• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.915-918
• /
• 2008

Hydration heat and autogenous shrinkage are generated essentially by the same hydration. Many researchers have studied the close relationship between hydration temperature and autogenous shrinkage but hardly any research has been undertaken to explain the specific numerical relation. In this study, early age properties of hydration heat and autogenous shrinkage of specimen whose section size was changed were analyzed, and relationship between hydration heat and autogenous shrinkage was investigated. In the results of the study, inner temperature and autogenous shrinkage increased as the section size increased. And rise and rise ratio of hydration temperature and autogenous shrinkage in hydration heating section and autogenous shrinking section are increased too. Temperature rise and autogenous shrinkage rise increased respectively, as hydration heating velocity and autogenous shrinking velocity increased. And autogenous shrinkage rise and autogenous shrinking velocity increased as hydration heating velocity increased.

• Journal of the Korean Ceramic Society
• /
• v.31 no.11
• /
• pp.1387-1395
• /
• 1994

Re-hydration properties of heated and ground CaO-SiO2-H2O system were studied under hydrothermal condition in order to examine the possibility of recycling ALC waste as raw materials of ALC. Powder of calcium silicate hydrates and ALC waste without heat treatment did not show further hydration while those of heat-treated at proper temperature showed re-hydration properties under hydrothermal condition. The lath-like shape of initially synthesized tobermorite was gradually turned into small debris during heating and plate-like tobermorite was crystallized during re-hydration of the heated powders. Heated and ground ALC waste could be added to natural raw mix for ALC at the ammount up to 20% with increased compressive strength and up to 30% with slightly decreased compressive strength. The optimum heating temperature of ALC for recycling was about 50$0^{\circ}C$.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.6
• /
• pp.164-172
• /
• 2008

The heat of hydration for early aged mass concrete induces high temperature with the hydration. Control of the temperature difference across a section is an effective strategy to minimize the hydration heat induced cracks for the structures where internal restraint is dominant. The current prevention methods for hydration cracking show some limitations for the control of thermal gradients, and these limitations could make micro and macro cracks in surface and core of concrete. Especially cooling methods can decrease the increasing hydration temperature, but it can not prevent the problem while decreasing temperature. Consequently heating pipes are added simultaneously with the cooling pipes in order to control the temperature gradients between core and surface of the concrete, followed by the finite element analysis (FEA). Based on the FEA, the proposed method using cooling pipe and heating pipes together has been found to be an effective alternative in thermal gradient control, in terms of controlling temperature induced cracks significantly.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.11a
• /
• pp.55-57
• /
• 2012

In this study, the field applicability on reducing the heat of hydration of mass concrete by using the hydration heat difference method is analyzed with the following summary. As a result of applying the hydration heat difference method by using low heating combination, the temperature difference between the central part and the surface part of mass material was reduced, and as a result of visual observation, there was no showing of cracks by the hydration heat on the upper surface part. Therefore, the cracking index of the field to apply this method was shown to be approximately 1.57 with very little crack occurrence probability of less than 3%.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.46 no.2
• /
• pp.179-184
• /
• 2020

Elasticity and softness of the skin depend on the level of moisture present in the stratum corneum, which is known to be affected by various environmental changes, such as cold and hot winds and dry environments. However, not many studies have been conducted on changes in skin moisture and the degree of recovery due to individual skin differences. In the present study, we aimed to investigate the effect of warm air heating on skin hydration levels and develop moisturizing formulas to improve lowered skin hydration levels. In order to deliver warm air heating condition, heating dryer (40 ℃, 6 m/s, 30 cm apart from forearm) was applied into inner forearm of healthy subjects (male: 10, female: 39, age: 25 - 63) Among 49 subjects, 26 subjects showed significantly lowered skin hydration levels until 30 min after warm air heating exposure (lowered group). In addition, moisturizing cream with high water holding capacity was applied to forearm of 10 subjects in lowered group for 3 weeks and skin hydration levels after warm air heating were significantly improved at the levels of before application of warm air heating. From this study, we found out that there is a skin type that skin hydration levels are significantly decreased under warm air heating condition (dehydrated skin) and this dehydrated skin can be improved by moisturizing formulas with high water holding capacity.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.315-316
• /
• 2009

In this study, latent heat material was used to reduce hydration heating velocity of high-strength mass concrete. And the properties of hydration heat and autogenous shrinkage, and the relationship between hydration heat and autogenous shrinkage of high-strength mass concrete were numerically investigated.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.05a
• /
• pp.114-115
• /
• 2021

The research team conducted a series of studies to use CGS as fine aggregate for concrete. In this paper, through the adiabatic temperature rising test, CGS' hydration heating performance and its usability as a mass concrete hydration heating agent were reviewed. According to the analysis, the maximum temperature of the mix of OPC 100 was 53.7℃, and the temperature of CGS 50% was 45.2℃, which was 8.5℃ lower than the OPC 100.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.2
• /
• pp.175-186
• /
• 2023

The buffer materials in disposal hole are exposed to the decay heat from spent nuclear fuels and groundwater inflow through adjacent rockmass. Since understanding of thermal-hydro-mechanical-chemical (T-H-M-C) interaction in buffer material is crucial for predicting their long-term performance and safety of disposal repository, it is necessary to investigate the heating-hydration characteristics and consequent T-H-M-C behavior of the buffer materials under disposal conditions considering geochemical factors. In response, the Korea Atomic Energy Research Institute developed a laboratory-scale 'Lab.THMC' experiment system, which characterizes the T-H-M behavior of buffer materials under different geochemical conditions by analyzing heating-hydration process and stress changes. This technical report introduces the detail design of the Lab.THMC system, summarizes preliminary experimental results, and outlines future research plans.

• Journal of the Korea Concrete Institute
• /
• v.20 no.5
• /
• pp.593-600
• /
• 2008

In this study, to analyze the correlation between hydration heat and autogenous shrinkage of high strength concrete at an early age, hydration heating velocity and autogenous shrinking velocity as quantitative coefficients which represent the main properties of hydration heat and autogenous shrinkage were proposed. Two coefficients were calculated by statistical analysis and were equal with the regression coefficient. The complemented semi-adiabatic temperature rise test as test method to evaluate the hydration heat and autogenous shrinkage of concrete were proposed. In results of proposed test and analysis method, it was possible that early age properties of hydration heat and autogenous shrinkage of concrete were expressed numerically, and autogenous shrinkage was represented by equation with coefficients of hydration heat.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.645-648
• /
• 2008

In this study, to evaluate the correlation between hydration heat and autogenous shrinkage of high strength concrete in early age, statistical method present numerically hydration heat and autogenous shrinkage was studied. First of all, hydration heating velocity and autogenous shrinking velocity as quantitative coefficients which represent the main properties of hydration heat and autogenous shrinkage were proposed. Two coefficients were calculated by statistical analysis and were equal with the regression coefficient. To verify the validity of the proposed statistical analysis method, data of hydration heat and autogenous shrinkage gathered by a real experiment were analyzed by it. In results, properties of hydration heat and autogenous shrinkage of high strength concrete in early age were analyzed quantitatively. Also evaluation and comparison of the correlation between hydration heat and autogenous shrinkage with numerical value were possible.