Influence of blast-furnace slag on behaviour of dolomite used as a raw material of MgO-type expansive agent

The content of MgO in cement is restricted to less than 5% (by weight) because of its expansive character. However, the cement, called dam cement, containing MgO more than 5% is used in both research activities and industrial applications. Turkey is rich in dolomite reserves and dolomite is abundantly found in several regions of the country. In this study, influence of blast-furnace slag (BFS) on expansion properties of dolomite was explored. Portland Cement (CEM I 42.5R) was replaced with dolomite up to 40% and blast-furnace slag up to 20%. Hydration heat, setting times, soundness and micro-structures of paste samples and compressive strength and length change of mortar samples were measured. As a result of experimental studies, dolomite used instead of cement caused up to 1.75 mm expansion. The results are in accordance with the values indicated in the standards. As a conclusion, it is possible to use blast-furnace slag in balancing the expansion properties of dolomite.