Effect of Types of Concrete on Flexural Behavior of Beams Reinforced with High-Strength Steel Bars

The main shortcomings associated with using high-strength steel (HSS) bars in concrete beams are related to the cracking behavior of these beams at service load and the possibility of concrete crushing prior to steel yielding. This paper investigates the effect of using high-strength concrete (HSC), fiber-reinforced concrete (FRC), and compression reinforcement to enhance the flexural behavior of HSS-reinforced concrete (RC) beams. Plain concrete, steel-fiber, and synthetic FRC were used to cast 24 beams of singly and doubly reinforced concrete sections. In addition, concrete compressive strengths of 7.25 and 11.6 ksi (50 and 80 MPa) were used in the investigation. Four-point bending tests were conducted on all beams. The experimental results showed that increasing the concrete compressive strength contributes the most to the flexural capacity in steel FRC specimens. Results also indicated that highest curvature ductility was achieved by synthetic FRC beams with f(c)' = 11.6 ksi (80 MPa). The crack widths and deep propagation of cracks were noticeably restrained at service and steel yielding load in fiber-reinforced specimens. In addition, the applicability of ACI ITG-6R-10 recommendations was evaluated using the results of plain concrete specimens then extended to cover fiber-reinforced concrete beams.