Cryogenic stability of C-S-H and how to improve it
Cryogenic environment represents a significant challenge for the service safety of concrete materials used for liquefied natural gas (LNG) tanks. Calcium-silicate-hydrate (C-S-H) is the primary binding phase of cement concrete materials, and the degradation of its nanostructure may affect the performance of cement-based materials at the macro scale. In this work, we combine experiment and molecular simulation to investigate the degradation of nanoscopic performances of C-S-H at cryogenic temperatures and the underlying mechanisms. Two practical approaches to improve cryogenic stability are proposed. The presentation is organized in four parts: 1- the stability of C-S-H under cryogenic attack; 2- the stability of Al-incorporated C-S-H under cryogenic attack; 3- the stability of C-S-H superstructure under cryogenic attack; and 4- the scaling law of nanomechanical properties of C-S-H at cryogenic temperatures.
First, we characterize the cryogenic stability of the nano/microstructure, nanomechanical properties, and the degradation route of C-S-H with varying compositions. In the second part, we show the effect of aluminum incorporation as a bottom-up approach to enhance the cryogenic stability of C-S-H. Herein, the nature of aluminates in crosslinked and non-crosslinked C-A-S-H are discussed in detail. Then, we report an expanded DNA code rule and a general structural-chemical formula for C-A-S-H nanostructure. In the third part, we present an organic-inorganic self-assembly strategy to construct a C-S-H superstructure that obtains a super-high modulus, super-low porosity, and low mass density. In the last part, we will present an expanded Zhurkov scaling law for the nanomechanical properties of C-S-H at cryogenic temperatures, which somehow clarifies the elementary physical mechanism for the effect of cryogenic temperature on the macroscopic mechanical properties of concrete.