• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.216-217
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• 2015

This study consist of research on the strength development properties of alkali activated slag(AAS) by differential combination of activators, initial protecting and curing conditions. 3 type of binders cured in the atmosphere, underwater and sealed were estimated compressive strength of 3, 7 and 28 days. Test results showed that strength development properties of binders varied with initial protecting and curing conditions because of ionized anions in pore water.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.52-58
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• 2017

Concrete made with ground granulated blast-furnace slag(GGBS) has many advantage, including improved durability, workability and economic benefits. GGBS concrete is that its strength development is considerably slower under standard $20^{\circ}C$ curing conditions than that of portland cement concrete, although the ultimate strength is higher for same water-binder ratio. GGBS is not therefore used in application where high early age strength is required. In this study, to overcome the limitation of the initial strength decrease due to the use of slag, the slag substitution rate was changed to 30% under the low temperature curing temperature condition and the slag used concrete composition with the same or higher strength performance as OPC(Ordinary Portland Cement).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.45-48
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• 2005

This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of qualify control. According to the result of cement mortar by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.79-87
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• 2011

Concrete incorporating high volume blast-furnace slag placed in cold weather regions might be in danger of initial frost damage because dependently on the mix proportions, the setting and the hardening would be remarkably delayed. Therefore, this study investigated to effect of the degree of frost on the strength development and the resistance to freezing and thawing of the concrete incorporating blast-furnace slag when being subjected to freeze at early age. As the experimental results, the concrete incorporating blast-furnace slag attacked by initial frost damage showed the remarkable reduction of both the compressive strength development and the resistance to freezing and thawing. Especially, the resistance to freezing-thawing of the concrete incorporating high volume blast-furnace slag became much lower than that of the normal concrete.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.191-202
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• 1998

The maturity method in which the strength increase of cement concrete is expressed as a function of an intergral of the curing period and temperature of the concrete has often been applied to its strength prediction. For the purpose of the application of the maturity method to the compressive strength prediction for lightweight polymer mortars using an unsaturated polyester resin as a binder, the lightweight polymer mortars with various catalyst and accelerator contents, are prepared. tested for compressive strength, and the datum temperatures for the maturity equations are estimated. The maturity is calculated by using the maturity equations with the estimated datum temperature. The compressive strengths of the lighweight polymer mortars are predicted from the maturity-compressive strength relationships.

• Journal of the Korea Institute of Building Construction
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• v.17 no.5
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• pp.419-427
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• 2017

In order to examine the possibility of practical use of aluminate cement concrete at low-temperature environment with insulation method, an experimental studies on flowability, setting time, freezing temperature, size variation and compressive strength of the mortar at low-temperature were conducted. Compressive strength was increased in use of CSA, aluminate cement with gypsum. Workability and physical properties were improved by using aluminate cement and gypsum. In addition, freezing resistance and physical properties were improved by applying the insulation curing method. Especially, when alumina cement and gypsum were used together, the insulation curing method was more effective in improving the compressive strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.116-127
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• 2014

The studies were carried out to process one cycle for a day to the large section tunnel lining concrete. Climatic characteristics of the tunnel inside are changed, when the temperature of the concrete placement is low, the mold remove time is increased that the heat of hydration speed be delayed because affects the strength development, to compensate for this, after installing the curing sheet on both sides of the steel form and installation of tunnel entrance, when it comes to providing the additional heat source of $28{\pm}2^{\circ}C$ therein, it was to be achieved early strength development control standards (4.5MPa) presented as a crack control scheme or more, thus, It was able to remove after age of 14hr from mold. On the other hand, under the conditions of $10{\pm}1^{\circ}C$ that a natural curing temperature in the tunnel, it was analyzed must ensure the curing time of 36hr or more after concrete placement. Throughout this study, the concrete strength development and the temperature in the early-age concrete, it can find that reverify the curing temperature is greatly affected, even concrete fly ash is mixed 10%, if it is possible to raise the surface temperature for a predetermined time, is not a problem in the early strength development.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.386-392
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• 2020

The self-weight of the 3D printing concrete increases with increasing printing height. Therefore, the lower layer must be hardened within a suitable time to secure continuous printing performance. In particular, the hardening speed of concrete is slow in the winter season when the temperature was low. Hence, the early strength of 3D printing concrete requires improvement. In domestic and international literature, cases of increasing the early strength of concrete using inorganic chemical additives, such as amine-based, nitrate-based, sodium-based, and calcium-based, have been reported. In this study, early strength improvement-type additive samples (amine-based, nitrate-based, sodium-based) were prepared, and their performance was evaluated. When using a nitrate-based additive, the early strength was increased significantly in a 10 ℃ environment. In addition, it was possible to secure a higher early strength than the existing 3D printing concrete mixed at 20 ℃.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.21-29
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• 2021

The objective of this study is to evaluate the effect of the application of double layered bubble sheet on the curing of slab and wall concrete placed at the job site in cold weather and to offer a feasibility of Concrete IoT Management System(CIMS), which is wireless sensor network developed by the authors, to manage early age quality of the concrete in terms of temperature, maturity and strength development. Test results indicated that the application of bubble sheet enhances the insulation performance, which results in an increase of the temperature by around 1~20. 6℃. It is found that CIMS can gather the temperature, maturity and strength development data from the sensors embedded from 30 m far from CIMS successfully. Predicted compressive strengths by CIMS had good agreement with measured ones within 2 MPa error level until 7 days. It is thought that the combination of the bubble sheet application for cold weather protection and CIMS for quality management tool in cold weather concreting contributes to shorten the time for the form removal by one day.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.309-316
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• 2016

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 MPa after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of $C_3S$ by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt's hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at $15^{\circ}C$. Also, it was shown that compressive strength of specimen cured at $5^{\circ}C$ was similar with plain specimen cured at $10^{\circ}C$. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.