Durability of low-carbon geopolymer mortar: Different responses to cryogenic attack caused by water content and freeze-thaw mediums. (May 2023) - Zhang, Hongen
Abstract: Durability is an important attribute that needs to be focused on during the life span of low-carbon geopolymer mortar (LCGM). The influence of water content (0.00%, 4.91%, and 6.46%) and freeze-thaw medium (air or water) on the performance of LCGM subjected to cryogenic attack up to −170 °C is evaluated by mass change, compressive strength, and microstructure. The results reveal that only water-saturated LCGMs subjected to air freeze-thaw medium experienced a mass loss of 0.66% and the other specimens exhibited different degrees of mass increase by up to 0.27%. Oven-dried and air-dried LCGMs in air freeze-thaw medium experienced a slight increase of compressive strength by about 4.0%. However, water-saturated LCGMs in the same condition experienced a compressive strength decrease of about 9.7%. Additionally, LCGMs exhibited an obvious compressive strength decrease of up to 24.3% in water freeze-thaw medium. The change of microstructure is responsible for the increase or decrease of compressive strength. The water transport and water-ice-water phase transition are the intrinsic motivation for LCGMs to exhibit different responses to cryogenic attack. The exposure of LCGMs to water freeze-thaw medium cryogenic attack exhibited the most severe performance deterioration, which is associated with the couple effect of internal frost-heave stress induced by phase transition and external frost-heave stress induced by ice contraction.