• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.55-61
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• 2023

This study aims to develop CLSM fill material for emergency restoration using landfill coal ash. As a result of examining physical properties such as particle size distribution and fines content of landfill coal ash, bottom ash, fly ash, and general soil were mixed, and SP was found to have a density of 2.03 and a residual particle pass rate of 7.8 %. CLSM materials that secure fluidity in unit quantities without using chemical admixtures such as glidants and water reducing agents have a high risk of material separation due to bleeding. As a result of this experiment, it was found that the bleeding ratio did not satisfy the standard in the case of the specimen with a large amount of fly ash and a lot of addition of mixing water. As a result of the compressive strength test, the strength development of 0.5 MPa or more for 4 hours was found to be satisfactory for the specimens using hemihydrate gypsum with a unit binder amount of 200 or more, and the remaining gypsum showed poor strength development. Although it is judged that landfill coal ash can be used as a CLSM material, it is necessary to identify and apply the physical and chemical characteristics of coal ash buried in the ash treatment plant of each power generation company.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.295-304
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• 2013

Ultra-High Performance Concrete (UHPC) has recently been one of the most active research fields in Korea as well as in foreign countries, because it can contribute to a longer life and economic efficiency of structures. Although precast-type UHPC fabricated in a factory is preferable in terms of quality control and reduction of construction period, there exist, even in the precast structure, some parts that need to be cast in-place such as the joints between precast segments. In the cast-in-place UHPC, however, it is probable that an optimum curing condition can hardly be realized in contrast to the factory production. In this study, therefore, the trend of compressive strength development of UHPC was experimentally investigated by assuming various inferior curing conditions that may be anticipated at a construction site. Concrete specimens were fabricated and cured under different conditions with the variables such as curing temperature, delay time before the initiation of curing, duration of curing time and moisture condition. The strengths were compared with those of the specimens cured by standard high temperature steam. Through the analysis of the test results, some minimum requirements for curing have been proposed that are required when the UHPC is cast in-place. It is expected, through this study, that practical use of UHPC in construction sites can be increased.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.75-83
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• 2004

The Indiana Department of Transportation (INDOT) has permitted the use of Lime Kiln Dust (LKD) as a low-cost construction material in creating a workable platform for soil modification (not for soil stabilization) since the early 1990s on selected projects. However, the enhanced strength of soils with LKD has not been accounted for in the subgrade stability calculations in the design process. This study was initiated to evaluate how the lime kiln dust is a comparable material to hydrated lime. A series of laboratory tests were performed to assess the mechanical benefits of lime kiln dust in combination with various predominant fine grained soils encountered in the State of Indiana, such as A-4, A-6 and A-7-6. In the course of this study, several tests such as the Atterberg limits, standard Proctor, unconfined compression, CBR, volume stability, and resilient modulus were performed. As a result, mixtures of fine grained soils with 5% lime or 5% LKD substantially improve unconfined compressive strength up to 60% - 400%. CBR values for treated soils are in the range of 25 to 70 while those for untreated soils range from 3 to 18. In general, significant increase in resilient moduli of the soils treated with lime and LKD was observed. This indicates that lime kiln dust may be a viable, cost effective alternative to hydrated lime in enhancing the strength of fine grained soils.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.357-366
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• 2010

This paper presents experimental results about shear wall with various lateral reinforcement details in boundary elements. The research objective is to study the structural behavior of shear wall with boundary column confined by rectangular spiral hoops and headed cross ties developed to improve workability in the fabrication of boundary columns. These two details can be fabricated in a factory and put together on-site after being delivered so that the construction work may be reduced. Main parameters in the experimental study were the types of hoop and cross tie: rectangular spiral hoop and headed cross tie vs. standard hoop and cross tie with hook. Four half scaled shear wall specimens with babel shape were made and tested by applying horizontal cyclic load under constant axial force, 10% of nominal compressive strength of concrete. Based on the test result, it was shown that the shear wall with rectangular spiral hoop and headed cross tie in boundary columns has structural capacity compatible with conventional shear wall. The specimen SW-Hh which has bigger hoop bar and higher volumetric ratio of transverse reinforcements than other showed improved energy dissipating characteristic but it presented a rapid reduction of strength after peak point. The results indicates that, it is necessary to consider volumetric ratio of transverse reinforcements as well as hoop space in designing of shear wall with boundary columns for improved strength and ductility.

• Environmental Engineering Research
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• v.21 no.1
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• pp.15-21
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• 2016

Magnesium potassium phosphate cement (MKPC) is an effective agent for solidification/stabilization (S/S) technology. To further explore the mechanism of the S/S by MKPC, two kinds of Cd including $Cd(NO_3)_2$ solution (L-Cd) and municipal solid waste incineration fly ash (MSWI FA) adsorbed Cd (S-Cd), were used to compare the effects of the form of heavy metal on S/S. The results showed that all the MKPC pastes had a high unconfined compressive strength (UCS) above 11 MPa. For L-Cd pastes, Cd leaching concentration increased with the increase of Cd content, and decreased with the increase of curing time. With the percentage of MSWI FA below 20%, S-Cd pastes exhibited similar Cd leaching concentrations as those of L-Cd pastes, while when the content of MSWI FA come up to 30%, the Cd leaching concentration increased significantly. To meet the standard GB5085.3-2007, the highest addition of S-Cd was 30% MSWI FA (6% Cd contained), with the Cd leaching concentration of 0.817 mg/L. The S/S of L-Cd is mainly due to chemical fixation, and the hydration compound of Cd was $NaCdPO_4$, while the S/S of S-Cd is due to physical encapsulation, which is dependent on the pore/crack size and porosity of the MKPC pastes.

• Advances in concrete construction
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• v.10 no.5
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• pp.393-402
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• 2020

The given research focuses on examining the effect of relatively humidity (RH) and curing temperature on the hydrates as well as the porosity of calcium sulfoaluminate (CSA) cement pastes. Numerous tests, which consist of mercury intrusion porosimetry (MIP), thermosgravi metric (TG) and X-ray diffraction (XRD) were conducted. Various characterization techniques which include, scanning electron microscopy, Fourier transform microscopy along with X-ray diffraction evaluations were conducted on the samples to examine phase formation and crystallinity, morphology and microstructure along with bond formations and functional groups, respectively. During long-term study, the performance of concrete which consisted of limestone and flash-calcined was close to those from standard Portland cement concrete. Traditional classifications and methods of corrosion were widely used for the assessment of steel in concrete which may get employed to concrete which contains LC3 to recalibrate the range of polarization resistance for passitivity condition. For example, there is up to 79.5% and 146% respective flexural and compressive strengths. Moreover, they developed more advance electrical and thermo-mechanical performance with a substantial reduction in absorption of water of close to 400%. These advantages allow this research crucial to evaluate how these methods can be applied. Additionally, the research evaluates developed and more advanced cement preservation and repair techniques. The conclusion suggests concerted efforts by various stakeholders such as policy makers to enable low-carbon rates.

• Environmental Engineering Research
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• v.25 no.3
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• pp.345-355
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• 2020

This study has been carried out to evaluate the leaching behavior of Tunisian phosphogypsum (PG) tailings in Skhira city (southern Tunisia). Two PG samples, including old and freshly deposited samples, were characterized in terms of physical, geotechnical, mechanical, chemical and mineralogical properties. Special attention was paid to their leaching behavior when subjected to standard leaching tests. Our results indicated that both samples are mainly composed of more than 31.85% CaO and 31.4% SO3, indicating the predominance of gypsum. This was further confirmed by XRD patterns that revealed the presence of characteristic reflections of gypsum, brushite, quartz and Maladrite. Compressive strength after 90 d exceeded 769 kPa, but still lower than that of natural sand (1,800 kPa). Leaching test was proposed as an appropriate method to determine the released contaminants from PG. The obtained results showed that Fluorine and Phosphorus are the most released elements from PG with 40 and 30%, respectively. The released Se, Cd, and Zn were the only trace elements that exceeded the threshold limits. It seemed that leached element concentrations were independent aging or particle size of the PG. Based on the assessment of leaching behavior, an integrated management approach of the PG deposits was proposed.

• Journal of Conservation Science
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• v.36 no.5
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• pp.339-350
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• 2020

This study attempted to apply a hybrid technology that integrated mineral-based fillers and water-repellent agents to control the efflorescence that results from the use of inorganic binders, for the conservation treatment (surface finishing) of cultural heritage materials made up of stone. Herein, different types of mixing ratios of a filler (silica fume 3.4%) and a water repellent (silane-siloxane 1%) were selected for fabricating the inorganic binder, and it was determined that the ratio selected by weight is effective in controlling efflorescence substances. In addition, it was identified that the inorganic binder with the mixing ratio resulted in a higher compressive strength than the standard (20MPa), and the water permeability resistance was high with low water absorption. The result of ion elution from the bilder showed that a smaller number of ions was observed to affect the efflorescence (directly and indirectly) as compared to that of the control group, which was considered to be relatively stable.

• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.425-434
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• 2007

The SC (steel-concrete) composite column was developed to take advantage of the relative economy of using concrete as opposed to steel in carrying large compressive forces. As the SC composite column is pre-fabricated, its use can minimize laborand can speed up the erection of a steel building. In this study, an experiment was conducted to analyze the influence of several parameters, such as the load ratio, the concrete ratio of an area, and its performance with or without fire protection, on the performance of the SC composite column. This paper proposes that the calculation of the strength reduction ratios of columns be done by increasing the temperature. Theoretical equations were used to evaluate the effectiveness of the fire resistance of the SC composite column, and the results of the test and analysis were compared. The fire resistance of the SC composite column was increased by decreasing its load ratio, but the concrete ratio of an area has minimal influence on the fire resistance of the SC composite column.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.334-408
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• 2006

In Hong Kong, large-diameter (${\ge}600mm$) bored piles and large-section excavated rectangular barrettes are commonly used to support tall buildings to resist both vertical and horizontal loads. These piles and barrettes penetrate through and may found in saprolitic soils and decomposed rocks. Generally, the design of these large bored piles and barrettes involves considerable amount of uncertainty and design parameters must usually be verified by field tests. In this paper, over 50 full-scale load tests on large-diameter bored piles and over 15 large-section of rectangular barrettes in Hong Kong are reviewed and interpreted critically, in particular the degree of mobilisation of side shear resistance using a mobilization rating (MR) factor and a displacement index (DI) for floating bored piles and barrettes and rock-socketed piles, respectively. The author was heavily involved with many of these load tests. The diameter of the bored piles tested ranges from 0.6m to 1.8m and the depth varies from 12m to 75m. Sizes of barrettes critically reviewed include $2.2m{\times}0.6m,\;2.2m{\times}0.8m,\;2.8m{\times}0.8m\;and\;2.8m{\times}1.0m$ (on plan) and the depth varies from 36m and 63m. Based on these field tests, a new failure load criterion for large-diameter bored piles and barrettes is developed and proposed. The side shear resistance of the bored piles and barrettes is quantitatively analyzed with respect to local displacements, standard penetration tests, unconfined compressive strength (UCS) for rock sockets and using the effective stress principle. In addition, the effects of construction including post-grouting, construction time, side scraping and excavation tools on side shear resistance are investigated and reported.