Geopolymerization kinetics of steel slag activated gasification coal fly ash: A case study for amorphous-rich slags. (15th December 2022) - Zhou, Xian
Abstract: The geopolymer processing of amorphous-rich slag required excessive soluble alkali usage severely limiting the application of geopolymer materials. In this study, industrial solid waste steel slag (SS) was introduced as alkali substitution for stimulating the potential activity of Shell gasification coal fly ash (SFA). Result shows that a 15%–20% addition of SS can reduce 14.5–23.3% NaOH consumption for the preparation of high-strength geopolymers. SS accelerates the dissolution rate of SFA promoting the early strength of geopolymer (ES) via alkalinity adjustment and reducing the wetting angle of refactoring globular particles in the slurry. The long-term strength of geopolymer (LS) is increased to 68.5 MPa with the higher devotion of SFA (67 ω%). During the geopolymerization course, Ca-rich hydrates growth are competed with the polymerization of amorphous minerals. The geopolymerization kinetics enlightens that the soluble tetrahedral SiO4 or AlO4 and hydrates in pozzolanic phase initially generated in paste then transformed to a more stable form of amorphous phase after a series of repeated processes of dissolution, homogeneous nucleation, and heterogeneous growth. This work paves a environmentally friendly way for disposing amorphous-rich slags with low activity and discloses the detailed mechanism of related geopolymerization. Graphical abstract: Image 1 Highlights: Soluble alkali could be replaced by steel slag partially by promoting the dissolution of raw materials in alkali activation. Amorphous is the dominant substance in geopolymer based on gasification ash and steel slag could promote the synthesis of geopolymer. The amorphous growth competed with the hydration products then obtained superior containing after periodical homogeneous and heterogeneous processes. A practical and complete recycling approach for massive amorphous-rich slags and steel slag disposal.