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26 OCTOBER 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 10 CATHODIC PROTECTION S Editor's note: This article, originally published in April 1974 MP, has been designated a classic by the MP tech- nical editors, as the applications and technologies described by pioneer- ing concrete corrosion expert Richard F. "Dick" Stratfull are still pertinent today. Subsequent to the continued construction S the Subsequent to the continued construction S continued construction of the interstate highway system, the state S the of the interstate highway system, the state S interstate of the interstate highway system, the state S highway system, the state highway departments have endeavored to S ghway highway departments have endeavored to S departments have endeavored to maintain them free of ice and snow. This S in maintain them free of ice and snow. This S them maintain them free of ice and snow. This S free of ice and snow. This "clea "clear pavement policy " has required in S ent "clear pavement policy " has required in S policy " has required in - creased us creased use of sodium chloride (NaCl) and S sodium creased use of sodium chloride (NaCl) and S chloride (NaCl) and sometime sometimes calcium chloride (CaCl S cium sometimes calcium chloride (CaCl S chloride (CaCl 2 ). As a re sult, chlori d e s have p en etrat ed th e S lt re sult, chlori d e s have p en etrat ed th e S i d e s re sult, chlori d e s have p en etrat ed th e S have p en etrat ed th e con concrete and caused the reinforcing steel S te concrete and caused the reinforcing steel S and concrete and caused the reinforcing steel S caused the reinforcing steel to rust in the same manner as marine structures. 1-2 This has led to spalling of the concrete. Ev e n t h o u g h t h e re a re p u b l i s h e d descriptions of techniques for measuring t h e h a l f c e l l p o t e n t i a l s o f c o n c re t e - encased reinforcing steel 1-3 and otherwise evaluating the properties of the concrete associated with corrosion of reinforcing steel, 4-6 only one report has been found on cathodic protection (CP) of an atmospher- i cal ly e xp o sed bri d ge sup erstr u cture. 7 However, even in this case, CP of the deck itself was not attempted. Theory of Application Concrete, when wet, has an electrical resistivity of 10,000 Ω-cm. 8 Therefore, to MATERIALS PERFORMANCE CLASSIC Cathodic Protection of a Bridge Deck: Preliminary Investigation R.F. S TR a TF ull, formerly with the California Department of Transportation, Sacramento, California transport current from an anode horizon- tally past each parallel and crossing piece of the reinforcing steel mat would require extrem ely high v oltages. Howe ver, if a highly conductive material were spread across th e top of th e bri dge deck and ano d es emb ed d ed in it, th en th e hig h resistance of the concrete would enter only in that part of the circuit, which was the thickness of the concrete cover over the reinforcing steel. In this case, conven- tional protective voltages would be ade- quate. Electrically Conductive Overlay One material investigated as an electri- cally conductive overlay was coke breeze. It was found that coke breeze could be mixed with ~17% asphalt and maintain a specific electrical resistivity of ~50 Ω-cm. However, the stability of the asphalt-coke breeze mix- ture with this percentage of asphalt is not sufficient to support the impact loading of vehicles. Thus, it was decided to overlay the asphalt-coke breeze with a 2-in (51-mm) thick l ayer of normal highway-quality asphalt concrete pavement. To test the composite design of the asphalt-coke breeze and asphalt concrete, a test pavement was placed for further evaluation. After placing the test pave- ment, a truck loaded to maximum legal weight limit passed over the section 3,802 times without evidence of failure of the road surface. The pavement was judged to have a high probability of success with- standing vehicular traffic.