The aim of this study was to help drive the Tunisian construction industry towards a more sustainable approach given the existence of abundant local raw material deposits that could be exploited for the production of low-CO2 binders. Various clay sediments from the Kebili region (southern Tunisia) were characterized by chemical analysis, X-ray diffraction, thermal analysis and geotechnical tests to determine their suitability for the preparation of geopolymer binders. The clays consist of illite and kaolinite with other accessory minerals. To test the possibility of using these materials as precursors for the production of low-CO2 and low-cost geopolymers, the raw samples were calcined and activated by addition of solid sodium silicate. Compressive strength tests performed on four alkali-activated clays show that promising mechanical performance may be achieved, with mechanical strength values as high as 25 MPa after 7 days, depending on the clay composition. The mechanical strength is related to the SiO2:Al2O3 and Al2O3:(NaO2 + K2O) ratios. Careful selection of the raw materials is, therefore, an essential step in the exploitation of clay deposits to be used for the production of ecological materials such as geopolymers.

The recent discovery of a Roman ceramics manufacturing workshop at Montelabate (Perugia, Italy), in use from the first century BC until the late-fourth to fifth centuries AD, offers a unique opportunity to study the technical processes for producing Roman amphorae. Ancient and modern clays were sampled and analysed; they do not differ significantly, supporting the hypothesis of the exploitation of the rich local clay source that allowed a continuity of production. Characterization of the clays was performed using geotechnical methods (Atterberg limits and size distribution) and by thermogravimetric and differential thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray fluorescence analyses. The material was suitable for pottery making with the addition of calcite and quartz sand temper. Production waste and discarded materials as well as good-quality products were also analysed with the same methodology. It is therefore possible to reconstruct the ancient technology by defining the recipe for the production of the amphorae and their firing temperature on the basis of the decomposition of clay materials and the presence of newly formed minerals.