Understanding the synergistic geopolymerization mechanism of multiple solid wastes in ternary geopolymers

Abstract

The use of ground granulated blast furnace slag (GBFS), fly ash (FA) and steel slag (SS) to form ternary geopolymers consumes several industrial solid wastes and produces high-performance construction materials. However, the unexplored synergistic geopolymerization mechanism of multiple solid wastes limits the design of high-performance ternary geopolymers. This study investigated the synergistic mechanism through testing the macroscopic performances such as unconfined compressive strength (UCS), final setting time (FST) and fluidity, and characterizing the microscopic structure of ternary geopolymers with different mixture proportions. In addition, the influence of variables on strength development of ternary geopolymers is analyzed by developing machine learning models. Results reveal that the highest strength of ternary geopolymers was achieved at a ratio of FA to GBFS to SS of 3:5:2, and alkali activator to precursor materials of 0.08. Addition of 20 % SS refines the pore network, reducing cumulative and detrimental pore volumes, thus enhancing compressive strength. In addition, the SS addition extends the heat generation peak during geopolymerization due to its slower reaction kinetics. Material components (Na/Al, Si/Al, Ca/Si) have a significant influence on UCS, with Na/Al ratio being the most sensitive variable. The study provides a new approach for utilization of bulk industrial wastes.