DISTRIBUTION OF SULFATES IN PORTLAND CEMENT CLINKER

摘要

A method for predicting the distribution of SO_3 between the sulfate and non-sulfate phases is presented. The method uses the phase rule and the phase diagram for the K_2SO_4-CaSO_4 system to identify the range of temperature and composition across which the solid solution of sulfates in the silicate phases can increase as a function of increased sulfate content in the system. More specifically, it is predicted that the content of SO_3 in the silicates will increase as a direct function of increasing SO_3/K_2O ratios, and that above the SO_3/K_2O ratio necessary for anhydrite formation, the concentration of SO_3 in the silicates will remain constant. This model was tested on experimental data for both industrial and laboratory clinker and found to be essentially valid. The maximum possible content of SO_3 in belite was found to be approximately 2 wt% in rapidly cooled laboratory clinker, and 1.5 wt% in industrial clinker.