Abstract: To develop low-carbon cementitious materials suitable for marine engineering,this study investigated the effects of simulated seawater mixing on the properties and hydration process of supersulfated cement (SSC).The setting time and compressive strength were tested,and the microstructural evolution and hydration-hardening mechanisms of SSC mixed with simulated seawater were systematically analyzed using X-ray diffraction,mercury intrusion porosimetry,thermogravimetric anal ysis,hydration heat measurement,and other methods.The results indicated that simulated seawater shortened the initial and fi nal setting times of SSC by 20 min and 25 min,respectively,and increased the compressive strength at 1 d,3 d,and 28 d by 15.8%,4.5%,and 4.0%,respectively.The performance improvement is mainly attributed to the simulated seawater (particu larly NaCl therein) promoting the dissolution and hydration of slag,thereby altering the composition and distribution of hydra tion products.The early-formed Friedel′s salt and C-(A)-S-H gel jointly filled the gaps between ettringite (AFt) crystals,re fined the pore size of the hardened paste,and significantly reduced the porosity of harmful capillary pores larger than 20 nm. This study provides a theoretical basis for the application of seawater-mixed SSC in marine engineering.

Key words: mixing with seawater,supersulfated cement,compressive strength,hydration products,microstructure,hydra tion mechanism