• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.813-816
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• 2008

This study is an experimental study on the properties and efficiency of mold-prevention mortar and the results are summarized as following. The flow, compressive stress, and the drying shrinkage ratio of mold-prevention mortar was similar with plain, so it was shown that the mold-prevention does not influence physical effect specially. However, the mold-prevention mortar which even mixed with few mold, the mold-prevention capacity greatly increased. Also, the mold-prevention capacity of 1:4 ratio mortar was better than 1:2 ratio mortar.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.89-90
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• 2018

The strength of cement mortar is one of the most important factors in design and construction. Strength can vary widely depending on factors such as water cement ratio, aggregate and materials and curing. In the study, it was found that the standardized method of making the cement mrtar was different from the standard method of preparing the cement mortar by the different process of the cement mortar. I wanted to know the difference. Experiments were carried out to investigate the differences in strength, physical properies and performance depending on the points when the sample were made long in vertical form.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1047-1052
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• 2003

The purpose of this study is to improve the productivity and constructability of permanent forms. The permanent forms will cut down the cost of production and make easier to install in the field; hence increase the use of forms in the today's market. The permanent form is produced in the factory and built in field. So this study is in two parts. The one is the productivity in factory, the other is constructability in the field. This study is the designing a new mold system as a solution to existing mold system's problems.

• Conservation Science in Museum
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• v.26
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• pp.161-182
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• 2021

A jungwangu, a type of medium-sized mortar, is a firearm with a barrel and a bowl-shaped projectileloading component. A bigyeokjincheonroe (bombshell) or a danseok (stone ball) could be used as a projectile. According to the Hwaposik eonhae (Korean Translation of the Method of Production and Use of Artillery, 1635) by Yi Seo, mortars were classified into four types according to its size: large, medium, small, or extra-small. A total of three mortars from the Joseon period have survived, including one large mortar (Treasure No. 857) and two medium versions (Treasure Nos. 858 and 859). In this study, the production method for medium mortars was investigated based on scientific analysis of the two extant medium mortars, respectively housed in the Jinju National Museum (Treasure No. 858) and the Korea Naval Academy Museum (Treasure No. 859). Since only two medium mortars remain in Korea, detailed specifications were compared between them based on precise 3D scanning information of the items, and the measurements were compared with the figures in relevant records from the period. According to the investigation, the two mortars showed only a minute difference in overall size but their weight differed by 5,507 grams. In particular, the location of the wick hole and the length of the handle were distinct. The extant medium mortars are highly similar to the specifications listed in the Hwaposik eonhae. The composition of the medium mortars was analyzed and compared with other bronze gunpowder weapons. The surface composition analysis showed that the medium mortars were made of a ternary alloy of Cu-Sn-Pb with average respective proportions of (wt%) 85.24, 10.16, and 2.98. The material composition of the medium mortars was very similar to the average composition of the small gun from the Joseon period analyzed in previous research. It also showed a similarity with that of bronze gun-metal from medieval Europe. The casting technique was investigated based on a casting defect on the surface and the CT image. Judging by the mold line on the side, it appears that they were made in a piece-mold wherein the mold was halved and using a vertical design with molten metal poured through the end of the chamber and the muzzle was at the bottom. Chaplets, an auxiliary device that fixed the mold and the core to the barrel wall, were identified, which may have been applied to maintain the uniformity of the barrel wall. While the two medium mortars (Treasure Nos. 858 and 859) are highly similar to each other in appearance, considering the difference in the arrangement of the chaplets between the two items it is likely that a different mold design was used for each item.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.240-246
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• 2023

This study was performed to convert NO_x in atmosphere by photochemical reaction utilizing the eco-friendly solar energy. The mortar specimen coated with photocatalyst was fabricated and the photochemical conversion efficiency of NO_x was analyzed. The photocatalyst coated concrete was fabricated by first adding TiO₂ photocatalyst on the bottom of mold first and next adding cement mortar and, then, curing the concrete mortar. The grease was sprayed on the bottom of mold in advance so that the concrete can be demolded easily after curing. The conversion efficiencies of NO_x by photochemical reactions were investigated systematically by changing the process variable conditions of amount of TiO₂ coating, UV-A light intensity, total gas flow rate, relative humidity and initial NO_x concentration. It was confirmed that the photocatalyst coated concrete fabricated in this study could convert NO_x successfully for various process conditions in atmosphere. In future, we believe this research result can be utilized as basic data to design the infrastructure of building, tunnel and road for controlling efficiently the air pollutants such as NO_x, SO_x, and VOCs.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.257-264
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• 2011

This paper contains the experimental performance evaluation results of bond-type anchorage systems with the CFRP(carbon fiber reinforced polymer) tendon. The preliminary tests were performed to find the appropriate filling materials in the steel molds. A total of five materials including epoxy or cement mortar have been used as fillers in the steel molds. Results of the preliminary tests showed that specimen filled with non-shrinkage mortar showed maximum tensile strength. Based on the finding, the non-shrinkage mortar was selected as filler for anchoring CFRP tendons. Additional tests were performed as a parametric study to select proper size of steel molds such as external diameter, thickness, and length. The proper size of steel molds with non-shrinkage mortar was selected based on the test results, which gave stable tensile performance.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.75-83
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• 2015

This study discusses the long-term antifungal effect and antifungal performance of Hwangtoh mortars with various natural antifungal substances on five types of mold: Chaetomium globosum, Aspergillus niger, Aureobasidium pullulans, Gliocladium virens, and Penicillium pinophilum, which can be easily detected in the indoors and outdoors of buildings in damp environments. The antifungal performances of various natural antifungal substances extracted from Marjoram, Phytoncide, Thyme, Ginkgo leaves, and Chitosan (oligosaccharide) were investigated on the five types of mold, as a basic experiment. Using the natural antifungal substances selected for the basic experiment, antifungal mortars were made, and their antifungal performance and long-term antifungal effects were also investigated. The results clearly showed that the marjoram extract and their associated mortars had excellent antifungal performance. Also, their long-term antifungal effects were outstanding and at an equivalent level to those of the mortars with organic chemical antifungal agents. The optimum addition rate of the marjoram extract in the mortar was 5% by mass of binder. It was also shown that the phytoncide extract in the mortar needed an addition rate of more than 10% according to the mass of binder, considering the long-term antifungal effect and the antifungal performance.

• Journal of the Korea Institute of Building Construction
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• v.8 no.4
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• pp.105-114
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• 2008

This study investigates the saturation level of surface dryness, quantity of adhesive mortar, and the alien substance content of recycled aggregates for concrete to develop an adequate quality testing method for understanding the properties of recycled aggregates, which differ greatly from preexisting aggregates. For tests that measure the saturation level of surface dryness, where detail methods are applied differently according to the tester, various testing methods from across world were compared and analyzed. This study revealed that when measuring the saturation level of surface dryness of a certain sample, aggregates must be supplemented immediately whenever the height of the sample becomes lower than the measuring mold, and allowing the tamper to free fall on the sample will provide the most accurate results. When measuring the quantity of adhesive mortar of recycled aggregates for concrete, an acid solution was used, and since the quantity of adhesive mortar increases as the particle sizes gets smaller, the sample for testing should represent the entire granularity. Sulfuric acid solution is adequate for immersion, and the concentration should be 20% for best results. According to the alien substance content measurement, which was examined by the naked eye, the error range caused by the difference in particle size was neglectable, and therefore the sample should be $2.5{\sim}5.0mm$ in size concerning the accuracy and measuring time. Also, for coarse recycled aggregates, the sample should amount to 1kg for measuring alien substance content by the naked eye, which proves that assortment by the naked eye is the most adequate method for measuring the alien substance content of a recycled aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.217-218
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• 2011

The advantages of blast-furnace slag concrete may include lower hydration heating velocity, restraint on concrete temperature increase, long-age strength improvement due to latent hydraulic reaction, improved water tightness, and repulsion to chemical erosion. These advantages contribute to the high quality of the blast-furnace slag concrete. However, the blast-furnace slag concrete has its limitations as well. These disadvantages may include retarded setting and elongated retention of mold due to the weak strength of early-age. Nevertheless, much research is currently under way to improve the aforementioned issues. To improve activity of blast furnace slag powder, alkaline irritants has been used. In this study, we analyze effect on activity fineness and rate of substitution of Alkali Activator toward activity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.23-24
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• 2022

In this study, the Prepacked infilling mortar to which IGCC Ultra-Fine Fly Ash was added was evaluated when grouting aggregates. Efflux, Consistency, and Compressive Strength were measured, and it was found to have high fluidity when mixing IGCC Ultra-Fine Fly Ash, but the initial compressive strength was low