Relationship between MO/(SiO2+Al2O3) of materials-amorphous gel structure-properties of the one-part FA-Slag-based AAMs

The study investigates the impact of different amorphous gel structure by MO (CaO+Na2O)/(SiO2+Al2O3) ratios (specifically 0.66, 0.69, 0.73, 0.76, 0.84, and 0.90) on the fresh and hardened properties of one-part alkali- activated materials (OP-AAMs) derived from fly ash-slag. Unlike traditional two-part AAMs, the "just-add-water" preparation process of OP-AAMs facilitates the transition of geopolymer products from laboratories to the engineering field. Higher (CaO+Na2O)/(SiO2+Al2O3) ratios in fresh pastes promote the dissolution of active aluminosilicate in the alkali-activators, resulting in the formation of Si-rich gel with low-Al amorphous gel. This leads to reduced setting time, increased fluidity, and the occurrence of a viscoelastic phenomenon in the fresh properties. Throughout the geopolymerization process, the main product with the shortest mean chain length and higher Si/Al ratios is the C-(N)-A-S-H and N-A-S-H gel in the (CaO+Na2O)/(SiO2+Al2O3)=0.76 composition, which exhibits the highest 28-day compressive strength of 46 MPa. The findings highlight the potential of OPAAMs and provide insights into the adjustment mechanism of MO/(SiO2+Al2O3) ratios to optimize the properties of OP-AAMs for engineering applications.