Why does it harden too slowly when producing magnesia cementitious materials?

the main raw material of magnesia cementitious materials is natural magnesite, which is calcined to obtain light burned magnesium oxide. When magnesium oxide is hardened with water, it is mixed with salt solution to obtain magnesia cementitious materials, mainly magnesium oxychloride and magnesium hydroxide. Magnesium hydroxide is insoluble and covers the surface, which prevents the reaction from proceeding further, so the hardening is very slow.