A multinuclear static NMR study of geopolymerisation

摘要: Geopolymers are inorganic binders obtained by alkali activation of aluminosilicates. While the structure geopolymers is now well understood, details geopolymerisation reaction and their impact on rheology paste remain uncertain. In this work, we follow elastic properties a made with metakaolin sodium silicate solution. After first sharp increase modulus occurring few hundred seconds after mixing related to heterogeneous formation an alumina–silicate gel molar ratio Si/Al < 4 located at grains boundaries, focus progressive in period hours during setting geopolymer. study, combine study rheological 23Na, 27Al 29Si static NMR measurement order better understand origin second modulus. Our results show that, hours, Al Na evolution liquid phase concomitant. This suggests precipitation aluminosilicate where tetrahedral position compensates charge. Furthermore, Si speciation confirms result allows us identify product, which has chemical composition close final provides strong evidence for glass directly from solution without need reorganisation Gel 1 into 2.