• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.68-77
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• 2020

The purpose of the paper is to evaluate the pore structure and mechanical properties of early frost damaged concrete using electric arc furnace slag as aggregate. From the results, when the concrete is exposed to frost damage at an early age, the peak point of pores 100 to 150 ㎛ in diameter were transferred into larger one. When the freezing duration is not exceeded 24 hours, it is possible that the pore distribution of under the 200 ㎛ is maintained and pore size of over 500 ㎛ is not formed, and, the freezing resistance of concrete using EFG could be improved. When BFS was mixed in concrete using EFG as coarse aggregate, the relative strength is higher than that of natural coarse aggregate. Meanwhile, the elastic modulus and resonance frequency did not change significantly due to the early frost damage as compared with the compressive strength. So, it is necessary to analyze the correlation between the experimental results in order to evaluate the performance degradation due to early frost damage.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.241-247
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• 1997

Reinforced concrete is in general known as high durability construction material under normal enviroments due to strong alkalinity of cement. Marine and harbour concrete as well as concrete mixed with seasand for fine aggregate are exposed to detrimental saltwater wich cause to accel-eate corrosion of reinforcing steel in concrete. If corrosion resistance of concrete gets to weaken due to carbonation and crack in cover concrete, concrete durability rapidly decrease by corrosion of reinforcement steel embedded in concrete. This research is to investigate basic physical properties of various corrosion inhibitors and to evaluate their corrosion resistance in concrete mixed with seasand. The object of this study is develop appropriate corrosion protection systems so as to enhance the durability of concrete.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.35-43
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• 2004

Skid resistance is an important factor that control braking distance and secure safety by preventing slipperiness between tire and pavement surface. Decrease of skid resistance at wet condition may cause fatal traffic accidents. Dirt materials such as sand and do-icings on the road surface also can be a factor for decrease skid resistance. This study makes an investigation into influence of skid resistance between varied cement concrete pavements about surface texturing method(transverse tining, longitudinal tining, exposed aggregate surface texturing method) and wearing condition of pavement surface texture(new constructed pavement's surface, wore pavement's surface) using accelerate concrete pavement wearing tester when remains of dirt material are obtained between tire and road surface on PCC pavement. As dirt material on road surface of concrete pavement, sand, calcium chloride and old oil were used with different amount of each cases.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.819-830
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• 2021

To evaluate the performance of concrete load bearing walls in a structure under horizontal loads after being exposed to real fire, two steps were followed. In the first step, an experimental study was performed on the thermo-mechanical properties of concrete after heating to temperatures of 200-1000℃ with the purpose of determining the residual mechanical properties after cooling. The temperature was increased in line with natural fire curve in an electric furnace. The peak temperature was maintained for a period of 1.5 hour and then allowed to cool gradually in air at room temperature. All specimens were made from calcareous aggregate to be used for determining the residual properties: compressive strength, static and dynamic elasticity modulus by means of UPV test, including the mass loss. The concrete residual compressive strength and elastic modulus values were compared with those calculated from Eurocode and other analytical models from other studies, and were found to be satisfactory. In the second step, experimental analysis results were then implemented into structural numerical analysis to predict the post-fire load-bearing capacity response of the walls under vertical and horizontal loads. The parameters considered in this analysis were the effective height, the thickness of the wall, various support conditions and the residual strength of concrete. The results indicate that fire damage does not significantly affect the lateral capacity and stiffness of reinforced walls for temperature fires up to 400℃.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.269-274
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• 1997

Recently, premature reinforcement corrosion in concrete structures exposed to chloride containing environments has an important problem. This is due to an increasing use of marine aggregate of chloride containing admixture a the mixing stage and due to an increase of concrete construction in marine environments. In this study, the behavior of chloride ions introduced into concrete from concrete surface by a marine environment was modeled. The physicochemcial processes including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ion with solid phase were analyzed by using the finite element method. The results of this study may be used to predict the onset of reinforcement corrosion, and identify the maximum limit of chloride ions contained in admixtures.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.557-560
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, this study is willing to propose fundamental data for accurate diagnosis of deteriorated concrete structure by fire damage with experiment according to the curing conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.465-468
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, this study is willing to propose fundamental data for quick and accurate diagnosis of deteriorated concrete structure by fire damage with experiment according to the design compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.203-204
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• 2019

Recently, exposed concrete designs have been placed everywhere due to increased interest in indoor residential environments. In addition, in order to overcome the disadvantages of litracon, which was developed by mixing optical fiber, LEFC(Light Emotion Friendly Concrete) was developed in Korea, which improved unit price and constructivity by inserting hard acrylic rods. LEFC, using foaming agent and lightweight aggregate for light weighting, has disadvantages that decrease mechanical properties, and thus improved mechanical properties by using ultra-high performance concrete. Also, due to the characteristics of UHPC materials, it showed excellent self-consolidating performance. Considering these characteristics, a LEFC mold with pattern design was developed. The LEFC blocks were built so that pattern shapes could be seen and these were applied on-site to Sewoon plaza, located in Seoul.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.163-168
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• 1994

If the concrete is exposed below freezing point of the outer temperature before hardened, the quality of the concrete will be lowered after hardened. Anti-freezing agent which doesn't corrode the steel bar and doesn't generate the alkali-aggregate reaction by noncholride recently developed in Japan and Northern Europe. But the effects of these agents are rarely known. Therefore, this study is desigend for analyzing the freezing properties at the condition of solution of solution and cement paste. And this study aims to present the reference data for practical use of the concrete works using anti-freezing agent.

• Computers and Concrete
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• v.10 no.6
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• pp.587-607
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• 2012

The purpose of this research is to propose a design technique of concrete mix proportions satisfying service life through genetic algorithm (GA) and neural network (NN). For this, thirty mix proportions and the related diffusion coefficients in high performance concrete are analyzed and fitness function for diffusion coefficient is obtained considering mix components like w/b (water to binder ratio), cement content, mineral admixture (slag, flay ash and silica fume) content, sand and coarse aggregate content. Through averaging the results of 10 times GA simulations, relative errors to the previous data decrease lower than 5.0% and the simulated mix proportions are verified with the experimental results. Assuming the durability design parameters, intended diffusion coefficient for intended service life is derived and mix proportions satisfying the service life are obtained. Among the mix proportions, the most optimized case which satisfies required concrete strength and the lowest cost is selected through GA algorithm. The proposed technique would be improved with the enhancement of comprehensive data set including wider the range of diffusion coefficients.