Investigation of the mechanical and durability properties of geopolymer mortars produced with a 3D printer based on metakaolin and fly ash containing nanomaterial

Nano-sized materials, which have a very large specific surface area and have very high chemical activities, contribute to the improvement of mechanical strength and durability properties when added to geopolymer mortars even in small amounts. This Ph.D. thesis study investigated the mechanical strength and freeze-thaw durability properties of geopolymer mortars produced with a 3D printer containing different nanomaterials. Metakaolin (MK) and fly ash (FA) were used as binders in the composites. Sodium metasilicate (Na2SiO3) and sodium hydroxide solution (NaOH, 12 M.) were used as alkali activators. Multi-walled carbon nanotube (MW-CNT), and nano-SiO2 (NS) were used as nanomaterials in the thesis. Geopolymer mortar samples without nanomaterials were determined as control samples and 3D-printed geopolymer mortar samples containing 0.25%, 0.5%, and 0.75% MW-CNT, and NS were produced. All produced samples were cured at 20±2 °C laboratory conditions for 7, 28, and 90 days. The cured 3D-printed geopolymer mortar samples were subjected to mechanical strength tests. The mechanical strength test results of all 3D-printed geopolymer mortar samples containing nanomaterials showed an increase compared to the control samples. The highest mechanical strength was obtained from 3D-printed geopolymer mortar samples containing NS. These samples were followed by geopolymer mortar samples containing MW-CNT. In addition, all samples cured at 20±2 °C laboratory conditions for 28 days were exposed to freeze-thaw durability according to TS EN 15177 standard. The mechanical properties of geopolymer mortar samples produced with a 3D printer before and after exposure to freeze-thaw durability were also compared. The highest mechanical strength after freeze-thaw durability was obtained from geopolymer mortar samples containing NS and the sample preserved its strength of 97.26%. These samples were followed by geopolymer mortar samples produced with a 3D printer containing MW-CNT.