• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.221-222
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• 2012

This study is to high early concrete development which reveals 14 MPa within 12 hours in order to reduce the mold time of dismantlement and not do the steam curing of the precast concrete product. About (40~50) min could shorten the final setting time if the coagulation test result cement amount 100 kg/m3 was increased. In the case of the compressive strength, it was exposed to be satisfied the target value with the cement amount 500 kg/m3 combination according to the hardening accelerator addition.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.5
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• pp.243-249
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• 2007

The age hardening behavior and mechanical properties of an extruded Al-Zn-Mg-(Cu)-0.1 wt.%Sc alloy were investigated with the Sc addition and ageing temperature. The results showed that the $Al_3Sc$ compounds were formed by Sc addition and distributed preferentially along the extrusion direction. The age hardening of Al-Zn-Mg-Cu-0.1 wt.%Sc alloy which was treated by T6 process was more significant than that of Al-Zn-Mg-0.1 wt.%Sc alloy. The tensile property of Al-Zn-Mg-Cu+0.1 wt.%Sc alloy was also higher than that of Al-Zn-Mg-0.1 wt.%Sc alloy, which is 691 MPa and 584 MPa in strength and 9% and 11% in elongation, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.333-338
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• 2000

The purpose of this study is to evaluate the compressive strength properties of municipal waste ash hardening using the unrefined fly-ash and paper sludge ash and to offer basic data to someone for recycling municipal waste ash. Unrefined fly-ash and paper sludge ash are used with admixture. MWA are tested that grading, specific gravity and pH value and observed microsructure of particle with SEM. The compressive strengths of MWA hardening which is mixed with regular ratio according to each admixture are measured. In the results of test, fly-ash is very effective for reducing content of cement by 50% in the recycling of MWA. But proper content mixed paper sludge ash is recommend by about 20% in binder.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.103-106
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• 2008

Because the physical·chemical properties of bottom ash are inferior, most bottom ash is disused. But the use of bottom ash helps in reducing environmental pollution and solving some bottom ash waste problems. So, we have been investigating about the optimum mixture, hardening mechanism, curing condition and environmental safety of a paste composed of a bottom ash and alkali. optimal mixing proportion of bottom ash solid was cement 5%, water 30%, NaOH 10%. After curing during 28days, bottom ash solid can be achieved compressive strength 15.13MPa. As a result, Compressive strength tests of alkali-activated bottom ash have potential as a replacement of coarse aggregate.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.147-150
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• 2004

In order to describe the mechanical behavior of highly anisotropic and asymmetric materials such as fiber­reinforced composites, the elastic-plastic constitutive equations were used here based on the recently developed yield criterion and hardening laws. As for the yield criterion, modified Drucker-Prager yield surface was used to represent the orthotropic and asymetric properties of composite materials, while the anisotropic evolution of back­stress was accounted for the hardening behavior. Experimental procedures to obtain the material parameters of the hardening laws and yield surface are presented for 3D Circular Braided Glass Fiber Reinforced Composites. For verification purpose, comparisons of finite element simulations using the elastic-plastic constitutive equations, anisotropic elastic constitutive equations and experiments were performed for the three point bending tests. The results of finite element simulations showed good agreements with experiments, especially for the elastic-plastic constitutive equations with yield criterion considering anisotropy as well as asymmetry and anisotropic back stress evolution rule.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.3
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• pp.55-63
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• 2011

The convex printing plate in particular securities is classified three physical properties. The main ingredient(component)of photosensitive plastic is composed of thermosetting polyamide. After being hardened specimen at $80^{\circ}C$ is shown to resist highly, the Glass Transition Temperatures of photosensitive plastic are $85^{\circ}C$. When hardened plate has reached at $80^{\circ}C$, abrasion loss is minimized. the cause is considered it is more effective in hardening when the temperature of photosensitive plastic is $80^{\circ}C$-the vitrification temperature of those. The hardness and the durability of the convex printing plate in particular securities are affected to the hardening treatment temperature. And the resolution of original drawing has being better when the durability is superior.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.135-136
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• 2014

In this study, the experimental study on the early age compressive strength of cement mortar using anti freezer and hardening accelerator at low temperature was conducted. For this study, all of materials for experiment were kept in a low temperature for 24 hours before mortar mixing. After mortar curing at low temperature, compressive strength was measured at the early ages. Furthermore, properties of hardened cement material was analysed using TG-DTA and MIP.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.44-45
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• 2014

On this study, initial crack index was evaluated by performing FEM analysis to crack propagation from hydration heat for development of precast concrete. On the result, as increased the usage of hardening accelerator, initial compressive strength were improved and setting time also was shortened. Additionally, central temperature of concrete was increased, the reaching time for the highest temperature could be shortened. By the result to assess crack index, there was no problem about crack despite of growth of initial high hydration heating. This result guessed because of small size element when analyzed trough FEM, realization for mass concrete's crack index should be performed.

• Macromolecular Research
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• v.14 no.3
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• pp.318-323
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• 2006

We investigated the rheological behaviors and orientation of three different types of layered silicate composite systems under external flow: microcomposite, intercalated and exfoliated nanocomposites. Rheological measurements under shear and uniaxial extensional flows, two-dimensional, small-angle X-ray scattering and transmission electron microscopy were conducted to investigate the properties, as well as nano- and micro-structural changes, of polymer/layered silicate nanocomposites. The preferred orientation of the silicate layers to the flow direction was observed under uniaxial extensional flow for both intercalated and exfoliated systems, while the strain hardening behavior was observed only in the exfoliated systems. The degree of compatibility between the polymer matrix and clay determined the microstructure of polymer/clay composites, strain hardening behavior and spatial orientation of the clays under extensional flow.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.469-472
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• 2006

The use of admixture(PNS type & PC type) played a important role in the development of rapid hardening concrete. This paper presents an experimental study on the effect of a kinds of admixture on hydration characteristics, mini slump, apparent viscosity of fresh cement pastes and workability, compressive strength properties of hardened concrete for rapid hardening. Measurements have showed that their characteristics depends on the type of the admixture. As a result, the excellent quality was obtained, also being widely used for the construction field is expected.