A review on evolution laws and mechanism of concrete performance under cryogenic circumstance from multi-scale perspectives

The surging demand for liquefied natural gas (LNG) has spurred the construction process of LNG storage tanks. As construction technologies and engineering materials are leaping forward, all-concrete LNG (ACLNG) storage tanks show more obvious advantages than conventional 9% nickel steel tanks. The crucial issues in the construction of ACLNG storage tanks consist of the safety and stability of concrete components in cryogenic circumstance. The multi-scale evolution laws of microstructures in concrete under cryogenic attack essentially account for the change of macroscopic physical and mechanical parameters. The continuous freezing and phase trans-formation behaviors of pore water result in significant nonlinear characteristics for thermal-mechanical characteristics of concrete. The uncoordinated thermal deformation between mortar and aggregates, steel bars and concrete are critical reasons for the deterioration of con-crete and the instability of prestressed concrete structures. With the construction of ACLNG storage tanks as the research background, this review summarizes the macroscopic thermal-mechanical characteristics of concrete with the dropping temperature under cryogenic sur-roundings. The degradation of concrete after cryogenic freeze-thaw cycles are presented, and the evolution of interface transition zone, pore water, porosity and calcium silicate hydrate (C-S-H) gel are systematically analyzed. The degradation mechanism of concrete under cryogenic attack is highlighted. Lastly, the performance of ultra-high-performance concrete (UHPC) in cryogenic circumstance is illustrated, the main results and limitations of existing research are summarized in the conclusion.