A slag cement includes ground granulated blast furnace slag and ground limestone combined in a predetermined weight ratio. Limestone and granulated blast furnace slag (GBFS) are fed to a grinding apparatus in a ratio of about 3-5% limestone by weight. The limestone is a cheaper raw material than the GBFS, resulting in a reduction in production costs for the slag cement. Moreover, the addition of limestone to the GBFS surprisingly results in improved compressive strength.