International Concrete Abstracts Portal

Corrosion of prestressing steel can threaten the durability of prestressed concrete. To ensure the durability of unbonded post-tensioning (PT) systems, it is crucial to investigate the effects of construction defects such as grease leakage and high-density polyethylene (HDPE) sheath damage. This study quantified the thickness of grease coating (PT-coating) and HDPE sheath damage as experimental variables. An accelerated corrosion test was conducted in two environments: 1) chloride ions only (Cl-) and 2) both chloride ions and dissolved oxygen (Cl- + DO). The corrosion current density and weight loss of prestressing strands and the suspended concentration density of corrosion cell solution were measured to quantify the corrosion performance. Increasing the grease coating thickness over 0.3 mm (0.012 in.) did not significantly enhance corrosion resistance. Realistic levels of HDPE sheath damage had no significant detrimental effects on durability; however, excessive HDPE sheath area loss must be avoided for long-term durability. It was examined to quantify the interrelationship between three data: electrochemical measurement, weight loss, and suspended concentration density as quantitative corrosion data. The findings of this study can serve as a basis for developing durability-related provisions, as well as controlling the construction defects of unbonded PT systems in field applications.

Sudden failure of reinforced concrete (RC) dapped-end beams of bridges and viaducts has occurred all around the world in the last few years due to corrosion of steel bars. The danger of sudden and brittle failure is often due to pitting corrosion of steel bars, concrete crushing, and loss of bond in steel bars. In this paper, the risk of failure of reinforced dapped end supports at the ultimate state under vertical and lateral loads is investigated, focusing on the consequences of pitting corrosion and loss of bond in steel bars. A simplified strut-and-tie model was developed to predict the load-carrying capacity of dapped-end supports. The model includes the effects of corrosion of steel bars, loss of bond, and concrete crushing due to the biaxial state of stresses. Several laboratory experimental tests regarding the flexural behavior of RC beams with dapped-end supports were collected to validate the proposed model.

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.

While many studies have evaluated the corrosion performance of hot-dip galvanized reinforcement (ASTM A767), few have evaluated that of the newer continuously galvanized reinforcement (ASTM A1094). This study compared the corrosion resistance of A767 and A1094 reinforcement, along with uncoated reinforcement, using the Southern Exposure (SE) and cracked beam (CB) tests. The galvanized reinforcement was tested both with and without damage to the coating, as well as after bending the bars. Both A767 and A1094 reinforcement exhibited better corrosion resistance than uncoated reinforcement, but corrosion rates on both types of galvanized reinforcement increased when the bars were bent. ASTM A767 and A1094 reinforcement exhibited similar corrosion resistance and can be used interchangeably.

This study characterized pitting corrosion in prestressed piles, linked it to stress concentration factors through ultimate strength tests, and incorporated the findings into a simple predictive damage assessment model. Six one-third-scale Class V concrete prestressed piles were exposed for 38 months to outdoor tidal cycles simulating a marine environment. At the end of exposure, 24 strands were extracted from the piles, and corrosion loss along the strands was quantified using a new Pascal’s law-based strand profiler. This identified regions of locally higher steel loss caused by pitting corrosion. The same data set was used to confirm gravimetric loss measurements by summing localized section losses over the specimen length. Profiler data was complemented by microscopic imaging to further define pitting geometry. Ultimate load tests were conducted to examine the effect of pitting on residual tensile strength and ductility. Similitude principles were used to develop a model for predicting in-service stress in pile strands using available inspection report crack width data.