• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.305-312
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• 2017

This paper presents a laboratory investigation into the effects of fillers using industrial by-product such as coal ash, IGCC slag on properties of hot-mixed asphalt concrete variation with filler content. For comparison, existing mixture with lime and dust have also been considered. Marshall and flow test has been considered for the purpose of mix design as well as evaluation of mixture. Other performance tests such as indirect tensile strength test, tensile strength ratio(moisture susceptibility), dynamic stability have also been carried out variation with filler content. It is observed that the mixes with industrial by-product exhibit conform with quality standard. Therefore, it has been recommended to utilize industrial by-product based on fly ash wherever available, not only reducing the produce cost but also partly solve the industrial by-product utilization and disposal problem.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.103-112
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• 2008

Pull-off test is generally used to evaluate bond strength of FRP composite with concrete at job site. However, some damages on FRP composites can not be avoided during pull-off test and moreover test range of pull-off strength is limited by maximum tensile strength of concrete. Accordingly, it is required to set-up a test method that can evaluate mechanical properties of structural adhesive indirectly prior to pull-off test. In this study, the standard test methods for structural adhesive which can simply evaluate mechanical performance of adhesive were suggested through comparative experiments from each different standard in various countries. Particularly, gluing thickness of adhesive in tensile lap-shear tests, the section dimension of compression and bending test specimens become unified, and standard test specimen size is achieved by test results.

• Tunnel and Underground Space
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• v.7 no.3
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• pp.221-229
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• 1997

Disc-type and ring-type specimens of four different materials were tested to investigate the tensile characteristics and their brief results are presented. Materials tested were marble, granite, cement mortar and plaster. Unizxial tensile strengths are compared with Brazilian and ring test strengths. It was found that Brazilian strengths were usually greater than uniaxial tensile strengths and affected by loading rates. In the ring tests, tensile strengths were generally found to be decreased as relative hole radius being increased. Ring test strengths, however, converged to some value in r$\geq$0.45 of marble, r$\geqq$0.29 of cement mortar and r$\leq$0.5 of plaster specimens. In such range of r, furthermore, transverse cracking of specimens were observed.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.5-16
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• 2015

The characteristics of tensile strength of fiber-reinforced grouting (cement paste) injected into rocks or soils were studied. A tensile strength of such materials utilized in civil engineering has been commonly tested by an indirect splitting tensile test (Brazilian test). In this study, a direct tensile testing method was developed with built-in cylinder inside a cylindrical specimen with 15 cm in diameter and 30 cm in height. The testing specimen was prepared with 0%, 0.5%, or 1% (by weight) of a PVA or steel fiber reinforced mortar. A specimen with 5 cm in diameter and 10 cm in height was also prepared and tested for the splitting tensile test. Each specimen was air cured for 7 days or 28 days before testing. The tensile strength of built-in cylinder test showed 96%-290% higher than that of splitting tensile test. The 3D finite element analyses on these tensile tests showed that the tensile strength from built-in cylinder test had was 3 times higher than that of splitting tensile test. It is similar to experimental result. As an amount of fiber increased from 0% to 1%, its tensile strength increased by 119%-190% or 23%-131% for 7 days or 28 days-cured specimens, respectively. As a curing period increased from 7 days to 28 days, its strength decreased. Most specimens reinforced with PVA fiber showed tensile strength 14%-38% higher than that of steel fiber reinforced specimens.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.33-41
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• 2011

This study presents modeling technologies applicable to an unbonded post-tension system using a finite element software package. In this study, both direct modeling method and multiple spring method were used. The direct modeling method adopts tube-to-tube contact elements to represent the physical feature of a post-tension system. The multiple spring method uses virtual tendons attached to the real tendons using a number of rigid axial springs that freely rotate at the ends. Both modeling technologies provide accurate predictions. However, only the multiple spring method provides numerically stable and reliable responses with a consideration of concrete tension stiffening effects. Therefore, the multiple spring method turned out to be a generally applicable modeling technology for the unbonded post-tension system. Comparisons were made for the analytical and experimental results for the verification of the selected method, and parameter studies were carried out to confirm the appropriateness of the modeling assumptions and parameters adopted in the analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1505-1516
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• 2014

In this study, a cylinder embedded within cemented soils was used to cause directly tensile failure of cemented soils. An existing dumbbell type direct tensile test and a split tensile test that is most general indirect tensile test were also carried out to verify the developed built-in cylinder tensile test. Testing specimens with two different sand/cement ratios (1:1 and 3:1) and two curing periods (7 and 28 days) were prepared and tested. Total 10 specimens were prepared for each case and their average value was evaluated. Unconfined compression tests were also carried out and the ratio of compressive strength and tensile strength was evaluated. The tensile strength determined by built-in cylinder tensile test was slightly higher than that by dumbbell type direct tensile test. The dumbbell type test has often failed in joint part of specimen and showed some difficulty to prepare a specimen. Among three tensile testing methods, the standard deviation of tensile strength by split tensile test was highest. It was shown that the split tensile test is applicable to concrete or rock with elastic failure but not for cemented soils having lower strength.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.549-555
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• 2005

To evaluate the posterior and anterior restoration of polymeric dental restorative composite (PDRC), PDRC was prepared using a silica filler treated by heat at various temperatures. Compressive strength (CS) and diametral tensile strength (DTS) values were investigated to study the effect of a heat-treated silica on the mechanical properties of PDRC using the recommended dental specifications. Both the particle size and specific volume of silica were decreased upon increasing the heat treatment temperature. CS and DTS values of PDRC containing a heat-treated silica showed 1.2 and 1.3 times, respectively, higher than that of the PDRC containing a neat silica. Also, it was found that the lower heat treatment temperature, the better mechanical properties of PDRC were observed because there was less agglomeration between silica particles. Specially, PDRC using a silica treated at $600^{\circ}C$ showed superior mechanical strength.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.109-125
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• 2023

Disposal repository for high-level radioactive waste secures its safety by means of engineered and natural barriers. The performance of these barriers should be tested and verified through various aspects in terms of short and/or long-term. KAERI has been conducting various in-situ demonstrations in KURT (KAERI Underground Research Tunnel). After completing previous experiment, a conceptual design of an improved in-situ experiment, i.e. K-COIN (KURT experiment of THMC COupled and INteraction), was established and detailed planning for the experiment is underway. Preliminary characterizations were conducted in KURT for siting a K-COIN test site. 15 boreholes with a depth of about 20 m were drilled in three research galleries in KURT and intact rock specimens were prepared for laboratory tests. Using the specimens, physical measurements, uniaxial compression, indirect tension, and triaxial compression tests were conducted. As a result, specific gravity, porosity, elastic wave velocities, uniaxial compressive strength, Young's modulus, Poisson's ratio, Brazilian tensile strength, cohesion, and internal friction angle were estimated. Statistical analyses revealed that there did not exist meaningful differences in intact rock properties according to the drilled sites and the depth. Judging from the uniaxial compressive strength, which is one of the most important properties, all the specimens were classified as very strong rock so that mechanical safety was secured in all the regions.

• Restorative Dentistry and Endodontics
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• v.32 no.5
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• pp.426-436
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• 2007

The objective of this study is to evaluate the effect of an additional application of bonding resin on the bond strength of resin luting cements in both the light-cure (LC) and self-cure (SC) modes by means of the ${\mu}TBS$ tests. Three combinations of One-Step Plus with Choice, Single Bond with Rely X ARC, and One-Up Bond F with Bistite II were used. D/E resin and Pre-Bond resin were used for the additional application. Twelve experimental groups were made. Three mandibular $3^{rd}$ molars were used in each group. Indirect composite blocks were cemented on the tooth surface. $1\;{\times}\;1\;mm^2$ dentin-composite beam for ${\mu}TBS$ testing were made and tested. When total-etching dentin adhesives were used, an additional application of the bonding resin increased the bond strength (P < 0.05). However, this additional application didn't influence the bond strength of self-etching dentin adhesives (P > 0.05). In conclusion, the results suggest that an additional application of the bonding resin increases bond strength and enhances quality of bonding when using total-etching dentin adhesives.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.476-492
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• 2018

In this study, various laboratory experiments were conducted on tuff, basalt and diorite specimens, which were obtained in the southern part of Korean Peninsula. Experiments were performed under dry and water saturated conditions. Results showed that strength degradation and change of deformation characteristics were remarkable although the specimens had small porosity. Based on the results, regression models that are capable of predicting important mechanical rock properties, such as uniaxial compressive strength, Young's modulus, Brazilian tensile strength were proposed. P-wave velocity and Shore hardness were selected as independent variables and the results showed satisfactory prediction performance for the experimental data collected in this study.