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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.

This paper presents the durability of concrete confined with carbon fiber-reinforced polymer (CFRP) composite sheets in sulfuric acid. An accelerated conditioning scheme is employed to comparatively assess the performance of CFRP-confined concrete relative to that of plain concrete, based on various test methods such as optical microscopy, chemical reaction with BaCl2, thermogravimetric analysis, and rapid chloride penetration. Test results reveal that the cement paste of the plain concrete gradually deteriorates through acid exposure, substantiated by the detection of CaSO4 and BaSO4, whereas the CFRP system lessens the detrimental chemical interaction between the core concrete and sulfuric acid. The confining system is effective in preserving the integrity of the concrete and lowering the extent of chloride penetration and conductivity.

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.

This paper presents the experimental investigation of concrete beams pre-tensioned with Carbon Fiber Reinforced Polymer (CFRP) strands. Four rectangular prestressed concrete beams were fabricated and tested under cyclic loading, and then the beams were loaded monotonically until failure. All beams were prestressed with one 0.5-in. diameter (13 mm) CFRP strand. The results showed that bond failure between CFRP strands and surrounding concrete was the main cause of early and brittle failures. Adding extra steel stirrups improved the slippage resistance capacity but was not adequate to prevent slippage at higher loads. A new technique was developed and used by anchoring the CFRP strand at the ends using a steel-tube anchorage system. The new technique prevented the slippage and improved the flexural moment capacity by 39%. An analytical computer model was created to predict the load vs. deflection responses of the beams. The behavior of beams with CFRP strands were compared to beams with steel strands using the same computer program. It was found that CFRP beams had more flexural strength but lower ductility if both beams were designed to carry the same service loads.

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.