Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

Abstract

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.

Mechanical Properties of Alkali Activated Material Based on Red Clay and Silica Gel Precursor

“…Illite clay has been valorized as a substitute of metakaolin in the synthesis of new geopolymeric materials and compressive strength reached 23 MPa, while hybrid system with 50 % metakaolin could reach 40 MPa [14]. Similar result was obtained by Ounissi et al which reached strength of 25 MPa at the age of 7 days [11]. Calcined illite clay chemical treatment with an 8 M NaOH solution can also lead to the formation of the zeolites and sodium aluminium silicate hydrate [15].…”

“…It has been reported that the red clays in Thailand have high potential to produce low-cost geopolymers [10]. Illite clay calcining temperature varies between 600-900 °C while the most cases select 800 °C [11], [12]. Some reports state that it has not yet been possible to synthesize meta-illite-smectite-based geopolymers of high strength (>20 MPa) without the addition of ____________________________________________________________________________ 2021 / cement additives [13].…”