利用磷石膏制备低热、微膨胀复合水泥的研究

为大量利用磷石膏,本文采用在复合水泥中掺加磷石膏的方法,开展了制备低热、微膨胀复合水泥的试验研究,并采用DSC、XRD、SEM及等温水化热仪表征了该复合水泥的水化特征.研究结果表明:磷石膏具有显著的缓凝效果,通过掺加Na2SO4和提高磷石膏掺量的方法,可大幅度缩短水泥的凝结时间、提高水泥的早期强度.当磷石膏掺量超过10％时,水泥水化产物中钙矾石量显著增加,并出现二水石膏,硬化水泥浆体呈现出微膨胀性.通过调整磷石膏的掺量,可控制复合水泥的膨胀率.

Preparation of Low Hydration Heat, Micro-expansive Blended Cements Using Phosphogypsum

To utilize phosphogypsum more efficiently in building materials,low hydration heat,micro-expansive blended cements were prepared by adding phosphogypsum and alkali activator in blended cements.Hydration properties of the blended cements were characterized by DSC,XRD,SEM and isothermal calorimetry.The results show the hydration process of blended cement can be delayed by phosphogypsum.Through adding alkali activator and/or larger amount of phosphogypsum,the setting time of blended cement can be reduced significantly and the compressive strength can also be improved.When the addition of phosphogypsum exceeded 10%,the hardened cement pastes exhibited micro-expansive behavior due to the generation of AFt(perhaps gypsum dihydrate).The expansion ratio of hardened cement pastes can be controlled by adjusting the addition of phosphogypsum.