The objective of this study was to establish the most suitable mixtures of Tunisian illitokaolinitic clay and industrial wastes (phosphogypsum [PG] and waste brick) to produce geopolymer binders. The raw clay sample was heated at 850 C and characterized by chemical and thermal analyses, X-ray diffraction, and infrared spectroscopy. Four mixtures with different ratios (4%, 8%, 12%, and 16%) of PG as a partial replacement for the calcined clay were investigated. The obtained mixture powders were dissolved in a strong alkaline solution (10, 14, and 17 mol (NaOH)/L) and the produced geopolymers were preserved for 28 days and then characterized by determining their compressive strength. Results showed that increasing the percentage of PG up to 8% reveals an enhancement in the mechanical properties. The highest value of 36 MPa was attained for NaOH concentration of 14 M. At this optimal condition, the calcined clay was replaced by the powder of waste red brick and the produced geopolymer binders had almost the same mechanical property.

Illito-kaolinitic clay rich in hematite from south Tunisia was investigated in view of producing geopolymer materials. Geopolymers with two different densities were elaborated: cement and foam. e effects of activator concentrations on compressive strength, water absorption (durability), open porosity, and bulk density of geopolymers cement were examined, in order to assure optimal geopolymerization conditions. Geopolymer cements aged 28 days with optimum performances were achieved for 13 M of alkaline solution concentration. At these conditions, the compressive strength of prepared geopolymer reaches 27.8 MPa. e addition of silica fume to reactant geopolymer mixture induces modification of geopolymer density and decrease in the compressive strength of the final product. Geopolymer materials based on calcined Tunisian clay can be suggested as sustainable and cost-effective cement that may be applied to alternate Portland cement in many construction applications.

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