Cold-sintered laterite-based geopolymers: Densification, microstructure and micromechanics

The consolidation of natural iron-rich aluminosilicates is enhanced using geopolymerisation, external pressure, and temperature in a ultra-low energy sintering context. Optimized formulations of laterite and Rice Husk Ash (RHA) are used to investigate the effects of the external pressure and temperature on the porosity, phases composition development, micromechanics and microstructure. FT-IR spectroscopy, scanning electron microscopy (SEM 0, Mercury Intrusion Porosimetry (MIP), Transmission Electronic Microscopy (TEM), and the Archimedes Porosimetry method were used to characterize the cold sintered products of geopolymerization of the iron-rich aluminosilicate binders and composites. Results showed that ultra-low energy sintering process allows the reduction of similar to 99 % of capillary porosity thank to the physico-chemical bonding and the formation of enhanced nanosized ferrisilicates. The indentation modulus > 50 GPa, the hardness modulus of 3,18 GPa and the fracture toughness > 1 MPa m0.5 are in agreement with the compact microstructure, high bulk density (> 2.00 g. cm(-3)), and low water Absorption. The interlocking of globular units of H-N-(A, Fe)-S with nanosized ferrisilicates leads to high performance ceramics that cannot be achieved with conventional sintering process. Therefore, the cold sintering process demonstrated here is promising for the manufacturing of sustainable matrices using natural iron-rich aluminosilicates.