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17 NACE INTERNATIONAL: VOL. 55, NO. 10 MATERIALS PERFORMANCE OCTOBER 2016 Information on corrosion control and prevention Corrosion can be seen around the patch repair of a bridge deck. Photo courtesy of Tourney Consulting Group, LLC. Continued on page 18 Material Matters continued f rom page 14 Test Protocol Evaluates Concrete Repair with Sacrificial Anodes O ne of the most common drivers of concrete repairs is corrosion of the concrete's steel reinforcement. This ty pe of corrosion is often caused by chloride ions in the environment entering the concrete and eventually reaching the embedded steel. When the build-up of chloride ions at the steel reaches a certain concentration, and moisture and oxygen are present at the concrete/steel inter- face, the steel's passive oxide layer will break down and corrosion can initiate. There are many ways to repair con- crete degradation and mitigate corrosion of the underlying steel; however, until recently there wasn't a standard method to evaluate the effectiveness of the numerous corrosion-control technologies incorporated into concrete repairs. This need prompted a research program, funded by the Strategic Development Council (SDC) of the American Concrete Institute (ACI) (Farmington Hills, Michi- gan) and carried out by the U.S. Bureau of Reclamation (Washington, DC), to develop a test protocol, M-82, 1 for evalu- ating concrete repairs—specif ically topi- cal surface treatments, surface mem- branes, and patch repairs with and without sacrif icial anodes. By comparing sample concrete specimens treated with different corrosion mitigation technolo- gies to control concrete specimens receiv- ing no corrosion treatment, the protocol provides a reliable way to predict corro- sion mitigation by a surface-applied or integral repair treatment. According to NACE International member Neal S. Berke, FNACE, with Tour- ney Consulting Group (Kalamazoo, Mich- igan), what has concerned practitioners in the past is that corrosion starts appearing around a new concrete patch once a repair has been made. Before the repair, he explains, the original corroding steel acts as a sacrif icial anode and keeps the reinforcing steel around it from cor- roding. When the patch repair replaces the corroding steel with new steel, he says, the new steel in the repair location often becomes a cathode, which causes the steel adjacent to the patch repair to act as a sacrif icial anode and start corroding. One way to mitigate corrosion of the reinforcing steel around a patch repair, which is known as ring corrosion or a halo effect, is to embed sacrif icial anodes into the patch repair to provide corrosion protection to the old steel adjacent to the new steel in the patch. This ty pe of repair removes an area of distressed or damaged concrete, replaces the corroded reinforc- ing steel if necessary and attaches a sacri- f icial anode to the steel, and then f ills the hole with a cementitious repair material, most often concrete. Patch repairs with sacrif icial anodes are most common on bridge decks and parking decks, Berke comments, but can also be used in appli- cations such as concrete walls and beams. The challenge is to determine which anode will work best in the f ield. How much steel the anode is able to protect depends on how much current it's able to produce, which is contingent on the anode's size and material of composition, he says. The M-82 test protocol, which took about three and a half years to develop, provides a standard method to test and evaluate how well a particular anode mit- igates corrosion in the areas adjacent to the concrete patch. This aspect of the test protocol is discussed in CORROSION 2016 paper no. 7524, "Test Protocol to Evaluate the Effectiveness of Embedded Sacrif icial Anodes in Reinforced Concrete." 2 To represent conditions in the f ield, the test protocol calls for relatively large steel-reinforced concrete samples—40 by 40 by 5.5 in (1,016 by 1,016 by 140 mm)— that are big enough to determine the range of protection provided by the