Influence of glass beads on alkali-activated slag-metakaolin-based novel grouting materials: Physical properties, leaching kinetics and microstructure

Alkali-activated grouting material (AAGM) is widely regarded as a new environmentally friendly material; however, metakaolin (MK) significantly impacts the system's rheology and is typically used as an auxiliary material in most AAGM-related literature. Therefore, this article aims to use MK as the main component and introduces glass microspheres (GB) as admixtures to explore the feasibility of using the GB "ball effect" to improve the overall performance of slag-metakaolin (SL-MK)-based AAGM and systematically studies its influence on the physical properties and microstructure of SL-MK binary mixed grouting materials, to promote the further development of MK in grouting engineering applications; In order to gain a deeper understanding of the reaction behavior of GB as a solid precursor in AAGM, the primary active ions in GB (Si4+, Al3+, and Ca2+) leaching behavior in alkaline solutions. The results indicate that GB demonstrates high reactivity in an alkaline environment. Thanks to GB's particular physical and chemical structure, the overall properties of AAGM are improved. When the GB content is 4 %, the mechanical properties are optimal. Through inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), it was found that the leaching of primary active ions promoted the polymerization reaction of AAGM, and additional gels were generated. Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) analysis further showed that GB also improves the AAGM strength by changing the propagation behavior of cracks in the matrix and the volcanic ash effect. In addition, the enrichment and potential filling effect of C-A-S-H gel contribute to the densification of the entire alkaliactivated material (AAM) system.