• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.703-711
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• 2016

The present study is mainly aimed at securing adequate pores which are applicable to the aquatic environment and satisfying the required strength of porous concrete as a structure by substituting pumice for crushed stone which is usually used for the fabrication of porous concrete. Accordingly, in order to deduce the optimum mixing conditions applicable to the aquatic environment, we sought to evaluate the porosity, coefficient of permeability and compressive strength of porous concrete based on the target porosity and the mixing factors for pumice. By examining the porosity and coefficient of permeability of porous concrete and the physical properties of its compressive strength based on the target porosity and the mixing factors for pumice, it is judged that the optimum mixtures for porous concrete applicable to the aquatic environment which satisfy both the necessity of securing adequate pores and the required strength for porous concrete as a structure are PC I I-10-0, PC I I-10-5 and PC I I-10-10.

• Journal of the Korea Institute of Building Construction
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• v.22 no.4
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• pp.337-345
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• 2022

The foundation of high-rise concrete building in coastal areas generally must be installed in an integrated manner, not separately, in order to prevent defects caused by stress on the upper and lower parts of the mounting surface and to manage the process smoothly. However, when performing integrated punching, there is a concern that temperature stress cracks may occur due to hydration heat. Due to the large member size, it is difficult to make a sufficient commitment, so it is necessary to mix concrete with high self-charging properties to ensure workability. In this research, the amount of high-performance spray and admixture used was adjusted as experimental variables to satisfy this required performance. Through the analysis of the results for each blending variable, it was found that the unit quantity was 155kg/m³ and the cement ratio in the binder was 18%, and the target values of the pre-concrete properties and compressive strength were satisfied. A four-component binder(18% cement, 50% slag fine powder, 27% fly ash, 5% silica fume) was used.

• 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 Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.315-325
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• 2017

This study aims to provide information for the design and use of structural lightweight concrete (SLWC) for floating concrete structures in a marine environment. An experimental program was set up and comprehensive experimental campaign were carried out to determine SLWC mix proportions that can satisfy specified concrete strength, density, and slump values all of them were determined from previous research. Comparisons with previous SLWC mix designs that have been utilized for actual floating concrete structures were made. Key aspects needed to be considered regarding to the use of SLWC for floating marine concrete structures were discussed.

• International Journal of Highway Engineering
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• v.2 no.4 s.6
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• pp.123-131
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• 2000

The compaction equipment and the Marshall stability head are the two important testing equipment for the Marshall test. The compaction equipment is closely related to the air void, VMA and compactability of the mixtures, and the stability head is related to the Marshall stability and the flow, therefore the size and the shape of the equipment is essential for finding the accurate optimum asphalt content for the asphalt mix design. However, the size and the shape of the equipment currently used and the condition of the installation of compaction pedestal in this country are different from each agency and manufacturer. The national inspection of the Marshall equipment is necessary because the difference can affect the test results and also the performance of the asphalt pavement.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.33-43
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• 2002

Recently, as large constructions on the coast increase, an application of a surface layer stabilization method which is one of the improvement methods for dredged soft clay has increased. However, there are few studies about this. The purpose of this study is clarifying characteristics of ultra-soft marine clay and hardening agent. Also, it is verifying an optimal mixture ratio of hardening agent through the laboratory tests according to designed experiments and proving by statistical analysis and pilot tests. Laboratory tests were performed with proper hardening agent and test soil in accordance with the design of experiments. Regression equations between hardening agents materials and unconfined compressive strength were derived from the tests. The applicability of regression equations were also verified by pilot tests. From the test results, it was found that hardening agent materials(cement, slag, fly-ash, inorganic salts, arwin, gypsum etc.) have some effect upon compressive strength. The optimal mixture ratio which satisfies the required compressive strength was derived from the statistical analysis. The effect of ground improvement by cements and hardening agents was confirmed through the pilot tests. This study will suggest data for design or construction criteria of stabilization of surface layer on ultra-soft marine clay.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.439-444
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• 2015

Several attempts to design the best-available thermosetting road markings by using MMA to improve the durability and retroreflectivity are presented in this paper. In order to improve field applicability, the components of main materials were designed by means of reducing the hardening time lower than eight minutes. The optimum mixing ratio of thermosetting road marking was TSRM-6 composed of 15.6 wt% of MMA monomer ($Tg=105^{\circ}C$), 6.0 wt% of PMMA (MW = 70,000, $Tg=60^{\circ}C$) and 1.2 wt% of TMPTA (MW = 338, $Tg=27^{\circ}C$). Also the homogeneous mixing of all components was necessary. The use of ceramic glass beads with an optimized TSRM-6 exhibited excellent performance by achieving retroreflectivity coefficients of 431, 354 and $172mcd{\cdot}m^{-2}{\cdot}lux^{-1}$ for dry, wet and rainy test condition, respectively at two hundred thousand cycles.

• Journal of Industrial Technology
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• v.16
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• pp.25-30
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• 1996

The waste foundry sand might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Experiments were performed with the variables of W/C ratio, S/A, Sand/Waste foundry sand ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that then W/C ratio is the most important factor to the concrete strength. The substitute of waste foundry sand up to 30% has little influence, saying that it can substitute the fine aggregate without damaging the concrete properties.

• Journal of Industrial Technology
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• v.16
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• pp.39-44
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• 1996

The waste basalt might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Experiments were performed with the variables of W/C ratio, S/A, Crushed stone/Basalt ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that the W/C ratio is the most important factor to the concrete strength. The substitute of waste basalt up to 100% has little influence, saying that it can substitute the coarse aggregate without damaging the concrete properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.189-190
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• 2010

Yeoju-Bo is a large massive concrete structures that require the reduction of working period of construction. In this study, we optimized the mix proportion of internal/external concrete and physical properties like compressive strength, semi adiabatic temperature rise in laboratory. And we also performed thermal analysis to verify the thermal cracking. Lastly we measured the hydration heat and the thermal cracking in site to verify the safety of massive concrete structure.