• Journal of the Korea Concrete Institute
• /
• v.17 no.4 s.88
• /
• pp.581-586
• /
• 2005

High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

• Journal of Digital Convergence
• /
• v.20 no.1
• /
• pp.309-316
• /
• 2022

This study is a study on the YouTube e-learning advanced service plan in the non-face-to-face era. The trends in education change were examined through literature research and prior research, and improvement measures were suggested through online surveys and in-depth interviews. As for the research method, the first online survey was conducted based on the Honeycomb model and the Likert 5-point scale targeting 90 MZ generation who have experience learning on YouTube for a total of 14 days from October 15 to 28, 2021. A second in-depth interview was conducted with 6 people who answered that the frequency of learning through YouTube is high. As a result of the experiment, users thought that there was an improvement point according to the purpose of learning, and they were able to derive elements that felt a problem in common. In addition, I proposed a new YouTube learning platform through additional questions. Through this study, it is expected that YouTube e-learning service reference materials can be used to respond to the post-non-face-to-face era.