It is shown that expansible ettringite forms in the topochemical reaction,and crystallizes in-situ on the surface of unhydrated aluminate minerals and orients radially.

发现能够产膨胀的钙矾石是由局部化学反应所；们在未水化的铝酸盐物表面原地结晶，呈放长。

The expansion mechanism of hydroxide expanding phase for oil well cement slurry are discussed on the basis of principle of chemical thermodynamics and topochemical reaction model.

要基于膨胀剂原地反应模型和化学热力学原理，讨论了晶体长压的源动力及水泥浆体体积膨胀与结晶压的关系。