A state-of-the-art review on the impacts of seawater and sea-sand together with main aggressive ions on the alkali-activated materials

Due to the excellent durable properties, alkali-activated materials (AAMs) are generally taken into account to utilize in the harsh marine environments to resist the chloride transport and sulfate attack. Moreover, aggressive ions-containing seawater and/or sea sand are tried to substitute freshwater and river sand as mixing water and fine aggregates to prepare AAMs, in the light of superior chloride binding capacities of matrices and exceptional resistance to sulfate attack. This paper attempts to review the recent investigations focusing on the effect of aggressive seawater ions primarily including chloride and sulfate ions on the macroscopic properties, phase assemblages, and microstructures of AAMs, and the transformation of AAMs induced by the immersion in aggressive seawater. Furthermore, existing studies on the fresh and hardened properties of AAMs fabricated using seawater and sea sand are also overviewed in detail. However, the challenges faced regarding the AAMs used as marine engineering materials remain severe, and the relevant research gaps are urgently required to be bridged. The perspectives proposed in this paper may show profound insight for the future studies to explore the application of AAMs in marine engineering.