Thermal behavior of acidic and alkali activated laterite based geopolymer: a comparative study

摘要

Laterite soils account for 70% of Cameroon territory. The present study aims to investigate the thermal behavior of geopolymer from both thermally activated lateritic clay and indurated laterite at 700 degrees C. The resulting calcined powder was consolidated with phosphoric acid (PA) and alkaline solution (AS), and after 28 days of cure, the geopolymer then was heated at 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C and 1000 degrees C. At room temperature (25 degrees C), applying an acidic medium developed best mechanical performance (85.6 MPa) using highly indurated laterite (CUPA) than clayey-rich laterite (EMPA) that gave 44.86 MPa. Increasing the heating temperature up to 1000 degrees C greatly affected the samples consolidated with an acid solution than with alkaline medium. This suggests the best stability of N-A-S-H than phosphate binder at high temperature. The high performance of acid-activated samples is related to the alteration of iron minerals in acid medium allowing the formation of Fe-O-P bonds, while the decrease in compressive strength with the increase of heating temperature up to 1000 degrees C is related to the dehydroxylation of formed binder phases that weakened the structure.