Durability and Improvement of Cement-Based Revetment Materials Serving in Subtidal, Intertidal, and Supratidal Environments

To improve the durability of cement-based revetment materials serving in different positions relative to the water level, slag powder and polypropylene fibers were added into cement to prepare paste, mortar, and concrete. Based on three simulated experiments of high-humidity air, dry-wet cycles-coupled chloride erosion, and complete immersion-coupled chloride erosion, the half-year durability of cement-based revetment materials was investigated. An abundant amount of Ettringite containing chloride was formed in the pores of the cement, and its formation was accelerated by dry-wet cycles. Replacing 30% of cement by slag powder and adding 0.1 vol.% of polypropylene fibers helped concrete in the intertidal zone to obtain a compressive strength of 47.58 MPa after erosion, equal to 159% of the reference. Slag powder was found to induce cement to form Friedel's salt and C-S-H with a more amorphous structure, increasing its chemical binding ability and physical adsorption ability to chloride ions, and reduce the chloride ions' penetration depth of concrete from 22.5 to 12.6 mm. Polypropylene fibers controlled the direction of surface cracks to be perpendicular to the specimen's sides. These findings lay a foundation for the design of high-durability cement-based revetment materials serving in costal environments.