Non-Destructive Investigation of A 44-Year-Old RC Structure Exposed to Actual Marine Tidal Environments Using Electrochemical Methods

Investigation of deterioration progress in marine structures without destroying them is crucial as early detection of damage before applying the suitable remedial measures. This study presents a series of non-destructive assessment on a 44-year-old naturally corroded RC structure exposed to marine tidal environments using observation of defective appearances and electrochemical tests. The visual observation was conducted by inspecting the corrosion condition of steel bars, crack patterns, and the spalling of concrete cover. The electrochemical investigations carried out in this research consisted of the half-cell potential mapping, the electrical resistivity of concrete, and the corrosion rate of steel bars. The results revealed that electrochemical test results conducted in this research were in good agreement with the actual deterioration degree checked by defective appearances. The RC structure was categorized as Grade II-1 (first half of the acceleration stage). Based on the deterioration degree, both applications of small direct current to control the potential of steel bars in immunity condition and patch repair method by removing the chloride contaminated concrete were recommended as appropriate repairing strategies, and they could extend the service life the of structure

COMBINATION OF IMPRESSED CURRENT AND SACRIFICIAL ANODE CATHODIC PREVENTION TO IMPROVE CORROSION PREVENTION SYSTEM IN REINFORCED CONCRETE

In this study, effectiveness of impressed current cathodic prevention (ICCP) and sacrificial anode cathodic prevention (SACP) in corrosion prevention of rebar in reinforced concrete (RC) is compared. Firstly, SACP method is applied in chloride-contaminated specimens which are kept in air curing condition for 150 days, then changed to dry/wet cycle NaCl solution cycle condition. Result shows that extremely high initial protective current, then decreased drastically until being stabilized. The depolarization value increases in dry/wet cycle condition than air condition. Secondly, ICCP method is applied with different protective current density, where corrosion of the steel bars were accelerated beforehand. Result shows that higher current density provides higher depolarization value. However, even smaller current density still able to reach 100 mV criterion after 56 days of test period. Based on both results, ICCP and SACP were combined as “hybrid system” to extend the service life of SACP. Initial current consumption was controlled in ICCP stage before changing to SACP stage. Result shows that on potential value increases gradually in ICCP stage and stabilizes after changing to SACP stage, while depolarization value in SACP stage shows more stabilized value compared to the value in SACP only.The Conference was canceled because of COVID-19

Polarization Characteristics of Steel Bar in Chloride Contaminated Mortar Mixed with Fly Ash and Blast Furnace Slag for Corrosion Prevention: 3 years’ test result

This research focuses on the effect of mineral admixture, such as fly ash, and blast furnace slag, in order to prevent steel corrosion embedded in chloride contaminated reinforced concrete mortar specimens. Three series of mortar mixture of different chloride content with 50% of water-to-binder ratio was set as mixing mortar of the specimens. Ordinary Portland cement was also prepared as comparative to common mortar specimens. Electrochemical measurement methods such as half-cell potential, corrosion current density and grade of passivity were conducted as evaluation of the steel corrosion. Measurement results indicates that even though corrosion condition remains passive in all specimens, specimens with fly ash and blast furnace slag show better performance in recovery of passivity grade and half-cell potential value of the steel bars

PARTIALLY REPAIR METHOD OF DETERIORATED RC BEAMS BY SACRIFICIAL ANODE CATHODIC PROTECTION AND CORROSION INHIBITOR

Patch repair of deteriorating concrete, which mainly involves the replacement of chloride-contaminated concrete with the fresh alkaline patch concrete is a common intervention to rehabilitate the defecting reinforced concrete (RC) structure while the concrete replacement of this process is expensive. Application of curative corrosion inhibitor directly on the surface of corroding rebar before new patch material casting is recommended as easy to use approach for new corrosion attack. Sacrificial anodes have been used to limit the extension of concrete replacement and extend the service life of patch repair to RC member. This study focuses on the utilization of sacrificial anode cathodic protection arrangement and corrosion inhibitor in partially repair RC beams. Two specimens of 44-years of serious chloride-induced corrosion condition having a length of 2400 mm and 200x300 mm cross-section were prepared as RC-1 and RC-2. The polymer-modified mortar as the patch repair material was applied to the middle tension area in the dimension of 70x150x800mm. Four cylindrical ribbed sacrificial zinc anodes with 30 mm diameter and 130 mm length installed in the parent concrete by LiOH cementitious coating material. A specially modified epoxy paint as corrosion inhibitor was applied to the tensile steel bar surface of the patch repair section in RC-2. The exposure condition of the specimens was on two-days wet and followed by five-days dry in laboratory air condition until 12-months observation. Depolarization test of rebar by the calomel-saturated electrode (CSE) on the side section of specimen’s surface, the current density of sacrificial zinc anodes and rebar, anodic-cathodic polarization curve are measured regularly until 12-months observation as the performance evaluation was presented in this paper. The sacrificial zinc anode tested in this research affects polarizing the potential of rebar in the deteriorated RC member. However, the high polarization is limited to 15 cm away from anodes in parent concrete, not in the patch repair section, due to the inherent differences in the properties of patch repair material and parent concrete. The application of corrosion inhibitor in the rebar surface of patch repair part may extend the polarization effect of anodes and significantly increase the polarization distance until two times