• International Journal of Highway Engineering
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• v.11 no.2
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• pp.229-238
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• 2009

This paper describes the methods to propose the optimal material properties and construction steps that prevent cracks due to the thermal stresses induced by the hydration heat under the construction of the concrete underpass structures. To achieve the goal of this study, the heat transfer theories were employed and the three-dimensional finite element model of the underpass structure was developed and used for the structural analyses. If the volume of the concrete member that is placed at one time is significantly large, the member is assumed to be the mass concrete and is easy to induce cracks. In order to minimize the cracks during the construction, two different methods can be utilized: one is to arrange the construction steps optimally and the other is to change the materials to reduce the probability of the crack occurrence. In this study, the analyses were performed by considering the changes in material properties with time, the characteristics of the hydration heat generation for cements and admixtures, the volume of the concrete placement at one time, and the environmental conditions.

• The Korean Journal of Food And Nutrition
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• v.27 no.2
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• pp.294-301
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• 2014

Rice (Oryza sativa L.) is one of the most important staple foods in Korea and the consumption of brown rice is increasing annually. The objective of this study is to investigate the physicochemical, hydration and textural properties related to eating quality of cooked brown rice by using glutinous, semi-glutinous, four non-glutinous and four colored varieties. The moisture, protein and total dietary fiber contents of brown rice are shown in the range of 11.1~12.6%, 6.6~8.7% and 6.28~12.40%, respectively. The amount of water uptakes for brown rice during the hydration has shown significant differences. The glutinous variety of Boseogchal indicate the highest water absorption levels by reaching $0.38gH_2O/g$. The hardness of hydration for Seolgaeng is distinctively lower than those of the other brown rice varieties. According to the textural characteristics of cooked brown rice when using the Tensipresser, the hardness of Boseogchal, Baegjinju and Seolgaeng all exhibit the lowest values out of ten varieties and the highest levels of adhesiveness.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.665-672
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• 2016

This study is conducted to investigate the effect of phase change materials (PCM) on hydration heat and strength characteristics of cement mortar. Two types of Barium and Strontium-based PCMs were used in this study and the addition ratio of each PCM to the cement mortar ranged from 1% to 5% by cement weight. Flow test, semi-adiabatic temperature rise test, compressive strength and flexural strength test were carried out to examine the PCM effect on heat and mechanical properties of cement mortar. Test results indicated that PCMs used in this study were effective to control hydration heat of cement mortar, and Barium-based PCM slightly reduce flow value. The compressive and flexural strength of cement mortar with PCM decreased with increasing the adding mount of PCM. The prediction model for compressive strength of cement mortar with different addition levels of PCMs are suggested in this study.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.10
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• pp.207-215
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• 2019

The aim of the research is analyzing the simple adiabatic temperature rising properties and the heat of hydration based on different placing timing of the mass concrete depending on various replacing ratios of blast furnace slag to comparative analyze the thermal cracking index and cracking possibility. As a result from the experiment, a suggested adiabatic temperature rising equation based on various blast furnace slag replacing ratios can be provide favorable correlation with over 0.99 of $R^2$ value by applying the initial induction period. With this relationship, more accurate prediction of the amount of the hydration heat rising and heating timing, and it is known that there is an approximately $13.1^{\circ}C$ of gap between plain concrete without blast furnace slag and concrete with 80 % of replacing blast furnace slag. To control the setting time and heat rising gap, the mix designs between top and bottom concrete casts were changed 15 cases, and D, E, H, I, and L models of controlling the heat of hydration showed 41.23 to $46.88^{\circ}C$ of core temperature and 0.98 to 1.27 of thermal cracking index. Therefore the cracking possibility was 15 to 52 % of favorable results of possibly controlling both the cracking due to the internal and external retainment and concrete temperature at early age.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.612-615
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• 2004

The objective of this experimental study was to understand inelastic strain of concrete incorporating hwangtoh or combination of hwangtoh and slag. Main variables were replacement level of admixtures, hwangtoh and slag. We studied the properties of concrete such as heat of hydration, drying shrinkage and creep according to the replacement level of hwangtoh and slag. Test results showed that the heat of hydration of concrete decrease with increasing hwangtoh and slag replacement. Also drying shrinkage and creep of concrete increase with increasing hwangtoh replacement.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.147-152
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• 1999

The purpose of this study is to offer foundmental information of fly ash concrete for field application. Through before study of fly ash concrete, various properties were checked. but when fly ash was added In concrete, entrained air quantity was decreased as fly ash substitution is increased in fresh concrete. so entrained air(below AE) quantity and a kind of AE according to fly ash substitution was tested basic properties. Also water-reducing efficiency was tested. And hydration heat according to fly ash substitution was tested by KR-100. As result of test, according to fly ash substitution increase, entrained air quantity is increase for target entrained air quantity, water-reducing efficiency and hydration heat are positive.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.683-686
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• 2005

This paper is related to investigate adding effect of fluorine-silicate hybrid type crack controlling agent(FS) on initial behavior, dynamic properties, adibatic hydration temp, and plastic crack behavior of concrete(Specification : 25-30-18). It is appeared that adding of FS contributed to strength elevation, lowering of hydration temperature as well as plastic crack reduction without disturbance of initial behaviors of concrete such as slump, air content and setting.

• The Korean Journal of Ceramics
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• v.3 no.4
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.203-204
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• 2010

In this study, We synthesized new generation of superplasticizer(SP) which show a shrinkage reducing effect as well as water reducing effect with adequate slump retention in a wide range of water cement ratio by introduction a shrinkage-reducing group into the molecular structure. To investigate effects of the SRS on the hydration of cement, DSC have been analysed. Also the general and shrinkage properties of the concrete were evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.259-260
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• 2010

This study is to investigate each mix property and physical properties and reduction properties of heat of hydration as basic experiment of reviewing the applicability of low calorific concrete.