This study deals with the microstructure and property profile of biomaterials within the Ca-aluminate system (CA). Hydrated CA materials are stable in bone tissue, and thus not resorbable as the Ca-phosphate materials are. Identified possible applications for CA-based materials are within vertebroplasty and odontology. CA with ZrO2 particles as well as CA with glass particles were examined with regard to mechanical properties, biocompatibility and bioactivity. The hydrates formed - examined by HRTEM - are in the size range of 20-50 nm. With the studied systems it is possible to obtain a combination of high and early strength, shape stability including low expansion pressure, and in vivo bioactivity.