• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.205-211
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• 2015

Most of the sulfur is obtained from desulfurization of natural gas and crude oil. In Korea, more than 120 tons of sulfur are produced by refinery, and about 50 % of the produced sulfur is used as a raw material for the production of fertilizer and sulfuric acid. Modified sulfur is manufactured from excessive sulfur that could be used to improve concrete properties, and this study evaluated concrete strength and durability that contains modified sulfur. Flexural and compressive strengths of concrete with sulfur modified polymer were comparable to those of OPC concrete with mixing water at similar temperatures, while the strengths increased a little as mixing water temperature increased. It was also confirmed that the resistance to freeze-thaw damage was more dependent on entrained air characteristics obtained by a proper use of air entraining agent than on the use of sulfur modified polymer. When concrete was immersed in 5 % sulfuric acid, the rate of reduction in compressive strength of OPC concrete was less than 1/4 of the strength reduction of concrete with sulfur modified polymer. Also, the resistance of concrete with sulfur modified polymer to scaling due to the use of de-icing salt was evaluated as Class 1, while that of OPC concrete was evaluated as Class 4, as aggregates were exposed. Accordingly, it is believed that sulfur modified polymer could be effectively used for bridge deck concrete since sulfur modified polymer improves the durability of concrete.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.157-165
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• 2016

It is possible to achieve high strength ranging from 40 MPa to 70 MPa in alkali-activated slag concrete (AASC), and AASC is also known to have a finer pore structure due to its high latent hydraulicity and fineness of slag cement, which makes it difficult for chloride ions to penetrate. Electrophoresis is mostly used to calculate the effective diffusion coefficient of chloride ions, and then to evaluate resistance to salt damage. Few studies have been conducted on the fixation capacity of chloride ions in AASC. For this reason, in this study the chloride fixation within the hardened paste was evaluated according to the type and the amount of alkaline activators. As a result, it was revealed that among the test specimens, the chloride fixation was greatest in the paste containing $Na_2SiO_3$. In addition, it was found that as more activator was added, a higher level of chloride fixation was observed. Through this analysis, it can be concluded that the type and the amount of alkaline activators have a high correlation with the amount of C-S-H produced.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.489-498
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• 2005

Recently, the deterioration of concrete structures have been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the deterioration of concretes have been taken. Among them, it has been often used that surface treatment which cut off the deterioration factors of durability by protecting the surface of concrete. The water proof and repair materials for concrete mainly use organic materials such as epoxy, these materials excel in intial bonding force and resistance to chemical agents. But they cause difference in the modulus of elasticity and the rate of shrinkage and expansion of concrete, and thus result in such problems as scaling and spatting in the progress of time. Therefore in this study it develop the performance Improving agent of concrete surface that can block a deterioration cause such as $CO_2$ gas, chloride ion and water from the outside and enhance waterproofing ability by reinforcing the concrete surface when applying it to concrete structures.

• Korean Journal of Heritage: History & Science
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• v.47 no.4
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• pp.58-73
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• 2014

In general, it is thought discoloration on wood is frequently found in decorative wood products. So this study was conducted focusing on white rot found lower parts of columns and baseboards of a wooden house, Hyunchungsa (shrine) to know whether microorganisms have any influence on discoloration or there is correlation with strength by investigating resistograph, occurrence of microorganisms and microscopy for analysis(SEM, tissue analysis etc.). The results obtained were as follows: (1) The result of measurement of resistograph showed there are little correlation between discoloration and strength though there was a spot indicating low resistance. (2) The moisture content of discolored part was relatively higher than that of normal parts, but occurrence of microorganisms was less in discolored parts while more kinds of microorganisms were identified in normal parts with high CFU(Colony Forming Unit). (3) The result of SEM (with a magnification of 500 times) on the surface of discolored parts, it was found out there are many kinds of particles in different sizes on the surface and those were composed of elements such as C, O, Si, Ca, and a small amount of Na and Cl (weight %) were detected in part. (4) The result of tissue analysis showed discoloration occurs limitedly to the outer surface of column. As these results, it is concluded that discoloration has nothing to do with strength, damage by microorganisms and salt.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.s02
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• pp.45-65
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• 1989

The Korean peninsular having the complexity of the photography and variability of climate is located within passing area of a lots of typhoon occurring from the southern islands of Philippines. So, there are various patterns of wind and flooding damages in paddy field occuring by the strong wind and the heavy rain concentrated during the summer season of rice growing period in Korea. The wind damages to rice plants in Korea were mainly caused by saline wind, dry wind and strong wind when typhoon occurred. The saline wind damage having symptom of white head or dried leaves occurred by 1.1 to 17.2 mg of salt per dry weight stuck on the plant which was located at 2. 5km away from seashore of southern coastal area during the period(from 27th to 29th, August, 1986) of typhoon &Vera& accompanying 62-96％ of relative humidity, more than 6 m per second of wind velocity and 22.5 to 26.4$^{\circ}C$ of air temperature without rain. Most of the typhoons accompanying 4.0 to 8. 5m per second of wind and low humidity (lesp an 60％) with high temperature in the east coastal area and southen area of Korea. were changed to dry and hot wind by the foehn phenomenon. The dry wind damages with the symptom of the white head or the discolored brownish grain occurred at the rice heading stage. The strong wind caused the severe damages such as the broken leaves, cut-leaves and dried leaves before heading stage, lodging and shattering of grain at ripening stage mechanically during typhoon. To reduce the wind damages to rice plant, cultivation of resistant varieties to wind damages such as Sangpoongbyeo and Cheongcheongbyeo and the escape of heading stage during period of typhoon by accelerating of heading within 15th, August are effective. Though the flood disasters to rice plant such as earring away of field, burying of field, submerging and lodging damage are getting low by the construction of dam for multiple purpose and river bank, they are occasionally occurred by the regional heavy rain and water filled out in bank around the river. Paddy field were submerged for 2 to 4 days when typhoon and heavy rain occurred about the end of August. At this time, the rice plants that was in younger growing stage in the late transplanting field of southern area of Korea had the severe damages. Although panicles of rice plant which was in the meiotic growing stage and heading stage were died when flooded, they had 66％ of yield compensating ability by the upper tilling panicle produced from tiller with dead panicle in ordinary transplanting paddy field. It is effective for reduction of flooding damages to cultivate the resistant variety to flooding having the resistance to bacterial leaf blight, lodging and small brown planthopper simultaneously. Especially, Tongil type rice varieties are relatively resistant to flooding, compared to Japonica rice varieties. Tongil type rice varieties had high survivals, low elongation ability of leaf sheath and blade, high recovering ability by the high root activity and photosynthesis and high yield compensating ability by the upper tillering panicle when flooded. To minimize the flooding and wind damage to rice plants in future, following research have to be carried out; 1. Data analysis by telemetering and computerization of climate, actual conditions and growing diagnosis of crops damaged by disasters. 2. Development of tolerant varieties to poor natural conditions related to flooding and wind damages. 3. Improvement of the reasonable cropping system by introduction of other crops compensating the loss of the damaged rice. 4. Increament of utilization of rice plant which was damaged.