• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.141-148
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• 2004

This paper present the experimental research investigating the influence of material factors such as a type or amount of superplasticizer, velocity agent, mineral admixture and steel fiber on the workability of high strength steel fiber reinforced cementitious composites. As for the test results, it was found that the workability of high strength steel fiber reinforced cementitious composites can be improved when the material factors were matched properly in amount and composition. Furthermore, it was shown that the smaller value of the aspect ratio of steel fiber improved the workability of fiber reinforced cementitious composites. And the steel fiber reinforced cementitious composites with better workability showed the enhanced compressive strength and flexural strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.269-272
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• 2005

Epoxy resins are gradually becoming some of the most important and versatile polymers in modem civil engineering. Because epoxy resins have some unigue properties, such as toughness, versatility of viscosity and curing conditions, good handling characteristics, high adhesive strength, inertness, low shrinkage compared to most other thermo-setting resins and concrete, and resistance to chemicals, they have found many applications in construction castings, repair materials, road or bridge deck pavements, coatings, and as structural or non structural adhesives. In this applications, epoxy resins are widely used for polymer concretes, grouting materials, injection glues, and sealants. In this paper, characteristics of deformation of repair material after repaired have been investigated by viscosity of repair material and the width of crack. It is believed that flexural strength of epoxy resin with low viscosity is high because tensile strength is high and elongation at break is low, fracture energy is low.

• Journal of the Korean Ceramic Society
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• v.53 no.5
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• pp.541-547
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• 2016

In developing high temperature molds with advantages of the sand and precision (investment) castings, mechanical properties of the mold were improved through homogeneous coating of starting powders with an inorganic binder and improvement of fabrication process. Beads with mullite composition were employed for properties of the mold under high temperature, which was compared with artificial sands. Precursors of silica and sodium oxide were used as starting materials for an inorganic binder to achieve homogeneous coating on the starting powders. Strength was enhanced by the glass phase converted from the inorganic binder through heat treatment process. Also, two kinds of process, wet and dry processes, were incorporated to prepare mold specimens. Consequently, fabrication process of the mold with superior strength and high temperature applicability, compared with the previous molds for sand casting, could be suggested through control of the starting material and enhancement of the vitrification efficiency.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.111-112
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• 2022

Lightweight aggregate is a porous material that has a lower density than natural aggregate and is a lightweight construction material. Lightweight Aggregate has a suitable purpose because it is effective in reducing the heavy unit mass in high-rise buildings. However, since lightweight aggregate has weak strength and high water absorption compared to natural aggregate, it is difficult to control the quality of concrete. Although lightweight aggregate has disadvantages such as high water absorption, it is expected that the demand for lightweight aggregate concrete will continue to use in the future because the advantage of being able to reduce the weight of concrete is greater. In this study, we conducted an experimantal study on the compressive strength property of cement matrix according to the type of lightweight aggregate.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.62-67
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• 2017

The automotive industry is in constant pursuit of alternative materials and processes to address the ever changing needs of their customers and the environment. Applications of laser welding have increased steadily in recent years due to its benefits including high speed, high productivity, and high energy density of heat source. This paper investigated the relationship between laser welding parameters and penetration characteristics. The Welding power was fixed at 5kW and welding speeds were varied for the thickness of the workpiece material. Full penetration occurred in the energy per unit area of $21J/mm^2$. The hardness of the weld zone was different for each strength of the workpiece material, however the lowest hardness values were the same in the heat-affected zone.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.148-149
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• 2014

In modern society, population overcrowding and concentration of facilities are happened because of the concentration on to city. So this phenomenon demands improvement of material's performance, technical development of structure analysis and design and improvement of constructing ability .High strength concrete has some merits. High strengthening makes the cross section reduced, and that cause decrease of structure weight. And using high durable and superplasticizer promote liquidity, thus high quality concrete can be produced. Because of these advantages, this study is for showing validity of using it by compression/tensile strength experiment. As this experiment's result, when concrete become stronger, interface intensity coefficient between cement and aggregate is different and they don't adhere to each other. So there is brittle failure. Fragility factor also steadily increase with strong concrete, it tells high strength concrete has problem. Therefore the sources used in high strength concrete like cement and aggregate must have great quality. So the source's performance must be supervised well because their quality decides performance criteria.

• Steel and Composite Structures
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• v.10 no.5
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• pp.373-383
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• 2010

This paper presents the experimental studies of the flexural behavior of steel-concrete composite beams. Herein, steel-concrete composite beams were constructed with a welded steel I section beam and concrete slab with different material strength. Four simply supported composite beams subjected to two-point concentrated loads were tested and compared to investigate the effect of high strength engineering materials on the overall flexural response, including failure modes, load deflection behavior, strain response and interface slip. The experimental results show that the moment capacity of composite beams has been improved effectively when high-strength steel and concrete are used. Comparisons of the ultimate flexural strength of beams tested are then made with the calculated results according to the methods specified in guideline Eurocode 4. The ultimate flexural strength based on current codes may be slightly unconservative for predicating the moment capacity of composite beams with high-strength steel or concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.399-402
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• 2005

In ultra-high strength SFRCC(Steel Fiber Reinforced Cementious Composites), much silica fume are used to improve strength, flowability and durability. Silica fume have merits of filling the voids, enhancement of reheological chracteristics, production of secondary hydrates by pozzolanic reaction in reactive powder concretes. However silica fume has been imported in high-cost in domestic industry, we need to investigate replaceable material in stead of silica fume in a view of economy Therefore, in this paper, in order to investigate replacement of silica fume in ultra-high strength SFRCC we used the granulate blast-furnce slag with finess 4000, 6000, 8000. As a results, we have evaluated that the bigger the finess the more increase compressive strength of ultra-high strength SFRCC using the blast-furnce slag and there was no problem from the viewpoint of flowability and compressive strength when we use blast-furnce $50\%$ with replacement ratio of silica fume

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.442-445
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• 2004

The mock-up test was carried out to solve several problems of the hot weathered high strength concrete. The workability of concrete could be guaranteed by using high range water reducer containing polycarboxylic acid. The compressive strength calculation by rebound value of Schumidt hammer underestimated the actual strength of concrete structure. The temperature of concrete should be lowered by control of raw material temperature and transportation.

• Steel and Composite Structures
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• v.14 no.2
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• pp.133-153
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• 2013

The concrete-filled steel tube (CFT) columns have several benefits of high load-bearing capacity, inherent ductility and toughness because of the confinement effect of the steel tube on concrete and the restraining effect of the concrete on local buckling of steel tube. However, the experimental research into the behavior of square CFT columns consisting of high-strength steel and high-strength concrete is limited. Six full scale CFT specimens were tested under flexural moment. The CFT columns consisted of high-strength steel tubes ($f_y$ = 325 MPa, 555 MPa, 900 MPa) and high-strength concrete ($f_{ck}$ = 80 MPa and 120 MPa). The ultimate capacity of high strength square CFT columns was compared with AISC-LRFD design code. Also, this study was focused on investigating the effect of high-strength materials on the structural behavior and the mathematical models of the steel tube and concrete. Nonlinear fiber element analyses were conducted based on the material model considering the cyclic bending behavior of high-strength CFT members. The results obtained from the numerical analyses were compared with the experimental results. It was found that the numerical analysis results agree well with the experimental results.