Structural build-up of slag-based geopolymer at early stage: Role of ionic correlation and hydrates bridge

Structural build-up behavior of slag-based geopolymers at early stage is vital for its applications like 3D printed concrete or shotcrete. However, the underlying mechanism remains poorly understood. The static yield stress development of slag-based geopolymer with silica fume as rheological modifier is investigated and the enhancement mechanisms are explored. Results reveal that the addition of silica fume leads to stronger ionic correlation interaction between precursor particles, enhancing the percolation particles network and increasing the static yield stress. The formation of C-A-S-H hydrate bridges dominates the development of yield stress at later ages, and the negative impact of silica fume could be related to its retardation effect on hydration. Furthermore, a new mathematical model is proposed and validated to describe the relationship between static yield stress and bound water content. For the first time, it is found that the enhanced hydrates bridge contributes to the nonlinear growth in static yield stress, providing a new insight into the structural build-up of fresh geopolymer.