This study addresses the current lack of insight into the microstructure evolution of cast geopolymers produced by combining two different precursors. Detailed investigations of micro- and nano-porosity developed during geopolymerization as a function of curing time are carried out and, for the first time, 1 H Time-Domain Nuclear Magnetic Resonance is applied diffusely. The results show that the metakaolin replacement with 35% ceramic tile waste addition induces coarsening of pore size distributions in the 0.08-1 μm range and a reduction in gel content. Furthermore, although a delay in the development of the 3D network was observed, the gel formation process was still completed within 24 hours, in contrast to the 5–6 hours required for 100% metakaolin geopolymers. These differences in microstructural evolution are also reflected in the development of compressive strength. • Combined precursors influence early-age microstructure. • Integrated MIP, N 2 adsorption, and 1 H TD-NMR analyses provide detailed microstructural insight. • Mechanical property–microstructure correlations guide formulation optimization.
Masi et al. (Sun,) studied this question.