• Journal of the Korea Institute of Building Construction
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• v.24 no.4
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• pp.393-402
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• 2024

The Korean Industrial Standard(KS) KS F 2527("Aggregates for Concrete") does not explicitly define criteria for clay mineral content in aggregates. This lack of clear quality standards and testing methodologies is further compounded by a scarcity of relevant research within both academic and industrial spheres. Consequently, the construction industry, encompassing both aggregate production and utilization, often overlooks the management of clay mineral content due to its perceived economic implications. This study addresses this gap by investigating the current state of regulations concerning clay mineral content in aggregates, exploring the causes of its occurrence, and evaluating its impact on concrete performance. The chemical composition of the clay minerals was determined to primarily consist of Al₂O₃, Fe₂O₃, and SiO₂, which are commonly found in clay. X-ray diffraction(XRD) analysis revealed that the predominant clay minerals were montmorillonite and illite, both known for their high absorption capacity. An examination of domestic and international standards for clay mineral content in aggregates demonstrated that the density and absorption rate specifications outlined in KS F 2527("Aggregates for Concrete") only offer indirect estimations of clay mineral levels. Furthermore, the investigation into the influence of clay mineral content on concrete performance suggests that a higher clay mineral content necessitates a corresponding increase in the unit quantity of aggregates to maintain adequate workability. This, however, has a detrimental effect on the compressive strength of the concrete.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.123-130
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• 2010

In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;=\;1.3$). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.533-549
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• 2017

In this study, drainage systems were proposed to drain the leakage of groundwater in the existing underground concrete structures. The system consists of drainage board, wire mesh, fixed nail, and mortar with mineral. In order to increase constructability, the drainage board and wire mesh were attached on the surface of cement concrete using the air nailer and fixed nail. The mortar with 30% of blast furnace slag was sprayed on the drainage board and wire mesh using the spray mortar equipment. The field test construction was carried out in a conventional concrete lining tunnel and concrete retaining wall for performance verification of the drainage system in the field. There was no problem with performance degradation in the drainage system for three years after construction. The bond strength tests were performed on the sprayed mortar at 14 days and about 3 years after field test construction. In case of attaching the wire mesh on the drainage board, the bond strengths of the sprayed mortar were 1.04 MPa at 14 days and 1.46 MPa about 3 years. In case of the drainage board without the wire mesh, the bond strengths of the sprayed mortar were 1.13 MPa at 14 days and 0.89 MPa, less than 1 MPa of bond strength criteria, about 3 years.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.259-266
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• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that reinforces shear force. CFP pile (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) developed in this study increases the shear stress by placing composite shear connector and filling the concrete into hollow part of the pile. By placing the reinforcement (H13-8ea) and the reinforcement (H19-8ea) into hollow section inside of PHC piles, it also improves the shear strength due to increasing steel ratio. It reinforces shear strength effectively by dowel force that is generated by putting reinforcement (H13-8) into the holes of composite shear connectors for the composite behavior of filled concrete and PHC pile. The study was reviewed and compared the calculated result of the shear strength by limit state design method highway bridge design standards (2012) and experiment result of the shear strength by KS F 4306. We can design the shear strength reasonably as the safety ratio of 2.20, 2.15, 2.05 is shown comparing to design shear strength, according to design shear strength on each cross sections and the experiment results of the CFP pile.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.629-634
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• 2017

In the case of the UHP (Ultra high performance) tire that the demand has increased rapidly, compared with the commonly used tire, severe deformation has been observed because of the low aspect ratio. When repeated deformations are applied to the sidewall rubber, accumulated fatigue damage may cause fatigue failure. Thus, the evaluation of the durability of the tire sidewall rubber has become a very important issue to prevent accidents that occur while the vehicle is running. However, the research and design criteria for the durability performance of the tire sidewall rubber hardly exist. In this study, we suggest a lifetime prediction formula using strain energy density obtained by performing tensile tests and fatigue tests on two different kinds of the tire sidewall compounds. Additionally, the applicability of our findings for low fuel consumption tires was reviewed by converting the fatigue life of the sidewall rubber into the expected mileage of the tire.

• International Journal of Highway Engineering
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• v.7 no.3 s.25
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• pp.31-42
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• 2005

This study evaluates the physical mechanical properties, durability and sound absorbtion of porous concrete for pavement according to content of silica fume and steel fiber to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of Korea National Housing Corporation as for every factor of mixture but in the case of the flexural strength, more than 0.6vol.% of steel fiber satisfied the Japan Concrete Institute proposition values. The mixture of silica fume and steel fiber presents the excellent intensity, though. The case when silica fume and steel fiber are used simultaneously presents the strongest durability because the durability shows the similar tendency to the dynamic characteristics. The case when 10wt.% of silica fume and 0.6vol.% of steel fiber are used at the same time shows that the loss rate of mass by Cantabro test became 27% better and freeze-thaw resistance became 60% better. As for the characteristics of sound absorption of porous concrete for pavement, Noise Reduction Coefficient is 0.48 to prove that it possesses almost 50% sound absorption.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.207-216
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• 2013

The components of concrete track (rail and rail fastening system) in railway bridge deck ends are damaged and deteriorated by track-bridge interaction forces such as uplift forces and compression forces owing to their structural flexural characteristics (bridge end rotation). This had led to demand for alternatives to improve structural safety and serviceability. In this study, the authors aim to develop a transition track to enhance the long term workability and durability of concrete track components in railway bridge deck ends and thereby improve the performance of concrete track. A time-history analysis and a three-dimensional finite element method analysis were performed to consider the train speed and the effect of multiple train loads and the results were compared with the performance requirements and German standard for transition track. Furthermore, two specimens, a normal concrete track and a transition track, were fabricated to evaluate the effects of application of the developed transition track, and static tests were conducted. From the results, the track-bridge interaction force acting on the track components (rail displacement, rail stress, and clip stress) of the railway bridge deck end were significantly reduced with use of the developed transition track compared with the non-transition track specimen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.447-455
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• 2019

When constructing LNG storage structures using the cast-in-place method in extreme areas, the construction cost and time may be increased due to the poor working environments and conditions. Therefore, demand for modular energy storage tanks is increasing. In this study, we propose using an SCP module as an alternative for lighter-weight LNG storage tanks. The purpose of this study is to evaluate the feasibility of LNG storage outer tanks by performing bending tests on the thickness of composite steel plate concrete under field conditions. The loads on specimens with thicknesses of 100 mm and 200 mm were linearly increased to the design final loads of 413 kN and 822 kN, respectively. The slope was rapidly changed, and fracture occurred. The two test conditions showed linear behavior until the steel plate yielded, and after an extreme load behavior, sudden yielding of the steel plate yield occurred in the SCP bending test according to the INCA guidelines. The results satisfied the design flexural load and showed the possibility of using the specimens in a modular LNG outer tank. However, it is necessary to evaluate the structural performance of the SCP by performing compression and shear tests in future research.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.632-638
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• 2022

As Korean coastal activity is high, the incidence of accidents caused by marine waste is extensive. An accident in which marine floating waste ropes and fishing nets are wound around the propeller of a sailing ship is termed "Rope wrapped accident." To prevent such accidents, this study applied the Finite Element Method (F.E.M.) for performance evaluation of the shaver type cutter, commercialized in Korea, through a structural safety review and water tank test. The results demonstrate that all parts constituting the rope cutter were damaged before reaching 0.5s, and the safety factor of each part was found to be at least 2 based on the maximum stress generated compared to the tensile strength. In the basin test, the cutting process of the shaver type rope cutter was reviewed, and the installation angle was set for each case considering that the rope floating in the sea actually enters at various angles. Consequently, as it was successful at cutting in all the cases, it can be concluded that there will be no problem in cutting the rope regardless of the mounted angle of the cutting blade.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.182-192
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• 2023

In this study, the efficacy of Engineered Cementitious Composite(ECC) jacket for masonry fences subjected to lateral dynamic load was experimentally verified through a shaking table test, comparing it with the performance of an unreinforced masonry(URM) fence. Firstly, dominant frequencies, modal damping ratios and deformed shapes were identified through an impact hammer test. URM and ECC-strengthened fences with heights of 940mm and 970mm had natural frequencies of 6.4 and 35.3Hz, and first modal damping ratios of 7.0 and 5.3%, respectively. Secondly, a shaking table test was conducted in the out-of-plane direction, applying a historical earthquake, El Centro(1940) scaled from 25 to 300%. For the URM fence, flexural cracking occurred at the interface of brick and mortar joint(i.e., bed joint) at the ground motion scaled to 50%, and out-of-plane overturning failure followed during the subsequent test conducted at the ground motion scaled to 30%. On the other hand, the ECC-jacketed fence showed a robust performance without any crack or damage until the ground motion scaled to 300%. Finally, the base shear forces exerted upon the URM and ECC-jacketed fences by the ground motions scaled to 25~300% were evaluated and compared with the ones calculated according to the design code. In contrast to the collapse risk of the URM fence at the ground motion of 1,000-year return period, the ECC-jacketed fence was estimated to remain safe up to the 4,800-year return period ground motion.