Structural and Physico-mechanical Investigations of Mine Tailing-Calcined Kaolinite Based Phosphate Geopolymer Binder

This work explores the possibility of using Mine tailing (MT) as a feedstock in the synthesis of phosphate geopolymer binder. MT was activated at different concentrations of phosphoric acid (4, 6, 8, 10 and 12 M). The modification of the Si/Al weight ratio was done by the incorporation of 5, 10, 15, 20 and 25 wt% of calcined kaolinite (CK). After 28 days of curing, the products obtained were analyzed using XRD, FTIR, compressive strength and water absorption. The results of the XRD and FTIR analyses reveal a partial dissolution of the crystalline phase of iron oxide in this medium and the formation of aluminium phosphate hydrate as new crystalline phase. The optimum values of compressive strength (45.5 MPa) and water absorption (3.0 %) show that the binder obtained by activation with 6 M phosphoric acid and 10 wt% CK incorporation can be used in the manufacture of structural materials. Acid activation of MT thus appears as an innovative way to recycle these fine wastes in the synthesis of geopolymer.