Abstract: A mineral wool waste cement that includes as an addition to portland cement vitreous and non-vitreous mineral wool plant waste materials. A separate ground mineral wool waste cement can be made by feeding mineral wool waste materials above or by feeding blends of mineral wool waste materials and cementitious furnace slags to a grinding plant and thereafter blending the resulting ground product with portland cement. An interground cementitious slag-portland cement clinker can be produced by feeding to a grinding plant portland cement clinker and cementitious slags made from mineral wool waste materials or combinations of mineral wool waste materials and cementitious furnace slags.