Development and Characterization of Geopolymers Based on a Kaolinitic Clay

Abstract

Geopolymers today constitute an alternative to be considered with the aim, not of completely replacing cement, but of widening the possibilities available at the time of decision-making because this type of clay-based binder has a low impact environmental and thermal compared to Portland cement. The methods used to obtain eco-friendly building units from waste materials can be separated into three general categories: firing, cementing and geo-polymerization. The reaction of solid aluminosilicate materials with a highly concentrated aqueous alkali hydroxide or silicate solution produces a synthetic alkali aluminosilicate material called a ‘geopolymer. Geopolymers based on clay materials from Burkina Faso were developed and then characterized for use in construction. The results of the characterization of the clay mineral material referenced TAN as well as its calcined forms TAN-700 and TAN-800 have shown by several analysis techniques (DRX, IR, ICP-AES) that TAN contains kaolinite (71%), quartz (20%), illite (4%) and goethite (2%). TAN-700 and TAN-800 are essentially made of quartz. These clays are each mixed with the alkaline solution (sodium hydroxide solution 8 mol.L^-1) in a mass ratio (alkaline solution/clay) ranging from 0.33 to 0.36. The results of the mechanical and mineralogical tests of the geopolymers produced showed that the grade GP-MK₀ produced had the best performance favorable for its use in construction. Indeed, its linear shrinkage (3.44%) is low and the compressive strength (22.50 MPa) is greater than 4 MPa. This performance of GP-MK₀ is due to the formation of a phase rich in silica and in alumina (Na₂(AlSiO₄)₆(OH)₂·2H₂O).