Abstract: The calcination process for activating fly ash with Na₂CO₃ as accessory ingredient was investigated.The concenta- tions of Si and Al in the fly ash activated under different calcination conditions（calcination temperature and calcination time）， that dissolved in the sodium hydroxide solution were measured by titering process.The phase composition of fly ash obtained under different calcination conditions（mass ratio of fly ash and sodium carbonate） was characterized by XRD.The best process parameters were obtained as follows：calcination temperature was 875 ℃，holding time was 1.5 h，and mass ratio of fly ash and sodium carbonate was 1∶0.87.The products after calcination were mainly made up of soluble NaAlSiO₄ and Na₂SiO₃，and the quartz and mullitein in the raw fly ash both almost disappeared.Therefore，the fly ash was activated adequately.

Key words: fly ash, calcination, sodium carbonate, process parameters