• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.173-176
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• 2005

Corrosion of reinforced concrete structures in marine environment is one of the most important mechanism of deterioration. For estimate of service-life for chloride attack, it is necessary to get exact surface chloride content. This paper reports the results of estimate for surface chloride content in domestic west and south coast.

• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.71-80
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• 2010

This study carried out to understand the thermal characteristics of various surface material which compose the city through the observation in the summer. To examine passive cooling effect of planting of building, it is arranged four different materials that is natural grass, grass block, concrete slab and artificial grass. The results of this study are as follows; (1) Natural grass and grass block show the lower surface temperature because of the structures of leaf can do more thermal dissipation effectively. (2) There is little surface temperature between artificial grass and concrete. But there is little high surface temperature difference between natural grass and concrete because of latent heat effect. (3) The concrete can play a role of the tropical nights phenomenon as high heat capacity of concrete compare with other materials. (4) It is nearly same color in artificial grass and natural grass but there is large difference between natural grass and artificial grass at albedo. There is different albedo in near infrared ray range. (5) A short wave radiation gives more effect at the globe temperature than long wave radiation. (6) The artificial turf protected the slab surface temperature increase in spite of thin and low albedo materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.63-67
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• 2002

The induced chemical and salt solution in water or admixture are originated to the corrosion process of the steeo rebar. These liquids penetrate into concrete as the accompanied by the chemical reaction and cause to attack the steel rebar in concrete. Concrete surfaces which it exposed to deicing, water and sea water is allowed to enter the chlorides in the structures. To prevent from the source of corrosion and deterioration Is subjected to put an end to corrode or reduce to contaminate on the steel rebar. As this reason the MCI 2022 products are applied to the surface of concrete and steel rebar. The concrete samples were made of to the kind of four, i.e. RF, MR, MS, and MM. Corrosion inhibitor is applied to coat on the surface of concrete after it had been cured for 28days. Specimen were immersed in a 3.5％ sodium chloride solution. Concrete specimen were tested to determine the changes of the resistance polarization, Rp, over a 22 weeks period. MCI 2022 is significantly shown the corrosion inhibition of steel rebar in 3.5% NaCl solution. In the each different concrete sample, MS and MM is seemed to be better than others. The results are proofed that MCI 2022 is promised to maintain the inhibition of corrosion with high resistance polarization of the steel rebar in concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.246-247
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• 2017

In this study, it reviewed the effect of moisture migration in concrete with heating rate on concrete spalling. Concrete specimens with compressive strength 30MPa and 110MPa are used and its size is □100×100×h200mm. And, two kinds of heating rate are set such as IS0 834 and 1℃/min. As a result, in the concrete specimen exposed to ISO 834 standard heating condition, moisture could migrate through pore network and surface concrete pieces fall out by generating moisture clog near the surface in 110MPa concrete specimen. Meanwhile, In the case of concrete specimens exposed to 1℃/min. heating condition, it is appeared that moisture could not migrate because temperature is distributed uniformly. Therefore, surface spalling is not occurred with low heating rate. However, in the case of 110MPa concrete specimen is exploded even though it heated by low heating rate.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.604-607
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• 2003

Recently, hybrid concrete structures such as a concrete-filled steel tubular(CFT), a steel reinforced concrete(SRC) and a composite material are popular in structure applications. They also have merit of high strength, high ductility, and large energy absorption capacity. But the analysis of hybrid concrete structures is very difficult owing to the complex behavior of concrete under passive confinement. This paper has analyzed CFT, which receives passive confinement using Tri-Surface concrete model for three dimension finite element analysis. By the result of that, the proposed model was properly forecasted a concrete behavior that receives passive restraint as well as non-linear analysis of concrete which receive uniaxial stress and high active confinement of 400Mpa. If the model through the steady study is set up especially on the factor of concrete under passive confinement, the proposed concrete model will be surely useful for analysis of the hybrid concrete structures.

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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• pp.287-293
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• 2013

Strength and some durability properties of concrete containing rice husk ash (RHA) predominantly composed of amorphous silica at a specific surface of 235 $m^2/kg$ produced using a charcoal incinerator were determined. The maximum ordinary Portland cement (OPC) replacement with the RHA increased with increase in water/binder (w/b) ratio of the concrete mixes. The results show that 15 % OPC could be substituted by the RHAwithout strength loss at w/b ratio of 0.50. The split tensile strength generally increased with increase in RHA content for the mixes.

• International Journal of Concrete Structures and Materials
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• v.8 no.2
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• pp.165-172
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• 2014

Recycled coarse aggregate (RCA) made from waste concrete is not a suitable structural material as it has high absorption of cement mortar, which adheres on the aggregate surface and on the tiny cracks thereon. Therefore, when using RCA made from waste concrete, much water must be added with the concrete, and slump loss occurs when transporting. Hence, its workability is significantly worse than that of other materials. In this study, surface of RCA was coated with water-soluble polycarboxylate (PC) dispersant so that its characteristics improved. Each possibility was evaluated: whether its slump loss can be controlled, by measuring its workability based on the elapsed time; and whether it can be used as a structural material, by measuring its strength. Moreover, the carbonation due to cement mortar adhesion was measured through a carbonation test. As a result, RCA coated with PC dispersant was found to be better than crushed coarse aggregate and RCA when the physical properties of the fresh concrete and the mechanical, durability of the hardened concrete were tested.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.815-820
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• 2001

This study is to set a new standard for using of the colorimetric method through grasping the character of the colorimetric method, and measuring the chloride concentration at the place of the change of color. Also, to predict chloride concentration around rebar and time reaching limit chloride concentration through measuring the chloride concentration of concrete surface by the colorimetric method and this study presents the new program of concrete degradation and diagnosis of the durability by salt damage. First the use of the colorimetric method was examinated, second the chloride concentration through slicing concrete submerged in artificial seawater for 6 months was measured. And the chloride concentration at the place of the change of color was calculated by using colorimetric method. Finally, the cloride concentration of the concrete surface was calculated.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.768-773
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• 1999

This study of concrete movement confronting a scope inspects the problems about the waterproofing method and leakage/repairment at present and research the mechanism with the variety of applying examples introducing adhesion and inflation using the flexible type of waterproofing and repairement and the subsititution method developed with polymer resign composite. The polymer resign transmited into adhesion or inflation materials under wet environment absorbs adjoining moisture, wraps impurities of concrete surface, get the waterproofing layer and concrete surface adhere toughly, reorganize the impaired waterproofing layer and get over the detachment of it from concrete surface.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.31-37
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• 2000

When a crack is produced in a concrete structure, a micro crack zone of fracture process zone (FPZ) appears at the crack tip. To investigate the behaviour of this the micro crack zone, nonlinear fracture mechanics (NLFM) must be applied. However, when a massive concrete structure such as a concrete gravity dam is considered, the micro crack zone can be neglected and the structure can be assumed to have linear elastic fracture mechanics (LEFM) behaviour. This study is divided into two main topics : (1) Calculating stress intensity factor (SIF) at the crack tip by surface integral method and (2) Investigating the propagation of the initial crack. If the initial crack propagates, the angle of the propagation is calculated by using maximum circumferential tensile strength theory. This study, also, contains the effects of body forces and water pressures on the crack face.