Abstract
•Alkali-activated SMF-BFS blended mortar can be applicable for both cast-in place and pre-cast components.•Oven-curing at 60 °C for 24 h resulted highest 3-day strength (42.6 MPa) and insignificant later strength gain.•Oven-curing at 60 °C for 6 h was found optimum for medium early strength (38 MPa) and linear thereafter.•Water- and room-curing yielded low early strength but later strength gain was exponential.•Formation of Mn-C-S-H, C-(A)-S-H, K-A-S-H contributed to strength skeleton.
In the reported study, silico-manganese fume (SMF) was developed into an alkali-activated binder (AAB) in combination with blast furnace slag (BFS) by adding NaOH and Na2SiO3. The effect of curing on the resulting AAB was studied by water-ponding, ambient-curing and heat-curing. In the first phase, the period of oven-curing (3–24 h) at 60 °C was optimized. This was then followed by optimizing the oven-curing temperature (25–95 °C) within the period of 6 h. Good synergy of precursors exhibited acceptable fresh properties and formation of notable phases like C-Mn-S-H, K-A-S-H, C-(A)-S-H that were responsible for strength skeleton. Early-age compressive strength gain was approximately 50% of the 28-day maximum values of 46.4 and 43.5 MPa obtained in water- and ambient-cured specimens, respectively. On the contrary, the 3-day strength gain of 42.6 MPa was recorded in oven-cured (60 °C) specimens with linear increment with time up to 24 h. However, a curing period of 6 h was considered optimum from energy and cost benefit points of view. This registered 3-, 7- and 28-day strength of 38, 41 and 45.2 MPa, respectively due to increased crystallinity of the C-A-S-H and quartz phases. The morphology of specimens cured by water-immersion, room temperature and optimum oven conditions was homogeneous, dense and consisted lesser traces of unreacted particles favored by high degree of dissolution and polymerization due to formation of stratlingite and gehlenite that acted as a crack filler and pore blocker.