This study explores the Taguchi fractional factorial design-of-experiment methodology to optimize alkali-activated pastes made with ground-granulated blast-furnace slag (GGBFS) and a novel combination of sodium silicate and Brucite slurry as alkali activators. The research aims to respond to the need for greenhouse gas emission reduction in the atmosphere by introducing Brucite slurry as a substitute for traditional caustic alkaline activators, i.e., sodium and potassium hydroxides. Preliminary findings of the study revealed the potential of prepared pastes for solidifications under ambient curing; indicating the higher potential for being optimized using the Taguchi method. An L9 orthogonal array was used to conduct the Taguchi design of the experiment, varying three factors: the sodium silicate-to-Brucite slurry ratio, Brucite slurry concentration, and the curing temperature. While the strength-oriented optimal was reported through the use of the plot of means, the influence of each factor on the strength result was analyzed using the analysis of variance (ANOVA). The study objects to develop a sustainable alternative to Portland cement by revolutionizing construction practices that could be used in 3D printing applications. To the knowledge of the authors, this research is the first to use Brucite slurry in the activation process of GGBFS pastes; offering a promising pathway for reducing the carbon footprint of the concrete industry.