Engineering properties, phase evolution and microstructure of the iron-rich aluminosilicates-cement based composites: Cleaner production of energy efficient and sustainable materials

This paper investigates the direct transformation of laterites (natural iron-rich aluminosilicates) to cementitious composites with principal mineral phases being Gismondine and Stratlingite. The effects of particles size distribution and cement content (2 to 8 wt%) on the mechanical properties and microstructure of laterite-cement composites are assessed. Four grades of granulometry with various percentages of fine and coarse particles were considered. The Environment Scanning Electron Microscopy (ESEM), Mercury Intrusion Porosimetry (MIP), Fourier Transformed Infrared Spectroscopy (FT-IR) and X-ray Powder Diffractometry (XRD) were performed after 1, 90 and 365 days, to assess the phase's evolution, mechanical performance and the microstructure of the laterite-cement composites. It is found that fines particles, essentially pozzolanic and amorphous, are responsible for the bonding strength while coarse particles improve the compressive strength. Dense and compact microstructure, water absorption under 18% and flexural strength above 6 MPa (compressive strength > 30 MPa) could be achieved as from 4 wt% of cement making the laterite-cement composite appropriate as building and construction materials. The choice of a highly corroded class of laterite and the selection of the particle size distribution allows the production of optimum composite that is presented as energy-efficient and sustainable. Thus, corroded or indurated laterites are considered as “green metakaolins” which do not require any energy for their transformation unlike clayey materials.