The use of permanent corrosion monitoring in new and existing reinforced concrete structures John P. Broomfield a, * , Kevin Davies b , Karel Hladky c a BGB Projects Ltd., 78 Durham Road, London SW20 0TL, UK b BGB Projects Ltd., 18 Craig Avenue, Flixton, Manchester M41 5PT, UK c BGB Projects Ltd., 9 Victoria Grove, Fallowfield, Manchester M14 6BF, UK Abstract Corrosion monitoring systems consisting of linear polarisation, concrete resistivity and other probes have been installed in new structurestomonitordurabilityandinexistingstructurestoevaluaterehabilitationstrategiessuchascorrosioninhibitorapplication and patch repairs. The types of sensors used, data collection techniques, results and interpretation are discussed. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Corrosion in concrete; Linear polarisation; Corrosion rate; Deterioration rate; Durability; Chloride attack 1. Introduction Many reinforced concrete structures have given ex- cellent service with minimal maintenance. However, as the infrastructure has aged it has become apparent that some environments were more severe than originally thought, and some construction and design problems have led to lower service lives and higher maintenance costs than originally envisaged. The worst of these problems is caused by corrosion of steel in concrete, either due to carbonation or chloride attack. One of the latest estimates from the USA [1] is that thecostofdamageduetodeicingsaltsaloneisbetween $325 and $1000 million per year to bridges and car parks. In the UK the Department of Transport esti- mates a total repair cost of £616.5 million due to cor- rosion damage to motorway bridges [2]. These bridges representabout10%ofthetotalbridgeinventoryinthe UK. The total problem may therefore be ten times the DoT estimate. There are similar statistics for Europe and particularly the Middle East. Deterioration occurs on buildings and other structures as well as bridges. This paper looks at how permanently embedded corrosionmonitoringdevicescanbeusedtomonitorthe developmentofcorrosionproblemsonaneworexisting reinforced concrete structure before embarking on re- pair or rehabilitation of the structure. There are many devices for investigating corrosion problems. This is because there is no single technique whichwilltelltheengineerwhatheneedstoknow,that is how much damage there is on the structure now and howrapidlythedamagewillgrowwithtime.Corrosion monitoring, when used in association with ‘‘snapshot’’ surveys can give a more complete picture of the chang- ingconditionofastructureintimeaswellasinthethree physical dimensions of the structure. 2. Corrosion monitoring The technique of conducting a condition survey on reinforced concrete structures suffering from corrosion of the reinforcement is now well documented [3,4] and there are a number of techniques that can be used to carry out such an assessment. Table 1 is a summary of the more widely used techniques. All of these techniques can be used in isolation or combinationtoprovidea‘‘snapshot’’oftheconditionof a structure. However, if we are interested in the rate of deteriorationofthestructure,itisusefultomonitorthe condition change with time. This is now being done on newstructureswithlonglifetimerequirementsandolder structures when corrosion damage has been found and repairisbeingdeferredtocost,logisticalorotherreasons. www.elsevier.com/locate/cemconcomp Cement & Concrete Composites 24 (2002) 27–34 * Corresponding author. Tel.: +44-20-8944-6161; fax: +44-20-8944- 6300. E-mail address: johnpbroomfield@aol.com (J.P. Broomfield). 0958-9465/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0958-9465(01)00024-5