Strength capacity of reinforced concrete columns is very important to resists and transmit the external loadings. For Architects the engineerings requirements to use small cross section of reinforced concrete columns or in case of poor control quality we need to increase the compressive strength of concrete or use a strengthening technique of the structural elements such as column. In the present paper, the behavior and strength of four steel fiber reinforced self-compact concrete columns reinforced by one layer of CFRP that is wrapped around a square of reinforced concrete columns subjected to static loads is investigated. Self-compacting concrete by using limestone powder is adopted and is mixed with different percentages of steel fiber such as 1%, 1.5% and 2%. Different tests are adopted to investigate the mechanical properties of self-compacted concrete mixed with different steel fiber percentages. Test results show that there is an increase in concrete mechanical properties such as compressive strength, splitting tensile strength and modulus of rupture that reflects on the increase in load capacity of column; specimens when wrapped by CFRP. The increment in columns strength capacity is more than 50% as compared with the control column. All the test specimens are modeled using finite element analysis by ANSYS and the numerical results are compared with tested specimens.

Bonding between reinforcement and concrete play an important parameter in the behavior and strength of reinforced concrete. Many parameters influence the bond between reinforcement and concrete such as concrete cover depth, concrete conditions, overall thickness of the structural element and curing. In the present study, a total of sixty specimens as cube with four different percentages of polypropylene fiber (0, 0.5,1 and 1.5) % is used to evaluate the bond strength and stress-slip relationship. The compressive strength of concrete, rebar diameter, concrete cover, and embedded length of reinforcement are taken into account as variables. The test results show that the ultimate bond strength increases with increasing each of the compressive strength of concrete, concrete cover, polypropylene fiber content and decreasing the nominal diameter of the reinforcing bar. The best percentage that gave the maximum failure load, is 1.5% of polypropylene fiber.

Studying the effect of bar size, embedded length, replacement ratio of RCA, concrete cover and yield stress of a reinforcing bar on its bond strength in RAC through an experimental program. Providing a wide range of bank data for the most effective variables through a parametric study on numerical analysis. Proposing a new design equation to predict the bond strength between the reinforcing bar and the surrounding RAC.

Improving the accuracy of load-deformation behavior, failure mode, and ultimate load capacity for reinforced concrete members subjected to in-plane loadings such as corbels, wall to foundation connections and panels need shear strength behavior to be included. Shear design in reinforced concrete structures depends on crack width, crack slippage and roughness of the surface of cracks. This paper illustrates results of an experimental investigation conducted to investigate the direct shear strength of fiber normal strength concrete (NSC) and reactive powder concrete (RPC). The tests were performed along a pre-selected shear plane in concrete members named push-off specimens. The effectiveness of concrete compressive strength, volume fraction of steel fiber, and shear reinforcement ratio on shear transfer capacity were considered in this study. Furthermore, failure modes, shear stress-slip behavior, and shear stress-crack width behavior were also presented in this study. Tests’ results showed that volume fraction of steel fiber and compressive strength of concrete in NSC and RPC play a major role in improving the shear strength of concrete. As expectedly, due to dowel action, the shear reinforcement is the predominant factor in resisting the shear stress. The shear failure of NSC and RPC has the sudden mode of failure (brittle failure) with the approximately linear behavior of shear stress-slip relationship till failure. Using RPC instead of NSC with the same amount of steel fibers in constructing the push-off specimen result in high shear strength. In NSC, shear strength influenced by the three major factors; crack surface friction, aggregate interlock and steel fiber content if present. Whereas, RPC has only steel fiber and cracks surface friction influencing the shear strength. Due to cementitious nature of RPC in comparisons with NSC, the RPC specimen shows greater cracks width. It is observed that the Mattock model gives very satisfactory predictions when applied to the present test results with a range of parametric variations; ranging from 0 % to 0.5 % in steel fibers content; from 0 % to 0.53 % in transverse reinforcement ratio; from 15 to 105 MPa in compressive strength of concrete. While it gives a poor prediction for a specimen with 1% steel fiber.

A knowledge of the concrete vibration after casting have led to improve the mechanical properties of concrete, reduce the deformations due to creep and shrinkage and reduce the concrete permeability. At the Structural and Material