• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.450-456
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• 2022

In this study, as the preliminary research on the development of heating concrete members, compressive strength and accelerated chloride diffusion behavior in the mortar specimens containing C₁₂A₇ based binder and anhydrite was evaluated. Also, the effect of the mixing ratio of the citric acid based retarder was quantitatively evaluated by considering 4 levels of mixing cases. The compressive strength tests of the mortar specimen were performed referred to KS L ISO 679, and the accelerated chloride diffusion tests were performed according to NT BUILD 492 and ASTM C 1202. In the mortar with 0.3 % of retarder, the highest compressive strength was evaluated, which showed the strength development ratio of 127.6 % compared to the control case. It was considered that engineering performance was improved by effectively securing setting and curing time with 0.3 % of citric acid based retarder. As the result of the evaluation of the passed charge and the accelerated chloride diffusion coefficient, the evaluation results had similar behavior with the results of compressive strength. According to the previous study, the strength behavior and the chloride diffusion behavior had a linear relationship. The mixture showing the highest strength performance had the highest durability performance for chloride ingress, and the heating concrete development from this study will be performed in the future.

• Journal of the Korean Ceramic Society
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• v.12 no.2
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• pp.21-25
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• 1975

As the major alumina source, domestic alunite was applied to synthesize the clinker for rapid hardening cement. The main minerals of the clinker were found to be C3S, C11A7-CaF2 and some C4AF by means of chemical treatment, x-ray diffraction analysis and microscopic observation. Rapid hardening cement was made of the clinker by adding suitable amount of hemi-hydrite and anhydrite. The setting time of the cement was regulated with citric acid as setter.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.449-452
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• 1997

Quick hardened property and compressive strength experimented to the C4A3 quantities. Workability experimented to the hydration behavior as retarder added to the C4A3. Compressive strength reached {{{{ delta }}3h=300~350 kgf/$\textrm{cm}^2$, {{{{ delta }}6h=400~450 kgf/$\textrm{cm}^2$, {{{{ delta }}24h=500~550 kgf/$\textrm{cm}^2$. Flow loss rate reached 70.1% to retarder addition 0.12% after 15 min. Test items were SEM, XRD, TG-DTA, MCC, porosity and zeta potential.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.529-535
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• 2007

Calcium oxide has been used as a demolition agent in fracturing rocks and old concrete structures, etc. With the agent, demolition work can be done in safety without a noise, vibration and any other pollution, since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the slurry into boreholes. But application of the non-explosive demolition agent is a time-consuming job, especially in winter. Essentially, this problem is related to the reaction rate of calcium oxide with water. This study examines the influence of additives such as cement and anhydrite on expansion pressure of calcium oxide at different curing temperatures. The expansion pressure of calcium oxide began to increase steadily with the rise of the curing temperature. When mixing calcium oxide alone with water, blown-out shot occurred. But as additives were added to calcium oxide, the reaction of calcium oxide delayed and the expansion pressure showed gradual increment. Especially, anhydrite showed a superior delaying effect than cement on the reaction of calcium oxide.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.144-151
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• 2010

In this study, it is investigated the mechanical chemical properties of cement matrix using phosphogypsum and kaolin as a admixture for the substitutive materials to silica fume which is so expensive. For the test, phosphogypsum is modified as dihydrate, hemihydrate, type III anhydrite, and type II anhydrite, respectively and furnaced kaolin at $900^{\circ}C$ was also manufactured into meta kaolin by air cooling and water cooling method. The chemical characteristic and mechanical properties of various type of blended cements contained above mentioned gypsum and meta kaolin materials analyzed and compared with those characteristics of cement matrix with silica fume. From the test, the cement mixed meta kaolin made in water cooling has more excellent quality than other material.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.410-417
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• 2000

In this study the effects of specifics surface area of cement, addition amount of gypsum and substitution ratio of gypsum anhydrite ont he physical properties of cement mortars were investigated by measruements of setting time, flow, compressive strength and hydration heat evolution rate. The results showed that fluidity of mortars was increased by 40 wt.% of maximum flow change with the decreasing specific surface area of cement from 3,500$\textrm{cm}^2$/g to 3,300${\pm}$50$\textrm{cm}^2$/g and affected by the relationship between the cement and balancing between the chemical activityof cement and solubility of calcium sulfate are desirable to prevent the fluidity of concrete from decreasing by high temperature in summer season.

• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.33-38
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• 1985

The hydration of supersulphated slag cement which is the mixture of granuloated blast furnace slag anhydrite $C_4A_3$ type clinker and calcined dolomite was studied by X-ray diffraction differential thermal analysis scanning electron microscope observation and measurement of the rate of heat liberation. The main hydrates were ettrigite and C-S-H. This supersulphated slag cement enhanced rapid-hardening and increased in strength at early stage due to the much of ettrigite. Furthermore the hardened cement became stronger due to the C-S-H that was produced from the hydration of the $eta$-$C_2S$ in $C_4A_3$ type clinker and the hydration of the dissolved components from slag at later period.

• Journal of the Korean Ceramic Society
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• v.12 no.4
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• pp.3-8
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• 1975

Hydration processes of the rapid hardening cement clinkers, which were synthesized from domestic alunite for major alumina source, limestone, kaolin and fluorite, were investigated by means of x-ray diffraction analysis, thermal analysis and microscopic observation etc. The clinkers were composed mainly of alite, calcium fluroaluminate (C11A7.CaF2) minerals. While the hydratio processes of the clinkers are altered by concentration of SO3 in the paste, calcium aluminate hydrates such as C4AH13, CAH10 and calcium monosulfate hydrate (C3A.CaSO4.12H2O) are formed at first and then some of them are transformed into ettringite(C3A.3CaSO4.32H2O) within 30~60 min. when the concentration of SO3 in the paste are enough. However the formed ettringite are changed slowly into calcium monosulfate hydrate as the concentration of SO3 become lowered, and the paste is hardened with these close-packed minerals. When the content of SO3 in clinker is so enough, calcium sulfoaluminate hydrates are found without any addition of anhydrite or hemi-hydrite.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.242-243
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• 2014

In this study, industrial by-products including blast furnace slag, incineration ash and waste gypsum were used with recycled fine aggregates to manufacture the zero-cement mortar. The replacement ratio of anhydrite gypsum was fixed as 0, 10%, 20% the replacement ratio fo WA1 was fixed as 0.5% and 1.0%, respectively. It could be identified that when the replacement of gypsum was 20% and WA1 of 1.0%, the strength could be in the range of normal strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.222-223
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• 2014

In this study, industrial by-products including blast furnace slag, incineration ash and waste gypsum were used with recycled fine aggregates to manufacture the zero-cement mortar.The replacement ratio of dihydrate gypsum and anhydrite gypsum was fixed as 0 and 10%, the replacement ratio fo WA1 was fixed as 0.5% and 1.0%, respectively. It could be identified that when the replacement of gypsum was 10% and WA1 of 1.0%, the strength could be in the range of normal strength.