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projects.bre.co.uk/conrepnet

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CCOONN RREEPP NNEETTNETWORK NEWSLETTER No.4

November 2004 Special Issue: Future performance - discussion on industry response to owners’ aspirations

Index

Mid term review Future performance: discussion on industry response to owners’ aspirations Methodology for monitoring and assessing performance Forthcoming events

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NEWSLETTER No.4

Mid Term ReviewNetwork Co-ordinator Dr. Stuart Matthews (BRE)

These activities have been supported by an extensive dissemination programme (27 events so far). Initially this focussed upon raising awareness about the project, but now as project technical information becomes available, dissemination activities will concentrate upon the findings and outputs of the technical work packages. As part of the dissemination activities, the CON REP NET project held a collaborative meeting with the REHABCON project on 15 October 2004. This event went very well as was attended by some 40 people. The pdf versions of the presentations given will shortly be available to CON REP NET Members on the project website.

This took place in Maastricht as a parallel session alongside the E-Core and ECCREDI confer-ence B4E entitled Building for a European Future. The B4E event was used to launch the ECTP – European Construction Technology Platform, which is expected to make a significant contribution to the formulation of the forthcoming Framework Programme 7.

Work has been progressing steadily on the technical work packages concerned with Past Per-formance of Concrete Structures (WP2) and also Current Practices (WP3). These are now sub-stantially complete, in spite of some difficulties encountered along the way - see the blue box be-low. Previous editions of the Newsletter (see below) have given an overview of some aspects of the findings from these WP’s. Progress with our mapping activities was also outlined on page 7 of Newsletter 3. We now need your assistance to populate the web-site which has been set up for this purpose with technical information. You will be contacted separately on this matter.

CON REP NET Technical deliverables completed or in an advanced state with drafts pre-pared [WP2 & WP3]

• Catalogue of past performances and review of problems of achieving durable repairs [D11]

• Current European practice in rehabilitation of concrete structures [D13] • Research state-of-the-art in rehabilitation of concrete structures [D14] • Client aspirations for durable rehabilitation of concrete structures and their wider implica-

tions [D16] • Methodology for monitoring and assessing performance of rehabilitated concrete struc-

tures [D12]

Web Based – available shortly to CON REP NET Members [Have you registered for your Password ?]

• Web-based Catalogue of Durability Issues, Past Performance and Case Histories [D10] • Mapping : web-site access

Network Co-ordinator Dr. Stuart Matthews of BRE

In September 2004 the Network had its Mid-Term Review andwe are pleased to be able to inform you that the EuropeanCommission’s Scientific Officer responsible for the CONREP-NET project, Mr Christophe Lesniak, has told us that he is con-tent for the project to proceed to the second half subject to thefinalisation of the mid-term review and TIP documents.

Since the launch meeting for the CON REP NET ThematicNetwork in Madrid in February 2003 we have produced 8 com-plete / draft main technical outputs [NB. 14No technical outputsare planned for the project overall]. We have also held 6 meet-ings for members and the public [11No planned for projectoverall].

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NEWSLETTER No.4

As a Network member you should so far have received the two electronic newsletters shown be-low describing progress with the work and future activity plans – please remember to let us know if you have changed your email or job in your organisation. Further progress in the process of addressing the challenging task of developing Performance Concepts (WP4) is described. The approach being used is to follow the supply chain, starting with the owners’ aspirations. The discussion on industry response to owners’ future performance aspirations was reported in Newsletter 3. This issue continues reporting on page 3 of this edition the discussions concerning a basis for a possible industry response to the owners’ aspirations for durable repaired concrete structures. As a contribution to performance based concepts, a prospective methodology for monitoring and assessing performance of repaired concrete structures is described – see page 10 of this Newsletter. Ongoing and future work upon performance based approaches to remediation of concrete struc-tures (WP4) are detailed in the yellow box below. Performance Based Approach to Remediation of Concrete Structures: Ongoing & Future Work [WP4]

• Review of owners’ expectations from rehabilitated structures • Identify key performance requirements • Establish limitations on current approaches to meeting these requirements • Consider options to improve industry’s ability to meet these requirements • Develop and promote a performance-based approach to meet the needs of the whole

supply chain Also a small reminder. We recently requested Members to forward their Cost Statements for travel and subsistence claims legitimately incurred in attending CON REP NET Member events in the second year period (October 2003 to end September 2004). I trust you submitted your claim. Please note these are capped at 1000 Euro plus a 20% overhead contribution (overall total 1200 Euro). Finally, important future Network activities are planned and these will include a series of meetings in Prague in June 2005 as detailed below: Open CONREPNET Seminar for all network participants. Opportunity for short presentations

by participants on repair or remediation topics. Partners meeting. Members and partners meeting – Day 1. Opportunity for short presentations by members on

repair or remediation topics. Members and partners meeting – Day 2.

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See page 15 for further details. We really hope that as CON REP NET Members you can be there with us, to hear about what has been achieved with you the information provided through your co-operation. Your contributions have been invaluable so far and we are extremely grateful to those that have been able to support us in this way. Thank you. We also need you to share with us your experiences and knowledge on a wide range of topics to help us move forward with the concepts for performance based rehabilitation of reinforced concrete structures. Come to Prague, contribute and (hopefully) make a difference to the way things are done in the future. Please remember to visit the CON REP NET web-site: www.projects.bre.co.uk/conrepnet and ensure that you have registered. We need technical details from you / your organisation to assist with the mapping exercise. More on this at a later time. Registering and contributing to the mapping activities will enable you to receive the downloadable technical outputs when they be-come available.

CONREPNET Network Launch Introduction General discussion on members’ expecta-tions Past performance Current practice Future performance Dissemination of information Review of dissemination activities

CONREPNET TN Interaction Meeting and Initial Results from Technical Tasks Introduction Past performance – the first results Current practice – the first results Meeting with owners, 13 November 2003 Mapping activities Future performance: discussion on owners’ expectations Forthcoming events

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NEWSLETTER No.4

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Future performance-discussion on industry response

to owners’ aspirations Dr. Vaclav Vimmr (STU-K)

While the first stage of the WP 4 package called Future Performance was devoted particularly to client aspirations the next stage is dealing with industry response to those. The analysis carried out within Work Package 2 “Past Performance” activities has brought quite interest-ing results as far as success of repairs is concerned. It has been rather disappointing to find out that only 75% of repairs survive 5 years. 25% of repairs survive 10 years and only 5% survive 25 years. There is no belief that situation has improved dramatically when comparing past performance and present performance. In principle we can distinguish four main categories of owners according to their

financial constraints technical knowledge and knowledgeable staff number of assets and their importance to public capability to organise effective quality assurance measures management methods

Consequently owners have a wide range of aspirations and different requirements. We suggest to rec-ognise the following types of owners:

National Authorities Large Commercial Organisations Small Organisations “Lay” Owners

As far as management process is considered the following procedures play an important role a) Procurement

Repair work is procured from contractors though the smaller organisations rather appoint consultants to carry out procurement process for them. Financial constraints usually lead to acceptance of the cheap-est tenders. This does not necessarily mean the best value for spent money. b) Whole Life Costing

In spite of the fact the most owners understand the advantages of whole life costing (WLC) in decision making it is rarely used in practice. Practical difficulty in applying WLC is caused by the relatively high values of discount rate set by National Banks (or Governments). High values of discount rate are inappropriate to long life structures such as for instance bridges. However, some advanced owners perform WLC calculations to aid maintenance decisions.

Dr. Vaclav Vimmr of STU-K.

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NEWSLETTER No.4

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tttooo ooowwwnnneeerrrsss’’’ aaassspppiiirrraaatttiiiooonnnsss c) Acceptance Testing

It has been found that the most owners do not practice acceptance tests and rather rely on goodsupervision of the repair work. Nevertheless in some countries acceptance tests are carried outexcept for minor works. It seems that would be useful to develop guidance on how to carry outacceptance tests. d) Maintenance Records

It has been reported that quality and quantity of the recorded data are not always adequate.There are a number of management programs available. Some organisations use systems devel-oped in-house. In some countries, Land Use Legislation and Building Legislation require mainte-nance records including information on repair materials and maintenance schedules. e) Factors that influence management

There are other external and non-technical factors influencing management. These are mainly thefollowing:

Government policies and initiatives Political implication Attractiveness of the neighbourhood Strength of local economy Available finance Environment Public awareness and media position Duty of care to the general public

The main owner aspirations can be briefly summarised just stating that repairs should be: durable, economic, operational and often also aesthetic. Two discussion meetings were conducted with the aim to clarify what industry can really do tosatisfy owners' requirements. The first meeting with Consultants and Researchers hosted bySTU-K took place at RSD Prague in May. The second meeting focused on discussion with Mate-rial Suppliers and Repair Specialist, was held at BRE in September 2004. The industry response should take into account attitude of owners. Owners are not clearly satis-fied with the performance of repairs. Too many repairs have unexpectedly short and uncertainduration. Due to this fact it is difficult to plan future maintenance.

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NEWSLETTER No.4

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---dddiiissscccuuussssssiiiooonnn ooonnn

iiinnnddduuussstttrrryyy rrreeessspppooonnnssseee

tttooo ooowwwnnneeerrrsss’’’ aaassspppiiirrraaatttiiiooonnnsss There is a conviction that many problems are caused by the acceptance of the cheapest tenders ratherthan best value for money. The cheap tenders force prices down to the satisfaction of budget holders butgenerate a number of negative side effects:

Irresponsible contractors are appointed to the job. In order to win work and stay in business, contractors take on cheap and less skilled labour. Cheap tenders have no scope for dealing with the unexpected problems that can become appar-

ent after work has commenced. Constraints on available time can force contractors to carry out work irrespective of the weather

(hot, cold, wet) that can reduce the quality of repairs. There is a tendency to treat symptoms rather than causes of deterioration.

Certification of workers who do the job is quite important. Approved contractor needs approved certifiedworkers. Evaluation of skills has to be made repeatedly. Stress on workmanship should be extended tothe design process. It has been found that incorrect diagnosis of the original cause of deterioration is quite frequent cause offailure. This has been indicated in bridges but in large panel buildings as well. It seems that methodologyof investigation of concrete structures should be improved. As far as selection and specification of products is concerned experience of consultants is essential.There is reluctance of consultants to use new materials. The performance of new materials should bebetter known especially in view of their long term performance. There is still need to develop ideas of criti-cal requirements on how test and gain information. Materials are to certain extend, still tested according to different standards. Some contractors may substi-tute alternative and cheaper material that complies but does not provide the same durability. Solutionmight be to make tighter specification corresponding to Performance Based Approach. It is believed thatdevelopment of classification system of materials would be useful.

The most owners prefer high level of site supervision as far as there is sufficient budget for that. The own-ers should seek appropriate warranty system without regard to the problem for subsequent rectification ofquality/durability of repaired structure. Owner should chose a reputable contractor supported by QA sys-tems and records. It is also important to develop an element of trust. It has been found that different practices exist throughout Europe regarding inspection and supervision. Insome cases consultants do both design and supervision. Partnership arrangement of a consultant and acontractor creating “package approach” is increasingly used in the UK. Sometimes there are two separateconsultants, one for specifications and other for supervision.

Manouchehr Hassanzadeh (Lund Institute of Technology), Mårten Janz (Swedish Cement and Concrete Research Institute) and Hans Danielsson (Team Danielsson Ltd) in the members meeting in Prague last May.

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NEWSLETTER No.4

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tttooo ooowwwnnneeerrrsss’’’ aaassspppiiirrraaatttiiiooonnnsss Method of an independent control engineer (bureau de contrôle) is common in France. This bringsadvantages but some disadvantages as well. The problem might be that control engineer is not toofamiliar with the background of the repair design. Similar approach – owner appoints independentcontrol engineer – is common in Finland. However, there are also special situations when continuityfrom design to repair is essential. In some countries approvals or certificates are needed to launch a new product. The example could befamous processes ATec (Avis technique) on ATEx (Appréciation Technique d´Expérimentation) com-monly used in France. Harmonised European Standards specify procedures leading to CE-marking. Standards address only properties of materials (products) and methods of their testing. Acceptancetesting is responding to the need for approach that address material properties and the whole systemused for application in practice. In fact acceptance testing is even more important for repairs than forthe newly built structures. Acceptance testing may partly avoid supervision. Number of test methods have already been avail-able. For example “pull-off” test to check adhesion to the initial material or in case of shotcrete meas-urements of geometry. It is believed to create set of requirements for acceptance testing would be veryuseful. There is a number of materials, methods and technologies for durable and effective rehabilitation.They might be suitable for application under certain circumstances. Some of the listed methods areincluded in a set of European standards EN 1504.

Concrete cover restoration Impregnation Corrosion inhibitors Coatings Replacement of black steel by stainless steel Shotcreting Electrochemical methods Cathodic protection Durability performance approach

In couple of large projects the durability performance based approach has already been adopted. Ex-pected durability ranges from 100 to 120 years. The method is based on use of specific durability indi-cators and acceptance treshold depending on environmental condition and a requested lifespan. Theprocess usually uses the following sequence

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NEWSLETTER No.4

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definition of structural elements and their requested lifespan definition of environmental conditions (namely agressivity, humidity, temperature changes) selection of durability indicators concrete mix design testing of concrete samples service lifespan prediction

Owners are not always aware of technical complexity of repairs. They would like to get solved their prob-lem quickly and as cheap as possible. The fundamental requests of owners are

certain level of performance for given amount of money clear definition of life of structures or repaired structures.

Some owners do not fully understand issues, risk involved and also obligations. Performance based approach to the rehabilitation of concrete structures is rather new way of deliveringdurable and cost effective repairs and rehabilitation of concrete structures. Consideration of durability offunctional properties, cost, environmental and social factors together with aesthetical needs will be re-quired to improve rational multi-parameter decision making for performance based approaches. Performance approach will enable a supply chain to be reworded for achieving stated objectives and notby reference to the amount of work done or materials used. This should promote better value and im-proved price certainity against service delivery. The intention is to develop a strategy that would help tocreate atmosphere of trust and accountability in which the members of a supply chain are motivated toinnovate and provide an excellent service and optimising value for money at the same time. There is no generally accepted expectation of the life of a repair. There is no reason to believe that themore recent state-of-art repairs are performing any better than those made in past. However, it is be-lieved that significant improvement in the performances of repairs could be achieved by the followingapproach:

The original cause of the deterioration must be properly investigated and correctly diagnosed. Independent checking of proposed designs of repair should be established to minimise failures

due to incorrect diagnosis, design of repair, selection of materials. Qualified and closer supervision of the repair work to minimise consequences of poor work-

manship and timing. Application of acceptance testing where useful Development of partnership of the supply chain and owners Application of performance-based approach to the repair and rehabilitation of concrete struc-

tures as a way for delivering durable and cost effective solutions

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NEWSLETTER No.4

MONITORING AND

ASSESSING PERFORMANCEBy C. Andrade, I. Martínez, G. P.Tilly and S. Matthews

INTRODUCTION This report relates to Task 2.4 of Work Package 2 ‘Past Performances of Concrete Repairs’ of theCONREPNET project. The objectives of the task are:

Review experience gained in preceding tasks in order to develop a standard methodology by which the performance of rehabilitated concrete structures can be monitored and assessed in the future (D12).

Prepare promotional abstracts/headline information for dissemination and communication activi-ties.

These objectives via the concrete deterioration model, the methodology of testing and monitoring, andthe ‘scoring’ of Repair Performance Indicators (RPI’s). METHODOLOGY PROPOSED The methodology is based in the definition of requirements, R, of the repair material or repaired struc-ture wich are qualified through Performance Indicators, PI, that are scored in levels from 4 (very bad) to1 (very good). A higher score means a bad performance while a low one represents success of themethod. If for a particular requirement there are identified several PI, each Performance Indicator shouldhave a relative or percentual weight, ImPI, depending of their ranking of importance. The final assessment is made through the calculation of a Repair Performance Index, RPI, which isobtained by averaging all PI multiplied by its relative Importance, ImPI. The Average value of the indica-tors would be calculated as the sum of the individual Performance Indicators multiplied by their individ-ual Importances.

∑=n

1PIIm.PIRPI

Where n is the number of PI used to qualify each repair and remediation intervention method. Figure 1shows a hypothetical plot of the evolution of the RPI in a particular structure as a result of its evaluationin periodical inspections. The evolution of RPI can be expressed as a score from 1 to 4, or can be normalized in percentage, %,by dividing the actual value of RPI by the predefined success threshold value.

Prof. Carmen Andrade of Instituto de Ciencias de la Construccion “Edu-ardo Torroja”.

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A pre-specified Target value of the Success Criteria for the performance of the repair system, RPI, must be set as a reference value. Notionally this target value would be specified at the time of making the re-pair. In figure 2 is shown by a dotted line the hypothetical value of this threshold. When the RPI reaches a value below a success threshold value previously defined, would mean the need to consider renewal of the re-pair or to apply an additional repair system.

1

2

3

40 5 10 15 20

Time (years)

RPI

1

2

3

40 10 20 30 40 50

Time (years)

RPI

Figure 1. Evolution of RPI with time. Figure 2. Hypothetical threshold value (dotted line) EFFECT OF ENVIRONMENT Another important consideration relates to the impact that the aggressivity of the environment can have on the durability of the repair method. The RPI can be modified by taking into account the impact of the envi-ronment in the durability of the repair method. This can be made by attributing as well a score to the ex-pected performance of the particular repair method in each aggressive environmental class. Thus, the aggressivity of the environment can be negligible in the case of cathodic protection or can be important in the case of patching. Table I shows the scoring (named as EA, environmental aggressivity), of the aggres-sivity classes of EN-206 in several repair methods. Table 1. Environmental aggressivity

Class

Repair method X0 X1 XC3 XC3 XC4 XD1 XD2 XD3 XS1 XS2 XS3

Patch 1 1 1 2 3 2 3 4 2 3 4

Coating 1 1 1 1 2 1 2 3 1 2 3

Crack injection 1 1 1 2 3 2 3 4 2 3 4

Sprayed concrete 1 1 1 2 3 2 3 4 2 3 4

Electrochemical techniques 1 1 1 1 1 1 1 1 1 1 1

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AAASSSSSSEEESSSSSSIIINNNGGG PPPEEERRRFFFOOORRRMMMAAANNNCCCEEE The effect of the environment on the durability of the repair method can be evaluated by defining a newRepair Life Indicator, RLI, obtained by averaging the RPI with the EA, giving for instance a relative impor-tance of 20% to this last one. RLI = 0,8.RPI+0,2.EA The RLI will substitute the RPI when the durability of the repair method is of importance. It can be evalu-ated and monitored equally as shown in Figure 2. Finally, it has to be emphasized that the methodology proposed is not a rigid framework, but it has beingconceived as a flexible tool to help to make more objective the assessment and the monitoring. REPAIR AND REMEDIATION METHODS BEING CONSIDERED IN CONREPNET Either because it is the most economically detrimental mechanism or because it is the most frequent, cor-rosion of reinforcement will be taken as an example. The repair and remediation intervention methods considered as the most frequents in corroding structures,following the results obtained on the previous parts of this task 2 are: Patch, Coating, Crack Injection,Strengthening, Sprayed concrete and Cathodic protection. The most common repair option of concrete structures deteriorated by corrosion is the so called “patchingrepair” in which deteriorated concrete is removed and the substrate and reinforcement are cleaned. Then,the geometry is restored by placing a primer on the reinforcements, a bonding agent between new and oldconcrete, a repair mortar and finishing with a coating. A patch can be simply a single repair material or atwo or three component system. This repair method has been recently complemented with the embedmentof zinc anodes in the repaired zones in order to avoid the progression of the corrosion in the zones adja-cent to the repaired ones. On the other hand, Cathodic protection is an old repair method that is gaining market in the case of con-crete structures. Less applications are made however of the realkalization or chloride extraction as thesetechniques are more modern, but few companies apply them. Finally, another recent technique that is still controversial in its efficiency is the application of inhibitorsfrom the concrete surface. However, the application of hydrophobic agents seem to be relatively efficientin keeping the concrete dry. As an example for consideration, tables 2 to 3 show the PI selected for two repair methods and the rank-ing of the PI used for the qualification.

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MMMOOONNNIIITTTOOORRRIIINNNGGG AAANNNDDD

AAASSSSSSEEESSSSSSIIINNNGGG PPPEEERRRFFFOOORRRMMMAAANNNCCCEEE Example 1: patching Requirements, Performance Indicators and weights on each indicator are proposed on Table 2. On each in-spection, the Repair Performance Index must be calculated averaging the weight of each requirement. Table 2. Patching

R P.I ImPI

Requirement Performance Indicator Relative Weight

ΣImPI = 1 Score Performance Criteria Score at Date...

4 >0,4 mm

3 0,1-0,4 mm

2 0,1mm Bond Debonding crack width (in situ,

visual) 0,1

1 <0,05mm

PI1.ImPI1

4 >0,4 mm

3 0,1-0,4 mm

2 0,1mm Cracking in the patch material 0,2

1 <0,05mm

PI2.ImPI2

4 >6mm/year0.5

3 3-6mm/year0.5

2 1-3mm/year0.5

Carbonation and chloride front rate 0,1

1 <1mm/year0.5

PI3.ImPI3

4 xxx

3 xxx

2 xxx

Permeability

Water sorption 0,07

1 xxx

PI4.ImPI4

4 >-350 mV (SCE)

3 -250 / -350 mV (SCE)

2 -100 / -250 mV (SCE) Reinforcement Potential 0,15

1 <100 mV (SCE)

PI5.ImPI5

4 >10µm/year

3 5-10µm/year

2 1−5 µm/year Reinforcement Corrosion Rate 0,2

1 <1mm/year

PI6.ImPI6

4 <50 Ω.m

3 50-100 Ω.m

2 100-500 Ω.m Concrete cover resistivity 0,1

1 >500 Ω.m

PI7.ImPI7

4 <10 MPa

3 10-20 MPa

2 20 MPa-Parent concrete

Durability

Concrete cover mechanical strength 0,08

1 >Parent concrete

PI8.ImPI8

Repair Performance Index (RPI) ΣPI.ImPI

Tarjet value for the success criteria (determined at the time of repair) XXX

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MMMOOONNNIIITTTOOORRRIIINNNGGG AAANNNDDD

AAASSSSSSEEESSSSSSIIINNNGGG PPPEEERRRFFFOOORRRMMMAAANNNCCCEEE Example 2: Cathodic Protection Requirements, Performance Indicators, Scores and relative importance on each indicator are proposed in Table 2. The only PI considered are based in the measurement of its efficiency Table 2. Cathodic protection system

R P.I ImPI

Requirement Performance Indicator Relative Weight

ΣImPI = 1 Score Performance Criteria Score at Date...

4 >-500 mV (SCE)

3 -500/-600mV (SCE)

2 -600/-700mV (SCE) Potential Off (Eoff) 0,3

1 <-700mV (SCE)

PI1.ImPI1

4 <100 mV

3 100-200mV

2 200-400mV

Instantaneous polarization from Initial Potential (Eini-Eoff)

0,2

1 >400mV

PI2.ImPI2

4 <30 mV

3 30-60mV

2 60-100mV

Bar Potential

Depolarization in 4 hours 0,3

1 >100mV

PI3.ImPI3

4 Non protected

3 moderately protected

2 Protected

Passivity Verification Technique

Efficiency 0,2

1 Well protected

PI4.ImPI4

Repair Performance Index (RPI) ΣPI.ImPI

Target value for the success criteria (determined at the time of repair) XXX

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Your contributions to this newsletter are most welcome! If you have anything to communicate through this newslet-ter please don't hestitate to contact us. Dr. John Morlidge / BRE e-mail: MorlidgeJ@bre.co.uk Project Co-ordinator: Dr Stuart Matthews / BRE e-mail: Matthewss@bre.co.uk Newsletter Editor and dissemination matters: Minna Sarkkinen / CT Group e-mail: Minna.Sarkkinen@ct-yhtiot.fi

Next issue June 2005

More information about the CON REP NET Network, can be obtained from the website http://projects.bre.co.uk/conrepnet

Forthcoming Events

June 2005, Prague CZ Open CONREPNET Seminar for all network partici-

pants. Opportunity for short presentations by partici-pants on repair topics.

Partners meeting.

Members and partners meeting. Opportunity for short

presentations by members on repair topics. Members and partners meeting.

Events hosted by STU-K. Dates will be confirmedlater.

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