• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.146-152
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• 1996

Polypropylene fiber reinforced mortar and concrete as civil material or architectural material have been used in America and British etc, and have been researched. Polypropylene fibers have many advantages in many points ; in economical costs, chemical stability and durability. It has been reported that polypropylene fiber can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. This study has been performed to obtain the properties of polypropylene fiber reinforced concrete such as compressive strength, flexural strength, toughness, slump, drying shrinkage crack and drying shrinkage characteristics. The test variables are fiber contents, fiber length, fiber types, and so on. From the results of this study, we can expect the effects of the admixtures of polypropylene fiber about strength and drying shrinkage properties in concrete and mortar.

• Polymer(Korea)
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• v.31 no.6
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• pp.491-496
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• 2007

In the polymeric dental restorative composites, the resin matrix mainly contains 70 wt% 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), as a base resin and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as a diluent. Even though the viscosity of the resin matrix is rapidly decreased by adding TEGDMA, addition of TEGDMA to the Bis-GMA results in reduction in the mechanical properties and increase in the curing shrinkage of the dental composite. In order to fabricate dental composite exhibiting excellent properties by reducing TEGDMA content in the resin matrix, in this study, Bis-GMA derivatives, which do not contain hydroxyl groups, were used instead of Bis-GMA. The curing characteristics of Bis-GMA derivatives were similar with those of Bis-GMA, while the former exhibited lower viscosity and water absorption than the latter. Comparing the curing shrinkage of the dental composite containing Bis-GMA derivative with that prepared from Bis-GMA, the reduction in curing shrinkage was about 25%. Dental composites prepared from new resin matrices also exhibited low water uptake and better properties in mechanical strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.76-83
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• 2022

Since the 3D printing mortar is exposed to the atmosphere immediately after printing, moisture is largely evaporated from the surface of the layer. The evaporation of moisture on the surface of the layer greatly causes drying shrinkage and increases the risk of cracking and damage to the structure due to drying shrinkage. This study experimentally evaluated the shrinkage behavior of the initial age using the mortar used for 3D printing. The change in shrinkage was evaluated by comparing the shrinkage of the specimen cured by the sealing method and the atmospheric exposure method. In addition, compared with the case where type 1 cement was used 100%, the shrinkage amount was evaluated when 20% of fly ash was replaced and 10% of silica fume was used. In particular, the effect of three chemical admixtures applied using 3D printing on shrinkage was evaluated experimentally. When fly ash and silica fume were used, the shrinkage amount increased by 60 - 110% compared to the case when type 1 cement was used. The application of viscosity modifiers and shrinkage reducers reduced the shrinkage by at least 18% and at most 70% depending on the curing conditions. The temperature of the specimen temporarily decreased to 15 ℃ at the beginning of curing, and the correlation between the internal temperature of the specimen and the shrinkage behavior was observed.

• Textile Coloration and Finishing
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• v.24 no.2
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• pp.113-120
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• 2012

Jacquard floor covering could be prepared from low-melting/regular sheath-core hybrid polyester, where the fiber is dyed in yarn state. With regard that the expected high shrinkage of the hybrid polyester in water makes problems in yarn dyeing, low-temperature dyeing properties of the hybrid polyester were studied. The rate of shrinkage of low-melting hybrid polyester exceeds 9% in hot water above $90^{\circ}C$, at such condition, cheese yarn dyeing is very difficult. Although disperse dyes exhaust in a relatively high speed on low-melting hybrid polyester, diffusion of these dyes to the core regular polyester was extremely slow under $90^{\circ}C$. Foron Blue E-BL 150, an anthraquinone E-type disperse dye, showed appreciable diffusion after 48hrs dyeing at $90^{\circ}C$. The fastness to rubbing and drycleaning were improved by one grade after reduction cleaning.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.357-360
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• 2005

This research investigates the drying shrinkage of non-sintering cement(NSC) matrix added phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators with various curing condition. The experimental results are follow: When the moisture is fully supplied at the early curing age, there is effect which carries out abundant generation of the ettringite which is an expansion nature mineral, and compensates for contraction with a chemical prestress concept.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.2
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• pp.219-225
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• 2011

Silicone resin is recently used as encapsulant for high-power LED module due to its excellent thermal and optical properties. In the present investigation, finite element analysis of cure process was attempted to examine residual stress evolution behavior during silicone resin cure process which is composed of chemical curing and post-cooling. To model chemical curing of silicone, a cure kinetics equation was evaluated based on the measurement by differential scanning calorimeter. The evolutions of elastic modulus and chemical shrinkage during cure process were assumed as a function of the degree of cure to examine their effect on residual stress evolution. Finite element predictions showed how residual stress in cured silicone resin can be affected by elastic modulus and chemical shrinkage behavior. Finite element analysis is supposed to be utilized to select appropriate silicone resin or to design optimum cure process which brings about a minimum residual stress in encapsulant silicone resin.

• Carbon letters
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• v.9 no.4
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• pp.308-315
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• 2008

In the present study, fast isothermal stabilization processes for rayon precursor fabrics were performed at $350^{\circ}C$ and $400^{\circ}C$ within 3 minutes and the chemical and physical characteristics of the stabilized fabrics were investigated. In addition, rayon precursor fabrics were pre-treated with three different phosphorous-based flame retardants and then stabilized. The effect of flame retardants on the chemical composition, thermal shrinkage, weight change, thermal stability and XRD results was examined, comparing with those of the precursor fabrics. The result showed that the stabilization of rayon fabrics was most effective as the stabilization temperature was $350^{\circ}C$, the stabilization time was 3 min, and the pre-treatment with phosphoric acid of 1 vol%. The carbon contents of stabilized rayon fabrics were increased with increasing stabilization temperature and time, whereas the oxygen contents were decreased. Also, it is likely that the pre-treatment with phosphoric acid plays a role in retarding the change of chemical structure of rayon fabric. The XRD result was quite consistent with the result showing the effect of phosphoric acid on the chemical composition, thermal shrinkage and weight reduction of rayon fabric.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.141-145
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• 1996

The primary purpose of this study is to investigate reusal techniques of by-product produced the combined heat power plant in the construction field, which may contribute to the savings of construction materials and the conservation of enviornment. This study is compared and evaluated by testing the chemical resistance, adiabatic temperature rising test, creep and drying shrinkage. As the result of the study, the following conclusions are derived : (1) hydration heat of the fly ash concrete is less than the plain concrete in adiabatic temperature rising test, (2) the fly axh concrete (FA 30%) is similar to the plain concrete in the chemical resistamce, (3) the fly ash concrete (FA 10, 30%) is similar to the plain concrete in drying shrinkage, but the fly ash concrete (FA 50%) is highly increased, (4) the fly ash concrete (FA 30%) is less than the plain concrete in creep test.

• Composites Research
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• v.30 no.6
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• pp.410-415
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• 2017

This paper predicted deformation due to thermal residual stress in composites using finite element analysis. Temperature cycle, Model shape, Laminate angle, Stacking sequence, chemical shrinkage of resin, and thermal expansion are affect composite deformation. Compare the results of the analytical model with the actual model of the same shape. This paper suggests that the analytical results can be applied to actual Model.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.301-308
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• 1999

With the shortage of the land and NIMBY syndrome, it is issued recently that the capacity of waste-landfill site is needed though the decreasing tendency of waste landfill. From this point, the stability is the most essential problem in the landfill that will be constructed. Advanced design and construction are most important for that. In this paper, for the study of desiccation, dry-shrinkage crack from drying and chemical reaction in cement hydration, which is occurred when the surface layer stabilization method is applied in wast landfill, laboratory test of the ground and specimen according to the mixture ratio of stabilizer is performed. From the result, it is notified that the uni-axial strength increases with the stabilizer, but dry-shrinkage increases too, therefore, it is important and the goal of this study to find the optimal mixture ratio of each stabilizer. Analysis of variance for regression with acting variables is performed to find optimal mixture ratio of each stabilizer.