Title: Shrinkage and Geopolymers
Author(s): Corentin Le Talludec, Annabelle Phelipot-Mardelé, and Christophe Lanos
Publication: Symposium Paper
Appears on pages(s): 52-61
Keywords: alkali activated binder, alternative material, drying shrinkage, geopolymer, shrinkage
Geopolymers are interesting solutions to avoid the use of traditional portland cement. Many studies focus on geopolymers formulation and final performances highlighting the short setting time and the rapid increase of mechanical performances. However, it is necessary to adapt the formulation regarding the components (including
origin, reactivity, chemical formula). The successive steps to achieve the geopolymerization of an aluminosilicate in alkaline media are very sensitive to any change in the molar ratios of Si, Al and M (cation) available in the solution. This study focuses on Na-geopolymers. Several formulations performed using metakaolin, silica fume and soda are tested. Samples are subject to mass monitoring and shrinkage measurement varying the curing conditions. Long stabilization times (one month), and significant shrinkage, in the order of 10 %, are quoted. The interaction between autogenous shrinkage and drying shrinkage is discussed. The link between volume and mass variations suggests a large contribution of the drying shrinkage. This phenomenon interferes with the last steps of geopolymerization leading to the hardening. The results show that a part of the formulation water remains trapped in the binder matrix after the geopolymerization. TGA analysis confirm the results. To limit the shrinkage, mix formulation is modified introducing various type of calcium silicate fillers.