• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.39-44
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• 1992

• Proceedings of the Korea Concrete Institute Conference
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• 1989.10a
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• pp.25-30
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• 1989

In this paper, morter and concrete specimens made with four cements were immersed in Mgcl2, MgSO4 Solution and artifical Seawater which was corresponded with Seawater. The hydration products of immersed cement pastes were looked over by using SEM, EDS and X-ray diffraction method. The results show that the concrete made with domestic flyash cement and blast-frrnace slag cement is superior to that of ordinary portland cement in resistance to chloride and sulphate solution. Especially, it is found that the attack of Cl-ion on the concrete plays an important role of the deterioration of concrete.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.67-75
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• 2000

It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.117-122
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• 1998

The misalignment state causes some problems in operating. These problems such as vibration, noise, make the reduce wear, as well as, a stress concentration on the coupling which is the very weakness point at the morter. In order to align the shaft, the dialgage method has used as a means of solution until now. The method using a dialgage require a great deal of labour and money due to making by hand, the accurate alignment is not up to the expectation. For aligning the shaft, all the rotor must come to accord. Also, the dialgage method cannot be compared with straingage measurement method, from the viewpoint, which can gage in short time.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.99-104
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• 2009

For recycling of waste foundry sands, researchers recently try to recycle them rather than depend on reclamation, and are studying on how to combine waste foundry sands with cement and use them for various kinds of construction material as the effective recycling method of waste foundry sand. In this research, The ways to find the proper replacement rate of waste foundry sands and to make use of them were suggested through the experiments on the range to apply waste foundry sands with two levels of 1:3 mixture rate of W/C 43% and 50%. The research result showed that in terms of liquidity as the characteristic of unhardened mortar, as the replacement rate of waste foundry sands increased, its flow tended to decrease. The amount of air also displayed a similar tendency to that of liquidity in that the higher the replacement rate of waste foundry sands became, the lower it became. With regard to the solidity trait of hardened mortar, it increased when the waste foundry sands were replaced more, and the replacement of waste foundry sands caused increased initial solidity. As for the amount of water permeated and that of water absorbed as the water tight proofing properties, the amount of permeated water was proved to decrease because of the gap recharge effect by the fine powder of waste foundry sands, and the replacement of waste foundry sands in the structures requiring watertightness is concluded to be very effective.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.75-85
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• 1985

This study is intended to find out the influence of Lignosulfonic Acid Type Admixture on compressive, tensile, flexural strength and dispersing action of mortar, and fixation of by-product of pulp industry. 1. The more Pozzolith-84 is added, the larger flow value is. The admixture of lignosulfonic acid type adhere to cement particles and the surface potential of particles is generated. On account of the repulsion among the cement particles, they are dispersed and the mortar get workable, so the production cost of precast product is curtailed and the amount of cement is reduced in a certain workability of mortar. 2. The strength of mortar is greater than plain mortar when P/C added is 0.2 and 0.4%. As time passed the potential energy is reduced and the distance of particles which lignosulfonic acid adhered to get near according as the amount of adhesion is increased. The setting and hardening reaction of morter is occurred in close state, so the strength of mortar is increased a little. The strength of mortar is less than plain mortar when amount P/C added is 0.8%. Pozzolith-84 is mainly composed of lignosulfonic acid and lignin does not influence the hardening of mortar, therefore the remained $SO_3$, $SO_3H$ are the reason of decrease of strength. 3. There is high significance between specific gravity and compressive strength. The larger specific gravity is, the more compressive strength is increased. There is high significance between 7 day's strength and 28 day's strength. The larger compressive strength is, the more tensile and flexural strength are increased. 4. Since Pozzolith-84 is a by-product of pulp industry, by using the Pozzolith-84 admixture the concreate quality is improved. The water pollusion is reduced according to fix by-products in concrete structure.