International Concrete Abstracts Portal

The use of Fiber-reinforced polymer (FRP) composite materials in new construction and repair of concrete structures has been growing rapidly in recent years. FRP provides options and benefits not available using traditional materials. The promise of FRP materials lies in their high-strength, lightweight, noncorrosive, nonconducting, and nonmagnetic properties. ACI Committee 440 has published several guides providing recommendations for the use of FRP materials based on available test data, technical reports, and field applications. The aim of these document is to help practitioners implement FRP technology while providing testimony that design and construction with FRP materials systems is rapidly moving from emerging to mainstream technology.

Coarse recycled concrete aggregate (RCA) has been studied as a replacement for natural aggregate (NA) in concrete for decades. RCA is still predominantly used in non-structural applications such as filler, road sub-base, drainage material, and low quality concrete. However, there is increased interest in using RCA in new structural concrete due to restrictions on landfilling of construction and demolition (C&D) waste and on the scarcity of natural aggregates, especially in urban megacities. The compressive strength of concrete with coarse RCA is typically 15–30% less than that with NA. This feasibility study was conducted to evaluate the effect of FRP strengthening on RCA beams as compared with NA beams also strengthened with FRP. Four RCA and four NA beams were strengthened in flexure and in shear using hand laid-up carbon-epoxy FRP materials. A combination of longitudinal strips on the beam soffit and intermittent closed hoop wraps along the length were used. The FRP-strengthened beams were designed to yield and then fail in compression with the FRP still attached. The results of the testing are described. The ability of FRP strengthening to, (1) change the failure mode of RCA beams, and, (2) to improve the reliability of RCA concrete beams constructed or repaired with FRP materials is discussed. It was found, surprisingly, that the FRP-strengthening was effective in increasing the capacity of the RCA beams. This is attributed to a different failure mechanism of the RCA beams from that of the NA beams tested.

Flexural strengthening of Reinforced Concrete (RC) beams using fiber reinforced polymer (FRP) has become a common practice in the construction industry. Such strengthening is typically performed by attaching FRP laminates to the tension side of RC beams. In many occasions reaching the tension side of the beam can be a major challenge due to existing ducts as in buildings or the need of large scaffolds underneath the beam as in bridges. This challenge makes FRP strengthening an expensive alternative. In this paper, we suggest an alternative flexural strengthening method using a composite system made of Ultra High-Performance Concrete (UHPC) and Carbon Fiber Reinforced Polymer (CFRP) laminates for RC beams without reaching the tension side of the beam. In this technique, the accessible cover of the RC T-beam is removed, the CFRP laminates are attached to top side of the beam then a thin UHPC overlay is cast over the FRP. We show that the combination of UHPC and FRP allows the FRP to act as additional tensile reinforcement and increase the flexural capacity of the RC T-beams. The proposed method might be effective for shallow to medium RC T-beams specifically T-beams with very wide flange.

This paper presents the results of an experimental study conducted to investigate the effectiveness of a glass fabric reinforced cementitious matrix (GFRCM) composite system to strengthen reinforced concrete (RC) beams. A total of fifteen beams were tested in two groups: Group A was designed to investigate the use of GFRCM to rehabilitate corrosion damaged tension lap splices in RC beams. Group B was designed to investigate the use of GFRCM to strengthen shear critical RC beams. The test results demonstrated that GFRCM is a promising system to enhance the load carrying capacity of RC beams.

Sustainability of CFRP materials is evaluated based on their long-term capacities that can be decreased by environmental exposure. Researchers regularly accelerate this process by various forms of hygrothermal conditioning. Results of both flexural and tension tests are presented. A comparison of flexural and direct tension test methods is proposed and compared to those obtained by other investigators. In addition, a simple predictive model is introduced. Accelerated ageing tests indicate that the sustainability of carbon fiber reinforced polymer (CFRP) repair systems is impacted by the coverage rate of adhesives. Test results indicate no change in strength for specimens with 91 to 233 percent of the manufacturer’s recommended adhesive application while accelerated ageing tests show a markedly lower strength for specimens with less than the manufacturer’s recommended coverage.