Hydroabrasive Erosion of Fiber-Reinforced Geopolymer Concretes

This study experimentally investigated the hydraulic abrasion performance of metakaolin-based geopolymer concretes reinforced with steel and polypropylene fibers. Twenty-four cylindrical discs (280-mm diameter×100-mm depth) were tested, including conventional concretes (C20, C30, C40) and geopolymer concretes with compressive strengths of 20, 30, and 40 MPa, fiber types (steel, polypropylene), fiber volumes (0.0%, 0.5%, 1.0%, and 1.5%), and exposure durations of 6, 12, 18, and 24 h. The underwater abrasion test simulated wear due to sediment flow by applying cyclic intervals with controlled agitation. In compression, geopolymer mixtures slightly outperformed conventional concretes at C20 and C40, with gains of 36% and 15%, respectively. Tensile splitting strength improved with increasing class, showing up to 77% gains in C40 mixtures. Fibers provided selective benefits: Steel fibers enhanced tensile resistance in higher-strength concretes, whereas polypropylene fibers were more effective in C20 mixtures. However, steel fibers reduced the modulus of elasticity compared with fiber-free matrices. For abrasion, mass loss ranged from 15% to 18% in conventional concretes, 10% in fiber-free geopolymers, 7%–10% in steel fiber–reinforced geopolymers, and about 10% in polypropylene fiber–reinforced geopolymers. Significant improvements occurred mainly at 1.5% fiber volume. Abrasion depth remained below 10 mm, well under standard concrete covers (35–50 mm). Overall, fiber-reinforced geopolymer concretes demonstrated improved durability, confirming their potential as eco-efficient alternatives for submerged and marine infrastructure.