HYDRATION IN THE SYSTEM CA2SIO4-CA3(PO4)2 AT 90-DEGREES-C

Compositions along the Ca2SiO4-Ca3(PO4)2 join were hydrated at 90-degrees-C. Mixtures containing 15, 38, 50, 80, and 100 mol% Ca3(PO4)2 were fired at 1500-degrees-C, forming nagelschmidtite + a'-CaSiO4, A-phase, and silicocarnotite and a-Ca3(PO4)2, respectively. Hydration of these produces hydroxylapatite regardless of composition. Calcium silicate hydrate gel is produced when Ca2SiO4 not-equal 0 and portlandite when Ca2SiO4 is >50%. Relative hydration reactivities are a-Ca3(PO4)2 > nagelschmidtite > alpha'-Ca2SiO4 > A-phase > silicocarnotite. Hydration in the presence of silica or lime influences the amount of portlandite produced. Hydration in NaOH solution produces 14-angstrom tobermorite rather than calcium silicate hydrate gel.