One-Part Fly-Ash-Slag Cements Activated by a Hybrid Activator and Cured at Ambient Temperature: Multi-Factor Optimization Design and Characterization
摘要
In the current trend of alkali-activated materials, one-part alkali-activated materials based on composite precursors and low-emission reactants meet most current requirements for low-carbon cements and concretes. This study examines the effects of blast furnace slag/fly ash, Ca/Si and Si/Al molar ratios, amorphous phase content, water to solids ratio, sodium metasilicate/sodium carbonate ratio, and total Na2O of alkali reactant on the workability, setting times, compressive strength, and embodied carbon index of one-part alkali-activated materials. Correlation-regression analyses were used to determine the significance of input variables and optimize the formulation of one-part alkali-activated materials. The novelty of the study lies in the finding that for one-part alkali-activated materials produced with a binary reactant, the most influential factor affecting flowability and setting times of fresh pastes is the sodium carbonate content. The most significant factor for the embodied carbon index is Na2O, while for compressive strength, the factors are Ca/Si, Si/Al, and amorphous phase. The optimal formulation for alkali-activated materials proposed involves a compressive strength of 60.5 MPa and an embodied carbon index of 1.44 kgCO2/t/MPa. XRD, DSC/TG, and FTIR analyses were conducted to understand the mechanism behind the changes in reaction products assemblage and to confirm the optimality of the formulated alkali-activated materials.