• International conference on construction engineering and project management
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• 2015.10a
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• pp.405-410
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• 2015

Today, the booming construction in Ethiopia is leading to an increased demolition of concrete structures whereby these demolished structures are disposed at landfills. The current practice is creating a huge amount of waste which is environmentally unfriendly and is becoming the main source of pollution in communities. This paper discusses the potential use of demolished concrete from site tested specimens as a recycled aggregate material for new structural concrete. The mechanical, physical and chemical properties of RCA are studied to understand the suitability in the production of recycled concrete. Tests including gradation, unit weight, soundness, density, and abrasion will be conducted to assess RCA properties. Since the percentage of RCA govern the strength of concrete, a C25 concrete is mixed by the ratio of 25%, 50% & 100% RCA with and without water reducing admixture and a control mixture composed of natural aggregate. The output of this study will highly impact the growing construction industry and communities in Ethiopia thereby reducing waste, saving cost, conserving natural aggregates, building capacity and setting quality standards.

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.151-161
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• 1996

This paper presents a series of tests to produce the h~gh quality concrete to be filled Inside the steel tube columns. Thls concrete filled steel tube system requires not only the high strength, but a150 the flowable concrete. Laboratory test has been performed to clarlfy the material characteristics and to produce the optlmal mix design proportion. Full scale site mock up test has been then carried out to slnlulate the actual construct~on conditions including the product~on of concrete at the rermcon batch plant, transportation to the construction site, proper workabil~ ty and man power required , 4ddit1onal mock up test has finally been performec to irivesti gate any unfavorable construction s~tuatioils since the actual concrete placement has been sched uled in cold weather period, so that the high quality concrete construction is convinced to be successfully carried out.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.100-101
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• 2020

In this study, the temperature history and compressive strength of the concretes according to the type of cement were measured and analyzed in comparison as part of the experiment on the material mixing side to reduce the hydration heat crack of the mat foundation constructed with mass concrete. As a result, the peak temperature and maximum temperature reach time of concrete using high rapid cement were shown to be similar to that of semi rapid cement. In particular, in compressive strength after three days, semi rapid cement was measured higher than that of concrete using high rapid cement. Therefore, if semi rapid cement is used in accordance with the site conditions, it is deemed possible to shorten the air due to reduction of temperature cracks and improvement of initial strength.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.105-116
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• 1999

The Inchon International Airport site was formed by reclaimed soil from the sea. The average thickness of soft soil Is about 5 m and most of soft soils are normally consolidated or slightly over consolidated. There are many box culverts which are being constructed under the runways in the airfield. Sometimes, differential settlement can be occurred in the adjacent of box culvert or underground structures at the top layer of runway Soil compaction at very near to the structure is not easy all the time. Thus, one layer of geogrid was placed at the bottom of lean concrete layer for the concrete paved runway and at the middle of cement stabilized sub-base course layer for the asphalt paved runway. The length of geogrid reinforcement is 5m from the end of box culvert for both sides. The extended length of geogrid was 2m from the end of backfill soil in the box culvert. The tensile strength tests of geogrid were conducted for make sure the chemical compatibility with cement treated sub-base material. The location of geogrid placement for the concrete paved runway was evaluated. The construction damage to the geogrid could be occurred. Because the cement treated sub-base layer or lean concrete was spread by the finisher. The magnitude of tensile strength reduction was 1.16%~1.90% due to the construction damage and the ultimate tensile strength is maintained with the specification required. Total area of geogrid placement in this project is about 50,000 $m^2$.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.405-408
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• 2005

The repair and reinforcement materials of the concrete structure in underwater is use to epoxy mortar for underwater-harding. Because it ensures the separation of material and a fluidity in construction, it is important to epoxy mortar This study dealt with the influence of the using of rapidly-chilled steel slag on flow, nozzle passing time, viscosity, and strength of mortar by experimental design. As results of study, this paper proved that the more the using rate of rapidly chilled steel slag increased, the more this affected the enhancement of flow, the decrease of O-lot, and the development of compressive strength, flexural strength. Also, considering the fluidity, nozzle passing time and strength of mortar, it is desirable to use RCSS300 of rapidly chilled slag.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.191-196
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• 2002

The bonding strength of the interface between the actual bridge concrete deck and overlay was primarily affected by the shear that depended on the flexural behavior than pure tensile, but the field bonding test measured bonding strength by the pure tensile due to simplicity and field applicability. Therefore, the purpose this study was to evaluate the required direct bond strength for bridge deck overlay using Finite element analysis with the many variavles such as bridge deck types, span length, material properties, lanes, and loading types. The commercial program LUSAS was used in analysis. The analysis results were compared to the value of specification currently used in highway construction site.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.46-55
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• 2006

There are many kinds of braced cut wall methods as the sheet pile, SCW, CIP and slurry wall which is adoptable for a deep excavation construction in a coastal filled land. The braced cut wall which has a strong stiffness is very stable but it has the weak point that the construction cost is high. Thus when a braced cut wall is designed, the geotechnical engineers choose the braced cut wall which has more safe and economic in the consideration of surrounding buildings near the construction site. Especially, when the sheet pile method as a braced cut wall is cheesed, the layer order and consistence of a coastal deposit stratum are considered and the pile driving method is also considered. This paper introduces the case that the originally box-type sheet pile wall was changed to U-type and high strength material after the pilot test at the subway construction site in a coastal filled land. This paper also introduces the case that the sheet pile's driving method was changed to special method in the section of the temporary coffer dam which had made when the present coastal filled land was formed.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.418-421
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• 1996

Carbon Fiber Sheet is very attractive for the upgrading damaged reinforced concrete due to its good tensile strength, handabilbity and resistance to corrosion. This paper discusses the applicability of continous carbon fiber sheet for a reinforcement of existeing reinforced concrete structure located in Pusan. Examples of site data and actual concrete rehabilitation project at slab structure related to construction method used carbon fiber sheet will be given.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.805-812
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• 2009

Permeation water resulting in the reclaimed land of waste can possibly cause the second pollution, such as the underground water and environmental pollution. Accordingly, Liner layer has been installed in the reclaimed land of waste to block and purify permeation water and prevent this second pollution. The material used as Liner layer is the one for water resistance and that of less than permeability coefficient $1{\times}10^{-7}cm/sec$ is widely used. As it is very difficult to secure in bulk this natural clay with low permeability around the field, the suitable way to secure low permeable material is that we use blend with good watertighness by mixing it with natural soil which is spread in the site. While this mixed soil which can resist water is commonly used in the site, bentonite mixed soil which is widely used as Liner layer in the reclaimed land of waste is recognized in Liner and durability. In this study, the engineering characteristics of soil-bentonite mixed liner are investigated using the laboratory hydraulic conductivity and uni-axial strength tests. The soil used for the liner is the clay soil located near the site. Mixing ratio of the bentonite which satisfies the requirement of hydraulic conductivity is determined and the optimum mixing ratio of bentonite is recommended for the landfill. After the mixed liner is constructed using the optimum mixing ratio of bentonite, the block samples of the constructed liner are obtained and the strength tests were performed. The hydraulic and strength properties of the liner for construction of the waste landfill were both satisfactory.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.138-139
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• 2020

With the rapid progress of industrialization, indoor air quality is a very important factor for modern people who spend most of their day indoors. The recent issue of fine dust and radon on the portal site's popularity search shows that interest in indoor air quality has increased. Fine dust causes respiratory diseases, and radon causes severe lung cancer. The new material was tested using plant activated carbon, palm activated carbon and bamboo activated carbon. Both palm activated carbon and bamboo activated carbon are porous materials and generate smooth physical adsorption. As a result of the experiment, both the activated carbon tends to gradually decrease in strength and fluidity as the replacement ratio increases. The reason for this is that both activated carbons have the property of absorbing moisture, so it is judged that the strength is lowered by absorbing moisture necessary for curing. In the case of fluidity, it is judged that the fluidity is reduced by absorbing the moisture required for the flow. In the future, if the problem of the color of the finished cured body is compensated, it will be possible to manufacture a functional finishing board to replace the existing interior finishing material.