Sustainability is one of the salient requirements in modern society. Structures frequently deteriorate because of aggressive service environments; consequently, federal and state agencies expend significant endeavors to maintain the quality of the structures. Among many factors, durability plays a major role in accomplishing the concept of sustainability. Extensive research has been conducted to understand the deterioration mechanisms of concrete and to extend the longevity of concrete members. Over the past decades, the advancement of technologies has resulted in durable construction materials such as advanced composites. This Special Publication (SP) contains nine papers selected from two technical sessions held in the ACI Spring Convention at Detroit, MI, in March 2017. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy.

Structures may need to be repaired for different reasons, such as, construction or design defects, or service stage changing which include, ageing of structures or deterioration due to exposure to aggressive environmental conditions. New materials are emerging, such as steel reinforced Polymer (SRP) composite, which can be used to strengthen and repair structures with greater durability and less maintenance over the life of the structure. An experimental test program was carried out to investigate the performance of repaired damaged concrete beams with (SRP) repair technique. Six full-scale reinforced concrete (RC) beams were designed and tested using 4-point load test setup to be failed in lap splice in the middle region of the beam. The damaged concrete was repaired, and SRP sheet (longitudinal soffit laminates and transverse U-wrapping strips) was applied to restore the original flexural capacity. All beams were 10 ft (3.0 m) in length, 18 in. (457 mm) in depth, and 12 in. (305 mm) in width. Different repairing configurations were investigated. The studied variables were the number of plies and the amount and distribution of U-wrapping strips. Ultimate load capacity, deflection, and mode of failure were recorded during testing. The test results were compared to beam results with continuous reinforcement. It was concluded that repairing beams with SRP plies and U-wrapping strips can restore the beam to a capacity similar to that of reinforced concrete (RC) beam with continuous reinforcement.

Fiber reinforced polymer (FRP) composites have emerged as a lightweight and efficient repair and retrofit material for many concrete infrastructure applications. FRP can be applied to concrete using many techniques, but primarily as either externally bonded laminates or near-surface mounted bars or plates. This paper presents the results of direct shear pull-out tests performed on aged concrete specimens reinforced with glass FRP (GFRP) and carbon FRP (CFRP) externally bonded laminates and near surface mounted (NSM) bars. An accelerated aging scheme consisting of freeze/thaw cycling in the presence of a deicing salt solution is implemented to determine the effect of long-term environmental exposure on the FRP/concrete interface in regions that experience aggressive winter environments. The results show that the NSM bar technique is superior to externally bonded laminates in terms of efficiency in the use of FRP material and the effects of accelerated aging. Generally, the performance of GFRP is affected less than CFRP after freeze/thaw cycling for both externally bonded laminates and NSM bars. For high strength NSM FRP bar applications, a spalled or cracked concrete surface caused by freeze/thaw cycling may drastically reduce the capacity of the FRP/concrete interface by inducing failure at the concrete/epoxy filler interface.

An exterior girder of a prestressed concrete bridge over Interstate 65 in Kentucky was damaged due to an over-height truck impact. The damaged section spanned two of the three northbound lanes of the highway. Two prestressing strands were severed and two additional strands were damaged by the impact. In addition, shear reinforcing bars in the vicinity of the impact were cut-off. CFRP Rod Panels (CRPs) were deployed to restore some of the load carrying capacity lost due to the severed prestressing tendons. CRP 195, with CFRP rods of 3.96 mm (0.156 in) diameter, having a capacity of 867 kN (195,000 lbs.) per 305 mm (1 ft.) width of panel, was selected for the flexural strengthening. A triaxial braided quasi-isotropic CFRP fabric was selected for shear strengthening and served as containment of crushed concrete in the event of future over-height impacts. Since the ACI and AASHTO Codes or Guides do not directly address the design with CRPs, strain limits based on debonding of the rods similar to externally bonded CFRP (EB-CFRP) are imposed when determining the retrofitted beam capacity. The load rating evaluation of the impacted beam, the retrofit analysis and design, and the field repair stages are presented and discussed.

Glass fiber reinforced polymer (GFRP) bars are emerging as a feasible, economical solution to eliminate the corrosion problem of steel reinforcements in concrete structures. Confirmation of GFRP long-term durability is crucial to extend its application especially in structures exposed to aggressive environments. The objective of this study is to investigate the performance of GFRP bars exposed to the concrete alkalinity and ambient condition in two bridges with more than a decade old located in the City of Rolla, Missouri: i) Walker Bridge (built in 1999), which consists of GFRP-reinforced concrete box culverts; and; ii) Southview Bridge (built in 2004), which incorporates GFRP bars in the post-tensioned concrete deck. In order to monitor the possible changes in GFRP and concrete after years of service, samples were extracted from both bridges for various analyses. Carbonation depth, chloride diffusion, and pH of the concrete surrounding the GFRP bars were measured. Scanning electron microscopy (SEM) imaging and energy dispersive X-ray spectroscopy (EDS) were performed to monitor any microstructural degradation or change in the GFRP chemical compositions. Finally, GFRP horizontal shear strength, glass transition temperature (Tg) and fiber content were determined and compared with the results of similar tests performed on pristine samples produced in 2015. SEM and EDS did not show any sign of GFRP microstructural deterioration or existence of a chemical attack. Horizontal shear strength and Tg showed slight improvements while the fiber content was similar to the pristine values. The results of this study suggest that GFRP bars maintained their microstructural integrity and mechanical properties during years of service as concrete reinforcement in both bridges.