Effect of Filler Type on the Thermo-Mechanical Properties of Metakaolinite-Based Geopolymer Composites

Abstract

Metakaolinite-based geopolymer binder was prepared at room temperature by mixing calcined claystone and potassium alkaline activator. Various granular inorganic fillers were added, amounting to 65 vol % to form geopolymer composites. The effect of four types of fillers (sand quartz, chamotte, cordierite, and corundum) on the thermo-mechanical properties of metakaolinite-based geopolymer composites were investigated. The samples were also examined by an X-ray diffraction method to determine their phase composition. The pore size distributions were determined by a mercury intrusion porosimeter. The XRD revealed the crystallization of new phase (leucite) after thermal exposure at 1000 °C and higher. Geopolymer binders had low mechanical properties (flexural strength 2.5 MPa and compressive strength 45 MPa) and poor thermo-mechanical properties (especially high shrinkage—total shrinkage 9%) compared to geopolymer composites (flexural strength up to 13.8 MPa, compressive strength up to 95 MPa and total shrinkage up to 1%). The addition of fillers reduced the shrinkage of geopolymers and improved their mechanical properties. The results have shown that the compressive strength tested in situ and after exposure to high temperature are in conflict. Geopolymer composites with the addition of chamotte had the best mechanical properties before and after thermal exposure (compressive strength up to 95 MPa). The average pore size diameters increased with the increasing temperature (from 10 nm to approx. 700 nm). The fillers addition decreased the pore volume (from 250 mm3/g to approx. 100 mm3/g).

Controlling the Thermal Stability of Kyanite-Based Refractory Geopolymers

“…The decomposition of kyanite particles into mullite and cristobalite started at 1200 °C [ 17 , 21 ]. The nucleation of cordierite crystals from mullite, enstatite and cristobalite was observed with the presence of an endothermic peak at around 1280 °C [ 6 , 8 , 16 ]. This justified the stability of the refractory matrices ( Figure 1 b).…”

“…[ 5 , 7 , 12 , 13 , 14 , 15 ]. Among others, Kohout and Koutnik [ 16 ] investigated the effect of four filler types (quartz sand, chamotte, cordierite and corundum) on the thermo-mechanical properties of metakaolin-based geopolymer composites. They revealed that the addition of fillers reduced the thermal shrinkage of the geopolymer products and positively affected the development of mechanical properties.…”

Thermally Treated Waste Silt as Filler in Geopolymer Cement

“…However, the best performance in terms of lower porosity and higher strength was observed when 20% quartz or chamotte was used in the mixture. In a similar study, calcined kaolinitic claystone and potassium silicate hardeners were used to produce geopolymer samples [ 21 ]. Quartz, corundum, chamotte, and cordierite were used as fillers.…”

“…The geopolymer samples had a stable structure at an elevated temperature of 1000 °C, and the shrinkage of the geopolymer samples significantly reduced at high temperatures when the filler was used. The best fillers were corundum or chamotte, which performed better compared to the other types of fillers [ 21 ].…”

Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers

“…The cementing or geopolymerization process of geopolymer precursors with alkaline activators can rapidly proceed to form a three-dimensional polymeric structure with complex Al-O-Si bonds and to generate continual material skeletons that enable high strengths [10]. With those advantages, geopolymer-based materials possess a series of excellent performances with promising potentials in engineering applications, including high mechanical strength, great fire resistance, enhanced leaching resistance, and improved contaminate stabilization [11][12][13][14][15].…”