One-part fly-ash-slag cements activated by a hybrid activator and cured at ambient temperature: multi-factor optimization design and characterization

In the current spiral of alkali-activated materials (AAMs), one-part AAMs based on composite precursors and low-emission reactants meet the majority of current requirements for low-carbon cements and concretes. This study investigates the effects of blast furnace slag (BFS)/fly ash (FA), Ca/Si and Si/Al molar ratios, amorphous phase content, water to solids (w/s) ratio, sodium metasilicate/sodium carbonate (SM/SC) ratio, total Na ₂ O of alkali reactant, on the workability, setting times, compressive strength, and embodied carbon index (ECI) of one-part AAMs. Correlation-regression analyses were used to establish the significance of input variables and optimize one-part AAM formulation. The novelty of the study lies in the fact that for one-part AAMs produced with a binary reactant, the most influential factor affecting flowability and setting times of fresh pastes is SC content. For ECI, the most responsible factor is Na ₂ O, while for CS, the factors are Ca/Si, Si/Al, and amorphous phase. The optimal formulation for AAM proposed involves a CS of 60.5 MPa and an ECI of 1.44 kgCO ₂ /t/MPa. XRD, DSC/TG, and FTIR were conducted to establish the mechanism underlying the reaction products assemblage alterations and the optimality of the arrived AAM formulation.