铝酸钙水泥、硅酸盐水泥和β-半水石膏混合物中钙矾石的膨胀性能

Expansive Properties of Ettringite in A Mixture of Calcium Aluminate Cement, Portland Cement and β-Calcium Sulfate Hemihydrate

本文利用现场同步加速X-射线衍射、等温量热仪和膨胀测量等手段,研究了在20℃,100%相对湿度下,由25%(重量比)的铝酸钙水泥、12.5%的硅酸盐水泥、12.5%的β-半水石膏和50%的水组成的浆体的水化。水化伊始,首先形成了石膏和钙矾石,同时半水石膏也相应消耗(0-45min内)。随后石膏继续消耗,钙矾石持续形成,2h45min后石膏消耗完毕,铝酸盐-AFm开始形成,同时钙矾石的数量在7h内保持不变。热曲线的第一个峰源自机械搅拌、初始润湿和溶解,还有钙矾石和石膏的形成,第二个峰为石膏被钙矾石所替代,第三个对应于铝酸盐-AFm的形成。石膏被钙矾石替代伴随着0.7%平均线性膨胀。

The hydration of a paste consisting of 25 wt.% calcium aluminate cement, 12.5 wt.% Portland cement, 12.5 wt.% b-calcium sulfate hemihydrate and 50 wt.% water was studied at 20°C and 100% relative humidity, using in-situ synchrotron X-ray powder diffraction, isothermal conduction calorimetry and dilatometric measurements. Initially, gypsum and ettringite form, while hemihydrate is consumed (0±45 min). Ettringite then continues forming at the expense of gypsum. When gypsum is depleted after 2 h and 45 min, aluminate-AFm starts forming, while the amount of ettringite stays constant up to 7 h. The first peak in the heat rate curve includes contributions from mechanical mixing, initial wetting and dissolution plus the formation of ettringite and gypsum, the second maximum involves the replacement of gypsum by ettringite, and the third corresponds to the formation of aluminate-AFm. The replacement of gypsum by ettringite is accompanied by an average linear expansion of 0.7%. D 2001 Elsevier Science Ltd. All rights reserved.