This review represents the micro-/nano-structure models of C-(A-)S-H and discusses recent advancements in understanding its evolution under common marine ions attack (i.e., Na⁺, Mg²⁺, Cl^- and SO₄^2-). This review elucidates the mechanisms by which aluminum-rich supplementary cementitious materials promote the formation of C-A-S-H, highlighting advancements in characterization techniques and the integration of molecular simulation and machine learning. These innovations significantly advance the development of models describing the micro-/nano-structures of C-(A-)S-H.

Advancements in characterization techniques supported by cutting-edge technologies such as molecular dynamics simulations and machine learning deepen our understanding of atomic ratios within C-(A-)S-H in relation to its degree of polymerization, average chain length, micro-mechanical properties, and durability. These developments facilitate the establishment of mappings between the micro-/nano-structures of C-(A-)S-H and its properties. Furthermore, this can contribute to advancing sequential studies of silicate (aluminate) tetrahedra on the Dreierketten chains.

At present, some aspects merit a further investigation and have a potential to emerge as future research focal points as follows: 1) the micro-/nano-structure model of C-(A-)S-H can be optimized and a framework utilizing first-principles calculations, molecular dynamics simulations, and machine learning techniques needs to be proposed. These aim to predict the mechanical properties and durability of Portland cementitious materials based on the micro-/nano-structure of C-(A-)S-H. It is thus feasible to enhance understanding and predictive capabilities concerning the performance and longevity of Portland cementitious materials at the microstructural level via integrating these advanced computational methodologies. 2) Atomic arrangement analysis of C-(A-)S-H is needed. It is thus feasible to determine the relative abundance of structural units within C-(A-)S-H by nuclear magnetic resonance (NMR). Chemical environment analysis techniques, such as X-ray photoelectron spectroscopy (XPS), enable elemental valence state analysis in C-(A-)S-H. The detailed atomic arrangement analysis of C-(A-)S-H can be obtained, which is crucial for directing the targeted production of Portland cementitious materials. 3) The micro-/nano-structures evolution mechanisms of C-(A-)S-H in marine environments need to be investigated. The micro-/nano-structures evolution mechanisms of C-(A-)S-H under complex ions attack conditions are investigated. The degradation mechanisms of C-(A-)S-H in simulated marine environment need to be further simulated via establishing a database of products under single-factor attack environments and employing thermodynamic simulation techniques, and the simulation results with the micro-/nano-structures of C-(A-)S-H in real marine service environments need to be compared. 4) Low-carbon green building materials are developed. The Ca/Si ratio in C-(A-)S-H can be adjusted based on the optimized models of micro-/nano-structures of C-(A-)S-H, meeting engineering requirements, while optimizing the raw material composition of cement. This approach can reduce CO₂ emissions during cement production, thereby promoting the development of low-carbon green building materials.