Evolution of room-cured alkali-activated silicomanganese fume-based green mortar designed using Taguchi method

Abstract This paper presents the results of a study conducted to synthesize alkali-activated mortars (AAMs) at room temperature. The AAMs were prepared using silicomanganese fume (SiMnF) and ground granulated blast furnace slag (GGBFS) as precursor materials (PMs) and sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as alkaline activators (AAs). The composition of the AAMs was designed and optimized using the Taguchi method. Five factors with four levels each were investigated in this study, including the ratio of GGBFS to PMs (0–4.5), sand to PMs ratio (1.5–2.4), molarity of NaOH (4–10 M), Na2SiO3/NaOH ratio (2–3.5) and AAs to PMs ratio (1.5–2.4). Based on the orthogonal array proposed by the Taguchi method, 16 AAMs were cast with varying flow and unit weight to evaluate the compressive strength at 3, 7 and 28 days. The strength data was statistically analysed by employing ANOVA and response surface methods to investigate the effect of experimental variables. AAM with 30:70 proportion of GGBFS and SiMnF, Na2SiO3/10 MNaOH of 2.5, AAs/PMs ratio of 0.5 and sand to PMs ratio of 1.5 attained optimum strength. Based on the SEM and EDS analysis, the molar ratios among the major constituent elements intertwined in the cemented matrix were established which contributed to the formation of alkaline products and microstructural densification of the optimum mixture.