• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.25-32
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• 2004

Some amount of cements can be added into the soil with high water content to improve the engineering properties. In such a case, it is difficult to predict and figure out the phase changes of the soil-cement mixture which is closely associated with workability of the soil-cement mixture. Changes in heat of hydration and hardness of the cement pastes are known to provide the useful information about the phase changes of the soil-cement mixtures. In this study, heat of hydration and cone penetration depth were measured from the specimens of cement paste and 3 soil-cement mixtures. From the experimental results, it was found that the phase changes of the soil-cement mixtures are the same as those of cement paste, and that shear strength of the mixtures abruptly increases when the heat of hydration is minimum. Initial setting time of the mixtures coincides with the state when fall cone penetration depth was 1.0 mm and it is defined as plastic limit of the mixtures. Initial setting time of the mixtures is retarded as soil/cement ratio is increased. Measurements of heat of hydration and fall cone apparatus could be the useful tools to predict the phase changes of tile soil-cement mixtures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.104-105
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• 2020

Red mud is a highly alkaline waste by-product of the aluminum industry. Although recycling of red mud is being actively researched, a feasible technological solution has not been found yet. In this study, we propose that neutralization of red mud alkalinity could assist in its use as a construction material. Neutralized red mud ( pH 6-8) was prepared by adding sulfuric acid to liquefied red mud (pH 10-12). After adding liquid and neutralized red mud to the cement paste, the heat of hydration was measured. As a result of the experiment, the calorific value of the cement paste with liquid red mud was lowered and delayed compared to the cement paste with neutralized red mud.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.228-229
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• 2017

MOCK-UP TEST was conducted in the extreme region of the cement which was researched and developed by using the reducing slag Experimental results show that the basic properties (air volume, slump) are improved compared with the specimens using Mongolian cement. The compressive strength achieved the target strength (target strength: age 3day: 7MPa, age 7day 14MPa) and the hydration heat was about 8 ℃ higher than that of Mongolian cement products. Therefore, it is considered that the cement powders developed by our company showed the strength of concrete due to high hydration heat even at extreme temperatures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.84-92
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• 2014

The purpose of study is to analyze mechanism with early high portland cement and hardening accelerator. As the result, it was concluded that hardening accelerator makes accelerates appearance of $Ca(OH)_2$ through experiment using TG-DTA when it hydrates with cement. On the result of compressive strength, as increasing the amount of hardening accelerator used, early compressive strength was improved. Also, as a result of hydration heat, hardening accelerator accelerates hydration of $C_3S$ that is cement's component. On the result of XRD's analyzation, hydration product for each age could be check and it was shown that as increasing the amount of hardening accelerator used, peak point of hydration product was recorded high. As the result of SEM, appearance of C-S-H was shown as the amount of $Ca(OH)_2$'s appearance and each age according to additive contents of hardening accelerator. Therefore hardening accelerator used on this study is effective on getting early compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.218-226
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• 2013

Of construction materials, cement and steel are the representative material that carbon dioxide. to reduce carbon emissions in the use of these materials The purpose of this study is low heat type blended cement, which is manufactured using a amount of cement than ordinary low heat blended cement. Low heat blended cement, mixing ratio of 10%, was investigated hydration properties and adiabatic temperature of concrete. The study in order to activate the reaction mineral admixture, a separate source of CaO and $SO_3$ areneeded. gypsum and lime, it expected amount of cement, low-carbon low-heat blended cement could reduce the hydration heat concrete than currentlyused low heat blended cement.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.496-501
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• 2007

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the PIC ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.

• Corrosion Science and Technology
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• v.8 no.3
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• pp.110-115
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• 2009

At the onset of corrosion of steel in concrete, hydrogen ions usually evolve in the process of electrochemical reaction, thereby decreasing the pH of the pore solution, which can be buffered by cement hydration products, as being representatively illustrated by calcium hydroxide. Hence, a fall in the pH is dependent on properties of cement hydration (i.e. hydration products and degree of hydration). The present study tested acid neutralization capacity (ANC) of cementitious binders of OPC(Ordinary Portland Cement), 30% PFA(Pulverized Fuel Ash), 60% GGBS(Ground Granulated Blast Furnace Slag), 10% SF(Silica Fume) to quantify the resistance of cement matrix to a pH fall. Cement pastes were cast at 0.4 of a free W/C ratio with 1.5% chlorides by weight of binder in cast. Powder samples obtained crushed and ground specimen after 200 days of curing were diluted in still water combined with different levels of 1M nitric acid solution, ranging from 0.5 to 20 mol/kg. Then, the pH of diluted solution was monitored until any further change in the pH did not take place. It was seen that the pH of the diluted solution gradually decreased as the molar amount of nitric acid increased. At some particular values of the pH, however, a decrease in the pH was marginal, which can be expressed in the peak resistances to a pH fall in the ANC curve. The peaks occurred at the variations in the pH, depending on binder type, but commonly at about 12.5 in the pH, indicate a resistance of precipitated calcium hydroxide. The measurement of water soluble chloride at the end of test showed that the amount of free chloride was significantly increased at the pH corresponding to the peaks in the ANC curve, which may reflect the adsorption of hydration products to chlorides.

• Journal of the Korean Ceramic Society
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• v.36 no.6
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• pp.599-603
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• 1999

In an effort to improve the mechanical properties of the belite cement active belite cement clinker was synthesized. Properties of the clinker were characterized by a XRD, FT-IE optical microscopy and SEM. The additive effects of slag on the hydration properties were investigated by the measurement of compressive strength heat evolution and SEM. The experimental results exhibited that the 3wt% borax was effective in stabilizing $\alpha$'-C2S and the addition of 5wt% anhydrite and 40wt% slag wee effective in the hydration.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.151-152
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• 2023

This study investigates the effect of nano-silica and nano-calcite on the hydration properties and mechanical performance of limestone calcined clay cement (LC³) paste. The pastes were synthesized by replacing limestone with nano-silica and nano-calcite in order to enhance the mechanical properties in both early and late stages of hydration. The nano-calcite enhanced the strength of LC³ pastes at 1 day of hydration, however, the strength decreased compared to the ordinary LC³ pastes afterwards due to excessive amount of carboaluminate produced in the pastes. On the other hand, nano-silica improved the mechanical properties of LC³ pastes at all ages of hydration. This is mainly due to the nucleation effect and pozzolanic reaction of nano-silica, affecting the early age and late ages of hydration, respectively. The nucleation effect of both nanomaterials were confirmed by the analysis of hydration heat, supporting the enhanced early age strength of nanomaterial incorporated LC³ pastes. Furthermore, the dense matrix was shown in the pore size distribution, and the increased C-S-H due to the pozzolanic reaction evidence the improved compressive and splitting tensile strength of nano-silica incorporated LC³ pastes.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.115-125
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• 2015

This study investigated the fluidity, heat of hydration, setting time, strength development, and characteristics of hydration and pozzolanic reactions of high-strength high-volume ground granulated blast-furnace slag(GGBFS) blended cement pasts with the water-to-binder ratio of 20% by experiments, and analyzed the effects of the replacement ratio and fineness of GGBFS on the hydration and pozzolanic reaction. The results show that, in the high-strength mixtures with low water-to-binder ratio, the initial hydration is accelerated due to the "dilution effect" which means that the free water to react with cement increases by the replacement of cement by GGBFS, and thus, strengths at from 3 to 28 days were higher than those of plain mixtures with ordinary Portland cement only. Whereas it was found that the long term strength development is limited because the hydration reaction rates rapidly decreases with ages and the degree of pozzolanic reaction is lowered due to insufficient supply of calcium hydroxide according to large replacement of cement by GGBFS. Also, the GGBFS with higher fineness absorbs more free water, and thus it decreases the fluidity, the degree of hydration, and strength. These results are different with those of normal strength concrete, and therefore, should be verified for concrete mixtures. Also, to develop the high-strength concrete with high-volume of GGBFS, the future research to enhance the long-term strength development is needed.