• Journal of the Korea Institute of Building Construction
• /
• v.18 no.2
• /
• pp.109-115
• /
• 2018

Since the current method of SCW cement milk pouring method uses one to one ratio of cement milk with OPC, there are some problems such as drying shrinkage, increased cost, difficulty of controlling mix proportions for various conditions of applied soil, and precipitation of $Cr^{6+}$ due to the excessively used cement. Specifically, in aspect of sustainability issues of cement manufacturing, the consumption of cement should be reduced. Hence, in this research, as a replacement of cement for SCW method, blast furnace slag with sulfate or alkali as a stimulant, and expansive admixture were used. By using blast furnace slag as a hardening composite of SCW, there are many advantages such as free controllable mix proportions, rapid setting time with less mud occurrence, less cost with less energy for mixing, constant strength development, and less precipitation of $Cr^{6+}$. Regarding the alternative composites for SCW, in this research, durability and chloride resistance were evaluated.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.2
• /
• pp.127-134
• /
• 2017

In this study, moist curing equipment was used in the exist gang-form system. By achieving sufficient spray curing, the quality of the concrete was improved and the cracking occurred in building's side wall was decreased. The following results could be made as the conclusion. For the compressive strength, all zones showed the similar results. Comparing with the zone without using moist curing equipment, the zone used moist curing equipment showed higher rebound hardness results. For the cracking, the zone utilized moist curing equipment showed the cracking averaged as 6.6 m and the zone without using moist curing equipment showed the cracking averaged as 10.3m. The effectof reducing cracking by utilizing moist curing equipment is about 36 %. Using moist curing equipment is considered as a good solution to reduce the cracking in the structure. Considering all the factors analysed, using moist curing equipment improved the quality of the concrete and decreased the cracking. When this equipment was used in the construction site, it is expected that the construction periodcan be shrunk and the ratio of defect caused by drying shrinkage can be decreased. In this research conditions, The 0.3mm sized moist curing equipment provided the most desirable results on concrete quality and preventing cracking.

• Journal of the Korea Concrete Institute
• /
• v.27 no.5
• /
• pp.531-539
• /
• 2015

Properties of normal-strength mortar containing coarsely-crushed coal bottom ash considering standard particle size distribution of fine aggregate were investigated. Mortar containing raw bottom ash was applied as a reference. By crushing the bottom ash with a particle size larger than fine binder but smaller than fine aggregates, i.e., coarse-crushing, water absorption and specific gravity of the particles could be controlled as similar levels to those of natural fine aggregates. Workability and strength of the mortar were not changed and even increased when the coarsely-crushed bottom ash was added considering standard particle size distribution in Standard Specification for Concrete, while those were decreased when raw bottom ash was added without any treatment. When a replacement ratio of coarsely-crushed bottom ash was less than 30 vol.%, there were no significant decrease in dynamic modulus of elasticity and dry shrinkage of the mortar.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.11
• /
• pp.1273-1281
• /
• 2014

Tissue engineering is an emerging research field that has the potential to restore, regenerate and repair damaged bone tissue and organs. Tricalcium phosphate and hydroxyapatite biomaterials-based calcium phosphate are excellent materials that have both osteoconduction and biocompatibility for bone tissue regeneration. In this study, solution structures were successfully fabricated using a fused deposition modeling system based on deposition and heating devices. The morphology characteristics of the bioceramic scaffolds sintered at a temperature of $1,300^{\circ}C$ were analyzed by scanning electron microscopy. The effects of various blended TCP/HA ratio on the microstructure and shrinkage were studied. The mechanical properties of the scaffolds were measured using a compression testing machine from stress-strain curves on the crosshead velocity of 1 mm/min. The fabricated scaffolds were evaluated by cell proliferation tests of MG-63 cells. The results of this study suggest that the blended TCP(75 wt%)/HA(25 wt%) scaffold is an appropriate scaffold for bone tissue regeneration.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.1
• /
• pp.68-75
• /
• 2017

The study investigates the effects of the content and using method of chemical admixtures such as superplasticizer and viscosity modifying admixture on the fluidity, bleeding ratio, volumetric change and compressive strength of the grout in order to provide basic data for the development of high-quality grout for prestressed concrete. It appeared that the combination of superplasticizer and viscosity modifying admixture decreased the fluidity of grout with small content of superplasticizer. On the contrary, Grout used more than 0.1% of superplasticizer appeared to have significant effect on the improvement of the fluidity. On the other hand, bleeding of grout reduced according to increasing the content of viscosity modifying admixture. Superplasticizer with less than 0.05% had practically no effect on the reduction of bleeding, whereas superplasticizer with more than 0.1% appear to have significant effect on the reduction of bleeding. Also the combination of superplasticizer with 0.15% and viscosity modifying admixture with 0.15% resulted in satisfactory fluidity accompanied with fair reduction of bleeding and shrinkage of the grout.

• Journal of Sericultural and Entomological Science
• /
• v.18 no.1
• /
• pp.27-39
• /
• 1976

In this study several kinds of spun silk yarn-synthetic filament compounded yarn was manufactured, and several fabrics woven from above mentioned silk compound yarn for evaluation of serviceability as clothing materials. The following results were obtained: 1. Degumming agents are in the order of sodium silicate, sodium hydroxide, sodium carbornate, soap and water. 2. When the concentration of sodium hydroxide is exceeded 3%, degradation of floss silk property is resulted because of excessive dissolving out of silk protein. 3. Degumming effect is much improved by concentration of degumming agent and less by its treating time. 4. Simultaneous application of more the 2 kinds of degumming agent is desirable for improvement of floss silk. 5. Application of natural organic acid brings very good results in keeping original scooping and color of the silk. 6. Load and elongation it increased by compound with synthetic filament yarn. 7. Even the evenness of compound yarn is largely dependent on the quality of floss silk and extent of degumming, the C.V.% of silk compound yarn in the experiment was 8-12%. 8. Single bath dyeing technique was impossible for their cloth, and dyeing was performed in 2 bath system separately for silk and synthetic fiber. 9. Shrinkage ratio due to the dyeing of fabric was 23% in case of polyester and spun silk fabric. 10. The final woven cloth can be applicable to (a) Blouse in care of thin cloth (compound silk fabric) (b) Korean costume for women in case of thick cloth. (compound hand spun silk fabric)

• Computers and Concrete
• /
• v.22 no.3
• /
• pp.261-267
• /
• 2018

Long-term deformation of a steel-reinforced concrete (SRC) column is different from that of a reinforced concrete (RC) column due to the different moisture distribution. Wide-flange steel in an SRC column obstructs diffusion and makes long-term deformation slower. Previous studies analyzed the characteristics of long-term deformation of SRC columns. In this study, an additional experiment is conducted to more precisely investigate the effect of wide-flange steel on the long-term deformation of SRC columns. Long-term deformation, especially creep of SRC columns with various types of wide-flange steel, is tested. Wide-flange steel for the experiment is made of thin acrylic panels that can block diffusion but does not have strength, because the main purpose of this study is to exclusively demonstrate the long-term deformation of concrete caused by moisture diffusion, not by the reinforcement ratio. Experimental results show that the long-term deformation of a SRC column develops slower than that in a RC column, and it is slower as the wide-flange steel hinders diffusion more. These experimental results can be used for analytical prediction of long-term deformation of various SRC columns. An example of the analytical prediction is provided. According to the experimental and analytical results, it is clear that a new prediction model for long-term deformation of SRC columns should be developed in further studies.

• Journal of Conservation Science
• /
• v.21
• /
• pp.49-58
• /
• 2007

Among the treatment results of test samples of the antique lacquer-ware, the treatment with PEG#3,350 40% solution displayed excellent effect with low shrinkage ratio; in weight gain the treatment with Sucrose 19%+Glycerin 1%(t-butanol 5% in water) solution showed consistent increase. However during the impregnation process of Sucrose, the weight of the testing samples decreased by dehydration because the inner part of the test samples and the treatment solution showed concentration gradient. Therefore, we concluded longer impregnation period should be necessary to prevent dehydration. Since both higher and lower molecular weight treatment chemicals could penetrate into the wood of the lacquer-ware, air drying and conditioning after impregnation treatment with high concentration chemicals would be possible, as well as vacuum freeze-drying.

• Journal of the Korean Wood Science and Technology
• /
• v.42 no.4
• /
• pp.467-476
• /
• 2014

The physical and mechanical characteristics of 10 Indonesian wood species were investigated. Mangium, Gandaria and Rambutan showed higher density. Mangium, Gandaria and Mangga appeared lower in shrinkage, and the ratio of tangential/radial was low in Albizia, Kupa and Mangga. The compression strength parallel to the grain and hardness were high in Mangium and Nangka. Gmelina, Mangium, Gandaria, Kupa, Nangka and Rambutan had valuable properties for commercial wood materials. Consequently, it is considered that the results of this study could be useful basic data for the improved use of planted and promising species in Indonesia.

• Journal of the Korea Concrete Institute
• /
• v.14 no.2
• /
• pp.231-238
• /
• 2002

Dry shrinkage md temperature change cause to develope concrete bridge decks on main girders have initial unidirectional cracks in longitudinal or transverse direction. As they receive traffic loads, the crack gradually propagate in different directions depending on the concrete dimension and reinforcement ratio. Since existing equations that predict crack width are mostly based on the one directional bond-slip theory, it is difficult to determine the actual crack width of a bridge deck with varying the spacing of rebar or strengthening material and to estimate the improvement rate in serviceability of the strengthened bridge deck. In this study, crack propagation mechanism is identified based on the test results and a new crack prediction equation is proposed for evaluation of serviceability. Although more accurate results are derived using the proposed equation, the extent of error is increased as the strain of the rebar or the strengthening material increases after the yielding of rebar Therefore, further research is required to better predict the crack width after the rebar yields under fatigue loading condition.