作者：I.R. Oliveira;F. S. Ortega;L. R. M. Bittencourt;
作者單位：Materials Engineering Department - Federal University of Sao Carlos, Rod. Washington Liz, em 235, Sao Carlos SP-Brazil;Materials Engineering Department - Federal University of Sao Carlos, Rod. Washington Liz, em 235, Sao Carlos SP-Brazil;Materials Enginee
刊名：Journal of the Technical Association of Refractories
ISSN：0285-0028
出版年：2008-01-05
卷：28
期：3
起頁：172
止頁：179
分類號：TQ175
語種：英文
關鍵詞：
內容簡介Castables with higher fluidity could present longer workability, leading to extended demoulding times. Because the hydration process of hydraulic binders is closely related to strength development, they must be controlled in order to reach the minimum time for demoulding. The control of this process depends on the knowledge of the variables that determine the kinetics of the involved reactions. Thus, in this work the kinetics of hydration process of aqueous suspension of hydratable aluminas and calcium aluminate cements was evaluated by means of electrical conductivity and temperature measurements when they were submitted to different temperatures or the presence of additives typically used in castables (inorganic and dispersants). The reactions involved on the hydration occurred fastly by increasing the temperature from 30 to 50 deg, as the formation of least soluble hydrate (C_3AH_6) was induced, which precipitates in a short time. The inorganic additive Li_2CO_3 also promoted acceleration of the hydrates precipitation stage by reducing the time required for nucleation. Therefore, the effect of inorganic additive was affected by the stoichiometry of ions in solution from dissolution of binders in water. Additionally, it was verified that the additives dispersants, mainly citric acid and diammonium citrate, acted as retarders of the hydration process of calcium aluminate cement, which could be efficiently combined to Li_2CO_3 in order to adjust the demoulding time of the shaped body.
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