Influence of blast furnace slag type on physical and mechanical properties of Portland cement

Physical properties, grain, chemical and mineral compositions of blast-furnace slags selected from the dumps of JSC 'EVRAZ Nizhny Tagil metallurgical plant' and PJSC 'Nadezhdinski Metallurgical Plant' were studied. Also, the same parameters of granulated blast-furnace slag of JSC 'Mechel-Materialy' currently used by cement plants in the Ural region as a mineral additive during Portland cement grinding were investigated. By chemical composition all of them are acidic. In contrast to granulated slag which mainly contains the vitreous phase dump slags are well crystallized and mainly contain the minerals okermanite, mervinite and monticellite. Dump slags have a Student's t-criterion of more than 15.0, i.e. they can be used as a mineral additive during Portland cement grinding. The introduction of 20 % of the studied slags reduces the water demand of Portland cement of joint grinding and accelerates the setting of the cement paste, reduces the bending and compression strength compared to the additive-free cement. Slag-containing cements after 7 and 28 days of hardening have similar values of compressive strength: 27.2–29.2 and 41.1–43.0 MPa respectively, they are normally hardening and have a strength class of 42.5. Chemical, physical and mechanical properties of these cements meet the requirements of Russian Standard 31108–2016.