Impact of Slag Content and Curing Methods on the Strength of Alkaline-Activated Silico-Manganese Fume/Blast Furnace Slag Mortars

In the reported study, the effect of slag content and curing methods on the strength development of alkaline activated (AA) silico-manganese fume (SiMnF (S)) and ground granulated blast furnace slag (GBSF (G)) blended mortar using NaOHaq and Na2SiO3aq was studied. The mixtures were prepared with 100% SiMnF (AAS100G0), i.e. control binder or 70% SiMnF plus 30% GBFS (AAS70G30), i.e. optimum binder and subjected to room-curing (CR) (25±2 °C) and heat-curing (CH) (60 °C for 24 h in oven) were examined. The raw materials and binders were characterized, while flow and compressive strength of mortar was evaluated. A linear increase in strength was noted in the room-cured specimens, regardless of binder type. The 3-day strength (42.6 MPa) of heat-cured AAS70G30CH specimens was 189 and 97% of the 3-day and 28-day strength, respectively, of room-cured specimens. However, a curing temperature beyond room-temperature did not favour the reaction of AAS100G0 system due to high Mn/Ca ratio and carbonation. It is postulated that the addition of 30% GBFS contributed to the strength and stability in the development of AASG mortar. Heat-curing of AAS70G30CH resulted in highest early-age strength due to dense microstructure induced by conspicuous embedment of Ca ions to the skeletal framework thereby increasing the amorphousity of the binder.