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.

This paper investigates the seismic performance of exterior beamcolumn joints in special moment frames (SMFs) with varying axial load ratios. Cyclic testing of four additional specimens with an axial load ratio of 0.45 is compared with four companion specimens at 0.10. Each specimen was designed and constructed with Grades 60, 80, or 100 (No. 420, 550, or 690) reinforcement in accordance with ACI 318-19 provisions for special moment frame joints, except for the provisions of joint shear and confinement. While ACI 318-19 tightens confinement requirements for SMF columns and joints, especially under high axial loads, this study reveals that increasing the axial load ratio benefits joint behavior. The study also demonstrates the feasibility of using high-strength reinforcement in exterior beam-column joints of SMFs, provided that appropriate modifications are made. The findings in this study have influenced modifications from ACI 318-19 to the Building Code Requirements for Concrete Structures in Taiwan.

The ACI 318-19 Building Code does not allow the use of headed bars larger than No. 11 (No. 36) due to insufficient experimental data. Thirty large-scale simulated beam-column joint specimens containing high-strength No. 11 (No. 36), No. 14 (No. 43), or No. 18 (No. 57) headed bars were tested to investigate the effects on anchorage strength of key factors, including bar stress at failure, bar size, bar spacing, embedment length, transverse reinforcement, concrete compressive strength, and loading condition. Specimens exhibited concrete breakout, side splitting, or a combination, with four exhibiting a shear-like failure. Anchorage of larger bars is noticeably influenced by joint shear demand and loading condition. Descriptive equations developed based on 164 tests accurately characterize anchorage strength for headed bars up to No. 18 (No. 57). They indicate that anchorage strength is proportional to concrete compressive strength to a power close to 0.2 and that the contribution of parallel ties for large headed bars is lower than that observed for smaller headed bars.

This paper presents experimental testing results on full-scale reinforced concrete (RC) column specimens subjected to quasi-static cyclic loading. Two types of lap-spliced steel reinforcing bars were used: hot-rolled thermomechanically treated (TMT) and coldtwisted ribbed bars. The specimens were tested under varying axial load levels: CD-10 and CD-20 specimens, reinforced with TMT bars, were loaded at 10% and 20% of the column’s axial load capacity, respectively, while the CT-20 specimen, reinforced with cold-twisted ribbed bars, was axially loaded at 20% capacity. In contrast to the cold-twisted bars, the TMT bars’ yield strength exceeded the specified strength by 38%, leading to an underestimation of the required reinforcing bar splice length and significantly impacting cracking patterns and curvature near the dowel end. The CD-20 and CT-20 specimens showed comparable lateral load capacity and initial stiffness, substantially higher than the CD-10 specimen. The CT-20 specimen exhibited symmetrical hysteretic behavior, indicating a consistent response to reversed cyclic loading, with (on average) 10% and 45% higher peak and ultimate displacement capacity than CD-10 and CD-20, respectively, and 45% higher displacement ductility capacity. Notably, only the CT-20 specimen met the acceptance criteria for structural testing described by the code of practice, while the lower ductility and ultimate rotation capacity of CD-10 and CD-20 resulted from the unintended increase in reinforcing bar yield strength.

This study employs advanced nonlinear finite element modeling to investigate Interface Shear Transfer (IST) behavior in RC connections, a crucial factor for bridge durability and safety. The research examines shear transfer mechanisms at the interface between precast girders and cast-in-place deck segments through three experimental methods: beam, push-off, and Iosipescu four-point bending tests. FE simulations evaluated stress distributions, IST capacity, and failure mechanisms. Validation against experimental data shows that the Iosipescu test provides the most accurate representation of IST behavior, exhibiting a stress distribution error margin of only 1%, closely aligning with observed failure patterns. In contrast, the push-off test showed a 30% deviation from empirical data, indicating reduced accuracy in predicting real-world IST behavior. These findings highlight the importance of incorporating the Iosipescu test into IST evaluation protocols, as its greater precision enhances design methodologies for concrete bridges, reduces structural failure risks, and informs future updates to IST-related codes.