カロリメーターによる3CaO・Al_2O_3の水和に関する研究 : セメントの凝結におよぼす薬剤の影響に関する研究(第1報)

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It is generally accepted that when portland cement is kneaded with water or the solutions of various chemicals the change in all stages, extending from setting, hardning, and finally to the development of the strength, will be observed, and that the change varies with the nature of the chemicals. And there are already some long period studies of the hydration products and the mechanism of hydration by measuring the rate of heat evolution using ice- and other similar calorimeters. These investigations, however, are limitted to the chemicals familier to the chemistry of cements, namely, gypsume and lime, and also there are only a few papers on the investigations on the initial stage of hydration with relatively large amount of water.Concentrating to the attention to the initial stage of hydration the authors followed up continuously the changes by measuring the heat of hydration of cement past using an adiavatic calorimeter of own construction, and the approach was made to the mechanism of the reaction through the analysis of the kinetics of the reaction. This paper concerns the hydration of 3CaO・Al_20_3 whose rate could be represented by Jander's equation of diffusion in membrane, and which suggested that the rate determining step was the diffusion of the component ions of C_3A through the membrane. Under electron microscope the membrane was observed as the pile of hexagonal thin plates of 300〜500 A and 2〜10 μ thick. The trend of the appearance of the hydration products of all agents, I.e. CaS0_4,CaC1_2,NaOH, suger, and alcohol, single and mixture, was the same except the difference of minor importance, although some of them accelerate and the others retered the hydration. As the reaction mechanism was shown to be the same through out all aditional agents it follows that another physical factors should be taken into consideration in order to interpret the change of the consistency during the setting. On the other hand, the coexistence of CaO, CaS0_4,Na_2P0_4,and Borax showed the linear rate of hydration, suggesting that the reaction proceded at the liquid solid interface. The authors assumed that these phenomena came from whether the reaction proceded without the formation of membrane or the solution was coming in direct contact through the cracks in the membrane. Moreover, in some cases of the addition of sugar and alcohol the hydration stopped completely after the period of violent reaction. In short, the analysis showed that the chemicals gave the very complicated effects from the initial to the final stage of setting.
社団法人日本セラミックス協会の論文
1962-11-01

カロリメーターによる3CaO・Al_2O_3の水和に関する研究 : セメントの凝結におよぼす薬剤の影響に関する研究(第1報)

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