Damage resistance of calcium sulfoaluminate cement-based engineered cementitious composite (CSA–ECC) under vehicle-bridge coupling vibration

The performance damage of newly placed concrete caused by vehicle–bridge coupling vibration is an inevitable phenomenon among widening of existing concrete bridge. Calcium sulfoaluminate cement-based engineered cementitious composite (CSA–ECC) was proposed to replace the conventional concrete to address the aforementioned issues. The effects of vehicle–bridge coupled vibration (involve the frequency and the amplitude) on the mechanical properties of CSA–ECC including compressive strength, flexural strength and flexural toughness were investigated. The distribution of air bubbles was analyzed by X-ray micro-computed tomography (X-ray CT) to explore the mechanism of vibration affecting the mechanical properties of CSA–ECC. The results indicate that the volume percentage of coarse air bubbles (>1.0 mm³) decreases from 54.70 to 25.94%, and the volume percentage of micro air bubbles (0–0.2 mm³) increases from 30.89 to 54.19%. As a result, the microstructure of matrix and fiber/matrix interface are densified due to the redistribution of air bubbles caused by the coupling vibration. Therefore, the application of vibration significantly enhances the flexural strength and flexural toughness of CSA–ECC, ascribing to stronger matrix fracture toughness and fiber/matrix interfacial frictional bond. These indicate that the CSA–ECC has a promising application scenario in highway bridge widening projects with exceptional vibration-induced damage resistance ability.