This paper presents the findings of an experimental study on the corrosion performance of both conventional and corrosionresistant steel reinforcements in normal-strength concrete (NC), high-performance concrete (HPC), and ultra-high-performance concrete (UHPC) columns in an accelerated corrosion-inducing environment for up to 24 months. Half-cell potential (HCP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion activities and corrosion rates. The reinforcement mass losses were directly measured from the specimens and compared to the results from electrochemical corrosion rate measurements. It was concluded that UHPC completely prevents corrosion of reinforcement embedded inside, while HPC offers higher protection than NC in the experimental period. Based on electrochemical measurements, the average corrosion rate of mild steel and high-chromium steel reinforcement in NC in 24 months were, respectively, 6.6 and 2.8 times that of the same reinforcements in HPC. In addition, corrosion-resistant steel reinforcements including epoxycoated reinforcing bar, high-chromium steel reinforcing bar, and stainless-steel reinforcing bar showed excellent resistance to corrosion compared to conventional mild steel reinforcement. There was no active corrosion observed for epoxy-coated and stainless steel reinforcements during the 24 months of the accelerated aging; the average corrosion rateS of high-chromium steel was 50% of that of mild steel in NC based on the electrochemical corrosion measurements; and the average mass loss of high-chromium steel was 47% and 75% of that of mild steel in NC and HPC, respectively. The results also showed that the LPR method might slightly overestimate the corrosion rate. Finally, pitting corrosion was found to be the dominant type of corrosion in both mild and high-chromium steel reinforcements in NC and HPC columns.

Corrosion of steel reinforcing bars in reinforced concrete (RC) structures is a matter of concern among practicing engineers and researchers are perpetually working over it. The development length of reinforcing bars at joints of RC structural frames are more prone to severe corrosion. Due to this, the design stress that needs to be developed in reinforcing bars is largely reduced. In addition, the development lengths of reinforcing bars create congestion at frame joints. This paper is an attempt to overcome these issues. In this paper, an epoxy-grouted nut coupler system is proposed that generates the required design stress in reinforcing bars with a very short development length at end anchorages, due to which congestion of the reinforcing bar at the joints can be avoided. The experimental investigation on the effect of corrosion on bond strength and development length of reinforcing bar in this epoxy-grouted nut coupler is also carried out by performing pullout tests. Statistical models are developed to predict the bond strength between the coupler and reinforcing bar corroded to different levels. This epoxy-grouted nut coupler is an effective tool for developing required stress in reinforcing bars by reducing the actual development length of reinforcing bars in the case of new structures. It is also useful and convenient in regeneration of stress in reinforcing bars at end anchorages that has been lost in corrosion-damaged structures.

This paper presents the findings of a systematic comparison of the corrosion behavior of corrosion-resistant steel reinforcements, including epoxy-coated steel, high-chromium steel, and stainless steel reinforcement in normal-strength concrete (NC) and high-performance concrete (HPC) columns in an accelerated chloride attack environment for 24 months. The corrosion potential and corrosion rate of the reinforcements were monitored using electrochemical methods, and the degradation of the axial compressive capacity of 40 corroded columns over time was obtained and discussed. Findings indicated that corrosion-resistant reinforcements showed significantly better corrosion performance: no corrosion was observed for intact epoxy-coated and stainless steel reinforcements, and less corrosion (54%) was found on high-chromium steel than conventional mild steel in NC, while similar corrosion rates were found for mild steel and high-chromium steel reinforcements in HPC. Results also indicated that HPC provided reliable protection to the embedded reinforcements, showing smaller corrosion rates than those in NC. The measured average corrosion rate of mild steel and high-chromium steel reinforcements in HPC was 17 to 37% of that in NC. In addition, an analytical model was synthesized to predict the axial load-axial shortening relationship of the corroded circular reinforced concrete columns.

Reliability-based durability design of reinforced concrete structures requires a probabilistic service life modeling approach. Probabilistic service life modeling of chloride-induced corrosion should consider the statistical distributions of key parameters that influence corrosion initiation and subsequent damage. For typical reinforced concrete structures (such as bridge decks), these are chloride exposure, chloride penetration resistance of the concrete, chloride-induced corrosion threshold, depth of concrete cover, and corrosion propagation time. Assessing the impact of the use of corrosion-resistant reinforcement, such as epoxy-coated reinforcing bars (ECR), is typically performed through a selection of the chloride threshold and/or propagation time. This paper provides recommendations for statistical distributions for the chloride threshold to be used in service life modeling for structures containing carbon steel and ECR based on both experimental work reported in the literature and field investigations of existing structures conducted by the authors.

The allowable range of epoxy coating thickness specified by ASTM A775/A775M is 175 to 400 μm (7 to 16 mils). This study investigates the impact on structural performance of increasing the upper limit of epoxy coating thickness to 460 μm (18 mils) with respect to deflections, cracking, and bond strength of tension splices. Twenty beam specimens containing single splices as well as splices of bundled bars were tested to failure. The experimental parameters were ranges of epoxy coating thicknesses (300 to 380 μm [12 to 15 mils] and 460 to 530 μm [18 to 21 mils]) and bar sizes No. 16 and 29 [No. 5 and 9]). Test results confirmed the applicability of current code requirements for development and splice length of epoxy-coated bars in tension in ACI 318-14 and AASHTO LFRD 2014, including bars in bundles, up to a coating thickness not to exceed 460 μm (18 mils).