Application of Plackett–Burman and Box-Behnken designs for the optimization of Tunisian dam sediment-based geopolymers

Abstract

In this study, Tunisian dam sediment (Bir Mcherga) was used as a raw material for the preparation of geopolymeric materials. The main minerals phases present in this sediment are quartz, calcite, illite, muscovite, kaolinite and amesite. The sediment was activated by heat treatment at 700 °C. Seven active factors, including L/S ratio, curing temperature, heating time, particle size, holding time, nature and concentration of the activating solution, were screened through Plackett and Burman design in order to determine the significant factors. Then, three significant parameters that mainly affected the compressive strengths of the samples which are L/S ratio, curing temperature and concentration of activating solution, were selected for further optimization using Box–Behnken design. It was found that the optimum mix design with L/S ratio of 0.88, concentration of NaOH of 6 M and curing temperature of 34 °C produced the highest 14-days compressive strength. The sample whose composition is closest to the optimum was characterized by X-Ray Diffraction, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. As a result, this dam sediment exhibit poor geopolymerisation potential that leads to low compressive strength.