• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4542-4551
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• 2013

Recently, much attention has focused on the study of eco-friendly concrete using recycled by-products for protecting marine ecosystem and durability of concrete exposed to marine condition. This study evaluated the durabilities of 4 different type of concrete mixtures(Control, Marine, Porous, New slag) with the seawater resistance by marine environment exposure experiment and freeze-thaw resistance, resistance to chloride ion penetration considering severe deterioration environment. In this study, we conducted seawater resistance using compressive strength according to the age(7/28/56 days) of specimen and curing conditions(standard(fresh water), tidal, immersion, artificial seawater). The results show that compressive strength of concrete exposed to marine environment exposure condition was lower than those of the standard curing condition. Also, compressive strength of New slag using eco-friendly materials for protecting marine ecosystem was lower than those of other concretes, there is need to improve the performance of New slag. The results for freeze-thaw resistance showed that all mixtures have excellent, but the Porous and New slag were lower than others. Also, the more improved resistance to chloride ion penetration than those of the Marine was measured in the New slag regardless of curing condition.

• Korean Journal of Agricultural Science
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• v.3 no.2
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• pp.214-224
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• 1976

This research was attempted as one of studies on the strength of mortar added admixtures at different curing temperatures. Variations of curing temperature to. test compressive strength, tensil strength and bending strength were $20^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$ and these results were summarized as follow : In strength of mortar added briquette ash, the compressive strength was increased: 1.58 percent, the tensile strength 0.96 percent, and the bending strength 1.26 percent compared with standard strength, by increasing one degree of celsius temperature. Also in strength of mortar added fly ash, the compressive strength increased on the average 1.3 percent, the tensile strength 0.99 percent, and the bending strength 1.18 percent at the above conditions. In case of using fly ash as admixture, maximum compressive strengths was attained at the level of 25 percent of fly ash, maximum tensile strength at the level of 20 percent of fly ash, and maximum bending strength at the level of 20 percent of fly ash. In case of using briquette ash, maximum compressive strength was attained maximum strength at 20 percent of the admixture, maximum tensile strength at the level of 15 to 20 percent of admixture and maximum bending strength at the level of 20 percent of admixture. Although addition of briquette ash was less effective in increasing the strength compared with the addition of fly ash, briquette ash might be used as one of admixtures because the control of curing temperature might affect in getting the required practical strength.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.367-381
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• 2020

This paper presents the seal material mixing ratio of tunnel umbrella arch reinforcement method. Currently, there is no clear standard for the proper gelation time and curing time of the Seal material in Korea, and the quality control is also difficult because it cannot be verified. In response, the ratio of the mixture of the seal material was composed of four types of indoor experiments, and the amount of gelation time and bleed was checked. In addition, a non-cart penetration test confirmed the curing time and compared the ratio of each combination. Further experiments on W/C 120% identified the effect of mixing speed and time on the seal material. A total of three field experiments were conducted based on indoor experiments, and the size and strength of bulb formation were compared by checking the curing time of the specimen and main injection. Comparisons show that the lower W/C, the stronger the strength, the larger the size of the bulb, and the faster the hardening time appears. Based on the results of the gelation time and curing time, it was deemed that the mixing ratio of W/C 120% is most appropriate when applied to the actual site.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.587-596
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• 2011

Ultra rapid-hardening cement is widely used for latex-modified mortar and concrete as repair and finishing material during urgent work. The purpose of this study is to evaluate the improvements in strength made to SBR cement mortars by the adding of various admixtures and by the use of different curing methods. SBR cement mortar was prepared with various polymer-cement ratios, curing conditions and admixture contents, and tested for flow, flexural and compressive strengths. From the test results, it was determined that the flow of SBR cement mortar increased with an increase in the polymer-cement ratio, and the water reducing ratio also increased. The strength of cement mortar is improved by using SBR emulsion, and is strengthened by adding metakaoline. The strength of SBR cement mortar cured in standard conditions was increased with an increase in the polymer-cement ratio, and attained the maximum strengths at polymer-cement ratios of 15 % and 10 %, respectively. The maximum strengths of SBR cement mortar are about 1.8 and 1.3 times the strengths of plain mortar, respectively. In this study, it is confirmed that the polymer-cement ratio and curing method are important factors for improving the strengths of rapid-hardening SBR cement mortar.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.9
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• pp.199-206
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• 2019

Experimental study on the durability characteristics to examine the feasibility of concrete with high water-tightness and self-healing performance to minimize maintenance of concrete for artificial ground is as follows. 1) When blending agent, swelling agents, and curing accelerator were added on the ternary system cement with blast-furnace slag fine particles and fly ash to give a self-healing property, higher blending strengths by 82% at design standard strength of 24MPa and by 74% at design strength of 30MPa, respectively could be obtained. 2) The permeability test for the specimens having high water-tightness and no shrinkage showed that the permeability was reduced at maximum of 98%. However, the permeability was decreased as the design strength was increased, showing the reduction rate of 87% at the design strength of 50MPa. 3) The depth of carbonation of blast-furnace slag and fly ash was increased in all the specimens compared with those of OPC only. However, as the material age was increased, carbonation penetration depth was decreased compared with the reference blend. 4) Compared with the reference blending using only OPC, the freeze-thaw resistance was higher in the case of blending with 40% of blast-furnace slag and 10% of fly ash at the design standard strength of 50MPa. In addition, the freeze-thaw resistance in general was superior in the design standard strength of 50MPa with the lower water-binder ratio (W/B) as compared with the design standard strength of 24MPa and 30MPa with the high water-binder ratios.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.2
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• pp.3778-3783
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• 1975

The objective of this study is to determine an appropriate cement of soil-cement in which silty soil of salty tidal flat with low plasticity was used. Physical, chemical and mechanical tests were conducted to find out the standard properties of the soil to be used. Various cement contents used in this test were 8%, 10%, 12%, and 14%, and the compressive strength was tested after 7 days and 28 days of standard curing in the above each cement content respectively. The results obtaind are summarized as follows. 1. As the cement content was increased from 8% to 14%, Maximum dry density (M.D.D.) and optimum moisture content (O.M.C.) were not changed remarkably. 2. Density of soil-cement was directly proportional to cement content and inversely proportional to water content. 3. OMC was generally decreased in proportion to the increase of cement content. 4. Compressive stranth was directly proportional to centent and inversely proportional to water content. 5. In freezing and thawing test, maximum loss of 10% in the total Weight was found on the 8% cement mixture. and This loss was rapidly decreased to 2% when the Cement content of the mixture was more than 10%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.181-182
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• 2016

We developed eco-friendly lightweight concrete in order to apply eco-friendly lightweight concrete into structural wall or slab of shallow depth urban railway system. However, since lightweight aggregate has different structural feature of porous and it has been overvalued at current KS standard when applied, we did compare the characteristics of freezing and thawing of normal weight aggregate concrete by comparative test method(KS, ASTM). According to test method, there was a big difference of dynamic elastic modulus in lightweight concrete rather than in normal weight aggregate concrete. The big absorption factor in lightweight aggregate is main reason for that. For more detail, in KS law in which only 14 days water curing is carried out, the big amount of moisture in lightweight aggregate is frozen and high heaving pressure occurs and finally that lead to destruction of lightweight concrete. Therefore, it is considered that in case of lightweight concrete, resistibility against freezing and thawing has been undervalued in domestic KS law compared to ASTM law, which is overseas standard. So, a variety of examination about testing criteria and rule would be necessary for exact assessment of lightweight concrete.

• Journal of Adhesion and Interface
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• v.3 no.1
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• pp.37-42
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• 2002

Adhesives are becoming increasingly accepted for advanced engineering/boding tasks. Therefore the understanding of the basic principles and the benefits of elastic bonding and structural bonding respectively is of utmost importance. Structural bonding means adhesive performance in load-bearing environments. Furthermore. the time to achieve handling strength has an impact on the economics of an assembly line. The paper gives briefly a summary about the fundamentals of elastic bonding and discusses different adhesive systems in the context of handling strength. Hereby the focus lies on the Warm Melt Technology, and its potential is compared to standard adhesives (l-part, 2-part and Booster Technology, a special 2-C system). Examples illustrate their economical benefits. Main Points : ${\bullet}$ The basic principles and benefits of elastic bonding ${\bullet}$ Warm-melt Technology in comparison with standard adhesives ${\bullet}$ Handling strength an economic issue ${\bullet}$ Combination with Booster-Technology, a special 2-C PUR system ${\bullet}$ Presentation of real world applications Learning Objectives: ${\bullet}$ Fundamentals of elastic bonding ${\bullet}$ Warm-melt Technology: correlation between chain length and cristallinity ${\bullet}$ Handling strength and curing speed of various systems in comparison ${\bullet}$ Real world applications illustrate the potential of the Warm-melt Technology.

• Korean Journal of Agricultural Science
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• v.7 no.2
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• pp.119-130
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• 1980

This study was conducted to determine the effect of curing temperature on the strength of briquette ash mortar hardened by cement. The six different kinds of briquette ash mortars were made by mixing the cement : briquette ash, ((cement (90%)+lime (10%)) : briquette ash and cement : standard sand at the ratio of 1:2, 1:3, 1:4, 1:5, 1:7, and 1:9, respectively and the cu ring temperatures were $20^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$. The strength of compression, bending and tensile were measured at ${\sigma}_7$ and ${\sigma}_{28}$. The summarized results were as follows. 1. At the ${\sigma}_7$ of 1:2 the compressive strength of the cement : briquette ash and (cement+lime) : briquette ash were 69.3% and 75.1%, respectively of the mortar made of the standard sand. At the ${\sigma}_{28}$ the strength of those materials were 56.4% and 49.0%, respectively. 2. At the ${\sigma}_7$ of 1:2 the tensile strength of the cement : briquette and (cement+lime) : briquette ash were 64.4% and 47.1%, respectively of the mortar made of standard sand. At the ${\sigma}_{28}$ the tensile strength of those materials were 69.6% and 64.8%, respectively. 3. At the ${\sigma}_7$ of 1:2 the bending strength of the cement : briquette ash and (cement+lime) : briquette ash were 46.3% and 65.9%, respectively of the mortar made of the standard sand. At the ${\sigma}_{28}$ the strength of those materials were 89.9% and 96.7%, respectively. 4. The increment of strength per $1^{\circ}C$ increase of curing temperature were on the average $0.92{\sim}1.75kg/cm^2$ of compressive strength, $0.12{\sim}0.16kg/cm^2$ of the tensile strength and $0.21{\sim}0.38kg/cm^2$ of the bending strength.

• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.22-30
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• 1999

This study was carried out to examine the compressive strength characteristics of solids solidified with the lead sludge with mixture of cement and fly ashes as additive. And the additives are commercial fly ash and ESP(Electrostatic precipitator) fly ash. The compressive strength of solidified lead sludge solid was increased by adding fly ash up to 46~62%, which was the results of pozzolanic reaction. When replaced the cement with 10%of commercial fly ash, the solid showed the highest value $210{\;}kg/cm^2$, and the solidification conditions were 0.55 of the water/cement ratio and curing for 14 days. Also, the results of leaching test by EPT(Environmental Protection Agency-Toxicity Test) were showed that the solidified lead has leached out under 10%, which was less than 0.173 mg/L of EPA standard. As leaching solutions, the demineralized water, 0.1N acetic acid solution, and synthetic brine were used. and the observations by SEM of the solidified lead-laden solid after EPT leaching test were indicated the severe erosion on solid surface.