Reliability evaluation of embeddable reference electrodes for use in reinforced cement concrete

It is now fairly well established that the steel reinforcement bars (rebars) embedded in reinforced concrete bridges and structures can undergo electrochemical corrosion under aggressive marine and or industrial environments and suffer premature deterioration. More recently, quite a number of electrochemical techniques have been adopted for monitoring the corrosion of embedded steel reinforcement. Apart from monitoring corrosion, control of reinforcement corrosion has assumed considerable significance and cathodic protection of reinforced concrete bridges and structures is rapidly gaining ground as a foolproof technology. In all these cases accurate measurement of rebar potential is an essential requirement. Experiences have shown that surface mounted reference electrodes may often lead to misleading data and embedded reference electrodes close to embedded steel reinforcement may aviod unpredictable ohmic resistance in concrete and give reliable data on the electrochemical behaviour. Scanning of the available literature on embeddable reference electrodes reveals that in depth investigation on the reliability of such electrodes has not been attempted. In this investigation, performance of different types of embeddable reference electrodes viz (i) graphite(Gr) (ii) Lead(Pb) (iii) Titanium based electrode (TSIA) (iv) Hydroxyl ion reversible electrode (HRE) has been studied for their stability and reliability in three media viz (a) Aqueous solution (b) Sand mixed with alkaline solution (c) Concrete. Comparison has been made with respect to a standard saturated calomel electrode. It is shown that the hydroxyl ion reversible electrode performs satisfactorily and hence can be considered as a candidate embeddable reference electrode