The present invention relates to a carrier composition for particulate and granular bone substitute materials which is a hydrogel comprising a mixture of ethylene oxide (EO)-propylene oxide (PO) block copolymers and silica nanoparticles embedded therein. The present invention further relates to a bone substitute material containing osteoconductive and/or osteoinductive particles or granules in addition to the novel carrier composition. Processes for producing the novel carrier composition and the novel bone substitute material are likewise provided in the context of the invention.