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 transformation 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 concrete 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 surroundings. 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.