The belite material produced from limestone and waste silica was the subject of numerous investigations. In order to improve
the hydraulic activity, some amount of barite was added to the raw mixture. The properties of belite phase were studied by
use of differential thermal analysis, calorimetry and other methods. The influence of barium on the hydraulic activity of
belite has been thus confirmed. The hydraulic activity increase in the presence of barium depends on the stabilizing action
of additive accompanied by the proper thermal treatment in the α′-Ca2SiO4 stability range.