A Novel Strategy for Developing Engineered Cementitious Composites: Synergistic Incorporation of Volcanic Materials and PE-PVA Fibers

Engineered cementitious composites (ECC) are primarily designed to enhance ductility, achieving strain-hardening behavior and controlled micro-cracking. Key constituents typically include cement, fine aggregates, fly ash, and polymeric fibers. This study aims to replace conventional materials, such as river sand (RS) and fly ash (FA), with volcanic materials consisting of volcanic ash (VA) and volcanic sand (VS) while utilizing two types of polymeric fibers: polyethylene (PE) and polyvinyl alcohol (PVA). A complete replacement strategy was adopted to evaluate its impact on the general properties of ECC. A series of tests was conducted to evaluate the mechanical and durability performance of ECC using specific sample geometries: 50 mm cubes for compressive strength, water absorption, and abrasion tests, while the tensile behavior test samples were dog bones with a gauge cross section of 30 mm × 80 mm, and the flexural performance was conducted using prisms of 40 × 40 × 160 mm. For accuracy, three specimens were tested for each test, and the average results were reported. The results demonstrated that utilizing a volcanic matrix improved the 28-day compressive strength by up to 48% compared to mixtures containing conventional materials. Furthermore, volcanic-based ECC mixtures exhibited a 90% increase in compressive strength at 28 days compared to 7-day results. Regarding mechanical performance, PE fibers yielded remarkable results in tension and flexural, with uniaxial tensile strength and flexural strength reaching 6.69 MPa and 20.70 MPa, respectively, particularly in the presence of VA. Moreover, the use of volcanic materials reduced the water absorption of ECC mixtures by up to 16%. Notably, the inclusion of volcanic sand enhanced the abrasion resistance of ECC mixtures by up to 20% across various cycles. Finally, microstructural analysis confirmed that volcanic materials promote a high-density cementitious matrix with superior bonding characteristics with the utilized fibers.