• 콘크리트학회논문집
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• 제12권2호
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• pp.43-51
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• 2000

This study is to investigate for the frost resistance of high-flowing concrete using finely ground granulated blast-furnace slag with experimental parameters, such as type of binder, type of superplasticizer and method of curing. The resistance to freezing and thawing of high-flowing concrete by type of binder and superplasticizer is presented differently. Though the frost resistance of high-flowing concrete is satisfactory under standard condition, it is required that high-flowing concrete has entrained air like plain concrete. Because the critical spacing factor, being capacity of frost resistance, of high-flowing concrete is longer that of plain concrete, the frost resistance of high-flowing concrete, using finely ground granulated furnace blast slag, is superior to that of plain concrete.

• Advances in concrete construction
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• 제9권4호
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• pp.367-374
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• 2020

Concrete surfaces, industrial floors, sidewalks, roads and parking lots are typically subjected to abrasions. Many studies indicated that the abrasion resistance is directly related to the ultimate strength of the cured concrete. Chemical reactions, freeze-thaw cycles, and damages under abrasion are among many factors negatively affecting the concrete strength and durability. One of the major solutions to address the abrasive resistance of the concrete is to use fibers. Fibers are used in the concrete mix to improve the mechanical properties, strength and limit the crack propagations. In this study, implementation of the steel fibers in concrete to enhance the abrasive resistance of the concrete is investigated in details. The abrasive resistance of the concrete with and without steel fibers is studied with the sandblasting technique. For this purpose, different concrete samples are made with various hooked steel fiber ratios and investigated with the sandblasting method for two different strike angles. In total, 144 ASTM verified cube samples are investigated and it is shown that those samples with the highest steel fiber ratios have the highest abrasive resistance. In addition, the experiments determine that there is a meaningful correlation between the steel fiber percentage in the mix, strike angle and curing time which could be considered for improving structural behavior of the fiber-reinforced concrete.

• 한국도로학회논문집
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• 제17권2호
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• pp.47-53
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• 2015

PURPOSES: The scaling of a concrete surface caused by the combined effects of frost and de-icing salts is one of the main reasons for the need to repair transportation infrastructures in cold-climate regions. This study describes the results of attempts to determine the scaling resistance of concrete incorporating mineral admixtures such as fly ash, GGBFS, and silica fume, and subjected to the actions of frost and salt. METHODS : Conventionally, to evaluate the fundamental properties of concrete, flexural and compressive strength measurements are regularly performed. Based on the ASTM C 672 standard, concrete is subjected to 2%, 4%, and 8% $CaCl_2$ salt solutions along with repeated sets of 50 freeze/thaw cycles, and the scaling resistance was evaluated based on the mass of the scale and a visual examination. RESULTS : It was observed that silica fume is very effective in enhancing the scaling resistance of concrete. Meanwhile, concrete incorporating GGBFS exhibited poor resistance to scaling, especially in the first ten freeze/thaw cycles. However, fly ash concrete generally exhibited the maximum amount of damage as a result of the frost-salt attack, regardless of the concentrations of the solutions. CONCLUSIONS: It can be concluded that the scaling resistance of concrete is highly dependent on the type of the mineral admixture used in the concrete. Therefore, to provide a durable concrete pavement for use in cold-climate regions, the selection of a suitable binder is essential.

• Structural Engineering and Mechanics
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• 제2권4호
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• pp.403-412
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• 1994

The durability of concrete is related to the permeation characteristics of its near surface. An attempt was made to use the permeation characteristics namely, absorptivity, permeability and diffusivity, to predict the freeze/thaw resistance of concrete. Test results indicate that in general, there was a trend that freeze/thaw resistance of concrete was enhanced with improved absorptivity and diffusivity whilst the freeze/thaw resistance of normal concrete was found to have the best relationship with its intrinsic permeability. The latter method is therefore proposed to be adopted to predict freeze/thaw resistance of normal concrete. Since Figg air test is an inexpensive and simple test method that measures indirectly the intrinsic permeability of concrete, it is further proposed that it could be used as a quality control tool to assess, non-destructively, the freeze/thaw durability potential of in-situ concrete.

• 한국해양공학회지
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• 제15권3호
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• pp.128-133
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• 2001

It is generally known that the concrete structure subjected to severe environment is much affected by the corrosion of reinforcement, the freezing and thawing action of concrete structure. The main objective of this study is to investigate the freezing and thawing resistance of concrete including fly ash. The effect of the air content in concrete using fly ash is investigated. The experimental study is conducted for 10 mix-ratio cases of concrete of which variables are content of fly ash, concrete compressive strength and containment of air-entrained admixtures. Test results show that the freezing and thawing resistance improves as the amounts of fly ash increase, and concrete with air-entrained admixtures has good freezing and thawing resistance. The concrete with fly ash is to be included air-entrained admixture according to content of fly ash in order to increase the freezing and thawing resistance.

• Advances in concrete construction
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• 제6권1호
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• pp.15-28
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• 2018

In the present investigation, influence of various material parameters on the cavitation erosion resistance of concrete was investigated on the basis of laboratory experiments. As there is no well-established laboratory test method for evaluating the cavitation resistance of concrete, a test set up called 'cavitation jet' was specially established in the present study in order to simulate the cavitation phenomenon experienced in the hydraulic structures. Various mixtures of concrete were designed by varying the grade of concrete, type and quantity of pozzolana, type of aggregates and cement type to develop good cavitation resistant concrete constructed using marginal aggregates. Three types of aggregates having three different Los Angeles abrasion values (less than 30%, between 30% and 50% and more than 50%) were employed in this study. To evaluate the cavitation resistance a total of 60 cylindrical specimens and 60 companion cubes were tested in the laboratory respectively. The results indicate that cavitation resistance of concrete degrades significantly as the L.A. abrasion value of aggregates goes beyond the 30% value. Incorporation of pozzolanic admixtures was seemed to be beneficial to enhance the cavitation resistance of concrete. Influence of other material parameters on the cavitation resistance of concrete was also noted and important observations have been made in the paper.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.517-520
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• 2008

본 연구에서는 균열 철근콘크리트에서의 철근의 부식 저항성 평가를 실험적 방법에 의해 수행하였다. 실험 배합으로서 보통포틀랜드시멘트(OPC), 30% 치환률의 플라이애쉬(30% PFA), 60% 치환률의 고로슬래그미분말(60% GGBS), 10% 치환률의 실리카퓸(10% SF)이 적용된 콘크리트보를 사용하였으며, 부식저항성 실험은 만능시험기를 사용하여 0.3mm의 균열을 도입하여 측정하였다. 실험결과, 혼합콘크리트 균열 철근보의 60일 양생 후의 부식저항성 순서는 OPC > 10%SF > 30% PFA > 60% GGBS로 나타남을 확인하였다. 또한, 무게감량법에 의한 부식량 측정결과도 OPC의 경우가 가장 높은 부식저항성을 가지면서 최소의 부식을 발생시키고 있음을 확인하였다. 실험결과로써 건전부 콘크리트보에서의 부식저항성이 균열부 콘크리트에서의 부식저항성보다 높게 나타나고 있음을 확인할 수 있었고, 또한, 이성분계 콘크리트보다 OPC 콘크리트가 부식 저항이 더욱 높음을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.148-153
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• 1996

Concrete with ground granulated blast-furnace slag can be affected by frost attack because the reaction of hydration is slow at the early age. In this study, therefore, the freezing and thawing test has been carried out to investigate the freezing and thawing resistance on concrete with ground granulated blast-furnace slag. The freezing and thawing test has been performed on concrete a blended cement, which was substituted by ground granulated blast-furnace slag with 4 kinds of ratio (non-admixture, 20%, 40% and 60%). And also tested on concrete added the AE agents to the concrete of same mix proportion to search the improvement effects about the resistance. As a result, the freezing and thawing resistance showed a tendency of reduction in proportion to the increase of the substitution ratio. For non-AE concrete, resistances of the freezing and thawing were very poor as the durability index indicated less than 5.8%. For AE concrte, resistance of the freezing and thawing were excellent as the durability index indicated more than 80.9%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.307-312
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• 1997

The sea water resistance of cement and concrete must be compared when it used for construction in the ocean. The sea water resistance of the concrete specimens using three types of cements such as ordinary Portland cement, sulfate resistance Portland cement, blastfurnace slag cement were studied. In this study, an accelerated test for access sea water resistance by subjecting the concrete specimens to repeated cycles of concentrated sea water immersion and hot wind drying was employed. This study proved that sulfate resistance Portland cement had higher resistance for sea water.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.513-525
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• 2016

The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.