• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.379-382
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• 2005

Ocher block has started to be studied recently as a new environment friendly alternative building material. This article investigates the use of Rice Husk Ask (RHA) as an additive to improve properties of the ocher block. Ocher mixtures incorporating various proportions of RHA were compared. Compressive strength at various ages of these ocher blocks was evaluated ad the resistance to wet environment was also examined. These test result help to determine the effect of RHA on such properties of the ocher block as compaction, mix proportion, compressive strength and water absorption indexes. Based on these results, the new alternative building material and low cost construction techniques might be developed through more intensive research efforts.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.407-408
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• 2009

Drying shrinkage have influence on the durability of concrete structure. Various models have been suggested to predict the drying shrinkage, experimentally. In this study, the drying shrinkage with Concrete strength and Curing condition was measured, and compared with representative model code. As a result, drying shrinkage was reduced as W/C ratio decrease, and total shrinkage greatly reduced in 4 week wet curing case. The test results agreed with EC2 model better than the other.

• Fibers and Polymers
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• v.5 no.3
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• pp.187-197
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• 2004

The compressive and flexural properties of hemp fiber reinforced concretes (FRC) were examined in this paper. Natural hemp fiber was mixed using dry and wet mixing methods to fabricate the FRC. Mechanical properties of the FRC were investigated. The main factors affecting compressive and flexural properties of the FRC materials were evaluated with an orthogonal test design. Fiber content by weight has the largest effect. The method for casting hemp FRC has been optimised. Under the optimum conditions, compressive strength increased by 4 %, flexural strength increased by 9 %, flexural toughness increased by 144 %, and flexural toughness index increased by 214 %.

• Journal of the Korean Wood Science and Technology
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• v.23 no.3
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• pp.33-39
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• 1995

To accelerate the cure of phenolic resin adhesives for plywood, the complexation with melamine resin and the addition of cure-accelerating agents were discussed. The hot-pressing temperature and time of phenol resin could be decreased by complexation with melamine resin. but the wet glue-joints strength of phenol melamine resin was lower than that of ordinary phenol resin in case of plywood using spruce veneer at core layer. Among the tested cure-accelerating agents. the sodium carbonate showed the greatest effect on shortening gelation time of phenolic resin. In addition, in the manufacturing scale test, the hot-pressing time of phenol resin with the addition of 5 parts sodium carbonate could be shortened about 20% compared with ordinary phenol resin which had same glue-joints properties.

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.21-27
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• 2011

This study was carried out to examine properties of water resistant plywood by using serum protein adhesive which is natural, environment-friendly and human-friendly. For the preparation of the serum protein adhesive, pig blood from slaughterhouse was centrifuged and serum was separated from corpuscles and concentrated to 30% by dry weight basis. This concentrated serum protein was modified with PF resin (50% NVC) with the ratio of 9 : 2.5. Plywood made by this modified serum protein gave 1.21 N/$mm^2$ of dry bonding strength, 0.80 N/$mm^2$ of wet boil bonding strength, 0% of cyclic delamination test value, and 0.025 ppm of HCHO emission, which met the excellent super $E_0$ grade and water resistant plywood.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.348-353
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• 1996

This study addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements. The marine tidal zone was simulated by alternate filling and draining of the tank (wet and dry cycled), and a galvanostatic corrosion technique to accelerate corrosion of reinforcement was used. Half-cell potentials and changes of crack width were measured periodically during the exposure and followed by ultimate strength testing. The significant findings include adverse effect of fatigue loading, existence of an explicit size effect, poor performance of epoxy coated steel, and negative effect of increasing water/cement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.388-393
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• 1996

This study evaluated characteristics and performance of recycled concrete as a pavement which was constructed on a low volume road. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Natural sand from a source was used as fine aggregate together with admixtures such as plasticizer and fly ash (0.8% and 5% by wt. of cement, respectively). The length, thickness and width of the pavement were 100mm, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were approximately 45Kg/$\textrm{cm}^2$, 250Kg/$\textrm{cm}^2$, and 240,000 Kg/$\textrm{cm}^2$, respectively. The pavement could be constructed by hand without much difficulty. The surface was finished smoothy by wet fabric and only minor cracks were found on the surface.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.584.1-584
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• 2001

The purpose of this study was to evaluate the effects of various cavity configuration on bond strength and micro leakage of composite restoration. The specimens were prepared as followed; For control group(C=1), bovine teeth were wet-ground to expose flat dentin surface and in experimental groups, cylindrical cavities, same all2mm deep and 6mm in diameter(C=2.3), 4mm(C=3.0), and 3mm(C=3.7) were prepared.(omitted)

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.560.1-560
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• 2001

To evaluate the micro-shear bond strength of current adhesive systems to cervical and mid-coronal enamel. Materials and Two commercially available resin adhesives were investigated; a self-etching primer system(Clearfil SE Bond, Kyraray) and a one-bottle adhesive system(Single Bond, 3M) intended for use with the total-etch wet-bonding technique were employed. Two regions of enamel, cervical and mid-coronal regions, were chosen from the buccal surface of extracted molars and were then bonded with each adhesive system and submitted to the micro-shear bond test.(중략)

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.50-55
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• 1997

This study was carried out to utilize old newspaper(ONP) and paper sludge more effectively, and also to elucidate the influences of pressing conditions on the medium density fiberboard(MDF) properties. MDFs were made from ONP and low grade of paper sludge by wet process with change of pressing time, temperature and pressure. MDFs of ONP were more affected by pressing conditions, especially pressing pressure, but temperature and pressing time were also important. According to mixing paper sludge to ONP tensile and bending strength of MDF were decreased, but density and dimensional stability were improved. These results indicated that some physical properties of MDF can be improved by paper sludge and it is possible to use it in MDF.