Dissolution–polycondensation coupling mechanism in clay-derived geopolymer

Clay-derived geopolymers are promising low-carbon cementitious materials, yet their performance in mixed-mineral systems is often limited by mismatched dissolution supply and polycondensation consumption. Here, thermo-mechanochemically activated kaolinite–muscovite blends were studied using solution–solid kinetic measurements and multiscale characterization to quantify dissolution–polycondensation coupling and its impacts on densification and strength. A 70% kaolinite–30% muscovite blend (KM-73) showed synergistic dissolution, with a Si–Al coupling index (CI) of 15% at 6 h. Calorimetry showed a more sustained polycondensation contribution, with a higher late heat increment in the R 3 test (ΔQ (22–168 h) = 260.25 J/g). 29 Si MAS NMR indicated more framework-like gel units in KM-73, with higher Q 4 (3Al) and lower Q 3 contributions. EDS point statistics showed fewer extremely alkali-depleted outliers and a reduced fraction of Si-rich domains, consistent with more effective Na⁺/K⁺ charge balancing at the point scale. Compared with single-precursor systems, KM-73 promoted progressive densification (<20 nm pore-volume fraction = 88.18%) and achieved the highest 28-day compressive strength (45.0 MPa). These results demonstrate that time-scale matching between dissolution supply and polycondensation consumption, together with effective alkali charge balancing, supports sustained network build-up and strength development in clay-based geopolymers.