• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.905-908
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• 2008

The existing concrete using ordinary portland cement has difficult in earth strength. so our study proceeded in using the micro cement. the result of experiment is follow that strength of micro cement was hard better than ordinary portland cement in early strength but flow of ordinary portland cement was better than micro cement. when OPC and MC mixed by fly-ash, flow degree is increased because of ball baring. fly-ash type wicked in early strength but flyash type hard than 28days strength of OPC. flow of GBFS is decreased, early strength is increased. when fly-ash mixed in MC, it was wicked strength.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.77-81
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• 1999

In order to investigate the effect of fineness on the properties of Portland cement, we prepared five kinds of portland cements with different Blaine values(2300, 2500, 3000, 3500, 45oo $\textrm{cm}^2$/g) and measured Ca(OH)2 analysis, hydration heat, the fluidity and the physical properties of them. According to the results, as the Blain value of cement is lower, the rate of hydration is delayed, and the hydration heat and the compressive strength are decreased. But the fluidity of cement paste is improved. Especially, the hydration heat of the cement with 2500$\textrm{cm}^2$/g of Blaine value is decreased about 15% compared with 3500 $\textrm{cm}^2$/g cement.

• KIEAE Journal
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• v.13 no.3
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• pp.3-13
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• 2013

As climate change is increasingly recognised as an important global problem, a wide variety of policies and measures are emerging at global and local level to deal with the challenges from the anthropogenic global warming. While national and inter-national efforts characterized by limiting GHG emissions shows very little progress because of their expanse spatial scale and complicated political situations, local efforts have the potentials to ensure effective implementation, monitoring and continual improvement. In the context of local-scale climate policy, the city of Portland is known as one of the best leading cities for its progress of implementing climate change strategies. This paper will briefly discuss the city's efforts to solve the climate change problem and its achievements. The latest climate action plan is selected for the analysis on the followings; the framework of the action plan, the types of implementation methods, and the coordinating agencies. The progress status of each action plans is also reviewed. The purpose of this paper is to describe the main characteristics of the climate action plans and their implications from the intensive analysis on the city of Portland's case.

• Safety and Health at Work
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• v.14 no.3
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• pp.340-346
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• 2023

Background: Truck driving is a highly sedentary occupation that places workers at risk for chronic health conditions, such as obesity and high blood pressure. The primary purpose of this study was to objectively describe truck drivers' typical physical activity (PA) patterns. Methods: We used ~7-10-day baseline PA actigraphy data samples from drivers in the Safety & Health Involvement For Truckers (SHIFT) study (n = 394). Driver PA patterns (e.g., average number of ≥10 minute Freedson bouts per week, time in bouts, and common days/times for PA) were summarized with descriptive analyses. We also compared objective accelerometer data to self-reports. Results: Drivers' weekly PA averaged 14.4 minutes (SD = 37.0), and most PA occurred between 5-6 pm on Tuesdays and Wednesdays. Drivers overestimated self-reported weekly exercise by over 60 min/week compared to accelerometer data. Conclusion: Our results suggest that objective PA assessment may be warranted over self-report when possible, and timing may be key in future PA intervention work with truck drivers.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.2
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• pp.1-8
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• 2012

The G-class cement is usually used for geothermal well grouting to protect a steel casing which is equipped in a geothermal well to transfer geothermal water from deep subsurface to ground surface. In geothermal grouting process, obtaining appropriate fluidity is extremely important in order to fill cement grout flawlessly. In this paper, a series of the V-funnel and Slump Flow test was performed on both of the Portland cement and the G-class cement in order to compare fluidity and filling ability of those kind of cements. In the result of V-funnel test, the fluidity of G-class cement was evaluated much better than the Portland cement at the water/cement ratio of 0.8. In the case of Slump Flow test, the fluidity of G- class cement was estimated slightly better than the Portland cement at both the water/cement ratio of 0.55 and 0.8. Even though the initial fluidity and filling ability of G-class cement were relatively higher than the Portland cement, the results could be considerably changed with time. The results show that the fluidity and filling ability for geothermal well cementation can be properly controlled with water content and additives for adverse geothermal well environment.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.59-68
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• 2017

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ($C{\bar{S}}A$) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $C{\bar{S}}A$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $C{\bar{S}}A$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze-thaw condition. When coarse aggregate with good freeze-thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $C{\bar{S}}A$ cement concrete in a freeze-thaw environment. The $C{\bar{S}}A$ cement concrete with poor performance of durability in a freeze-thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $C{\bar{S}}A$ concrete with good performance aggregate also exhibits less surface scaling in a freeze-thaw environment, losing 11 % less mass after 297 cycles.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3172-3179
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• 2011

Several materials using polymer-portland-cement concrete have developed to have not only strength of attachment with body, but also waterproof function and strong anti-sodium chloride properties. Especially, in case of railway, unlike other public transportation, it is very difficult to doing the repair and reinforcement work of structure during service time. Therefore, the development and study of materials having characteristics of structural strength, unification behavior with body, and resistance of crack are very important. Accordingly, the characteristic of material of polymer based concrete is indicated compared with the experiment and analysis through this study, and suggested application to railway tunnel, bridge, and concrete track structure.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.260-265
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• 2012

Impedance spectroscopy was used to monitor the hydration in the electrical/dielectric behaviors of chemical mechanical planarization (CMP)-blended cement mixtures. The electrical responses were analyzed using their equivalent circuit models, leading to the separation of the bulk and electrode based responses. The role of the CMP slurry was monitored as a function of the relative compositions of the CMP-blended cements, i.e. water, CMP slurry, and ordinary Portland cement. The presence of $Al_2O_3$ nanocrystals in the CMP slurries appeared to accelerate the hydration process, along with a more tortuous microstructure in the hydration, with enhanced hydration products. The frequency-dependent impedance spectroscopy was proven to be a highly efficient approach for evaluating the electrical/dielectric monitoring of the change in the pore structure evolution that occurs in CMP-blended cements.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.532-540
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• 1988

Even the finest cement as having a specific surface area of 6.000~8.500$\textrm{cm}^2$/g (Blaine) is to convert into low-porosity hardened cement paste by the use of appropriate plasticizer. In this study, tests were carried out on such a special cement mix(fineness of 6.000$\textrm{cm}^2$/g, Ca-lignosulfonate plus k2CO3 as plasticizer and W/C=0.25) in comparison with ordinary Portland cement. Owing mainly to the high fineness of the cement powder and the low water-to-cement ratio, the hardened low-porosity cement paste showed a very tight microstructure, the pore texture of which consisted of micropores and wide pores only of small radii. The consequence of such mix was hence that the low-porosity special cement had excellent properties of early-high and very high strengths as compared to ordinary Portland cement. Its volume change when dried in the air or re-wetted, exhibited superor behaviour as well.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.687-692
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• 1998

This paper covers concrete durability made with portland cement type I and V, and granulated blast furnace slag blended cements 40 and 60%. Typical properties of cements and compressive strength development, drying shrinkage, carbonation, freezing and thawing properties of concretes were investigated. In addition, effects of CI penetration on various concretes with/without a freezing and thawing treatment were also studied. Portland cement type I and V were superior to the blended cement in the properties of compressive strength development, drying shrinkage, carbonation and freezing and thawing durability. In the respect of resistant of CI Blended cement showed better than the portland cement due to high permeability. But the blended cement with a freezing and thawing treatment presented a much decreased resistance of CI penetration.