• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.883-887
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• 1998

Hydration is the main reason for the growth of the material properties. A exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development all material properties should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The latter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.176-177
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• 2019

As a result of the Rietveld analysis to determine the effect of carbon nanotubes on the hydration products of cement composites, the quantitative difference of hydration products according to the addition rate of carbon nanotubes was not significant. Ettringite, an early hydration product, was measured to be slightly higher than the planes with carbon nanotubes over all ages. Therefore, it seems that carbon nanotubes have no effect on the hydration production in cement paste.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.449-454
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• 1988

The effects of salts which was used as a catalysis in formation of $\alpha$-calciumusulfate hemihydrate from dicalcium sulfate hydrate were investigated on the hydration of $\alpha$-calciumsulfate hemihydrate. The hydration of $\alpha$-calciumsulfate hemihydrate was studied by the measurements of crystalline water, heat evolution. Also the hydrates were analyzed by XRD, DSC and SEM. The promotive effect each salts on the hydration was as follows: NaCl>NH4Cl>NaNO3>NH4NO3, and the hydration rate was accelerated with concentration of salts. The effect of Al2(SO4)3 and potassium sodium tartrate on the hydration was slmilar to water, whereas sodium succinate and gelatin retarded the hydration in comparision with water. These salts affected the hydration time but total heat evoution was similar.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.118-125
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• 2002

Hydration is the main reason for the growth of the material properties. An exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development of all material properties and the formation of microstructure should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of W/C ratio on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The tatter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration. In this study, the effects of chemical composition of cement, W/C ratio, temperature, and moisture conditions on the degree of hydration are considered. Parameters that can be used to indicate or approximate the real degree of hydration are liberated heat of hydration, amount of chemically bound water, and chemical shrinkage, etc. Thus, the degree of heat liberation and adiabatic temperature rise could be determined by prediction of degree of hydration.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.565-566
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• 2009

Supplementary cementing materials (SCM), such as silica fume, slag, and low-calcium fly ash, have been widely used as mineral admixtures in high strength and high performance concrete. Due to the chemical and physical effect of SCM on hydration, compared with Portland cement, hydration process of cement incorporating SCM is much more complex. This paper presents a numerical hydration model which is based on multi-component concept and can simulate hydration of cement incorporating SCM. The proposed model starts with mixture proportion of concrete and considers both chemical and physical effect of SCM on hydration. Using this proposed model, this paper predicts the following properties of hydrating cement-SCM blends as a function of hydration time: reaction ratio of SCM, calcium hydroxide content, heat evolution, porosity, chemically bound water and the development of the compressive strength of concrete. The prediction results agree well with experiment results.

• Computers and Concrete
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• v.9 no.3
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• pp.179-193
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• 2012

The hydration of cement contributes to the performance characteristics of concrete, such as strength and durability. In order to improve the utilization efficiency of cement and its early properties, the particle size distribution (PSD) of cement varies considerably, and the effects of the particle size distribution of cement on the hydration process should be considered. In order to evaluate effects of PSD separately, experiments testing the isothermal heat generated during the hydration of cements with different particle size distributions but the same chemical composition have been carried out. The measurable hydration depth for cement hydration was proposed and deduced based on the experimental results, and a PSD hydration model was developed in this paper for simulating the effects of particle size distribution on the hydration process of cement. First, a reference hydration rate was derived from the isothermal heat generated by the hydration of ordinary Portland cement. Then, the model was extended to take into account the effect of water-to-cement ratio, hereinafter which was referred to as PSD hydration model. Finally, the PSD hydration model was applied to simulate experiments measuring the isothermal heat generated by the hydration of cement with different particle size distributions at different water-to-cement ratios. This showed that the PSD hydration model had simulated the effects of particle size distribution and water-to-cement ratio on the hydration process of cement with satisfactory accuracy.

• Journal of the Korea Institute of Building Construction
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• v.2 no.2
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• pp.145-150
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• 2002

The hydration of cement paste occurs when the cement is miked with water. During the hydration, hydration heat causes the thermal stress depending on the site of concrete and the cement content. Especially in the high-strength concrete, we must give care to the concrete due to its large cement content. In this study conduction calorimeter and concrete insulation hydration heat meter were used to investigation the hydration heat characteristics of cement and concrete. To reduce hydration heat of high-strength concrete, several types of replacement of fly-ash and blast-furnace slag powder were used in this experiment. As a result of this study, it was found that hydration heat of high-strength concrete was reduced by replacement of fly-ash and blast-furnace slag powder. In case of high-strength concrete using blast-furnace slag powder, the max-heat arrival time was delayed but an effect of heat reduction was lower than a case of high-strength concrete using fly-ash, because it was considered that the heat-dependence property of blast-furnace slag powder was higher than that of fly-ash.

• Journal of the Korean Ceramic Society
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• v.33 no.8
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• pp.889-894
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• 1996

This study was subjected to the stabilization of heavy metals using DSp cement. Heavy metal Cr and Pb ions were mixed with cement paste and hydration behavior and leaching property by heavy metal were exami-ned. It was found that, Cr ion accelerated the early hydration of the cement and has no accelerating effect in later hydration period. However Pb ion retarded the hydration of the cement for a early hydration periods. As a result of leaching test the quantity of leachant has a very low value and the influence of leached heavy metal effected on the environments is very weak.

• Journal of the Korean Wood Science and Technology
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• v.21 no.3
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• pp.74-81
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• 1993

This experiment was carried out to investigate the reaction of hydration of paper sludge during the setting of portland cement in a paper sludge, wood-cement-water mixturte. The percentage of paper sludge per cement is 7.5%, 15%, 30% respectively. The result indicated that the sludge of 7.5% had the most effect on reaction of hydration, and the sludge of 15% had moderately inhibitory effect but there is still possibility to make sludge-cement board. Paper sludge of 30%, Pinus koraiensis Sieb. et Zucc and Populus euramericana Guinier were proved to have the worst inhibitory effect on cement hydration, so pretreatment will be needed before making board with paper sludge-cement mixture.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1055-1063
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• 1990

The early hydration characteristics of the system $C_3S-C_3A-C_4AF$ according to the clinker composition variations, in order to establish the mutual interactionof clinker minerals during the portland cement hydration, have been studied. The early hydration rate of $C_3S$ was greatly effected by the change of $C_3S/C_3A$ ratio. The lower the $C_3S/C_3A$ ratio was, the faster the apex reaching time and the rate of heat liberation of the 2nd exothermic peak originating from the formation of $Ca(OH)_2$ were. The effect of $C_3S/C_3A$ ration on the amounts of $Ca(OH)_2$ formation was decreased, in process of hydration time, but the effect of $C_3S$ content was increased.