• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.169-177
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• 2011

In this study, an impact resistance of concrete segmented composites adopted shell's structures which have the excellent impact resistance was assessed. In order to enhance the performances of concrete segmented composite, the bond strength of mortar between the concrete blocks should be improved. Hence, in this study polymer mortars were applied to increase the bond strength of mortar. From the results of bond tests, the 15% latex mortar was selected and static and low-velocity impact tests were carried out for the specimens applied the plain and latex mortar. The concrete segmented composites, of which the bond strength of mortar was enhanced, showed improved low-velocity impact resistances. A Nonlinear finite element analysis using the discrete crack model showed similar energy dissipating capacities to the impact test's results. Consequently, by improving the analysis models for segmented composites, the impact resistances for manifold variables can be predicted and assessed.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.99-111
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• 1999

The frictional capacity of auger-cast piles is often very small because of the disturbance of the soil surrounding the pile during the excavation process. Usage of expansive agents and a pressurized injection technique for auger-cast piles should improve the frictional resistance between pile and soil. This paper presents the test results of auger-cast model piles installed with expansive mortar in laboratory compacted weathered soil. The model piles were installed in a calibration chamber with a variation in the amount of expansive agent, the injection process and the chamber pressure. It was observed that the pile shaft resistance increases with the increased amount of expansive agent, and also increases when mortar is pressure injected. The shaft resistance increased up to 24% for the pile installed only with expansive mortar and increased up to 56% for the pile installed with the pressurized injection of expansive mortar, compared with that of piles with plain mortar.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.19-22
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• 2007

This study discussed the prevention of the spalling and improvement of the fire resistance performance how to fill up lightweight foamed concrete on high strength RC column attached with the stone panel. The destructive spalling extremely occur caused by sudden high temperature and increased vapor pressure corresponding to falling the ston panel at all RC column, and the steel bar is exposed. The stone panel fall off about 30 minutes and spalling occur about 70 minutes on Plan RC column, fire endurance paint, and fire endurance mortar, so it can be confirmed that fire endurance paint and mortar, which is used as fire endurance material, are not effective. In the other side, it can be protected from fire about $120{\sim}140$ minutes when the lightweight foamed concrete is used as fire endurance material. For the weight loss after the fire test, plain is 33, fire endurance paint is 37%, and fire endurance mortar s 40.7%. And W/B 60%-3 is 53.4%, 60%-1.5 is 40.1%,65%-3 is 39.4%, and 65%-1.5% is 47.1. Overall, the weight loss of the plain is lower than that of the lightweight foamed concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.78-85
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• 2023

In this study, synthetic fibers were applied to reduce shrinkage cracks that may occur in mortar produced by 3D printer. We used a biopolymer in powder form made from cactus stem (CS) as an admixture. The material properties of 3D printed mortar were experimentally evaluated. Replacing methylcellulose(MC) with 10% CS increases compressive strength by 9.84-23.92% regardless of the casting method. In addition, regardless of the casting method, shrinkage change, freeze-thaw resistance, and crack resistance are more effective than Plain. Incorporation of CS increases the polysaccharide macromolecular structure and improves durability. Mortars reinforced with synthetic fibers do not affect compressive strength and freeze-thaw. It is also effective for shrink deformation and crack resistance. Incorporating CS and fibers from 3D-printed mortar was found to be effective for durability and crack resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.53-60
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• 2019

The purpose of this study is to evaluate the degree of improvement in strengths by mixing blast-furnace slag and fly ash in polymer cement mortar(PCM). The test specimens are prepared with EVA polymer dispersion, two types of Admixtures (blast-furnace slag and fly ash), five kinds of polymer-cement ratios (0, 5, 10, 15 and 20%), and six kinds of admixtures (0, 3, 5, 10, 15 and 20%). Plain cement mortar is also made for comparison. From the test results, the flowing of PCM is greatly improved with the mixing of the admixtures, and strengths of PCM compared to ordinary cement mortar are also improved due to a decrease in water cement ratio. In addition, the strength characteristics of PCM by admixtures are greatly improved in flexural strength with fly ash compared to other strengths. It is apparent that the optimum mix proportions with polymer-cement ratio of 10% or more, admixture contents 5 to 10% of flay ash for flexural strength improvement of EVA-cement mortar are recommended in this study.

• Journal of the Korea Institute of Building Construction
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• v.22 no.5
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• pp.441-450
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• 2022

In this study, the fluidity and strength characteristics of NSC mortar according to the type and rate of addition of superplasticizer were analyzed to secure the fluidity of NSC composed of only slag and ash. Through the flow test, it was found that the fluidity of NSC was related to the basicity according to the binder condition, and the lower the reactivity, the higher the fluidity. When polycarboxylate is added, NSC mortar is considered to be more advantageous than plain mortar in terms of securing fluidity. As a result of the strength tests of NSC mortar containing Lignin or Polycarboxylate superplasticizer, it was found that the strength tends to increase as the basicity increases. In addition, when polycarboxylate is added, it is judged that the NSC mortar can secure adequate fluidity and strength at the same time. Through this experiment, an appropriate binder condition that satisfies the flowability while securing the strength was derived.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.313-314
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• 2009

With the purpose of reducing autogenous shrinkage of high strength mortar, shrinkage reduction effect was examined in this study using plant oils as the compound for shrinkage reduction. As a result of examination, satisfactory reduction effect was shown using plant oils in comparison to plain mixture. Most excellent effect was shown by soybean oil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.130-131
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• 2014

In this study, Analyse about flowability for fiber-reinforud mortar has been focused. Organic and inorganic fibers with different length have been combinatiorly used. The results showed using combination length of the fibers decrease the flowability, comparing with plain, fracture styess has been increased, Results also showed when several kinds of fibers used together showed the highest fracture stress.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.229-232
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• 2003

Recently, it is increased on the concern for the reuse of waste concrete because of the shortage of natural aggregate and the increase of waste concrete. And recycled coarse aggregate is used variously, but the existing wet method producted recycled fine aggregate has problems like the high price facilities, the long time progress of the work and recycled fine aggregate of poor. The aim of this study is to investigate the possibility of the method of dry producted high qualities recycled fine aggregate. The results of this study have shown that the possibility of the method of dry is certificated as the qualities of recycled fine aggregate satisfied the KS and the compressive strength of mortar was similar to plain.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.103-106
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• 2003

Recently, it is increased on the concern for the reuse of waste concrete because of the shortage of natural aggregate and the increase of waste concrete. And recycled coarse aggregate is used variously, but the existing wet method producted recycled fine aggregate has problems like the high price facilities, the long time progress of the work and recycled fine aggregate of poor. The aim of this study is to investigate the possibility of the method of dry producted high qualities recycled fine aggregate. The results of this study have shown that the possibility of the method of dry is certificated as the qualities of recycled fine aggregate satisfied the KS and the compressive strength of mortar was similar to plain.