Analysis of Long-Term Durability Monitoring Data of High-Piled Wharf with Anode-Ladder Sensors Embedded in Concrete

Hongbiao Liu,Zifan Ji,Baohua Zhang,Haicheng Liu

doi:10.3389/fmats.2021.703347

Abstract

The structural durability monitoring (SDM) system for a high-piled wharf in the Tianjin Port of China is devised and deployed with an anode ladder sensor, which provides a means to monitor the state of steel corrosion for the wharf. In this project, the anode-ladder sensors are installed on the reinforced concrete components of the front platforms. After the installation, the monitoring data from the anode-ladder sensor was collected for 40 months. Based on the monitoring data for 40 months, it is proven that the resistance of concrete will be significantly affected by the change in temperature, and the increase in temperature will cause the drop in concrete resistance. Furthermore, the data of the anode-ladder sensor set in the track beam of the front platform shows that the current in anode A1 and A2 relative to the cathode exceeded 15 μA during the four-month period, which is abnormal. The main reason is the influence of concrete temperature and humidity. Therefore, the monitoring data for current, voltage, resistance, and temperature should be combined to determine the activation state of the anode, and cannot be determined simply using the current value.

Highlights

Corrosion of the reinforcing steel in concrete induced by chloride-ion penetration and carbonation of concrete cause serious damage to concrete structures exposed to aggressive environments, e.g., the chloride-induced corrosion of reinforcement in concrete structures in tidal zones and coastal areas (Kassiret et al, 2002; Pech-Canul et al, 2002)
Based on the results of laboratory tests, anodes of 150 mV and 15 μA buried in dry concrete relative to cathode after a short circuit time of 5 s are used as limit values for the activity of the single anode under the usual conditions, and the limit value may be larger when the anode-ladder sensor was set up in a wet environment, such as marine environment (Raupach et al, 2001; S+R Sensortec GMBH Munich, 2009)
This conclusion can be used to determine whether the anode is active and to predict the critical depth related to reinforcement corrosion

Summary

Introduction

Corrosion of the reinforcing steel in concrete induced by chloride-ion penetration and carbonation of concrete cause serious damage to concrete structures exposed to aggressive environments, e.g., the chloride-induced corrosion of reinforcement in concrete structures in tidal zones and coastal areas (Kassiret et al, 2002; Pech-Canul et al, 2002). A large number of harbor structures like wharves, harbor bridges, piers, dams, and other harbor structures are attacked severely the penetration of chloride ions from seawater, which caused many of them to be repaired or replaced (Melchers et al, 2006). In reinforced concrete structures such as wharves and sea-crossing bridges in marine environments, concrete cracking caused by the corrosion of the reinforcement in concrete induced by chlorides is more serious than carbonization of the concrete. Chloride-penetration causes faster rusting of the reinforcement and makes increases the loss, which is the main factor that affects the durability of concrete structures in the marine environment and has been paid extensive attention by those in engineering and academia.

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