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        검색결과 60

        21.
        2012.09 구독 인증기관 무료, 개인회원 유료
        This paper has fabricated insulation gang-form adhering general gang-form to the polyisocyanurate board and analyzed type of members, temperature record by locations and strength development after placing the concrete, in order to ensure efficient concrete quality under cold weather. According to our test, we can see that general gang-form member with curing under the same conditions as the actual field has a trend of constantly decreasing concrete temperature regardless to surface or central area due to rapid outdoor air temperature reduction, while in the case of insulation gang-from I and II, temperature increased up to around 25℃ after 12 hours under rapid outdoor air temperature change and temperature distribution did not appear large separation according to hydration reaction measurement locations. In addition, results of measurement for temperature records on weak insulation area by types of gang-forms showed that the temperature record distribution on the form tie surface and horizontal bar surface of angle bar has generally similar trend as the temperature records on the surface of the insulation gang-form, while corner area of the insulation gang-form did not have large insulation effect. It is determined that it requires additional curing measure for the weak corner area of the insulation gang-form in the future.
        4,000원
        22.
        2012.09 구독 인증기관 무료, 개인회원 유료
        In this study, prediction of later-age compressive strength of ultra-high strength concrete, based on the accelerated strength of concrete cured in hot water was investigated. Comparing other acceleration method, hot water curing method is relatively easy and intuitive to use in the real construction site. The amount of time for evaluation of the concrete strength using the hot water curing method in KS and JIS is too long to predict the strength of the ultra-high strength concrete that are used in the tall building structure. For that reason, curing temperature of 40, 50, 60℃ 3 levels were examined to shorten the amount of time for the evaluation of the strength. When curing in warm water, different strength characteristics are verified from the experiment. In case of F3 substituting 30% fly ash in combination, because of the curing temperature sensitivity of fly ash, differences of strength expression velocity was verified according to the curing temperature at the same age. In case of B4 substituting 40% ground granulated blast furnace slag, there were no big strength expression velocity differences of the specimen cured in 3 different level of curing temperature(40, 50, 60℃). The results show reliable accuracy by regression relation between 28day strength cured by standard curing method and accelerated strength of concrete cured in warm water.(y=1x-0.0002 R2=0.9866) As a result, the feasibility of 3day-prediction was confirmed using warm water curing method with accelerated strength of concrete cured for three days in warm water.
        4,000원
        23.
        2012.03 구독 인증기관 무료, 개인회원 유료
        In this study, the drying shrinkage of concrete used for the reduction of expansive additive and shrinkage reducing agent committed to the concrete Mixing characteristics, compressive strength and drying shrinkage of examining my new honhwajaeryoin elements by putting in concrete Their characteristics were compared and analyzed. Experiments, SP was fixed jeryangeul equally expansive additive and shrinkage reducing agent in the formulation of the Injection rate increased with increasing fluidity, shrinkage reducing air flow rates increase the amount of air even if the input Increases with, and if the expansion of re-injection rates increase rather than decrease was found that the volume of air. I committed to the elements of the concrete, but an increase in inputs even if the air content of concrete or no liquidity Were confirmed to have no effect. In addition, the compressive strength test Shrinkage Reducing the dosage increases, Tended strength falls, inflation 5.0% of material inputs in the formulation was found to be the highest. Element material Concrete with Shrinkage Reducing committed a similar compressive strength falls with increasing dosage tended Unlike the small degree of shrinkage reducing agent was affected. Shrinkage characteristics include all three admixture With increasing dosage can reduce the drying shrinkage was observed that, if the shrinkage reducing agent, of the elements and almost Reducing the level of contraction was found to be. Therefore, the element first, if you commit to concrete admixtures to Characteristics of the concrete mix does not affect the lapse rate contract that can be used as a highly admixture is judged to be here.
        4,000원
        24.
        2012.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To investigate the effect of single windbreak and combination of hill and windbreak on pollutant dispersion in neutral boundary condition, CFD (Computational Fluid Dynamics) modeling was used. The validity of the CFD model was confirmed by wind tunnel and field experiments of single closed windbreak. The results show increased windbreak height increasing the height of maximum concentration position and decreasing surface concentration (x=50 m) from 1.5 to 5.0 times smaller than that of non-windbreak case. In combination of hill and windbreak case increasing hill height decreasing surface concentration from 1.0 to 1.1 times smaller than that of single windbreak case.
        4,000원
        25.
        2012.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Because many recent epidemiological studies have reported the associations of population’s proximity to high traffic roadways with adverse health effects, interest in how roadside structures affect the concentration of motor vehicle emitted pollutants in the near-road microenvironment has increased. These noise barriers may affect pollutant (for example: odor, carbon dioxide, particle et al.) concentrations around structure by blocking initial dispersion. This study examined the effects of roadside barriers on the flow patterns and dispersion of pollutants from high traffic highway. The effects of noise barriers were examined using commercial software FLUENT. The results show noise barriers increase concentration of near noise barrier wake region and decrease concentration in the faraway distance from noise barrier. The results also show far from emission position (between 100 m and 200 m) surface concentration of multi-barrier cases are 2 times lower than that of no barrier case.
        4,000원
        26.
        2011.09 구독 인증기관 무료, 개인회원 유료
        This study is analyzing a member kind after placing concrete, the location-based temperature record, and the strength development, by making insulation gang-form with application of polyurethane form to general gang-form for securing efficient concrete quality in the condition of cold weather. According to our experimental results, the member of general gang-form with curing in the same condition as the actual field didn’t drop to under 3˚C until before 24 hours in the early part, but fell to under 0˚c from 36 hours later because a large rise in temperature caused by hydration reaction didn't occur. On the other hand, in case of insulation gang-form, the temperature on the surface and the central part didn't go down to under 3˚C before 12 hours in the early part and didn't fall to under it even until 72 hours after it while the peak temperature went up to 12˚C. Thus, it could be known to definitely have excellent insulation effect compared to space heating curing, which is generally performed on the spot. In comparison with space heating curing whose error in curing temperature is big every field, it is judged to likely have great effect on improvement in concrete quality given the work construction in cold weather and on early demolding in a cast during winter.
        4,000원
        27.
        2011.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was conducted to induce the effective counterplan of odor management in the Sihwa industrial complex(SIC) utilizing to CALPUFF model with sensory odor. The CALPUFF model was applied to simulate a sensory odor, and was evaluated for odor applicability and the distribution status of odor in SIC was predicted. The simulated concentration showed lower than observed concentration but the prediction of odor was so excellent. The simulation result of CALPUFF model for SIC showed that annual mean odor unit was 5∼7 OU/㎥ (min. 3 OU/㎥, max. 25 OU/㎥). The annual mean odor unit in residential area was not high as 1∼3 OU/㎥ but was predicted to be affected by the weather status in the industrial complex. The odor emission sources of high concentration were distributed in the seashore. Therefore the management of the high concentration sources will be further demanded.
        4,000원
        28.
        2011.03 구독 인증기관 무료, 개인회원 유료
        In case of general concrete, autogenous shrinkage is about 10% of the drying shrinkage. Therefore it was not considered significant to be a subject matter about managing the crack control and design. It was reported that cracks can be generated from the autogenous shrinkage. Because of the low W/B rate and the high unit binder of the high strength concrete. In this study, autogenous shrinkage and drying shrinkage are examined which is the main reason of the cracks of the high strength concrete based on the previous studies. Comparing the data from this study and previous studies, we developed the shrinkage reduced concrete using shrinkage reducing agent. The purpose of this study is to provide the data for reducing and managing the column shortening of the high strength concrete structures.
        4,000원
        29.
        2011.03 구독 인증기관 무료, 개인회원 유료
        In this study, prediction of later-age compressive strength of ultra-high strength concrete, based on the accelerated strength of concrete cured in hot water was investigated. Comparing other acceleration method, hot water curing method is relatively easy and intuitive to use in the real construction site. The amount of time for evaluation of the concrete strength using the hot water curing method in KS and JIS is too long to predict the strength of the ultra-high strength concrete that are used in the tall building structure. For that reason, curing temperature of 40, 50, 60˚c 3 levels were examined to shorten the amount of time for the evaluation of the strength. As a result, the feasibility of the three days hot water curing method was confirmed.
        4,000원
        30.
        2011.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We examined the relationship between breakfast eating, nutrient intake, and health outcomes using dietary intake, anthropometric, and biochemical measurements in Korean adults. Data from the 2007 National Health and Nutrition Survey were obtained, and 2,514 adults aged 20 to 64 years were analyzed. The prevalence of skipping breakfast, using a 24-hour diet recall, was 54.5% in the 20-29 age group, 31.2% in the 30-49 age group, and 19.2% in the 50-64 age group. In the 20-29 age group, waist circumstance and serum cholesterol were significantly higher in breakfast skippers than in breakfast eaters. In the 30-49 age group, breakfast skippers had higher triglyceride levels than breakfast eaters. Energy intake of breakfast skippers in every age group was significantly lower than that of breakfast eaters. Furthermore, in the 20-29 and 30-49 age groups, the percent of energy from carbohydrates in breakfast skippers was significantly lower than that of breakfast eaters, whereas the percent of energy from lipids in breakfast skippers was significantly higher than that of breakfast eaters. Additionally, in the 20-29 and 30-49 age groups, breakfast eaters showed higher carbohydrate and iron intake per 1,000 kcal than breakfast skippers and lower lipid intake per 1,000 kcal than that of breakfast skippers. Breakfast skippers showed intakes of less nutrients than EAR was higher than breakfast eaters except vitamin B2 and calcium intake in males of the 20-29 age group. In conclusion, nutrition education, and policy should be implemented to teach the importance of breakfast, appropriate dietary intake, and proper food choice for each age group.
        4,000원
        32.
        2010.03 구독 인증기관 무료, 개인회원 유료
        Existing non-destructive test for evaluation of concrete compressive strength may show deviation in results analysis due to deterioration of precision by strength calibration and dry or humid condition by age, so there needs be testing method to determine long term structural internal force by collecting specimen with no damage of structure and measuring compressive strength through destruction test. This research applied to mock-up member the compressive strength evaluation method using joint separation mold that can plan and produce specimen cured in the same composition environment as concrete structure by attaching arbitrary(joint separation) to the form before concrete piling, and as a result, the management specimen was contrary to the hydration temperature of the member or was affected by external atmospheric temperature, however the joint separation specimen connected to structure and managed in the same environment showed a temperature curve similar to the member and decrease in temperature difference. Additionally, from initial age, with the compressive strength of joint separation specimen most similar to core strength,stable compressive strength can be evaluated up to design criteria strength 100MPa, so the method is proposed as an evaluation technique that can confirm highly reliable concrete quality.
        4,000원
        33.
        2009.09 구독 인증기관 무료, 개인회원 유료
        As architectures have recently become high-risers and mega-structured, stable high strength products have been ensured. Accordingly, use of precast concrete accouplement has been increased in order to facilitate air compression and rationalize construction. Since external rising by the steam heating and internal rising by the accumulation of cement hydration heat for the temperature of members, precast concrete members with large cross-section used for high-rise mega-structure's columns and beams may exhibit different temperature history compared to the precast concrete members for wall and sub-floor with relatively small cross-sections. Therefore, this study aims to elucidate the characteristics of temperature history of mass concrete members cast with high-strength concrete for precast concrete application. In this study, large cross-sectional precast concrete mock-up, unit cement quantity, and temperature histories in manufacturing precast concrete member under different curing condition were inclusively investigated.
        4,000원
        34.
        2009.09 구독 인증기관 무료, 개인회원 유료
        Recently, as architectural concrete structures become high-rise and megastructured, concrete become high-strengthened and, by ensuring products of more stability, and rationalization of construction are required.large cross-sectional precast concrete members such as columns show large temperature increase in manufacturing process not only by external heating but also by concrete itself's hydration heating. Therefore, it is expected that specimen for management to predict strength and compression strength of precast concrete member shows different strength characteristics. Conceming this, in order to suggest strength characteristics of high strength mass concrete suitable for precast concrete application, this study comprises the inclusive investigations on the relations between core strength and the strength characteristics per member cross-section dimensional value and per water-bonding material ratio value.
        4,000원
        35.
        2009.03 구독 인증기관 무료, 개인회원 유료
        Precast concrete produced in the industry is advantageous in a sense that it meets certain requiring standards and thus is easy to manage, and it saves construction period by shortening concrete curing time in the field. Nevertheless, studies on the strength evaluation of PC material by steam curing have rarely been done. In addition,as concrete becomes of high strength, it is speculated that relevant steam curing temperature history is also required. Therefore this study is on the steam curing method in manufacturing precast concrete products, and cement mortar has been used for experiments to exclude the possibility that concrete aggregate granularity and aggregate shape change may affect on strength development by cement hydration. In addition, this research is to provide the fundamental information of industrial manufacture of PC member by suggesting the optimal steam curing condition. The optimal steam curing condition has been investigated from the relations between temperature history condition and strength development, via modifying temperature patterns in various ways such as pre-tirne, curing maximaI temperature, maximaI temperature maintenance time which are factors that affect on high strength concrete product in steam curing.
        4,000원
        36.
        2009.03 구독 인증기관 무료, 개인회원 유료
        An evaluation of the concrete strength has very important meaning in the maintenance and the structural safety. The reliability of ferroconcrete building is weakening and enlarging the life is strongly demanded due to the early deterioration of concrete. Like this social demand, concrete strength presumption is being indirectly executed using the result in parallel with the concrete pouring by material age. This data is usually different as concrete poured practically and the way of hardening and curing. Although existing concrete strength presumption formula is proposed, the material used and the concrete strength is different. And as a matter of remicon, the concrete strength varies according to the site and the way of curing. So the objective of this research is strength evaluation of the structural body concrete according to the concrete pouring and curing temperature change seasonally after using the system which evaluates the structural body concrete strength which is applied the transparent junction-separation mold that is presented. Also there is an objective to present the fundamental data for the constructional quality technique proposal of the structural body concrete developed in relation to field specimen and the strength evaluation method by non-breaking.
        4,000원
        37.
        2008.09 구독 인증기관 무료, 개인회원 유료
        As the durability, reparability and maintainability of reinforced concrete structures are emphasized, the early perfomance degradation of concrete structures becomes a serious problem. Moreover, defects in construction materials and constructions inconsistent with the design promote the degradation of perfomance. Some worst buildings have fallen into an irreparable state within a few years. In particular, carbonation in concrete structures has been handled as the most fundamental and critical factor related to the durability of reinforced concrete. As a result, there have been efforts to develop repair materials to control carbonation. As one of these efforts, alkali recovery agents have been presented as materials for increasing the re-alkalization and durability of carbonated concrete structures. However, in applying them in the field, the performance and quality of concrete recovered after an alkali recovery agent is applied has not been fully assessed. Therefore, to examine the recovered perfomance of concrete structures resulting from the application of an alkali recovery agent, the present study assessed the depth of carbonation and the degree of deterioration of 20 years or older reinforced concrete structures, and analyzed the quality of concrete after applying an alkali recovery agent to the structures. This study aimed at providing basic infomation for the application of alkali recovery agents in the fleld. In this experiment, alkali recovery agents of the lithium silicate line, which are most common in Korea, were applied and cured using concrete of the same size. The degree of recovery was investigated according to the length of time in the initial curing stage, and based on the investigation, the maintenance perfomance of the alkali recovery agent was assessed according to the age of exposure to the open air. For these tasks, this experiment sampled concrete of different degrees of deterioration, applied alkali recovery agents to them, and observed re-alkalization and changes in the internal texture of the concrete.
        4,000원
        38.
        2008.09 구독 인증기관 무료, 개인회원 유료
        Concrete Carbonation is usually measured as discoloration, as it has one of strengths to be economical, and simple and immediately confirm the given results in the spot. And, when Carbonation is measured as Phenolphthalein Solution, it is possible to confirm the scope of alkali through acid and basic reaction. Then, Concrete Basic Reaction is decided according to alkali concentration depending on Potassium Hydroxide Now that Carbonation is gradually produced toward inner side from outer side, with time going by, it doesn’t work, to some adequate depth, in as fast time as compulsory facilitating test. Thus, this research thesis made a comparative analysis on concrete phenomenal discoloration borderline following Phenolphthalein Solution, as part of a bid to measure Carbonation. Also, the thesis measured 'Concrete Alkali Concentration. The result showed that concrete coloring is classified into red and scarlet according to alkali concentration, and into borderline breakpoint of the speckle of scarlet and carbonation reaction. The higher chroma becomes with concrete decolorizing, the higher alkali concentration becomes. Also, it was demonstrated that for long-term concrete discoloration borderline, discoloration degree can be determined by amounts of Potassium Hydroxide. Such result proved that limiting the extent of only red color as alkali, in the process of deciding on the scope of concrete alkali, can be served as an error in measuring service life of Concrete Carbonation.
        4,000원
        39.
        2008.03 구독 인증기관 무료, 개인회원 유료
        Furnace slag powder used currently in Korea needs to add special functions in response to the increase of large-scale projects. In addition, it is advantageous in that it has a lower hydration heat emission rate than ordinary Portland cement and improves properies such as the inhibition of alkali aggregate reaction, watertightness, salt proofness, seawater resistance and chemical reslstance. However, furnace slag powder is not self-hardening, and requires activators such as alkali for hydration. Accordingly, if recycled fine aggregate, from which calcíum hydroxide is generated, and furnace slag, which requires alkali stimulation, are used together they play mutually complementary roles, so we expect to use the mixture as a resource-recycling construction material. Thus the present study purposed to examine the properties and characteristics of furnace slag powder and recycled aggregate, to manufacture recycled fine aggregate mortar using furnace slag and analyze its performance based on the results of an experiment, to provide materials on mortar using furnace slag as a cement additive and recycled fine aggregate as a substitute of aggregate, and ultimately to provide basic materials on the manufacturing of resource-recycled construction materials using binder and fine aggregate as recycled resources.
        4,000원
        40.
        2008.03 구독 인증기관 무료, 개인회원 유료
        Previous researches for increasing the durability of concrete structures examined the characteristics of concrete using glycol ether admixture, and determined the optimal addition rate and evaluated durability of concrete. However, today’ s ready mixed concrete uses various industrial byproducts in order to improve the performance of concrete, and the quality of concrete changes depending on the addition of glycol ether admixture and curing condition. Considering this, we need to understand the characteristics of curing methods according to field condition. Thus, the present study evaluated the effects of replacement with fly ash as a binder and curing conditions (temperature and humidity) on the performance of concrete, and obtained data from a mock-up test for the practical use of concrete containing glycol ether admixture. According to the results of this study, the concrete showed resistance performance of around 30% to carbonation and around 40% to drying shrinkage. In addition, as for resistance to freezing and thawing, the relative dynamic modulus of elasticity was over around 85% through atmospheric curing. These performances prove the effect.
        4,000원
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