• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.561-567
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• 2001

It is reported that a lot of sludge powder is produced during the process of manufacturing crushed fine aggregate in mines. However, there is a limitation on the its use that most of them are disposed and wasted, which cause environmental pollution. Therefore, in this paper, tests are carried out in order to recycle sludge powder as filler for cement mortar products. Kinds of aggregates and mix proportion of mortar are varied under various contents of sludge powder. According to test results, it is found that cement mortar products using sludge powder as substitution of fine aggregate about 10% have better qualities than those without sludge powder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.342-347
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• 2016

This study examined the effects of the coarse aggregate maximum size and grading of fine aggregates to acquire the characteristics of very low shrinkage on normal strength concrete mixed in the field. In addition, the shrinkage characteristics of concrete under construction were evaluated in accordance with the curing temperature. The compressive strength and drying shrinkage tests were performed for nine mixing factors composed of the coarse aggregate size (13, 20, and 25 mm), types of fine aggregate (see sand, crushed sand, and blended sand), and curing temperatures (5, 20, and $35^{\circ}C$). To acquire low shrinkage properties under $350{\mu}{\varepsilon}$ strain on normal strength concrete, a 25 mm maximum of coarse aggregate was available, and the grading of fine aggregate affected the shrinkage of concrete. In addition, very low shrinkage properties were acquired in the curing temperature range except cold and hot weather concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.536-544
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• 2016

Recently, with the increase in the number of high rise and huge scaled buildings, ultra-high strength concrete with 80~100 MPa has been used increasingly to withstand excessive loads. Among the components of concrete, the effects of the kinds and properties of fine aggregates on the performance and economic advantages of ultra-high strength concrete need to be evaluated carefully. Therefore, this study examined the effects of the type of fine aggregates and mixing methods on the engineering properties of ultra-high strength concrete by varying the fine aggregates including limestone fine aggregate (LFA), electrical arc slag fine aggregate (EFA), washed sea sand (SFA), and granite fine aggregate (GFA) and their mixtures. Ultra-high strength concrete was fabricated with a 20 % water to binder ratio (W/B) and incorporated with 70 % of Ordinary Portland cement: 20 % of fly ash:10 % silica fume. The test results indicate that for a given superplasticizer dose, the use of LFA resulted in increases in slump flow and L-flow compared to the mixtures using other aggregates due to the improved particle shape and grading of LFA. In addition, the use of LFA and EFA led to enhanced compressive strength and a decrease in autogenous shrinkage due to the improved elastic properties of LFA and the presence of free-CaO in EFA, which resulted in the formation of C-S-H.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.231-232
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• 2010

In this study, we assessed on quality of mortar using the steel slag powder as binder. Then we investigated properties of mortar in the long term using steel slag for fine aggregate. As a result of experiment, quality of the mortar using steel slag powder appeared too low compared with using only OPC and compressive strength of specimen using the steel slag fine aggregate have similar using crush sand.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.121-122
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• 2016

Recently in the domestic construction industry, source depletion has resulted in instances of ready-mixed concrete companies using river sand or crushed sand with high fine particle content. But the use of such low-quality fine aggregate is known to cause concrete quality to decline and have negative effects. So this study analyzed how much of an impact changes in fine particle content have on cement mortar's engineering characteristics. As a result, the flow rate and air quantity, which are characteristics of unhardened mortar, were shown to decrease as fine particle content increased, and compression strength, a characteristic of light mortar, was shown to subtly increase as fine particle content decreased.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.641-644
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• 2008

This paper investigated the plant and raw material of the ready-mixed concrete company which could supply to the second Lotte World on Pusan. the results were summarized as following. Almost plants were mainly using Twin shaft mixer which was 210m$^3$/hr and horizontal type. There was different the number of admixture silos at each plants, and they were separated by types. The mixtures mainly consisted of the ordinary portland cement, fly ash and blast furnace slag. For favorable quality control, each materials had to carry from same factories, and the monitering standard for quality control should be prepared. The coarse aggregates were used with many different producing districts, so they were only used from Y caused by exclusion of quality difference. The crushed, washed and river sands were generally used as fine aggregates, so the fine aggregates which could be possible to supply stable quality were chosen. This study used Poly Carbonic Acid Admixture which was developed to satisfy maintenance of performance till 2 hours and 10MPa at 15 hours.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.229-236
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• 2006

Recently, the use of crushed sand produced by the crushing of stone is continuously increasing to reach an utilization rate of about 20% of the whole fine aggregates that is foreseen to grow larger in the future. However, the lack of recognition concerning quality during the production of crushed sand results in the use of crushed sand that do not satisfy the KS F 2527 standard during the manufacture of concrete. And, studies investigating the effects of such crushed sand on concrete are still neglected. Therefore, this study intends to provide data that can be exploited for concrete using crushed sand through the analysis of the effects of the grain shape of crushed sand on the quality of concrete. Results revealed problems in the workability, air entraining and durability for a value of 53% for the solid volume percentage for shape determination specified by the current KS F 2527. Analysis showed that the adjustment of the solid volume percentage for shape determination from the currently specified 53% to 55% will improve the quality of concrete using crushed sand in high strength concrete particularly.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.596-603
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• 2020

In this paper, an experimental study was conducted to investigate the applications of bottom ash, which is an industrial by-product obtained from thermal power plants. Bottom ash was used as fine aggregate in this study, and an experiment was conducted to determine the characteristics of the bottom ash aggregate. In addition, 25, 50, 75, and 100% contents of crushed (natural) fine aggregate were replaced with bottom ash aggregate to produce concrete mixture including bottom ash. Thereafter, test results of the unit weight, ultrasonic velocity, compressive strength, and thermal conductivity of bottom ash concrete were obtained. Moreover, the effect of the curing ages of 28 and 91 days on the material characteristics of bottom ash concrete were identified. Test results showed that bottom ash used as fine aggregate had pozzolanic reaction. Finally, based on the extensive experimental results, relationships between thermal conductivity and unit weight, ultrasonic velocity, and compressive strength was suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.455-458
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• 2005

This study compares the concrete using natural sand with the concrete using crush sand for the examination for the properties of a concrete. In the fresh concrete, the concrete using crush sand has less of the quantity of consistency, the content of air, and bleeding than the concrete using natural sand, and the concrete using crush sand has faster setting time than the concrete using natural sand. In hardening concrete, the concrete using crush sand has higher compressive strength and tensile strength than the concrete using natural sand because minute particles fill up a gap. Drying shrinkage of the concrete using natural sand is less than the concrete using crush sand.