  Crystalline calcium-aluminates include the phases essential in the setting of
Portland cements developed over the last century. It is only within recent
decades, however, that calcium-aluminate melts and glasses have begun to
attract attention, bringing new functionalities in photonic and electronic
applications. These studies, though, have been limited to compositions close to
a deep eutectic from where glasses easily form. With the development of
contactless levitation furnaces the glass forming region can now be hugely
extended. We have taken advantage of these developments to rationalise, for the
first time, melt rheology with structural properties across this expanded
compositional range, substantiating this with atomistic simulation. In the
process, we have discovered that supercooled calcium-aluminates comprise a new
system where fragile-to-strong phase transitions are ubiquitous. Taking this
holistic approach, we have quantified the common basis of thermo-physical and
structural diversity in this novel glass-forming system, together with its
inherent polyamorphism.
