Synergistic effect of hybrid micro- and macro- fibers on the flexural properties of concrete

The overall performance of concrete can be improved by hybridization with different fibers dimensions and fiber types. This study aims to explore the fracture mode and toughening mechanism of concrete reinforced with hybrid fibers for the development of more durable and resilient concrete structures. The hybridization methods of macro basalt fibers and various micro fibers of polypropylene, polyvinyl alcohol, micro basalt and steel were evaluated in this study. The flexural properties of concrete were explored by four-point bending tests. The damage modes, load-deflection curves, flexural strengths, the hybrid synergy and hybrid mechanism were discussed. The results showed that microfibers with a modulus of elasticity matched to the concrete obtained the optimal cracking strength. The ductility of concrete after peak load was improved by the addition of macro basalt fibers. The equivalent flexural strength of concrete reinforced with hybrid fibers (pp-B, pva-B, b-B and s-B) was increased by 318 %, 398 %, 443 % and 127 %, respectively, as compared to single fiber (pp, pva, b and s fiber) reinforced concretes. The micro fibers are used to bridge micro cracks, thereby increasing initial cracking strength, while macro fibers hinder the propagation of macro cracks, thus improving the flexural toughness and post-cracking performance. The prediction of stress deflection model for concrete reinforced with hybrid fibers is proposed, which agrees well with experimental data with regression coefficients ranging from 0.877–0.967. •Clarification of the difference in load-deflection behavior of concrete reinforced with single and hybrid fibers.•Analysis of synergistic effect of the hybrid micro- and macro- fibers on flexural properties of concrete.•Elaboration of hybrid mechanism of concrete reinforced with micro- and macro- fibers.