• Proceedings of the KSME Conference
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• 2003.04a
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• pp.241-246
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• 2003

In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities, corrosion fatigue strength, and determination of fatigue design criterion considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The corrosion fatigue strength in $25${\circ}$, 3.5wt.% NaCl solution is very lower than that of in air. And also, it was decreased with the frequency decrease in the same environment. It is expected that the developed corrosion fatigue design method for TMCP steel is useful. However, it is necessary to verify its reliability for actual application.

• Advances in concrete construction
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• v.4 no.3
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• pp.221-230
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• 2016

This paper presents a preliminary study on the influence of laterite soil replacing conventional fine aggregates on the strength properties of GGBS-blended-concrete. For this purpose, GGBS-blended-concrete samples with 40% GGBS, 60% Portland cement (PC), and locally available laterite soil was used. Laterite soils at 0, 25, 50 and 75% by weight were used in trails to replace the conventional fine aggregates. A control mix using only PC, river sand, course aggregates and water served as bench mark in comparing the performance of the composite concrete mix. Test blocks including 60 cubes for compression test; 20 cylinders for split tensile test; and 20 beams for flexural strength test were prepared in the laboratory. Results showed decreasing trends in strength parameters with increasing laterite content in GGBS-blended-concrete. 25% and 50% laterite replacement showed convincing strength (with small decrease) after 28 day curing, which is about 87-90% and 72-85% respectively in comparison to that achieved by the control mix.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.87-93
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• 2014

PURPOSES : To evaluate the feasibility of cut waste fishing net as a reinforced fiber for concrete. METHODS : Strength characteristics of fiber reinforced concrete using waste fishing net were investigated. The cut waste fishing nets with 4~5cm length were putted into the soil-cement and cement concrete for pavement slab. RESULTS : Compression and tensile strength of fiber reinforced concrete using waste fishing net were increased. CONCLUSIONS : It was concluded that cut waste fishing net can be used as a reinforced fiber for cement concrete. However, sometimes using cut waste fishing net leads to decrease the strength; therefore, further researches are needed for real project.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.757-762
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• 2000

The target of this study is to compare and analyze the strengthening effect of damaged reinforced concrete beams under unloading and loading conditions through the simulation of strengthening condition in real structures. The conclusion of test results are as follows : For the concrete beam wrapped at the side in addition to be strengthened at the bottom, the strength and stiffness increase. although the flexural capacity depends on the strengthening method, it generally shows that the strength improve in the range of 22% to 39% in comparison with the specimen without strengthening. In case of applying th equation suggested by CangaRao & Vijay for the wraped concrete beam, it must be modified because it is likely to overestimate the flexural capacity considering the height of wrapping as the width of concrete. The strength an stiffness of reinforced concrete beams in proportion to the percentage of damage decrease. Damaged beams, which are strengthened by CFS, is structurally efficient and show reduction of strength comparing with the specimen without strengthening but stiffness is increasing.

• Journal of Industrial Technology
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• v.15
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• pp.217-222
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• 1995

In this paper, the importance of the size effects on the strength ratio is demonstrated by numerical results. The rate of decrease of tensile strength is for glass fiber, based on the experience of a composite manufacturing specialist. For other material, similar procedure may be used until detailed test result on such material is available. The strength criteria used is that of Tsai-Wu for stress space. The factors influencing the ratio are, reducing the tensile strength alone or both tensile and compression strengths, selection of the normalized interaction term, that is, the generalized Von Mises criterion or the Hill's criterion, and the status of applied stresses. Some of the numerical results are presented for a guideline for the furture study.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.117-122
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• 2005

Prepacked polymer mortar that is mainly composed of MMA monomer and used for the patching and restoring materials of concrete structures was developed, and its hardening and strength properties were experimentally surveyed. Results of study show that the permeance of binder into the aggregate was excellent for the case of PMMA mixing ratio of below 10%, the surface hardening inferiority was not generated for the case of the ratio of over 5%. Working time of the prepacked polymer mortar and hardening shrinkage tended to decrease as the PMMA mixing ratio increased. On the other hand, the ratio turned out not to decisively affect on compressive and flexural strengths. Regardless of PMMA mixing content, the adhesive strength was about 2.5 MPa. Occurring the desquamation on the substrate of cement concrete showed the adhesive strength of MMA prepact polymer mortar was excellent.

• Economic and Environmental Geology
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• v.23 no.4
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• pp.411-424
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• 1990

Mechanical, physical and petrographic properties of seventeen marble specimens collected from ten marble mines in Korea were investigated. Studied marbles were mainly composed of calcite, dolomite, and various amounts of serpentine, tremolite, olivine, quartz and opaque minerals. Complete and sutured textures were dominant. Compressive strength measured normal to the bedding plane is larger almost two times than that measured parallel to the bedding plane. From the results of Shore hardness test on marbles, water content was an important factor to decrease Shore hardness values. Engineering geological properties, especially, compressive strength, Young's modulus, wear resistance and water absorption could be controlled by the presence of quartz, and the type of marble texture. Water absorption-porosity, compressive strength-Young's modulus, and impact strength index-Los Angeles abrasion couples show good correlation. According to the comparative utility as commercial stone, it could be concluded that marbles from the Banglim mine, Songbo mine, Kwangdeok mine and Bongjeong mine were superior to that of other studied marbles.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.101-109
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• 1996

The mechanical propertieso f sintered AlN with the addition of alumina were investigated The flexural strength of the AlN dispersed ALON specimens was higher than that of ALON and fracture toughness showed similar tendency. The high-temperature flexural strength of specimens which 50 and 64.3 mol% alumina was added to AlN was constant up to 100$0^{\circ}C$ with about 290 and 420 MPa respectively but abruptly decreased at 120$0^{\circ}C$ In the specimens which contained 5 and 30mol% alumina the flexural strength increased to about 14% at 100$0^{\circ}C$ and did not decrease at 120$0^{\circ}C$ compared to at room temperature.

• Journal of Welding and Joining
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• v.12 no.1
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• pp.80-93
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• 1994

The microstructure and fractography of the friction welded joint of Al to Cu have been investigated in order to understand the formation of intermetallic compounds and their effects on the failure in tensile test of the joint. The variation of welding pressure did not affect significantly the tensile strength of joint. However, the tensile strength of joint decreaed as welding time increased. The thickness of reaction layers of welded joints was several micro-meters and mainly composed of intermetallic compounds of $CuAl_2$, $Cu_9Al_4$ and Al+$CuAl_2$. The thickness of $CuAl_2$, $Cu_9Al_4$ was increased with welding time. However, $CuAl_2$ was gradually changed to $Cu_9Al_4$ which caused the decrease of tensile strength . Even though the morphology of fractured surfaces depended upon the welding time, the failure occurred along $CuAl_2$ intermetallic compound itself or between $CuAl_2$ and $Cu_9Al_4$ in most cases.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.24-30
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• 1996

Nowadays, Government is modifying envioronment regulatons, but PC factories, having been constructed in 1990, are running out heavy cost in disposal of waste concrete, and hardly studying how accelerator curing method affects in compressive strength. In this study, possibility that waste concrete, produced in PC factory, can be used in PC products, is reviewed, and them captures strength characteristics by curing method. The results can be summed as follows. In order to recycle concrete the mix ratio of recycled aggregate to 50 percent of less than must decrease also in summer of four seasons strength gap by curing method is very small.