Assessment of Physical Properties and Potential Elemental Leaching from Bauxite Tailing-Based Alkali-Activated...

Alkali-activated materials (AAMs) are emerging materials with enhanced properties, including high compressive strength, low shrinkage, adjustable curing rates, resistance to acids and fire, and low thermal conductivity. These materials are synthesized by reacting aluminosilicate-rich precursors with highly alkaline solutions. Given these advantageous characteristics, this study investigates the synthesis of AAMs using bauxite washing clay from the Amazon region. Specimens were prepared with bauxite washing clay and a 1.3 M NaOH solution. The raw material was characterized by using X-ray diffraction (XRD), thermal analysis (TGA-DSC), Fourier transform infrared spectroscopy, and X-ray fluorescence. The specimens were further analyzed by XRD and tested for compressive strength, water absorption, apparent porosity, and acid leaching using HNO₃. The bauxite washing clay sample primarily comprises aluminum- and silica-rich minerals such as kaolinite and gibbsite, making it a suitable precursor for alkali activation. The synthesized specimens demonstrated low water absorption (18.61% ± 0.25) and significant mechanical strength (25.83 MPa ± 1.33). Regarding the potential release of metals and metalloids, the highest concentrations were observed for Al, Si, and Na - key elements in geopolymer formation.