Evolution characteristics of engineered cementitious composite pore structure and its correlation with the tensile property under simulated traffic vibrations at an early age

The repair construction of bridge decks typically involves the method of half-width traffic and half-width construction, where traffic vibrations (TV) can disrupt newly laid cementitious materials on the bridge deck. Engineered cementitious composites (ECC), owing to their high ductility, are widely applied in the repair of bridge deck surfaces. While there have been studies on the fundamental performance of ECC in road surface repair projects, the impact of TV on ECC’s tensile properties (TP) and pore structure (PS) remains unclear, and the mechanisms through which TV affects ECC are not well defined. To analyze the effects of TV on ECC’s TP and PS, a custom-built vibration platform was utilized to simulate bridge deck TV. Experimental investigations were conducted on ECC specimens using uniaxial tensile (UT) tests and mercury intrusion porosimetry (MIP). Results indicate a significant impact of TV on the TP of freshly mixed ECC, particularly during the initial setting (IS) to final setting (FS) stages. TV-induced structural damage, resulting in identifiable cracking, increased porosity and reduced uniaxial tensile strength (UTS) by approximately 2–23%. However, TV did not substantially affect ECC strain hardening and ultra-high toughness; the tensile strain remained above 3% under different vibration parameters. Applying pulses before the IS improved the PS of ECC to some extent and enhanced UTS. Post-FS, ECC exhibited enhanced resistance to external disturbances, with minimal impact from TV. A strong correlation was observed between UTS and PS characteristics, indicating that the evolution of PS reflects the UTS of ECC. Utilizing the gray relational theory, this study investigated the influence of different vehicular vibration conditions on ECC’s tensile performance and pore structure. The findings reveal a significant impact of age at which the specimens were vibrated (AV) and vibration frequencies (VF) on ECC’s pore structure and tensile performance. Furthermore, gray target theory was applied to rank the effects of different TV conditions on ECC performance, revealing minimal impact post-FS. The ECC specimen subjected to vibrations at 4 Hz frequency, initiated after 36 h, and sustained for 5 h exhibited the optimal comprehensive performance. This research contributes to the design and application of ECC in practical construction scenarios, mitigating material damage during construction processes.