is proposed also for the first time that ensures a satisfactory seismic performance of existing reinforced concrete structures, strengthened by using composite materials. The weak point of the use of such materials in repairing and strengthening of old R/C structures is the area of beam-column joints. According to the proposed solution, the joints can be strengthened with a steel fiber ultra-high-strength concrete jacket, while strengthening of columns can be achieved by using CFRPs. The experimental results showed that the performance of the subassemblage strengthened with the proposed mixed solution was much better than that of the subassemblage retrofitted completely with CFRPs.

• International Journal of Concrete Structures and Materials
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• 제7권4호
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• pp.273-285
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• 2013

An experimental investigation was conducted to compare the shear strength of full-scale beams constructed with chemically-based, self-consolidating concrete (SCC) with conventional concrete (CC). This experimental program consisted of 16 rectangular beams (12 without shear reinforcing and 4 with shear reinforcing in the form of stirrups), 8 beams for each mix design. Additionally, three different longitudinal reinforcement ratios were evaluated within the test matrix. The beam specimens were tested under a simply supported four-point condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (U.S., Australia, Canada, Europe, and Japan) and a shear database of CC specimens. This comparison indicates that chemically-based SCC beams possess comparable shear strength as CC beams.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 2005년도 춘계임시총회 및 제25회 학술발표대회
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• pp.109-112
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• 2005

The electrical pulse separation of concrete samples for the recycling purpose has been investigated by the electrical disintegration method using the discharged high voltageimpulse. First, when the consumed energy increased in electrical crushing, fracture section area increased clearly. This result suggests that crushing energy was consumed efficiently. Secondly, when conventional crushing after electrical disintegration is compared with only conventional crushing, gravels are more stable after electrical crushing. Thus, electrical crushing makes it easy to recover gravels from wasted concrete. In the next year, more efficient recovery of gravel for wasted concrete by electrical disintegration will be investigated. Thus, actual wasted concrete crushing by electrical separation and combination of conventional crushing will be carried out.

• 한국건축시공학회지
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• 제7권1호
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• pp.107-113
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• 2007

This study investigates the filed application in Daebul Free Trade Zone applying both a flowing method using drying shrinkage-reducing superplasticizer(SRS) and an insulating curing method using double layer bubble sheet. Test results showed that fresh concrete satisfied target slump and air content. A structure adding SRS significantly decreased the total bleeding capacity and accelerated the setting time. As for the crack occurrence, the structure applying the flowing method and double bubble sheets simultaneously exhibited the most favorable crack endurance, while conventional concrete showed more than 1mm size of crack in overall. In addition, a structure applying the flowing concrete method partially presented the micro crack. For the area proportion of crack occurrence, the structure using the double bubble sheets indicated 9.8%, while others applying flowing concrete method was 28%, compared with that of conventional one. For the compressive strength of specimens, standard curing specimens indicated $3{\sim}33%$ higher value than that of specimens cured besides the field construction. The specimens containing SRS improved the strength of $2{\sim}6MPa$, which is $10{\sim}22%$ higher than that of conventional concrete.

• 한국재난정보학회 논문집
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• 제7권1호
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• pp.32-42
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• 2011

현재 개질 아스팔트 콘크리트 혼합물의 공용성을 평가하기위한 많은 연구가 진행되었다. 본 연구는 개질 아스팔트 바인더 중에서 D사에서 개발된 Elvaloy개질 아스팔트 바인더를 사용한 아스팔트 혼합물의 기계적 특성을 평가하기위하여 수행되었다. 연구의 목적을 달성하기위하여 간접인장강도와 회복탄성계수 시험이 수행되었다. 시험결과, Elvaloy개질 아스팔트 콘크리트 혼합물의 간접인장강도와 회복탄성계수 값은 일반 밀입도 아스팔트 콘크리트 혼합물보다 높은 것으로 나타났다. 따라서, Elvaloy개질 아스팔트 혼합물의 공용성과 안정성은 일반 밀입도 아스팔트 혼합물보다 우수할 것으로 예상된다.

• Smart Structures and Systems
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• 제24권4호
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• pp.541-552
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• 2019

Construction development and greenhouse gas emissions have globally required a strategic management to take some steps to stain and maintain the environment. Nowadays, recycled aggregates, in particular ceramic waste, have been widely used in concrete structures due to the economic and environmentally friendly solution, requiring the knowledge of recycled concrete. Also, one of the materials used as a substitute for concrete cement is wollastonite mineral to decrease carbon dioxide (CO2) from the cement production process by reducing the concrete consumption in concrete. The purpose of this study is to investigate the effect of wollastonite on the mechanical properties and durability of conventional composite concrete, containing recycled aggregates such as compressive strength, tensile strength (Brazilian test), and durability to acidic environment. On the other hand, in order to determine the strength and durability of the concrete, 5 mixing designs including different wollastonite values and recovered aggregates including constant values have been compared to the water - cement ratio (w/c) constant in all designs. The experimental results have shown that design 5 (containing 40% wollastonite) shows only 6.1% decrease in compressive strength and 4.9% decrease in tensile strength compared to the control plane. Consequently, the use of wollastonite powder to the manufacturing of conventional structural concrete containing recycled ceramic aggregates, in addition to improving some of the properties of concrete are environmentally friendly solutions, providing natural recycling of materials.

• 한국방재학회 논문집
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• 제3권2호
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• pp.89-97
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• 2003

폐타이어 재활용 아스팔트 콘크리트의 기술개발과 기초 자료의 확립을 위해서 건식공법 및 습식공법으로 생산되어진 폐타이어 재활용 아스팔트 콘크리트와 재래식 밀입도 아스팔트 콘크리트 공시체를 제작하여 아스팔트 혼합물의 내구성을 평가할 수 있는 간접인장강도시험과 회복 탄성계수시험을 수행하였다. 간접인장강도시험 결과 골재 입도의 영향으로 간접인장강도는 재래식 아스팔트 콘크리트가 폐타이어 재활용 아스팔트 콘크리트보다 우수하게 나타났지만, 인성과 최대수직변형률의 경우 골재 입도의 영향에도 불구하고 폐타이어 재활용 아스팔트 콘크리트가 우수하게 나타났다. 또한, 회복 탄성계수시험 결과에서도 폐타이어 재활용 아스팔트 콘크리트가 재래식 아스팔트 콘크리트보다 우수한 성능을 보여줌으로써 폐타이어 재활용 아스팔트 콘크리트의 공학적 특성이 우수하게 나타났다. 특히, 습식공법 활용 폐타이어 재활용 아스팔트 콘크리트의 모든 공용특성은 건식공법활용 혼합물보다 우수한 것으로 평가되었다.