Mitigation and mechanism of cracking behavior for high-performance concrete with sea sand based on expansion compensation strategy

The development of high-performance concrete with sea sand (SS-HPC) offers a sustainable solution to river sand shortage, yet its widespread application is limited by shrinkage cracking risks. This study introduces UEA, MEA and HCSA into SS-HPC to mitigate such risks, encompassing studies on workability, strength, restricted expansion, shrinkage, long-term durability, cracking under the ring restrained and three-point load fracture behavior. Additionally, by the thermogravimetric and scanning electron microscopy techniques, the hydration products and microscopic morphology of SS-HPC were obtained to analyze the main sources of expansion and compensation mechanisms. The results show that the appropriate EA type and content controlled fresh slurry bleeding. Specifically, 3 % HCSA enhanced SS-HPC strength by 1.77 %, while expansion effectively suppressed shrinkage, and EA-induced expansion in water pre-compensated for later shrinkage development. All three EAs improved the cracking resistance of SS-HPC despite the concrete remaining in brittle fracture mode, reduced ring restraint cracking potential by 82.71 % and increased three-point loading fracture energy by 277.89 %. Notably, the three EAs triggered distinct major hydration products as expansion sources. Among them, 4 % HCSA exhibited the most stable expansion behavior, with hydration products (C-S-H, Ca(OH) 2 , and AFt) contributing to a denser microstructure and smaller pores. This study can promote the wide application of SS-HPC and provide a new strategy for river sand replacement problems. • Sea sand is employed as the total aggregate for preparing high-performance concrete. • Expansion of EA in water pre-compensates the shrinkage of SS-HPC in later stages. • HCSA is identified as the optimal additive to increase the crack resistance and mechanical strength of SS-HPC. • (4)EA improves the hydration behavior to achieve densification of SS-HPC by different products.