Synthesis of consolidated materials from alkaline solutions and metakaolin: existence of domains in the Al–Si–K/O ternary diagram

The activation of metakaolin using an alkaline solution is a method for producing high quality consolidated materials. Si, Al and K are the main factors that influence the nature of the consolidated materials. This study focuses on the effects of the composites on the final network formation. Two types of alkaline solutions, one (Sc) based on a commercial potassium silicate solution and the other (S l ) synthesized by mixing KOH and amorphous silica, were studied, and their effects on the network formation of consolidated materials were compared and discussed. Four types of materials were observed and identified based on different Si, Al and K contents, including a geopolymer, gel, sedimented materials and hardening materials. These behaviors are manifested in the various polycondensation mechanisms and microstructures, which were characterized using FTIR spectroscopy, thermal analysis, X-ray diffraction measurements and Scanning electron microscope observations. The influence of Si, Al and K is discussed according to network formation.