• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.589-592
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• 2008

Recently, as importance of quality control of the structure has been recognized, non-destructive testing, determining quality of the structure without damage, has been widely applied. However, its application has been primarily focused on laboratory development because variety of parameters in field has been not fully experienced and understood. This study aims to evaluate the field applicability of the ultrasonic testing method for PC beams. Material properties of 18 cylinders, cured in the same field condition, were measured up to 60 days and compared to those of the ultrasonic measurements from 34 PC beams in field before tensioning. Test results indicate that uni-axial strength and elastic modulus of PC beams can be predicted within reasonable range using the ultrasonic technique. However, it is also noted that considerations on field condition is required to increase the reliability of estimation.

• Journal of the Korean GEO-environmental Society
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• v.21 no.9
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• pp.25-32
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• 2020

The underground utilities installed under the ground is an important civil engineering structure, such as water supply and sewerage pipes, underground power lines, various communication lines, and city gas pipes. Such underground utilities can be exposed to risk due to external factors such as concentrated rainfall and vehicle load, and it is important to select and construct an appropriate backfill material. Currently, a method mainly used is to fill the soil around the underground utilities and compact it. But it is difficult to compact the lower part of the buried pipe and the compaction efficiency decreases, reducing the stability of the underground utilities and causing various damages. In addition, there are disadvantages such as a decrease in ground strength due to disturbance of the ground, a complicated construction process, and construction costs increase because the construction period becomes longer, and civil complaints due to traffic restrictions. One way to solve this problem is to use a liquid filler. The liquid filler has advantages such as self-leveling ability, self-compaction, fluidity, artificial strength control, and low strength that can be re-excavated for maintenance. In this study, uniaxial compression strength test and fluidity test were performed to characterize the mixed soil using marine clay, stabilizer, and in-situ soil as backfill material. A freezing-thawing test was performed to understand the strength characteristics of the liquid filler by freezing, and in order to examine the effect of the filling materials on the corrosion of the underground pipe, an electrical resistivity test and a pH test were performed.

• Composites Research
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• v.25 no.4
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• pp.110-116
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• 2012

Recently, the development and field applications of Ternary Blended Cement(TBC), where blast furnace slag and fly ash are recycled in Ordinary Portland Cement(OPC) in order to obtain improvements in the durability and heat of hydration reduction performance in large scale civil structures, have been increasing. Also, there are continuing efforts by construction companies to reduce the construction time with the aim of reducing construction costs. Therefore, there is a need to improve the performance of TBC, which has a relatively slow early strength development. In order to improve the early strength of TBC mortar, the compressive strength, SO3 content, and SEM analysis was determined in this study on mortar with the fineness and content of blast furnace slag and anhydrite regulated. As a result, to secure the early strength of TBC mortar, using blast furnace slag with a fineness of approximately $4,200cm^2/g$, adding 3.5% anhydrite with a fineness of approximately $10,000cm^2/g$, and managing the $SO_3$ content to roughly 3.72% was found to provide the most outstanding early strength properties.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.59-64
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• 2005

Although high pressure discharge method is widely used for improving soft ground, it has various problems including lack of strength increase and the possibility of water pollution and soil contamination. MJM(Morta Jet Method) uses sand in addition to cement as the injection material. MJM uses triple rods with a built-in nozzle that allows easier discharge of the slime, resulting in higher replacement area ratio and more uniform formation of pillar hydrates, and thus results in significant increase in strength. MJM is expected to perform especially well as piles in marine clays. This study investigates the field applicability of the MJM through extensive laboratory and field tests.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.531-542
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• 2022

As buildings become taller, the strength of structural materials must increase and the amount of rebar reinforcement also increases while the application of an appropriate rebar splice method in the construction process become one of the essential factors. In this research, the current status of quality check for rebar coupler is identified by an expert questionnaire and an appropriate quality check method is proposed through a quality test on specimens similar to actual on-site construction. In the test results, it was revealed that, among the quality check methods for rebar coupler joints, the coupler tightening method and face to face degree of between upper and lower rebar did not affect the strength the specimen. Therefore, it is considered to be an appropriate way to check the coupler quality check to check whether the threads are completely assembled during on-site construction through manufacture the number of threads of rebar and coupler with a margin beyond the calculated thread number.

• Korean Journal of Construction Engineering and Management
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• v.7 no.2 s.30
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• pp.71-80
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• 2006

It is required to study systematical on the concrete quality management to extend structure life because rebuilding effect is reducing under present condition of large sized and high stories structure. Concrete, which shows its intensity by hydrating action and a big change in quality according to hot weather and temperature, produces a lot of quality problem under hot and cold weather. Because of each specification and construction plan which does not have basic standard on site, concrete's quality is irregular and makes some defect. As a result, Dae-gu is fumed out to be the longest area after investigating application period and days focused on 8 cities weather information about t relationship between hot weather circumstance and construction environment. Therefore, we first surveyed the curing construction processing in the region and found out the problem of quality management. Then figure out the way of solution. Moreover, we integrated curing quality management, which is applied differently to each site, to have equal quality and to reduce defect from construction site. And then, based on various test of construction condition and analysis of quality management item, we suggest effective concrete quality management to make curing construction standard guide and plan under hot weather.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.145-157
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• 2017

Because of Recent intensive rainfall, nationally landslides and slope failure phenomenon has been frequently occur. Providing proposed-measures to the natural disasters that occur in these localities and the slope, must be derived ground of strength parameters(shear strength) as a design input data. However, it is such as extra deforestation and a lot of economic costs in order to make the access to the current area and the slopes ground survey is required. Thus, by small dynamic cone penetration test machine using the human to carry in the field, it is possible to easily measure the characteristics and strength constant of the ground of more than one region. In this study through researching analysis of the domestic and foreign small dynamic cone penetration test method, it has proposed a cone material and test methods suitable for the country. Cone penetration test Nc in the field has comparated with analysis of the value and the standard penetration test N value. And, in addition to this, direct shear test and borehole shear test were performed by depth, bedrock, and soil type and passing #200 and the correlation of the Nc value. In particular, in the present study, for the sandy soil that has distict distribute in mountain, it is proposed relation of shear strength corresponding to the Nc value (cohesion and internal friction angle) in order to calculate such effective ground shear strength.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.99-107
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• 2011

This study is to performed to find the optimum mix proportion of the high strength and self compacting concrete for the above-ground LNG storage tank construction and field application. If LNG storage tank wall thicknesscan be reduced, the construction cost and quality can be improved by using self-compacting high strength concrete with compressive strength 60~80 MPa. For this purpose, low heat cement (Type IV) and class F fly ash are used in concrete mix to control hydration heat, flowability, and viscosity. Mix design variables of unit water, fly ash replacement ratio, water-binder ratio, and fine aggregate ratio are selected and tested for material properties and manufacturing cost of the concrete. Also, fly ash replacement ratio is considered using confined water ratio test. The test results showed that the optimum mix proportion of the self-compacting high strength concrete characteristics are as follows. 1) In case of the concrete with specified compressive strength of 60 MPa, the optimum mix proportion is fly ash replacement ratio of 20% and water- binder ratio of 27~30%. 2) In case of the concrete with the strength of 80 MPa, the optimum mix proportion is fly ash replacement ratio of 10% and water-binder ratio 25%. But unit water and fine aggregate ratio are 165 $kg/m^3$ and $51{\pm}2%$, respectively, regardless of the traget concrete compressive strength range. Also, test results showed that concrete manufacturing cost of 60 MPa and 80 MPa concrete require additional costs of 14~22% and 33%, respectively, compared to the manufacturing cost of 40 MPa concrete. Therefore, application of the self-compacting high strength concrete has proven to be economical in the perspective of the material cost, quality control, and site management.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.7-13
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• 2008

Geosynthetic damage has attracted a major attention since the introduction of geotextiles for civil construction applications. Geotextile is one of the most useful and effective polymer material in civil construction works and the main function of geotextile is separation, reinforcement, filtering and drainage. Recently, because of the shortage of natural rock, traditional forms of river and coastal structures have become very expensive to build and maintain. This study tries to suggest the method of estimating valid stitching rate and the methodology of sea dyke construction over soft soils for more reasonable application of geotextile mat by studying tensile strength, bursting strength, punching strength, tear strength that are considered when analyzing and designing geotextile mat of a field.

• International Journal of Highway Engineering
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• v.4 no.1 s.11
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• pp.161-170
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• 2002

This study is a fundamental research for recycling waste polyethylene film(WPF) in asphalt concrete for roadway pavement. The objective of this study is to develop technology of making waste polyethylene asphalt mixture and evaluate properties of the asphalt concrete containing WPF. Asphalt concrete for surface course of pavement was produced through an appropriate mix-design using dense-graded and gap-graded aggregates. Marshall mix design, indirect tensile strength test, wheel tracking test and tensile fatigue test were performed. Test result showed that some WPF asphalt mixtures had a high tensile property and good resistances against rutting and fatigue cracking, compared with normal asphalt mixture.