Enhancement in the utilization of lime-silica solids for flue gas desulfurization has been experimentally investigated on the basis of their physical and chemical properties. Along the pozzolanic reaction, the utilization of Ca(OH)(2) in the solids increased because of the increase in their BET specific surface area resulting from formation of a calcium silicate phase. Continued hydration of the excess SiO2 after the reaction had been completed, however, reduced the utilization of the sorbent particles because of undesirable precipitation of Si on the silicate. Increases in the initial SiO2/Ca(OH)(2) ratio and the reaction temperature drastically reduced the period of preparation for solids having the same utilization and increased the maximum utilization. It is proposed that the changes in morphology and effective distribution of Si and Ca in the silicate phase were responsible for the latter utilization enhancement.