Performance of geopolymer composites made with feldspathic solid solutions: Micromechanics and microstructure

This study investigates the high performance of feldspathic solid solution-based geopolymer composites. The results show that a feldspathic solid solution with incongruent dissolution in an alkaline medium produces a differential amount of N-A-S-H+ polysialate geopolymer, depending on the mineral nature of the raw solid precursor. In turn, the presence of both N-A-S-H and polysialate geopolymer reduced the cumulative pore volume to a nanometric size, leading to flexural and compressive strengths in the range of 26–36 MPa and 86–100 MPa, respectively. The limited dissolution in the alkaline medium of the feldspathic powders allowed for a direct correlation among the Young modulus, the hardness, and the N-A-S-H + polysialate geopolymer. The findings show that when the amount of N-A-S-H and polysialate geopolymer is sufficient to cover the incongruent dissolved grains of solid solutions with no excess of geopolymer gel, the bonding strength developed exhibits high mechanical performance in the final composite The results confirm the possibility of reproducing dimensioned stones by geopolymerizing the feldspathic solid solutions.