International Concrete Abstracts Portal

This research establishes a systematic methodology for selecting a migratory corrosion inhibitor (M-CoI) as a repair strategy for reinforced concrete structures exposed to aggressive environments. Conducted in two phases, Phase 1 involves corrosion testing in pore solutions to evaluate inhibitor efficacy, while Phase 2 examines the percolation ability of M-CoIs in different concrete systems and the performance of M-CoI in RC with corroded reinforcing bars. The findings reveal that the efficiency of the compounds as repair measures is significantly lower than their preventive performance, primarily due to the presence of corrosion products on the steel surface. Additionally, the effectiveness of the M-CoIs is influenced by their concentration and form at the reinforcing bar level; specifically, 4-Aminobenzoic acid (ABA) achieved maximum concentration in its purest form, whereas Salicylaldehyde (SA) and 2-Aminopyridine (AP) reached the reinforcing bar in lower concentrations. Importantly, the study highlights that compounds effective in pore solution may not perform well in concrete, underscoring the necessity of considering the intended application, preventive or repair, when selecting inhibitors. Thus, a comprehensive approach involving both pore solution testing and migration ability assessments is essential for optimal corrosion protection in reinforced concrete.

Geopolymer, an inorganic polymer material, has recently gained attention as an eco-friendly alternative to Portland cement. Numerous studies have explored the potential of geopolymer as a primary structural material. This study aimed to examine the efficacy of geopolymer composites as repairing and strengthening materials rather than as structural materials. We collected and analyzed data from 782 bond strength tests and 164 structural tests including those on beams, beam-column connections, and walls. The analysis focused on critical factors affecting the bond strength of geopolymer composites with conventional cementitious concrete, and the structural behaviors of reinforced concrete members repaired or strengthened with these composites. Our findings highlight the potential of geopolymer composites for enhancing the resilience and toughness of existing damaged or undamaged concrete structures. Additionally, they offer valuable insights into the key considerations for using geopolymer composites as repair or strengthening materials, providing a useful reference for future research in this field.

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.

This paper describes the experimental testing of a reinforced concrete tessellated shear wall. The wall specimen was tested as part of a National Science Foundation-funded research project designed to demonstrate the concept of tessellated structural-architectural (TeSA) systems. TeSA systems are constructed of topologically interlocking tiles arranged in tessellations, or repeating geometric patterns. As such, these systems are designed with easy repair and reuse in mind. The specimen discussed in this paper is a TeSA shear wall constructed from individually precast I-shaped tiles. This paper presents the results of reverse cyclic loading of the specimen, including load-displacement behavior, crack propagation, and energy dissipation. A simplified analytical model for predicting the wall’s flexural capacity is also discussed.

This paper investigates the efficacy of ultra-high-performance concrete (UHPC) jacketing as an option for seismic retrofit (repair or strengthening) of structural components that have been damaged by reinforcement corrosion. Previous work has illustrated that UHPC cover fully mitigates corrosion in the absence of service cracks and significantly reduces the corrosion rate in the case of preexisting cracks. In the present experimental study, cover replacement by UHPC is used to repair and strengthen corroded columns. Six lap-spliced columns designed based on pre-1970s design standards were constructed and subjected to artificial corrosion. Parameters of the investigation were: a) the aspect ratio of the specimens; b) the bar size (to account for the effect of bar diameter loss on bond); and c) the condition of the specimen (repair or strengthening after damage due to application of simulated seismic load to assess the effectiveness of retrofitting corroded components, even after having endured earthquake damage). The results show that thin UHPC jackets replacing conventional concrete cover suffice to impart a significant increase in strength and ductility of the columns. The jackets also endow the corroded and unconfined lap splices with significant force and deformation development capacity, thus alleviating a source of excessive column flexibility in existing construction.