Strengthening and embrittlement effect of cryogenic temperature on fiber reinforced geopolymer composite

Understanding the cryogenic behaviour of geopolymer composite (GPC) is essential to implement them in real structural elements at cryogenic temperatures. The paper presents a comprehensive investigation on the compressive strength, flexural behaviours, and energy absorption capability of both plain GPC and fiber- reinforced geopolymer composite (FRGPC) containing different fiber types and contents subjected to in-situ-170 degrees C. The results demonstrate that the compressive strength of plain GPC and FRGPC increases by 104.9 %-213.6 %, and the flexural strength increases by 73.4 %-212.5 %, exhibiting a significant cryogenic strengthening effect. Moreover, compared to flexural strength, compressive strength of GPCs displays a higher sensitivity to the cryogenic strengthening effect. The failure mode of FRGPCs changed from ductile failure to ductile-brittle failure at-170 degrees C, which is due to the decreased ductility induced by the cryogenic embrittlement effect. Additionally, cryogenic exposure has a greater impact on reducing the ductility of FRGPCs containing PP fibers than those with steel fibers. However, the negative effects of cryogenic embrittlement effect on ductility can be mitigated by incorporating steel fibers and increasing fiber content. The further analysis reveals that strengthening and embrittlement effect are associated with the increased cumulative energy and the sudden release of local energy, respectively. These findings contribute to the understanding of GPC performance at cryogenic temperature, which can guide the development of more resilient and durable GPC for cryogenic applications.