High-strength high-performance concrete incorporating different macro fiber types and contents: Engineering and durability performance

Generating a synergistic response by combining the advantages of different fiber types in concrete is of current scholarly interest. This study investigated the effects of different hooked-end steel fiber (SF) volume fractions up to 1.6% and three macro fiber types including polypropylene (PP), SF, and typical hybrid fibers (HF: 50% SF + 50% PP) at a fixed dosage of 1.6% on properties of high-strength high-performance concrete (HSHPC). A novel densified mixture design algorithm was used to incorporate a high quantity of fly ash and rice husk ash as an eco-binder. Results showed the specimens with added macro SF exhibited improved mechanical strength, dynamic modulus of elasticity and rigidity, and lower drying shrinkage while the ones with added PP exhibited reductions in compressive strength and dynamic modulus. Interestingly, the incorporation of macro fibers, regardless of fiber type and content, reduced electrical resistivity, ultrasonic pulse velocity and increased the total charge passed in the chloride ion penetration test, resulting in likely underestimation of the reinforcement corrosion resistance, especially for SF specimens. The findings also confirm that HF demonstrating synergistic response may be effective and creative in improving most of the concrete characteristics, contributing to the efficient use of HSHPC in real-world structures.