• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.155-160
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• 1998

In this study, the estimation method of adiabatic temperature rise of concrete was developed by using hydration heat generation of mineral compounds of clinker and pozzolans. Specific heat considered the effects of mix proportion and temperature was calculated with experimental data. The adiabatic temperature rise calculated by developed method were compared with experiments in which many types of cement and admixtures were used. As the results of this study, it was found that the developed method could calculate adiabatic temperature rise of concrete accurately without the experiment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.117-118
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• 2016

This paper evalutes properties of extruding cement panel using Ca-extracted convert slag and air-cooled blast furnace slag. Flexural strength of extruding cement panel has measured in air dry and autoclave curing as basic study for use as silicious source. As a result, when Ca-extracted converter slag replaces 25% in autoclave curing, flexural strength measures 13.1MPa better than panel control mix. In result of using air-cooled blast furnace slag, Ca-extracted air-cooled blast furnace slag dose not show increase of flexural strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.316-320
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• 1996

It is now increasingly recognized that the fluid properties of superplasticized high flowing concrete can be affected by numerous parameters which characterize either the cement, the mineral or chemical admixture, the mix proportion. Particularly performance of superplasticizers used to enhance the workability and obviously plays a key role in the rtheology of fresh and engineering properties of hardened concrete. In this experiment, it is aimed to investigate and compare the each fluidities and engineering properties of high flowing concrete by performance in each 3 kinds of superplasticizers. And there is to aim the considering about fluidity and viscocity, hardened properties of hig flowing concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.821-824
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• 2006

As this study is to estimate long term resistance of cement mortars using crushed sand under chemical attacks. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of silica fume and fly ash(up to 15% and 50% by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days, 90days, 180days, 365days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of silica fume and fly ash was performed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.153-162
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• 2001

This paper presents the fundamental study on rational manufacture of Ultra High Strength(VHS) concrete using industrial by-products as like silica fume, slag and fly ash. In this study, we had tested various mixing cases to manufacture the UHS concrete(target compressive strength : over $1,000kgf/cm^2$) which is easily workable (target slump flow : $60{\pm}10cm$). The main variables are studied: 1) to find the optimum replacement ratio of mineral admixture. 2) to find a rational water-binder ratio and a proper binder content. 3) to find the method for reduction of slump loss. From the test results, it is concluded that the rational mix design can be made by using 40% slag, 10% silica fume. We found that compressive strength of UHS concrete increases according to decreasing W/B ratio but in W/B ratio 18~20%, the difference is vague and the compressive strength does not necessarily increase according to increasing binder content over 700kg.

• Structural Engineering and Mechanics
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• v.47 no.5
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• pp.701-711
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• 2013

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.79-90
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• 2004

Rutting on asphalt pavement surface is an important damage in most roadways in the world. Most of researches have developed prediction model for rutting on asphalt pavement as a function of physical properties of asphalt binder. But this study was devised to estimate rutting based on fundamental properties of asphalt mixture, not binder. Therefore this study objective is to estimate rutting based on volumetric properties, that is Air void, Void in mineral aggregate(VMA) and Void filled with asphalt(VFA), of asphalt mixture with various asphalt binders, aggregates and aggregate gradation. Results showed that it was possible to estimate rutting depth based on volumetric variables of asphalt mixture. In addition, VMA, the variable which is nor used In mix design in Korea, showed a significant correlation with rutting, It is recommended that VMA is adapted as a variable in domestic mix design. Also, It showed that VFA in the specification should be lowered at least 5% point since VFA was somewhat higher than optimum.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.124-133
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• 2012

Compressive strength in concrete increases with time. Regression analysis with time is conventionally performed for strength evaluation and prediction. In this study, hydrate amount is assumed as a function of hydration rate and porosity, and modeling on compressive strength is carried out considering decreasing porosity with time, which does not need the regression analysis with time. For twenty one mix proportions of HPC (High Performance Concrete), DUCOM (FE program) which can simulate the behavior in early aged concrete is utilized, and porosity from each mix proportions is obtained with time. For HPC with OPC (Ordinary Portland Cement) concrete, modeling on compressive strength is performed considering hydration rate, unit content of cement, and porosity with time. For HPC with mineral admixtures, a long-term parameter which can handle long-term strength development is additionally considered. From the comparison with the previous test results, the applicability of the proposed model is verified.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.999-1009
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• 2014

In this paper, $CO_2$ emission and storage amount are evaluated for real RC (Reinforced Concrete) underground structure considering $CO_2$ amount including material manufacturing, moving, and construction, repairing timing stage regarding extended service life. Four mix proportions with mineral admixtures are prepared and $CO_2$ diffusion coefficient are obtained based on a micro modeling. Referred to carbonation durability limit state, $CO_2$ emission and storage amount are evaluated, which shows higher initial $CO_2$ emission is caused due to larger unit content of cement and the storage increases with more rapid carbonation velocity. Furthermore various $CO_2$ concentration is adopted for simulation of $CO_2$ evaluation including measured $CO_2$ concentration (600ppm). With higher concentration of $CO_2$ outside, carbonation velocity increases. In order to reduce $CO_2$ emission through entire service life, reducing initial $CO_2$ emission through mineral admixture like fly ash is more effective than increasing $CO_2$ storage through OPC since $CO_2$ is significantly emitted under manufacturing OPC and $CO_2$ storage in cover concrete of RC structure is not effective considering initial concrete amount in construction.

• The Korean Journal of Food And Nutrition
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• v.22 no.3
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• pp.430-442
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• 2009

This study was designed to investigate the relationship between the dietary intake according to calorie intake from a coffee containing beverage and the bone health status of 189 female collegians. The study was conducted through questionnaires, anthropometric checkup, 3-days food records and ultrasound measurement of calcaneus bone mineral density. Subjects were divided into three groups: students not drinking coffee(non-coffee group, N=56), students consuming <100 kcal daily from coffee(low-calorie coffee group, N=84), and students consuming $\geq100$ kcal of their total daily calories from coffee(high- calorie coffee group, N=49). There were no significant differences in weight, height, body mass index, body fat and calcaneus bone mineral density among the three groups. The low-calorie coffee group usually drank black coffee or instant coffee mix, and the high-calorie coffee group habitually drank coffee with milk or sugar syrup. There were no significant differences in the mean daily energy and food intake among the three groups. However, vitamin $B_2$(p<0.05) and calcium (p<0.01) intake in the high-calorie coffee group were higher than in the non-coffee group. Also, mean intake of sugars, fish and shellfishes, milks and beverages in the high-calorie coffee group were also significantly higher than in non coffee group(p<0.05). There was no significant difference in the Korean Dietary Diversity Score(KDDS) among the three groups. The main calcium source was milk in all three groups, and milk intake(total and included with coffee) was highest in the high-calorie coffee group. Although no significant difference was apparent between the high-calorie and non-coffee groups concerning anthropometric factors and calcaneus bone mineral density, consumption of coffee may have influenced food and nutrient intake. The results suggest that consumption of milk-supplemented coffee may be of nutritional benefit.