Journal of Composites for Construction

A concise state-of-the-art survey of fiber-reinforced polymer (also known as fiber-reinforced plastic) composites for construction applications in civil engineering is presented. The paper is organized into separate sections on structural shapes, bridge decks, internal reinforcements, externally bonded reinforcements, and standards and codes. Each section includes a historical review, the current state of the art, and future challenges.

Fiber-reinforced polymer (FRP) composites represent an alternative construction material without many of the performance disadvantages of traditional materials. The use of FRP as a pile material can eliminate deterioration problems of conventional piling materials in waterfront environments and aggressive soils. The driveability of traditional piling can be predicted using wave equation analysis of piles (WEAP). The input parameters used in WEAP are obtained by back-analyses of actual case histories. The properties of FRP piling differ from those of conventional piling, so conventional WEAP input parameters may not work as well for FRP composite piling. In this paper, WEAP input parameters for three composite pile types are calibrated using available driving records. The driveability of FRP composite piling is also compared with that of piling made of conventional materials such as timber, steel, and concrete.

Bonding composite laminates to the tension face can effectively increase the flexural strength of the reinforced-concrete flanged beams. In comparison to rectangular concrete beams, the flange provides a larger area of concrete to resist compression stresses, and considering the role of the composite in resisting tensile stresses, its addition to flanged beams can efficiently upgrade the flexural capacity. Failure of the strengthened beam may result from crushing of concrete or rupture of the plate; however, the beam must be properly detailed to avoid local shear failure at the plate cut-off point. In this paper, equations required for strengthening of the flanged beams for gravity loads will be presented. The equations have been developed based on load and resistance factor design, and have been verified through a comparison with available experimental results. Close agreement with the experimental results indicates the accuracy of the equations. Terms, definitions, and notations compatible to ordinary reinforced-concrete design codes have been used to facilitate the application of the equations.

The paper aims to contribute to a better understanding and modeling of the shear behavior of reinforced-concrete (RC) beams strengthened with carbon fiber reinforced polymer (FRP) sheets. The study is based on an experimental program carried out on 11 beams with and without transverse steel reinforcement, and with different amounts of FRP shear strengthening. The test results provide some new insights into the complex failure mechanisms that characterize the ultimate shear capacity of RC members with transverse steel reinforcement and FRP sheets. After the discussion of the above topics, a new upper bound of the shear strength is introduced. It should be capable of taking into account how the cracking pattern in the web failing under shear is modified by the presence of FRP sheets, and how such a modified cracking pattern actually modifies the anchorage conditions of the sheets and their effective contribution to the ultimate shear strength of the beams.

Galvanic corrosion is a possible form of deterioration when carbon fiber-reinforced polymer (CFRP) composites and steel are in direct contact in concrete, as in stirrups tied to prestressing CFRP tendons. Laboratory experiments were performed to determine the magnitude of galvanic currents that may take place as a consequence. Preliminary results show little galvanic corrosion of steel (between ${10}^{-6}$ to 0.08 μA/cm² of steel current density) when coupled with CFRP composites in mortar free of chlorides with a 0.5 water-to-cement ratio (w/c=0.5). However, significant galvanic action (steel current densities as high as 1.5 μA/cm²) was observed in chloride contaminated mortar. The study suggests that steel corrosion caused by deicing salts or marine exposure may be aggravated by the direct contact between steel and CFRP.

Studies were conducted to understand the galvanic interactions between CFRP and steel in chloride-contaminated concrete. CFRP-pultruded rod samples (6 mm in diameter), #3 deformed plain rebar (PR, uncoated), and #4 epoxy-coated reinforcing (ECR) steel bars were tested. After 350 days, potential measurements of CFRP and steel samples in chloride-contaminated concrete were −200 and −600 mV (versus CSE), respectively. These results confirm that chloride contamination in concrete could allow galvanic corrosion between CFRP and steel. The measured galvanic current densities were up to 0.7 and 100 μA/m² for the CFRP-PR and CFRP-ECR couples, respectively, raising concerns about the degradation of both CFRP and steel. The results showed that PR steel was unaffected, as the corrosion rates estimated before and after the coupling with CFRP were similar. In contrast, coupling CFRP and ECR steel showed an increase of 10 times of the estimated corrosion rate, suggesting that galvanic interaction might affect the ECR steel.

This paper presents the experimental results of large-scale concrete-filled glass fiber reinforced polymer (GFRP) circular tubes and control hollow GFRP and steel tubes tested in bending. The diameter of the beams ranged from 89 to 942 mm and the spans ranged from 1.07 to 10.4 m. The study investigated the effects of concrete filling, cross-sectional configurations including tubes with a central hole, tube-in-tube with concrete filling in between, and different laminate structures of the GFRP tubes. The study demonstrated the benefits of concrete filling, and showed that a higher strength-to-weight ratio can be achieved by providing a central hole. The results indicated that the flexural behavior is highly dependent on the stiffness and diameter-to-thickness ratio of the tube, and, to a much less extent, on the concrete strength. Test results suggest that the contribution of concrete confinement to the flexural strength is insignificant; however, the ductility of the member is improved. A strain compatibility model has been developed, verified by the experimental results, and used to provide a parametric study of the different parameters, significantly affecting the behavior. The parametric study covered a wide range of FRP sections filled with concrete, including under-reinforced, balanced, and over-reinforced sections.

The paper analyzes the structural behavior of concrete beams reinforced with hybrid fiber-reinforced polymer (FRP)-steel reinforcements. The analysis refers to concrete beams reinforced with FRP rebars placed near the outer surface of the tensile zone, with low cover thickness values, and steel rebars placed at the inner level of the tensile zone, with high cover thickness values, able to protect the steel from the corrosion. Such reinforcement allows one to optimize the structural behavior of beams and guarantees a good level of ductility and rigidity. Results of an experimental and theoretical investigation are presented and discussed. Significant features of the structural behavior regarding deflection, curvature, ductility, crack width, and spacing are pointed out. Ultimate and serviceability conditions are examined, highlighting the influence of mechanical and geometrical parameters affecting the behavior of hybrid reinforced-concrete beams.