Abstract: A cement composition consists essentially of (a) from 50% to 97% by weight (calculated on the total composition) of a Portland cement clinker, the sulfur content of which is from 0.5% to 10% by weight expressed as SO.sub.3 and the fluorine content of which is from 0.13% to 1.00% by weight expressed as F, and (b) from 3% to 50% by weight (calculated on the total composition) of an extender containing a carbonate selected from calcium carbonate, magnesium carbonate, calcium magnesium carbonate and mixtures thereof as its main constituent and having a median particle size (d.sub.50) of below 14 .mu.m. Preferably, the total content of C.sub.3 S and C.sub.2 S in the Portland cement clinker is at least 65%. A preferred carbonate is electrostatic precipitator dust extracted from cement kiln exhaust gases. The cement composition may be mixed with further components such as other extenders, retarding agents and aggregate.