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While the properties of hybrid fiber-reinforced concrete (HyFRC) have been well-reported in the literature, the behavior of reinforced HyFRC (i.e., HyFRC with embedded steel rebar) is less understood. This paper investigates the mechanics and failure characteristics of reinforced HyFRC under direct tension. Samples with a low longitudinal steel reinforcement ratio were studied to evaluate the feasibility of reducing rebar congestion in structural applications through the use of fiber-reinforced concrete. Although reinforced HyFRC forms multiple cracking sites when loaded, rebar strain and HyFRC crack opening are generally concentrated at a single location under post-yield displacements. The onset of rebar plastic deformation and the exhaustion of fibers’ bridging load capacity are coincident events at a dominant crack. For a cracked reinforced HyFRC section to strengthen, the magnitude of load resistance increase from strain hardening rebar must exceed the magnitude of load resistance decrease from fiber pull-out processes. Comparisons are made with studies reported in the literature to demonstrate how longitudinal reinforcement ratio and fiber type influence cracking behavior and ultimate strain capacity. The research presented herein has far-reaching impacts on the structural design of all types of reinforced fiber-reinforced concrete materials detailed for a ductile response under large displacements.

While fiber-reinforced concrete has been proposed for corrosion damage control of reinforced concrete, long-term behavior of these composites remains largely uninvestigated. In this study, reinforced concrete and reinforced hybrid fiber-reinforced concrete (HyFRC) were subjected to a chloride environment for 2.2 years. Samples were mechanically loaded prior to chloride exposure to induce varied matrix cracking characteristics. When precracked, the time to corrosion initiation is correlated to flexural stiffness degradation. After corrosion initiation, fiber reinforcement restricts corrosion-induced cracking, causes more extensive diffusion of corrosion products into the cementitious matrix, and lowers overall mass loss of steel reinforcing bars. The mechanical responses of corroded samples are also reported.

© 2018 Elsevier Ltd In this paper, we investigate the influence of cementitious matrix cracking on the electrochemical polarization and impedance behaviors of corroding reinforced concrete and crack-resistant reinforced hybrid fiber-reinforced concrete (HyFRC). Samples were exposed to a chloride environment for 2.5 years while in either a continuous tensile stress state or in a nonloaded condition, and were periodically monitored for Tafel polarization responses. Electrochemical impedance spectroscopy (EIS) was additionally performed at the conclusion of the test program. Greater severity of corrosion-induced matrix splitting cracks along the length of embedded steel reinforcing bars and subsequent formation of anodic surfaces were found to affect several electrochemical parameters, including increase of the corrosion current and decrease of the ohmic resistance of concrete. Cathodic and anodic Tafel coefficients and Stern-Geary coefficients for passive and active samples are also reported, highlighted by a Stern-Geary coefficient of B = 28.1 mV for active corrosion.

Concrete production requires significant consumption of raw materials and is a major contributor to global greenhouse gas emissions. Because concrete is placed in varied, damage-inducing conditions, its durability performance is crucial for allowing the material to reach its intended service life and avoid premature replacement. In this multidisciplinary research program, a concrete is developed for both reduced environmental impact and enhanced durability compared to conventional solutions. These goals are realized through a novel combination of design parameters: recycled concrete aggregates (RCA) that increase reuse of construction demolition waste; a high-volume fly ash (HVFA) matrix that further incorporates industrial waste products while reducing portland cement content; and internal fiber reinforcement that increases composite crack resistance. The resulting high-performance concrete, designated as green hybrid fiber-reinforced concrete (GHyFRC), contains 39% waste materials by volume and is evaluated by life cycle assessment (LCA), exposure to a corrosive environment for 4.3 years, and structural loading. Corrosion activity of steel rebar embedded within GHyFRC was reduced through the low chloride permeability of a high-volume fly ash matrix and fiber reinforcement that limited crack propagation, maintaining the low designed matrix permeability. GHyFRC can be a more sustainable alternative to concrete under certain conditions by contributing to greater retention of flexural strength after corrosion has begun and lowering global warming potential (GWP) when normalized by flexural strength.