Elaboration of geopolymer binders from poor kaolin and dam sludge waste

The aim of this study is to synthesize geopolymer binders as an ecological alternative for conventional cement. It is intended to have geopolymer binders with molecular composition close to (4SiO₂.Al₂O₃.K₂O). They were obtained from Algerian poor natural kaolin and dam sludge after calcination at 800 °C. The mixture was attacked by KOH-alkaline solution of 8M and dried in an oven to 40 °C. Fluorescence X analysis, X-ray Diffraction, Thermal Analysis, Infrared analysis, BET technique and Scanning Electronic Microscopy were used to characterize the synthesized geopolymer. Mechanical tests of pure paste were carried out on cylindrical specimens of 20mm diameter and 20mm height to evaluate the mechanical performance of these geopolymers. The results showed that the elaborated products were composed from an amorphous phase of geopolymer molecules with other crystallized phases of aluminosilicates. The infrared analysis revealed functional groups of (-Si-O-Al- and -Si-O-Si-), which could testify to the formation of geopolymer binders. The mechanical test results indicated that these geopolymers have a compressive strength of over 33 MPa after 28 days of hardening.