• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.41-56
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• 2012

This study is focused on evaluation of the tensile properties of concrete exposed to acid rain environment. Acid rain environment was simulated by the mixture of sulfate and nitric acid in the laboratory. The dumbell-shaped concrete specimens were submerged in pure water and acid solution for accelerated conditioning. Weighing, tensile test, CT, SEM/EDS test and microanalysis were performed on the specimens. Tensile characteristics of the damaged concrete are obtained quantitatively. Evolution characteristics of the voids, micro cracks, chemical compounds, elemental distribution and contents in the concrete are examined. The deterioration mechanisms of concrete exposed to acid rain are well elucidated.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.159-162
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• 1999

The paper presents results of an investigation on the permeability characteristics and pore structure of concrete containing different levels of fly ash, silica fume, or blast furnace slag. The total cementitious content was 351kg/㎥, and the water/cementitious materials ratio was 0.55. The porosity and pore structure of representative pastes of the matrix were measured using mercury intrusion porosimetry, and the permeability characteristics of concrete were also determined by water and oxygen permeability, chloride ion penetration. The results show that significant reduction in permeability of concrete containing pozzolanic materials due to formation of a discontinuous macro-pore system which inhibits flow. And, the permeability of concrete and pore structure(capillary porosity or total porosity) shows linear relationship.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.319-324
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• 1994

Bond test was carried out to assess the effect of several variables on bond characteristics between reinforcing bar and concrete. Key variables are concrete compressive strength(low, medium high, and ultra-high), bar diameter(13mm and 22mm), and concrete cover(25mm; 1-inch, 38mm; 1.5-inch, and 51mm; 2-inch). Confining effect and bar spacing are not taken into account. Thirty-two specimens subjected to uniaxial tension were tested under hypothesis uniform bond stress distribution along the reinforcing bar embeded in concrete. Test results(ultimate bond stress) were compared with bond and development provisions of the ACI building Code(ACl 318-89) and local bond stress versus slip relationship diagram represented to show effect of the above variables.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.229-234
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• 1994

Various of batches of recycled concretes were produced with different rations of recycled aggregate (20% and 50%) and admixtures based on workable range of slump value and using a fixed w/c ration. Mechanical characteristics of the recycled concretes were evaluated. Test results showed that, in general, relatively high strength recycled concrete could be obtained using a plasticiser. The concrete using fly ash showed somewhat reduced strength, lower elastic modulus and relatively high strain, in general. However, the strength reduction ratio of the recycled concrete due to adding fly ash was relatively minor, compared with normal concrete. Since it has been known that the fly ash is used in place of cement and gives an improved long term strength, a further study may be warranted for a possibility of using fly ash without degrading the strength required.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.2
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• pp.132-139
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• 2001

This study deals with coal-mine waste (CMW) for use in concrete as a replacement of normal aggregates. The CMW was collected from Sabuk region. Ganwon-do. Fine and coarse aggregates from CMW were prepared by using a crusher and separating debris with #4 sieve. CMW aggregates showed good physical and mechanical properties with having specific gravity over 2.65, absorption less than 1%, and abrasion ratio below 20%. However, particle shape of CMW was poor because of non-isotropic nature of matrix which cause particles to be long or flat. Since irregular particles caused a poor workability, to make workability better, a 1/4 of coarse aggregate was replaced with normal aggregate together with a superplasticizer. Compressive strength and other mechanical properties of CMW concrete were very good. Color of the concrete was darker than normal concrete due to black color of CMW. In conclusion, characteristics of CMW concrete was acceptable for use as a structural concrete material.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.691-694
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• 2005

The present study was to examine the influence of porosity and moisture content on the water permeability, strength and plant-growth characteristics of porous concrete. The result of the experiment verified that the coefficient of permeability of porous concrete with porosity between $30\%\;and\;36\%$ increased by 2cm/sec and the compressive strength decreased 1MPa at every $3\%$ increase of porosity. In addition, the plant growth of porous concrete showed 5cm at $36\%$ porosity and 2.5cm at $30\%$ porosity respectively. Thus, the higher the porosity, the more the plant grew. When $2\%$ moisture content was used in porous concrete with the same porosity, the plant growth was accelerated two times faster than the case without it.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.417-420
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• 2006

Recently, the attention is paid to the problem of thermal crack by hydration heat according to the increase of high strength and mass concrete structures. At this point, various research has been carried out for the control of hydration heat in high strength and mass concrete. As a part of the research, it was investigated application of hydration heat reduction agent (HR) for the control of thermal crack by hydration heat in this study. To investigate the application, it was selected HR which can reduce hydration heat of concrete with effect in series I and II. Also, it was investigated the characteristics of hydration heat generation of low heat concrete using HR with binder types in seriesIII.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.129-136
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• 1998

In this study, lightweight aggregates were developed to see the possible application as a structural uses. For the evaluation purpose, several testings were conducted to compare the physical characteristics between the controlled lightweight aggregates and other lightweight aggregates purchased from different sources. The tests included property changes of fresh concrete and strength characteristics of hardened concrete for both normal and high strength ranges. In addition, a experiment was performed to analyze the freezing and thawing resistance of new lightweight aggregate concrete against other lightweight aggregate concrete against other lightweight aggregate concretes with some experimental parameters such as lightweight aggregates, curing conditions, and water-cement ratio. The test showed that the new lightweight aggregate could be used structural components. Continuous study will be planned for future evaluations.

• Magazine of the Korea Concrete Institute
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• v.2 no.1
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• pp.109-119
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• 1990

This study was accomplished to investigate the characteristics of hardening shrinkage and initial creep of epoxy resin concrete depending on the presence of filler. According to the test results, the hardening shrinkage was increased with increment of sLOrage temperature, and the ef¬feel of tempemture on the hardening shrinkage of epoxy resin concrete with 6% filler was more Significant than that of epoxy resin concrete without filler. Also, the initial creep strain was increased with loading times, stress--strength ratio and elastic strain, and the values for opoxy resin concrete with 6 % filler are higher than that for eposy resin concrete without filler.

• Journal of the Korean Society for Railway
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• v.9 no.3 s.34
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• pp.298-304
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• 2006

An active application of concrete track is being expected for the future constructions of Korean railroad. For the successful concrete track construction and design in earthwork areas, the roadbed behavior should be reasonably estimated using the proper analysis method. In this paper, behaviors of concrete track on the reinforced roadbed constructed with the standard stiffness and depth were estimated thorough numerical analyses and field measurements. A three dimensional finite difference method was employed to model the concrete tracks and subground. The settlement and vertical pressures caused by train load were estimated by the numerical method and compared with the field measurement results. The bearing characteristics of roadbed were presented and the proper method for the analysis of concrete track was proposed.