Abstract
Hydration reaction of a calcium sulfoaluminate-type expansive additive (CSA)-Alite system was investigate at a quantitative viewpoint. Free lime and anhydrite rapidly reacted at initial period but hauyne did slowly. In special, at early days, the anhydrite showed extremely high reaction ratio. As the formed hydrates, calcium hydroxide and ettringite could be identified. And, from materials balance of the hydration, presence of a large amount of gel was presumed. SO3 contents in the gel showed a high value within 1 in reaction period, and after reducing to half value by 3d in reaction period, it showed a nearly constant value. As a result of investigation on forming mechanism of the ettringite, it was thought that at initial period SO42- was adsorbed on C-S-H, and that after a matrix was formed, it reacted with hauyne and aluminate hydrates to form the ettringite in the matrix.
