• Fire Science and Engineering
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• v.18 no.1
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• pp.31-36
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• 2004

The purpose of this study is to present data for the reusing, rehabilitation and estimation of safety of RC structure damaged by fire, and for the prevention of explosive spatting by investigation the properties of explosive spalling, compressive strength and ultrasonic pulse velocity according to kinds of fine aggregate, admixture and water-cement ratios. In explosive spalling properties with kinds of aggregate, explosive spalling does not appear or little at surface in the case of used sea sand, but the case of using recycled sand or crushed sand is worse and worse. Property with the kind of admixture does not appear specially. And high strength concrete with W/C 30.5% was taken spalling, but 55% does not appear. It is found that residual compressive strength after exposed at high temperature showed 45％ in W/C 55%, and 64％ in W/C 30.5％ of its original strength averagely. Ultrasonic pulse velocity is different with kinds of aggregate. W/C. and heating time. When 3 month age after heating ultrasonic pulse velocity is recovered abut 1.3％～8.4％ of its 1 month age after heating.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.1
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• pp.1-8
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• 2013

This study will not only prove experimental dynamic properties which are classified to slump, compressive strength, tensile strength, flexure strength and toughness granite soil concrete with a fine aggregate of granite soil and blast-furnace cement and polypropylene fiber over 45 mm, but also establish a basic data in order to use environment-friendly pavement through prove useful pavement mixed with granite and polypropylene (PP) fiber which is a kind of material to prevent a dry shrinkage clack, a partial destruction and useful and light. The value of slump test was gradually increased by PP fiber volume 3 $kgf/m^3$, but compressive strength took a sudden turn for the worse from 5 $kgf/m^3$. The compressive strength indicated a range of 13.72~18.35 MPa. On the contrary to compressive strength, the tensile strength showed to decrease with rising PP fiber volume, and the tensile strength indicated a range of 1.43~1.64 MPa. The tensile strength was stronger about 2~15 % in case of mixing with PP fiber volume than normal concrete. The flexural strength indicated a range of 2.76~3.41 MPa. The flexural strength was stronger about 20 % in case of PP fiber volume 0 $kg/m^3$ than PP fiber volume 9 $kg/m^3$. The toughness indicated a range of 0~25.46 $N{\cdot}mm$ and increased proportionally with PP fiber volume. The toughness was stronger about 8.3 times in case of PP fiber volume 9 $kg/m^3$ than PP fiber volume 1 $kg/m^3$. The pavement with PP fiber volume over such a fixed quantity in the park roads and walkways can have a effect to prevent not only resistance against clack but also rip off failures.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.457-463
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• 2014

The permitted limit, ${\pm}12%$, of the change in solid contents based on ASTM C 494 as an interim standard in Korea Expressway Corporation, can not reflect the kind of chemical admixture and the characteristics of solid content so that it differed depending on the admixture types. In this study, effect of cement concrete quality was investigated by solid changes which can be used chemical admixtures acceptance criteria. As a result of an evaluation of a change in the quality of concrete due to solid content, since Ligno-sulfonate based (LG) had a low water reducing ratio, the range of the change in solid content was great while Naphthalene sulfonated based (PNS) and Poly-carboxylate based (PC) High Range Water-reducing Admixtures (HRWR) had a high water reducing ratio, the permitted limit of the difference in solid content currently used as the acceptance criterion should be readjusted. As a result, it is found that the acceptable range must be managed within 10% and 5% when the solid contents less than 25% and more than 25%, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.972-978
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• 2008

Quality Assurance of Deep Mixing to fulfill the requirements of geotechnical design cannot be achieved only by the process control During production conducted by the deep mixing contractor but it should involve relevant activities that are carried out prior to, during and after the construction by all the parties involved in a deep mixing project. The requirement is different for different application, and hence, QA/QC method/procedure and verification technique may be different for different application. In order to maintain the high quality of deep mixing work in the global market, it is necessary to conduct a research project, such as investigation of illustrations, the variety of existing QA/QC methods/procedures, the correlation between the outcomes of different QA/QC methods. In these reason, it has been held the international meeting to discuss them, in that kind of activities in 2009 it will be held Symposium. Also Collaborative study for QA/QC is on goin, and conduction by all participated members. The subject for collaborative study are, task 1 : investigation of laboratory tests procedures, task 2 : comparing of different laboratory tests procedures, task 3 : QA/QC method/procedures, task 4 : integrated Task1 ~task 3. The discussion of the results in all task will be held in the Symposium separately. In this paper, it was presented four tasks. Also the results in task 1 and 2 conducting domestically until now, such as investigation of laboratory test procedures, effect on the unconfined compressive strength by aging temperature and by delayed time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.133-140
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• 2010

The purpose of this study is to evaluate the new eco water tank which is made of high density polyethylene and concrete with low temperature cement. The strength and failure mode of eco water tank was examined through tensile test with mixture of concrete and HDPE, temperature monitoring for various kind of concrete, admixture contains etc. The strength and failure mode were examined through tensile test with mixture of concrete and HDPE, temperature monitering for different kinds of concrete, strength test with different admixtures etc. It was found that shear connector between concrete and HDPE effects significantly contributed to the combined structures. ㄱ type shear connector results in tensile strength of up to 40% compared to that of V type shear connector. Based on test result, the new eco composite tank improved the stability and safety the old one and demonstrated the applicability and capability.

• Resources Recycling
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• v.16 no.6
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• pp.20-27
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• 2007

This paper presents a detailed experimental study on the durability properties of mortar matrix made with two kind of recycled fine aggregates(RAA, RAB) and five replacement levels (0, 25, 40, 75 and 100) of the recycled fine aggregates as a partial replacement of natural fine aggregate (NA). The durability properties of mortar matrix was evaluated using compressive strength, chloride ion ingress, sulfate attack and carbonation. The test results indicated that the water absorption and Adhered mortar of the recycled fine aggregate was a major factor controlling durability properties. Hereafter, when using built recycled fine aggregate is expected, appropriate removal Adhered mortar and reasonable replacement ratio of recycled fine aggregates was 25% weight of cement are advised to apply to the concrete materials.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.55-60
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• 2018

In this study investigated the Controlled Low Strength Materials using coal ash and steel slag(KR slag) as the main material in the thermal power plant classified as waste resource. Bottom ash and KR slag are mixed at a ratio of 7: 3 to expand the use of industrial by-products through carbonate($CO_2$-fixation) reactions and inhibit the exudation of heavy metals. The results showed that the water content increased as the content of bottom ash increased. It was confirmed that as the powder content increased, the bleeding ratio decreased. Also, as the content of one kind of ordinary portland cement (OPC) decreased, activation of hydration reaction decreased and compressive strength decreased. However, when the mixed composition is appropriately adjusted, the compressive strength of 2.0 MPa required for the controlled low-strength material can be satisfied.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.449-458
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• 2006

The discharge of fly ash that is produced by coal-fired electric power plants is rapidly increasing in Korea. The utilization of fly ash in the raw materials would contribute to the elimination of an environmental problem and to the development of new high-performance materials. So it is needed to study the binder obtained by chemically activation of pozzolanic materials by means of a substitute for the cement. Fly ash consists of a glass phase. As it is produced from high temperature, it is a chemically stable material. Fly ash mostly consists of $SiO_2\;and\;Al_2O_3$, and it assumes the form of an oxide in the inside of fly ash. Because this reaction has not broken out by itself, it is need to supply it with additional $OH^-$ through alkali activators. Alkali activators were used for supplying it with additional $OH^-$. This paper concentrated on the strength development according to the kind of chemical activators, the curing temperature, the heat curing time. Also, according to scanning electron microscopy and X-Ray diffraction, the main reaction product in the alkali activated fly ash mortar is Zeolite of $Na_6-(AlO_2)_6-(SiO_2)_{10}-12H_2O$ type.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.75-82
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• 2014

Recently, public works becoming bigger in Jeju are implemented various kinds of ground reinforcement method including the chemical grouting method. In this study, we have been investigated on the proper material and the injection condition for the excellent injection effect and the excellent strength of injection material and the permanent waterproof and reinforcement through the experiment. The kind of injection material has been selected through the uniaxial compression test and the endurance test of injection material as the chamber test. An experiment was performed with model ground made of scoria, the injection performance of selected material has been identified through the evaluation test of injection range using the decision test of injection amount and the calibration chamber test. As a result of test, it has been analyzed that MSG appeared to have the excellent strength, durability and injection performance all compared with the ordinary cement, this result is judged to be possible as the ancillary data of design at time of design and construction with the chemical grouting method in the future.

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.61-66
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• 2014

The various recycling methods of mixed coal ash have been developed considerably and it's recycling quantity has been increased. However, the more relatively finer grain content of coal ash in ash pond is increased the more it's quantity is increased in recycling as products for drainage in soft ground etc. Accordingly, the geotechnical properties of mixed coal ash in ash pond would be inferior and it's recycling rate should reach the limitations in increase. In this study, to recycle mixed coal ash contained fine grain in considerably amount as products for strength, etc. By adding binder to it and manifesting, it's compressive strength is stronger than the criteria, these are suggested; 1) the variety of compressive strength test performed on mixed coal ash of various grain distributions as main material, 2) the kind of binder, it's mixing quantity and the optimum content rate range of fine grain coal ash that the compressive strength stronger than a certain compressive strength is manifested. Cement is more excellent than quicklime as binder in manifesting stronger compressive strength and the sieve type to sort it is #40 sieve in order to recycle all mixed coal ash in ash pond efficiently as products for drainage as well as products for strength, etc. And, it could increase insufficient compressive strength remarkably that content of pure sand is more in the rate as pure sand and the part of mixed coal ash in ash pond to pass through #40 sieve is mixed in the ratio of 2 to 8.