International Concrete Abstracts Portal

This study investigated the shear bond behavior, with and without optimized interfaces, between conventional and geopolymer steel fiber–reinforced concretes. Sixteen prismatic and eight cylindrical composite specimens were cast with interface inclination angles of 45° and 27°, respectively. In prisms, the inclined interface area was varied: eight were optimized by 50% to balance compressive and shear stresses, allowing a more accurate determination of cohesion and friction coefficients under steel fiber effects. Fiber volume fractions of 0.0, 0.5, 1.0, and 1.5% were tested, and the influence of epoxy at the interface was also assessed. Optimized prisms exhibited adhesive failure along the interface, matching the internal friction angle, whereas non-optimized prisms showed cohesive failure with a friction angle deviating from the interface. Increasing fiber content improved performance, especially when combined with epoxy. A new bond shear strength model is proposed, incorporating friction, cohesion, and fiber effects.

Through uniaxial tensile tests, the mechanical behavior of bone shaped concrete reinforced with glass textile and carbon textile impregnated with epoxy resin was verified using a stress-strain response curve. It was observed that elements reinforced with glass fabric presented different mechanical responses depending on the textile reinforcement rate. In samples with two layers of glass fabric, three stages were formed, as predicted in the literature. In the specimens reinforced with only one layer, the structural incapacity of the element was observed. For samples reinforced with carbon textile, there were problems with slipping and spalling caused by the concentration of stress at the ends of the piece. Even so, it was possible to clearly determine the three stages in the curve response of the material. The stresses experimentally obtained in the elements reinforced with carbon textile obtained results approximately five times greater than those of the glass fabric.

Pourbacks and overlays are commonly used in bridge elements and repairs, as it is crucial to corrosion protection that the bond between grout and concrete in these regions is carefully constructed. The integrity of the bond is crucial to ensure a barrier against water, chloride ions, moisture, and contaminants; bond failure can compromise the durability of concrete structures’ long-term performance. This study examines the influence of surface preparation methods on the bond durability and chloride permeability between concrete substrate and grouts, including both non-shrink cementitious and epoxy grouts. A microstructural analysis of scanning electron microscopic (SEM) images was conducted to characterize the porosity of specimen interfaces. Pulloff testing was performed to quantify tensile strength. Results show that a water-blasted surface preparation technique improved the tensile bond strength for cementitious grout interfaces and reduced porosity at the interface. In contrast, epoxy grout interfaces were less affected by surface preparation. The study establishes a relationship between chloride ion permeability, porosity, and bond strength. The findings highlight the importance of surface preparation in ensuring the durability of concrete-grout interfaces.

Despite improvements in nondestructive testing (NDT) technologies, the quality assurance of concrete reinforcing bar placement is still primarily conducted with conventional methodologies, which can be time-consuming, ineffective, and damaging to the concrete components. This study investigated the performance of two commercially available cover meters and one groundpenetrating radar (GPR) device. A cover meter was found to have the greatest accuracy for depths smaller than 3.19 in. (81.0 mm), while the GPR performed better for greater depths. The effect of reinforcing bar depth, diameter, and type; neighboring reinforcing bars; and concrete conditioning on the performance of the devices was quantified. The use of epoxy-coated reinforcing bar, galvanized reinforcing bar, and stainless-steel reinforcing bar were found to have a negligible effect on cover meter accuracy. A model was developed to predict the precision of the GPR post-measurement analysis given a depth and concrete dielectric constant.

This study reviewed, synthesized, and extended the service life prediction models for conventional reinforced concrete (RC) structures to those with advanced concrete materials (that is, high-performance-concrete [HPC] and ultra-high-performance concrete [UHPC]), and corrosion-resistant steel reinforcements (that is, epoxy-coated [EC] steel, high chromium [HC] steel, and stainless- steel [SS]) subjected to chloride attack. The developed corrosion initiation and propagation models were validated using field and experimental data from literature. A case study was performed to compare the corrosion initiation and propagation times, and service life of RC structures with different concretes and reinforcements in various environments. It was found that UHPC structures surpassed 100 years of service life in all studied environments. HPC enhanced the service life of conventional normal-strength concrete (NC) structures by over three times. In addition, the use of corrosion-resistant reinforcement prolonged the service life of RC structures. The use of HC steel or epoxy-coated steel doubled the service life in both NC and HPC. SS reinforcement yielded service lives exceeding 100 years in all concrete types, except for NC structures in marine tidal zones, which showed an 88-year service life.