Experimental study of freeze-thaw resistance of a one-part geopolymer paste

This study was aimed at experimentally evaluating the freeze-thaw (F-T) performance of a one-part geopolymer (OPG) paste. A binary precursor (ground granulated blast furnace slag plus fly ash) activated by sodium hydroxide (NaOH (NH)) or sodium metasilicate (Na2SiO3 (NS)) was used to prepare the OPG pastes. To simulate the freezing temperatures in various frozen regions of the world (such as Canada, China, Greenland, Norway, Russia, and the United States), four temperature values were selected: -5, -10, -20, and -40 ?. The F-T durability of the OPG paste was studied based on the visual appearance, mass loss, pH variation, and compressive strength deterioration under the action of F-T cycles (up to 50 cycles). The experimental results revealed that because of the formation of a dense structure, the NS-activated OPG paste had better F-T resistance than the NH-activated OPG paste. The increase in the number of F-T cycles or decrease in freezing temperature led to an increase in the porosity of the OPG paste, thereby causing mass loss and compressive strength reduction. The increase in porosity was due to the volumetric expansion of ice crystals, and the failure stress was caused by the difference in temperature. These two factors were found to cause the deterioration of the mechanical properties of the OPG paste. Accordingly, a deterioration model of the OPG paste under F-T cycles was proposed based on the experimental observations. The results of this study are expected to provide guidance regarding the use of the novel OPG paste to improve frozen soil layers or build frost-resistant geotechnical structures.