Abstract
The local acidification of secondary anode mortar was regarded as the primary reason for the degradation of the anode system, leading to a decreased service life and uneven distribution of the protection current within the impressed current cathodic protection system for reinforced concrete structures. In related previous studies, a novel type of lightweight functional aggregate was designed and prepared for the secondary anode mortar system, aiming to improve anode performance via acidification mitigation. However, the relationship between optimization effects and this functional component has not been fully clarified. In this study, two sets of experiments were carried out to investigate the effects of lightweight functional aggregates on acidification mitigation and the protection of current distribution. Research results proved that the presence of this functional aggregate was beneficial for mitigated acidification propagation and a more uniform distributed protection current, which demonstrated the importance and effectiveness of acidification inhibition on the optimization of anode performance.
Highlights
Impressed current cathodic protection (ICCP) is proved to be a very effective rehabilitation technique for corroded reinforced concrete structures under a chloride contaminated environment [1]
The obtained results indicated that the presence of the lightweight functional aggregate (LFA) could effectively respond to the acidification, and the higher the volume of the LFA was, the more significant prolonging effect on acidification inhibition could be expected: taking samples (1-1) and (4-3) as an example, when the anode pH value fell below 12.65, the accumulative electric charge quantity was 2005 C for sample (4-3), 224% longer than that of sample (1-1), which is equivalent to 1275 days of service life extension for a primary anode that polarizes with a current density of 200 mA/m2
Samples with a high-volume fraction of the LFA phase present lower fitted slopes and slighter numerical fluctuation. These results demonstrated that the presence of the LFA within the anode system has a positive influence on the maintenance of anode performance
Summary
Impressed current cathodic protection (ICCP) is proved to be a very effective rehabilitation technique for corroded reinforced concrete structures under a chloride contaminated environment [1]. During ICCP treatment, the potential of the corroded reinforcement is negatively polarized to corrosion of the immune region by the external power supply; further, chloride withdrawal and alkalinity recovery [2] can be achieved as secondary beneficial effects for rehabilitation. In the past few decades, investigations on improving the performance of cementitious anode materials were mainly focused on the optimization of its conductivity with conductive enhancement materials, e.g., carbon fibers [4,5], graphite [6], etc. These components generally exhibit low resistivity (10-2~10-3 Ω·cm for carbon fibers [7] and 10-3 Ω·cm for graphite [8]) and are able to decrease the bulk resistivity of cementitious anode materials for one or two orders of magnitude [9]. During ICCP treatment, a series of electrochemical reactions occur on the surface of the primary anode [13]:
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