International Concrete Abstracts Portal

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.

Bridge embankments serve a vital role in raising the roadway profile to the bridge deck elevation for passage of vehicles. It is common practice to construct embankments utilizing compacted lifts of soil obtained from nearby borrow pits. Soil borrowed from regions of predominantly expansive clay soils can be problematic for bridge embankment construction. High plasticity soils swell in contact with moisture, inducing vertical and lateral pressure on embankments. Mechanically Stabilized Earth (MSE) walls are particularly susceptible to soil expansion as they try to confine high soil expansion pressures through soil reinforcement and mobilization of a stabilized volume behind the face of the wall. This paper provides insight into the investigation of MSE wall movement, abutment movement and corresponding bridge beam distress, and reinforced concrete failures resulting from high plasticity soil backfill in existing bridge embankments. Remediation strategies are discussed which are directed at the expansive soil behavior within the embankment.

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.

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.

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.