• 한국세라믹학회지
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• 제47권5호
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• pp.401-406
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• 2010

For the lower-temperature preparation of calcium monoaluminate(CA, C:CaO, A:$Al_2O_3$) clinker which is hard to synthesize purely within its melting point, an equimolar hydrate was obtained and then used as a starting raw material of clinker burning. The hydrate was prepared from a mixture of waste oyster shell and industrial aluminium hydroxide by heating to $1200^{\circ}C$, grinding and mixing with water. The hydrate was composed of amorphous aluminium hydroxide and $C_3AH_6$(H:$H_2O$) formed by resolution-precipitation mechanism of the system C-A-H. By heating the hydrate, nearly pure and porous calcium monoaluminate clinker was formed at $1400^{\circ}C$ which is fairly lower temperature than that of its melting point. The formation of calcium monoaluminate was performed mainly by the reaction between amorphous alumina and $C_{12}A_7$ caused by the decomposition of $C_3AH_6$. The immediate and earlier formation of $C_{12}A_7$ seemed to be accelerated by not only high surface area and instability of the thermally decomposed hydrate but also the catalytic effect of water decomposed from the hydrate. The final calcium monoaluminate clinker was very porous because of the influence of highly porous shape of the thermally decomposed hydrate.

• 한국세라믹학회지
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• 제27권2호
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• pp.211-218
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• 1990

CA2-based clinker with highly activated surface and hydraulic properties was synthesized at a comparatively lowr temperature than that of conventional synthesis by "hydration-burning method". This consists of calcining the mixture of CaCO3 and Al2O3 to obtain a primary clinker, hydrating the primary clinker and reburning the hydrates to obtain final clinker. Burning of primary clinker above 1200℃ was necessary to eliminate free CaO in it and to obtain it's solid hydrate. However, rising the burning temperature above 1300℃ is ineffective due to the decrease in hydraulic properties of the primary clinker with the temperature. Hydration of primary clinker at the elevated temperature(>35℃) was required to obtain the hydrate with more porous structure and final clinker with more active surface. CA2 was formed and increased with temperature at above 1150℃, finally became a primary phase of the final clinker. However, burning at the temperature above 1300℃ resulted in reverse effect on the hydraulic properties of the final clinker due to rapid decrease in it's surface area with the temperature.

• 한국세라믹학회지
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• 제44권9호
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• pp.517-523
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• 2007

For the preparation of tricalciumaluminate $(C_3A)$ clinker, in traditional clinkering method using oxides and carbonates as a raw material, uneconomical repetition of burning have been necessary to avoid the melting of clinker by eutectic reaction in the system $CaO-Al_2O_3$. In this study, special starting raw materials for the clinker burning were prepared from a mixture of oyster shell and aluminium hydroxide by heating to $1100^{\circ}C$ and hydrating at $30^{\circ}C$. The starting raw materials, hardened body with weak hydraulic strength, were mainly composed of $C_3AH_6$ formed by resolution-precipitation mechanism of the system $CaO-Al_2O_3-H_2O$. By heating them, relatively pure $C_3A$ clinker could be obtained by one-time burning at the fairly lower temperature than that of conventional method. The easier formation of $C_3A$ clinker seemed to be caused by higher compositional homogeneity and stoichiometry of the starting materials, high surface area and crystallographic instability of the thermally decomposed products, and the catalytic effect of decomposed moisture on the early-stage crystallization of calciumaluminates. The basic hydration behavior of the clinker was also confirmed.

• 한국세라믹학회지
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• 제27권3호
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• pp.383-388
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• 1990

Hydraulic properties of CA2-based clinker synthesized by Hydration-Burning Method was studied by calorimetry, analysis of suspension, thermogravimetry, scanning electron microscopy and X-ray diffractometry. Hydraulic properties of the clinker was so activated that heat of hydration of the clinker evolved faster than that of CA synthesized by conventional method. In suspension of W/C=33, dissolution of the clinker began at nearly same time as that of CA, but precipitation of AH3 and rise of [OH-] occurred fairly faster in the suspension of the clinker than that of CA. From the beginning of hydration, AH3 was produced and became a main phase of the hydrate with minor phase of CAH10 and C2AH8, but C3AH6 was not produced at ambient temperature.