【摘要】 本文介绍了β系列三种石膏脱水相——半水石膏、无水石膏(Ⅲ)和无水石膏(Ⅱ)的试验室制备条件。运用XRD,DTA,IR和OM对此三种脱水相进行了鉴定。 通过对水化放热、液相CaO浓度和电导度等的测定,研究了三种脱水相的水化动力学特征,对它们的水化性质进行了阐述,并通过陈化后各脱水相的相变化和水化动力学特征的研究,对熟石膏的陈化机理进行探讨。 水化动力学特征表明:半水石膏进入溶液后,几分钟内产生了二水石膏的过饱和溶液,一小时左右即完成水化过程;无水石膏(Ⅲ)的初始水化速度更快,几乎在接触水后立即就发生形成半水石膏的水化反应,然后再进一步形成二水石膏,使整个水化过程要比半水石膏长,无水石膏(Ⅱ)的活性很低,水化反应非常缓慢。 无水石膏(Ⅲ)的剧烈初始水化作用和未脱水二水石膏的核晶作用是造成熟石膏需水量和凝结时间不正常的主要因素。“陈化”可使无水石膏(Ⅲ)和二水石膏发生相转变,从而改善熟石膏的水化性质。更多还原

【Abstract】 Preparation of dehydrated gypsum phases of β-series in forms of hemihydrates, anhydrite(Ⅱ) and anhydrite(Ⅲ) in laboratory is presented in the paper.XRD, DTA, IR and OMwere employed in the study. Characteristics of the hydration kinetics of the three dehydrated phases were studied bymeasuring the heat of hydration, CaO concentration in the liquid phases and electric con-ductivity.Their hydration properties were described.The ageing mechanism of gypsum plas-ter is discussed in the light of the phase changes of the dehydrated phases and their hy-dration kinetics. Test results show: (1) when hemihydrate is mixed with water,supersaturated solution ofdihydrate is formed in a few minutes and the hydration process is completed in about an hour.(2)Initial hydration velocity of anhydrite(Ⅲ) is much faster.After its mixing with water,hemihydrate forms almost immediately and transforms further into dihydrate and hence thewhole process lasts longer.(8)The reactivity of anhydrite(Ⅱ) is low and the hydration pro-ceeds very slowly. Anomaly in water requirement and setting of plaster is attributed mainly to the vigor-ous initial hydration of anhydrite(Ⅲ) and the nucleation of non-dehydrated gypsum."Ageing"causes phase transformation of both anhydrite(Ⅲ) and gypsum,so that hydration propertiesof plaster are improving.更多还原