Abstract: A kind of cementing material with a mass proportion of sea-discharged ash (SDA) is prepared with solid SDA as the main raw material and a small amount of rock forming agent composited by several minerals.  Its hydrates and paste structures at different ages are analyzed using XRD, SEM and FTIR. The results show that ettringite is one of the main sources for the early strength of this cementing material; its hydrates mainly occur in frame-structural silicon oxygen tetrahedral gel with high polymerization degree, in addition to some chain-structural CSH gel; and with the hydration going on, the content of Ca(OH)₂ decreases gradually along with an increase in the polymerization degree of silicon oxygen tetrahedron and a gradually denser paste structure.

Key words: Sea-discharged fly ash, Cementing material, Hydrate, Paste structure