Development of galvanic anode performance (GAP) test for assessing the longevity of galvanic anodes for reinforced concrete structures

Abstract

NACE impact report (2016) states that nearly 50% of reinforced concrete (RC) structures experience major repair in about ten years. The existing approach of patch repair does not address the root cause and may not be durable – resulting in re-repair and huge economic loss. Galvanic anodes (GAs) are gaining widespread acceptance to achieve maintenance-free repair life for a few decades. However, a few GAs with inadequate characteristics are prematurely failing (within a few months). There are no short-term test methods to evaluate the longevity of GAs. Therefore, this work focuses on developing a short-term test method (Galvanic Anode Performance (GAP) test) to assess the longevity of GAs. For this, the GAP specimen was designed by simulating CP-protected RC structure as follows: (i) GA embedded in bedding mortar (i.e., anode), (ii) Nichrome mesh (i.e., cathode simulating rebars in RC structures), (iii) position of anode and cathode, (iv) application of potential difference (0.5, 1, 5, 10, 20, and 30 V) to accelerate the degradation of GAs, and (v) electrolyte to simulate conductivity of concrete. Applied potentials > 5 V could not capture the difference in characteristics of GAs. However, potential differences of 0.5, 1, and 5 V could show the true behavior of GAs in various exposure conditions. Then, an approach is proposed to evaluate the service life of GAs. Possible reasons for the premature failure of anodes were investigated by evaluating pH and pore volume of encapsulating mortar. The GAP test can help practicing engineers to estimate the longevity of GAs.