Expansive cement compositions for use in subterranean wellbores that include a monophase amorphous hydraulic binder material (MAHBM). The MAHBM may include a plurality of particles having a silica core and an amorphous coating substantially surrounding the silica core. The coating may comprise, for example, a plurality of amorphous α-dicalcium silicate hydrate nanoparticles or microparticles. The MAHBM may be used as an expansion agent in a cement composition or used as an expansive cement by itself.