Osaka Paper

 

Introduction to the Osaka Paper

 

Readers can check out the contents of this paper by using the hyperlinks (as underlined in this Introduction) to open up to pre-set bookmarks in the Osaka Paper.

  

With a theme of ‘Concrete Structures in the 21st Century’, the First fib Congress was held in Osaka, Japan. 13th October to 19th October 2002. What is referred to here as the “Osaka Paper” was actually Paper No E-163 in the published Proceedings of the Congress and the author’s current CV may be checked out by clicking here.

 

The Osaka Paper was written as a commentary on concreting practice in infrastructure construction projects;  and contained a number of recommendations aimed at all levels of the industry, for improving the quality of major concrete work – and thereby reducing the life cycle costs of our structures. In its scope, the paper ranges from basic practical construction issues to the political considerations affecting procurement and tendering policies. The paper also takes a close and critical look at the limitations of ISO 9001:2000 for quality planning and auditing purposes.

 

The presentation – which was a pre-recorded PowerPoint presentation of 15 minutes duration – can be seen and heard by clicking here. This presentation is focussed on the practical problems created by the constraints of formwork and reinforcement – which make it difficult to make the concrete flow into the all important cover zone – thereby ensuring durability. This is not rocket science!

  

The section headings of the paper are as follows:

  

1 GETTING BACK TO BASICS

 

 

2 PAINTING THE BROADER PICTURE 

 

             2.1 The politics of contract management

 

             2.2 High level application of QA and ISO 9001

 

 

3 CONCRETING FAILURES AND POTENTIAL DURABILITY FAILURES

 

 

4 HOW DID WE GET INTO THIS MESS?

 

             4.1 Some background in contractual realities

 

             4.2 Some historical background

 

 

5 HOW CAN QA GET US OUT OF THIS MESS?

 

             5.1 Adapting ISO 9001 for concrete construction

  

             5.2 From ineffective ISO 9001 requirements to effective concreting procedures

 

 

6 RECOMMENDATIONS

 

 

7 REFERENCES

  

Author’s Update March, 2009 (for potential supporters/contributors to website)

  

1) With respect to quality, I do believe that my Osaka Paper (2002) with its ideas or objectives.* and also its recommendations (Nos 1 – 7) is still relevant to concrete construction work today. It is really very “low tech” – about getting concrete in and around reo and such like. Discussions with a variety of experienced engineers and supervisors from many countries over the last 15 – 20 years have convinced me that the opinions expressed in this paper are sound – and widely held.  

Before reading any further, I encourage those viewers who have a keen interest in the standards of execution for concrete structures, to take the 15 minutes required to watch and listen to the PowerPoint presentation. (Hopefully, the “song of the concrete vibrators” will keep you from falling asleep.)

2) The first person I know of who campaigned for clients to take the initiative on quality issues, was Steen Rostam – who subsequently became Chairman of fib Commission 5. I heard him preach that message in i994 and I have included quotes from that paper to support my recommendations in Osaka. Soon after this, Steen got caught up in other issues, but I expect he was disillusioned by the lack of response to his preaching. Since that time, I have hoped that as an “owner’s engineer”, I might be able to get more response from owners than he did as a consultant. I believe Steen’s statements are generally correct. (He also stated that an international approach was essential). I am naive enough to believe that by striving for an international agreement – which is seen to be technically and contractually sound - we may be able to short-circuit some of the local impasses that occur at state or provincial level in many countries.

3) In view of the reluctance of ISO and European standards to specify the use of ISO 9001, I would particularly appreciate comments on the need for its more effective application (as in Example 2) – and the need for an “effective” interpretive document ( I consider that the best model  for such an interpretive document is RTA Part Q – despite its many limitations). If anyone knows of a better model, please let me know.

These are problems which I have addressed in Appendix G of fib Bulletin 44 * (see below) – and referred to in the Yantai Paper. Although Appendix G needs more than a little fine-tuning, it does break new ground with its proposed integration of the new ISO/European Execution Standard for Structures and a substitute for ISO 9001 which combines the strengths of the 1994 version with the necessary interpretational document as modelled by RTA Q.

I realise that the International/European Execution Standard for Concrete Structures does not cover the specification, manufacture, supply and testing/control of concrete. One major reason for this is the difficulty in achieving consensus over requirements for curing. I admit that the current lack of integration between concrete and concreting requirements is a remaining stumbling block in the road to realistic quality assurance in concreting operations. However, I believe there is a relatively simple solution to this problem – and this must take a high priority in the ongoing quest for quality improvements – even though it is not particularly relevant to safety issues.

*It was this Osaka Paper and its presentation which opened up the door for me to get more involved with fib Commission 5. This Commission deals with all aspects of the life cycle of concrete structures – mainly focussing on repair and rehabilitation and the monitoring and assessment of structures etc. However, they accepted my argument that every “reconstruction” job – even a small one – is in fact “construction” - and usually more complex than new construction. So I got the job of drafting the construction chapters in fib Bulletin 44 – (this is a hyperlink to a website which has some significant extracts from this document.)

4) The Osaka Paper was focussed on QA for concrete structures – and included examples of some dramatic quality failures (Fig 4). While these principles are still very relevant, they now need to be widened to address safety issues – and to incorporate the world of steel structures.

5) The fundamental link between safety and quality is that the potential problems and risks are associated with the same construction process. As each process is visualised by people who are experienced and competent in that process, these potential problems and risks can be identified in an integrated manner. Specified requirements can then be drafted which have a good chance of ensuring that effective preventive procedures will be prepared and implemented during construction. This is the thrust of Appendix G (with respect to quality) and, in the Yantai proposals, these ideas have been extended into the safety arena.

6) Another preliminary recommendation in the Osaka Paper which has become a primary thrust of the Yantai Proposals relates to the place of inspectors and inspection procedures as internationally acceptable specifications are developed for major construction processes. It is now recommended that a “new breed” of inspectors/project verifiers/ technical auditors should be trained in understanding and administering these new process-based specifications – both in the office and in the field. These “inspectors” will be available for employment by owners, consultants, contractors, independent verifiers – or any combination of these: and the inspection requirements for critical construction processes will be built into the relevant standard process specifications.

 

Stuart Curtis

 

March, 2009

For proposed application (2002) see Recommendation No. 9  

       

 

The effective application of quality assurance

 

 principles For producing durable concrete

 

structures The problems and the solutions

 

Stuart Curtis

 (Retired) Manager, Bridge Construction Services

Roads and Traffic Authority, New South Wales, Australia

 

Keywords: concreting processes, reinforcement cages, cover concrete, preventive planning

 

1 getting back to basics

 

The experience of many engineers and concerned construction personnel around the world is that quality assurance (QA) has not given them assurance about the quality of their concrete structures. The increasing implementation of QA contracts over the last 15 years has coincided with an increasing recognition that the durability of many of our recently built concrete structures is significantly lower than for most of those built several decades ago. The durability failures of recent years are symptomatic of what many experienced engineers recognise as a long-term, continuing decline in overall standards of workmanship in the construction industry.[1,2]

 

Durability, however it is specified or evaluated, is a property of the cover concrete, which is that part of a reinforced structure which is most vulnerable to all aspects of poor workmanship, particularly when the structure is built in an aggressive marine environment. Just a glance at the reinforcement cage shown in Fig. 1 should convince anyone that the quality of the concrete cover depends greatly on concreting operations being planned and executed for compatibility with the reinforcement system; and for these matters to be considered adequately during planning and design of the structure.[3]

 

This paper will examine a wide range of factors affecting the quality of concrete and the assurance of that quality. In every case, discussion will focus on how these factors affect the complex, variable, difficult-to-control, difficult-to-observe, difficult-to-specify, and poorly-understood process, by which the cover concrete is placed and compacted, (and subsequently cured)

 

To observe this concreting process effectively, we need to use imaginary, transparent formwork so that the movement of the concrete into the cover zone can be followed, as it is forced through the available openings in the cage ‘wall’ to work its way along and up the (say) 50 mm wide cavity between the near-solid wall of bars and the formwork.

Fig.1 Congested reinforcement in bridge plinth showing gaps available for “flow” of concrete (photo courtesy of the Storebaelt Authority)

Fig.2 Rise in level of cover concrete as it flows and/or is forced through the larger gaps in the wall of reinforcing bars.

 

2 PAINTING THE BROADER PICTURE 

 

2.1 The politics of contract management

 

With durability now being recognized as the primary criterion for the design of marine structures, it is usual for a structural designer to specify, either directly or indirectly, a selected value of some standard resistance criterion as the minimum acceptable resistance for the concrete in a structure. There are various levels of sophistication to the methods used for specifying and evaluating such criteria.[4] However Steen Rostam and Peter Schiessl, currently chairmen of fib Commissions 5 and 3 respectively, made the following statement a few years ago.[2] It is still true today:

 

"Improved specifications, which include long-term qualities, are needed. However they will not by themselves improve in situ quality without a changed attitude towards on site production and towards the interaction between design and production. The competence and experience of the workforce is crucial; and knowledge which long has been left unattended by those responsible. Hence the need for a fundamentally changed approach. This need for change includes the awareness of the problem by the owner from the beginning” Rostam and Schiessl have put their finger on the heart of the problem, and the heart is not in good shape. One of the most basic causes of this "heart disease" is what has been called the “low- bid-syndrome”. Government engineers, particularly those with limited construction experience, find it very difficult to justify why the lowest tender should not always be accepted, at least not without going through a thorough, engineering evaluation process.. To quote again from Rostam and Schiessl:[2]

 

“The construction industry has no motivation to provide anything better than the client demands, clients’ demands are reflected through the legal or contractual conditions regulating their co-operation. In practice the economic conditions and the conditions of liability dominate this co-operation over the technical requirements. The present system of bidding/contracting/awarding/liability governing the owner/contractor/consultant interactions does not promote quality. On the contrary it is a counter-quality system, based on short-term concerns not capable of handling long-term effects. Cleansing is needed. Because of the economic implications involved, the owner should take the lead in this renewal....... the public owners are the most important owners and they show the way ahead also for private owners. However, the public owners are to a large extent guided by their political bosses laying out the short and long-term strategies of their governments".

 

This paper attempts to address the issues of concrete durability in a way that relates the unresolved problems of concrete microstructure research and service life prediction for concrete structures, to the lack of effective interfacing within and between the concrete industry and their government clients, and ultimately between those clients and their political masters. To quote Rostam and Schiessl once more, “these problems are international, hence an international initiative is required”

The author considers that such an initiative is now imperative However it must address the political/contractual challenges in order to solve the design/construction problems. Fig. 3 is intended to provide the overall framework for such an initiative.

2.2 High level application of QA and ISO 9001

Fig. 3 encapsulates all processes which contribute to the quality of construction, as well as the verification of that quality, for the cover concrete,(and is applicable for all concrete work). The diagram includes the primary organisations, (01 - 07), and (S1 - S7), and documents, (D1-D8), which drive or control these processes. It also shows the flow-paths by which effective QA should be achieved.

The diagram demonstrates the need for effective input with respect to concreting practice, concrete technology and applied QA, not only during design and construction contracts, but also during all the tender and pre-tender activities, including input into the owner's standard specifications and process procedures. Two paths are shown for this input. Path B represents input of this technical expertise during a construction contract, where construction auditing is an effective tool for imparting this expertise for the mutual benefit of the owner and the contractor, and ideally, his subcontractors. It focuses on early identification of nonconformities followed by prompt and effective corrective actions. As far as possible it goes one step further, so as to identify potential nonconformities and to develop effective preventive actions to prevent them from occurring.

 

Path A represents the input of technical expertise and technology into the senior management levels of client organisations, and ultimately into the budgets and programmes which determine the finances which will be made available for pre-contract investigation and research for each project. This input should also lead to the release of sufficient finances to support the ongoing development of standard specifications, design details and guide procedures

With reference to Fig. 3; Path B extends from B1 through B2 and B3, and B4 to B5

as shown by the hyperlinks above

Potentially, the most effective way “to get the ear of the politicians” is to present well prepared, well-documented reports demonstrating the financial losses which accrue because of the weaknesses (nonconformities) in our construction and contractual systems. It is absolutely essential that true, believable, and verifiable costs be assigned to selected “failures” (as described below), and that well prepared proposals, including reliable cost estimates, be presented in support of the necessary changes to a public owner’s contract management system.

The recommendations (R 1) shown on Path A, will only develop in substance as they are able to draw from reports (R 2) from individual construction projects, both locally and internationally. As will be illustrated in the following section, (with the exception of structural collapses and falsework failures), concreting/durability failures provide the most promising material for demonstrating the financial wisdom in establishing construction-effective contract management systems. (See Fig. 4)

In this context attention is drawn to the new thrust in the latest version of ISO 9001, compared to the 1994 version.[5]In the 2000 version, a major change has been to introduce the concept of addressing customer satisfaction through ‘application of the system, including processes for continual improvement’, as well as by prevention of nonconformity". This version, even more than previous versions, applies primarily to organizations, and only indirectly to projects, particularly civil engineering construction projects.

ISO 9001: 2000 needs to be applied in the first instance by the owner, in order to satisfy its customer - the politicians and the people. Owners should also expect the continual improvement requirements of ISO 9001 to be applied by contractor and sub-contractor organisations. However, only the relevant requirements of ISO 9001 should be required of the organisations, once they have been selected for a particular project. What are now needed are effective and practical administrative and construction procedures, which will ensure that all available efforts are concentrated on achieving the required quality and assurance for the finished structure. ”Guide Procedures” need to be prepared by owners, and made available for contractors to adapt for their “Contract Quality Plans.”[6]

 

 

3 CONCRETING FAILURES AND POTENTIAL DURABILITY FAILURES

 

The Storebaelt Authority is to be congratulated for making the most determined effort anywhere in the world to apply the QA requirements of ISO 9001 to a major engineering construction project. The concreting challenges were enormous, and the concrete industry is indebted to the Authority for sharing its experience, both good and bad, in a very comprehensive, well illustrated book, [7] from which the accompanying illustrations have been reproduced by permission.

Fig 3 and 4

 

Fig. 4 is typical of the concreting failures which occur far too often on projects both large and small. For all the obvious honeycombing that has to be chopped out and repaired, how many incidents of dubious compaction are not observed, or not investigated, or not properly repaired? While the nonconformity exposed in Fig. 4 should not be regarded as a durability failure, it must be recognised that repairs are not easy to do well, and there is often some doubt about their long-term effectiveness.

   

Finally, just because most of the cover concrete looks all right, and feels all right, can we really be sure that its durability is consistently and truly represented by the tests made on samples taken from the concrete before it was forced through the reinforcement sieve?.

 

It doesn't take much questioning along these lines, before other very important questions have to be asked. How effective can service life prediction methods be, if they are based on the measured or predicted properties of standard cast and cured test samples, or even on test results from cores drilled from structures; when the cover concrete, the life of which we are trying to predict, is subject to such great potential variations in quality. These concerns are addressed in recommendations Nos. 5 and 6.

 

There is another very relevant set of questions which need to be asked. Observing the concreting failure in Fig. 4, the contractor may be able to blame the designer for the congested reinforcement, (including the perceived difficulty of providing access for workers to get inside the cage to operate their vibrators effectively); or the concrete plant controller for sending out a couple of dry batches; and of course the "knife-edge" sensitivity of the prescribed mix to variations in water content! However may not the owner/specifier blame the contractor for failing to control and observe the flow of the concrete at this location, when it seems that he could do it everywhere else?.

 

4 HOW DID WE GET INTO THIS MESS?

 

4.1 Some background in contractual realities

 

The concreting/durability failures of recent years are symptomatic of what many experienced engineers recognise as a decline in construction standards in general. The basic problem is poor workmanship and this applies just as much to senior engineers as it does to labourers, tradesmen and other skilled workers. Few employees want to execute their work poorly, but they do so because of time and/or financial restraints. The greater responsibility rests with the employers who are not prepared to pay for the necessary time, or the right skills, experience, material, or equipment, to do the job properly. However, employers are caught in the same trap as their employees. Contractors are caught in a tough, even ruthless, commercial environment where they can't afford to submit a tender price which provides for doing the job properly. Therefore, if they are to make a reasonable profit and stay in business, they must either cut corners or rely on making successful claims during the course of the contract.

 

What is true of contractors is even more true for sub-contractors, whose pre-tender quotations are often subjected to a downward “screwing” pressure by the various tenderers for a contract. When the contract is eventually awarded, the sub-contract agreements are often far from satisfactory - but this is seldom investigated during the tender evaluation process

 

4.2 Some historical background

In the author's experience, during the 1970s, many construction-contracting companies found that, to stay in business, they had to lower (often drastically), their standards of technical excellence. Those who resisted this tendency were unable to compete in an open tender system, and disappeared from the industry. In welcoming these changes to the contractual environment, owners, including public owners, were just as guilty as the company's shareholders; because they saw only the immediate so-called "bottom line", without realising that they were ultimately going to pay a much higher price, through contract extras, (variations), and increased maintenance. Unfortunately, the often large increase in final contract cost, compared with the initial tender price, was not often publicised. Thus the "low-bid-syndrome" continued to prevail over better engineering judgment.

 

One practical outcome of this commercialization process was that contractors no longer retained their experienced workers. Instead, on each new project, they hired local labour, and sub contracted as many processes as possible, the contractors sometimes being represented only by a site manager.  

 

The greatest single cause for the decline in concreting standards was the effect of the subcontracting system in separating the formworkers’ trade from concrete workers’ “trade”. In the “good old days”, most foremen and leading hands were carpenters, and they took responsibility for concreting operations. They knew that the appearance of an otherwise beautifully-formed concrete structure would be ruined by the presence of any significant surface defect, such as honeycombing or a cold joint. They therefore gave a lot of thought to how they would place that concrete, and make it “flow”, so as to completely surround the reinforcing bars and fill the forms.

 

A really good foreman was thinking sufficiently far ahead to realise that the interior of the reinforcing cage had to be constructed, (and therefore redesigned if necessary), to provide convenient access for all steel fixing and concreting personnel until the concrete had been placed. If it was considered that the concrete could be placed effectively from the top of the cage, it became imperative to provide an adequate system of access holes to insert pump hoses, (or chutes), as well as vibrators. The most experienced carpenters and labourers were chosen to work the vibrators, and above all, they watched the concrete as it moved along the formwork and around the reinforcing bars. They knew the concrete was fully compacted, because they had seen it happening with their own eyes. This is what monitoring really means.

 

The second greatest cause for the decline in concreting standards was the advent of plasticisers and then superplasticisers. It was no longer necessary to use intense vibration to force low-slump, low water/cement ratio concrete through the reinforcing cage, so as to fully fill the space which would become the cover concrete. The specified concrete strength could now be achieved with relatively high slumps, and the skill of the vibrator operator became disregarded, along with the general concreting skills of a generation who had to think about what they were doing before they did it.

 

The loss of, and disregard for general concreting skills has had a crippling effect on the technical competence and morale of engineers as well as construction workers. In the author's experience, it has opened the way for the misapplication of so-called quality management systems, whereby many of the planning, execution and monitoring responsibilities have been delegated to inexperienced engineers and “quality professionals” who lack the necessary construction experience to know what “quality concrete” is, and don’t know how to make it happen.

 

Mention should also be made of the greatly increased cracking tendency due to the changing nature of cement.[8].The cement industry has made these changes over the last few decades in response to demands by contractors for increasingly higher early strengths (for early formwork stripping).

 

Individually and together, all these factors obviously have had their greatest impact on the quality of the cover concrete, and particularly its durability. The impact of these factors must be properly appreciated by concrete technologists and research scientists The tremendous amount of work being done by academics [4],[10]&[11]in this area must be assessed and adapted where necessary, to ensure that it is relevant to the actual processes by which concrete is placed and cured in the field. To make “labcrete” test results applicable to “realcrete” design and acceptance criteria, we need the involvement of people with relevant construction experience, who can systematically evaluate the differences and their effects.

 

5 HOW CAN QA GET US OUT OF THIS MESS?

 

5.1 Adapting ISO 9001 for concrete construction

 

Construction by QA contract is becoming increasingly common, at least in Europe, and in 1997, one of fib's predecessors, CEB, published a Bulletin providing guidelines "to assist in the creation and implementation of a user friendly and flexible quality system based on the ISO 9001 series" [9] However, additional guidelines and examples are needed in view of the major changes in ISO 9001:2000,(as discussed in Section 2 above). Such guidance is necessary because ISO 9001 was developed for factory-based manufacturing industries, and focuses on the inspection and testing of product samples. Consequently ISO 9001 assumes that all processes can be controlled, whereas most concreting processes can't be fully controlled, because they are subject to the vagaries of weather and other site and human factors which are partly uncontrollable

 

Auditing needs to be process-oriented, with the greatest focus on those processes with greatest risk. Audits and auditing requirements must be planned around identified problems, and effective auditing can only be carried out by people with the relevant technical experience to visualize the processes and the potential problems associated with them. Furthermore, the critical construction and monitoring procedures need to be prepared and implemented by people with appropriate experience and authority as well as a belief that QA does work, and a commitment to make it work.[6].

 

ISO 9001 is not a sacred document. Its principles can be applied effectively under a variety of contractual arrangements. For example, while it is usual in Europe for the contractor to be contractually responsible for monitoring the processes, recording non-conformities, and developing corrective and preventive actions, these QA responsibilities could be assigned to the owner or his agent.[6].Most importantly ISO 9001 should not be regarded as a stand-alone document. In a contract specification it should be intimately linked with an interpretive document, which makes the relevant ISO 9001 requirements specifically applicable to the critical construction processes.

 

5.2 From ineffective ISO 9001 requirements to effective concreting procedures

It is not just the ISO 9001 requirements which are ineffective in themselves. Most technical specifications are also ineffective These documents say the right things, but under the constraints of time, cost, and legal liability, the owner or his agents usually find them very difficult to enforce. The contractor does what he considers to be his best, and in the end everybody has to live with that.

It doesn't really matter much whether the specification is prescriptive or performance based, or somewhere in between. Performance-based specifications would be preferable, if we knew what performance to specify, and how to verify that we had achieved it. Unfortunately, most critical concreting processes are what used to be classified in ISO 9001, as "special processes", and which are now defined as "processes where the resulting output cannot be verified by subsequent measurement or monitoring".

Example 1 (Maintaining cover to reinforcement): It could be argued that the quality and thickness of the cover concrete can be verified by inspection and testing of the structure after stripping of the form work. But practically, and economically, this is usually impossible, as in the case of trying to use a cover-meter to make a thorough inspection of the soffit of a box girder bridge located 10 metres above deep water? The only practical solution is to make sure the reinforcement cages are built well, and supported well, and don't get disrupted or displaced during concreting operations. This means "somebody" has to be monitoring the concreting process, as well as the pre-concreting processes. This "somebody" has to have the resources, as well as the authority, to report effectively on any uncorrected nonconformities which are observed during these processes.

Example 2 (Placing and compacting concrete in the cover zone of the vertical face of a heavily reinforced structural member): The technical specification may include such requirements as “The contractor shall (a) place and  move the concrete inside the cage in such a manner and  sequence, that the fresh concrete will pass  through the main gaps in the reinforcement cage, and progressively and totally fill the space between the cage and the form work; without segregation, air or water voids, or cold joints and (b) shall fully illuminate the cavity between the reinforcement cage and the form work, and shall keep it free of concrete droppings from above, and shall continuously observe the cover concrete as it rises progressively to the top of the form work; and shall record the location, nature and size of any nonconformities in this process”. But what do these words really achieve?

Under QA, the contractor is supposed to carry out the work according to the above specified technical requirements, and to provide appropriate records verifying that this has been done. The only convincing way the contractor can do this, is to submit his detailed technical procedures showing how the specified process requirements are complied with, (including when, where and by whom), together with verification reports by the monitoring personnel, including details of any observed or suspected nonconformities.

Unfortunately, ISO 9001 requirements fall far short of calling up such procedures. While Clause 7.5.1 (operations control), states," the organisation shall control production ... through ... where necessary, the availability of work instructions ;and the implementation of monitoring activities" it is left to the contractor to determine whether he needs any work instructions,(whatever he interprets a “work instruction” to be!), let alone detailed  procedures. He is not required to demonstrate in his "work instructions", how he will comply with the specified technical requirements. Yet it is only in the “hows” of the documented procedure, that effective preventive action can be demonstrated.

The owner must make his own interpretation of all ISO 9001 requirements, and must state these unambiguously in the tender documents. All such interpretations should be stated systematically, in an ancillary specification which integrates the technical requirements with those of ISO 9001.This lets each tenderer know what will be expected of him, so he can work out  what it is likely to cost.) (Of course he may be able to develop acceptable alternative procedures.)

The final step is for owners and the industry to develop a comprehensive set of technical specifications, and the accompanying guide procedures, which will ensure that effective control of processes is carried out and paid for. This is the ultimate key to quality-assured concrete structures.

  

6 RECOMMENDATIONS

 

The following recommendations, when converted into detailed guide procedures, will generate the necessary preventive actions, to restore quality to our concrete structures and pride of workmanship to those who build them. Durability failures should be progressively eradicated from our experience.

 

No.1: 0wners' organisations, and the concrete construction industry, should be encouraged to apply the principles of Fig 3 at the local, national and international level. Senior engineers and managers need to be reminded, (and accountants need to be shown), that the real "bottom line" is determined "where the concrete hits the forms", or, to be more precise, "where the concrete meets the reinforcement on its way to hit the forms." Get the cover concrete right and the rest will follow!.

 

No.2: The trade/semi-profession of "concrete worker" should be established at selected technical colleges, with its initial focus being on "durability failures" - identifying the potential problems and developing preventive actions, and with its ultimate aim to infiltrate all influential segments of the construction industry and owner organisations, particularly 05, 06, S2-S6, as well, of course, as S7.

The responsibility of concrete workers at every level will be, firstly, to ensure that the formwork- reinforcement configuration is designed and constructed to facilitate the effective "flow" of concrete, so as to completely fill the forms, and so that the "flow" of the concrete can be observed at all times, and, secondly, to ensure that the batching, placing and compacting processes are so controlled that variability in the concrete supply will not jeopardise the homogeneity of the cover concrete.

 

No.3: The inappropriate use of ISO 9001 by owners, (in contract specifications), and by suppliers, (in quality manuals and quality plans), should be abandoned. Instead, guidelines should be developed for the effective application of those clauses in ISO 9001, (considering both 1994 and 2000 versions), which are relevant and important to concreting and engineering construction processes. These guidelines should demonstrate how the selected quality system requirements must be integrated with the specified technical requirements for each process. The guidelines should also demonstrate how the supplier's process control and monitoring procedures must be documented to conform to specified requirements, and thereby provide assurance that the specified product characteristics (quality) will be achieved. Application should be designed to maximize effectiveness, but with minimal unnecessary costs, and should focus on:

(a) pre-validation of critical concreting processes, (including monitoring), to augment, or even replace product inspection and testing, as the basis for acceptance of the finished concrete product.    

(b) preparation and review of process control and monitoring procedures, together with procedures for identification and control of nonconformities, and development of corrective/preventive action, to form the basis of a supplier's quality system.

   

(c) auditing of those processes with the greatest potential problems, and highest assessed risks, and should be done by people with the right, construction experience and technical expertise.

 

No.4: Validation, or pre-validation, of each critical concreting process, together with the mix proposed for that process, should be carried out through mock-ups and trial pours, which should be designed to reproduce typical worst-case scenarios, combining (a) most congested regions of reinforcement, (b) the concrete mix batched at the lowest acceptable total water content, (lowest equivalent water/cement ratio)(c) most difficult access for depositing concrete cleanly to the bottom of the pour, (d) most difficult access for insertion and/or operation of vibrators, (e) poorest lighting conditions for observing flow of concrete and rising surface level, particularly within the cover zone.

Validation should be demonstrated by both observation and taking of appropriately selected cores, which should demonstrate homogeneity and absence of entrapped air at all locations. A separate validation exercise should also be carried out with the same mix batched at the highest possible total water content,(highest equivalent water/cement ratio).

 

No.5: Validation of the selected concrete mix should be carried out by sampling and testing, (using both cast cylinders and drilled cores), to demonstrate that the hardened concrete, under the proposed field curing regime, will conform to the required durability requirements, including resistance to cracking; and this should be done separately for batches at the highest acceptable total water content as well as at the lowest. (Ideally a third set of tests should be made at the nominal water content, so the set of property versus water content (or w/c) can be produced and interpolated from.)

 

No.6: (a)Concrete acceptance criteria and testing procedures, (both laboratory and field), should be re-evaluated, and redesigned where necessary, to ensure that the test samples are truly representative of the manner in which the concrete has been placed, compacted and cured; and that both the test samples and the results are reasonably reproducible.

    (b) The mix design process must include a thorough investigation of the factors causing variability in the concrete supply process, and must ensure that neither workability nor durability characteristics are adversely affected at the upper or lower limits of the acceptable range of variation.

 

    (c) Effective methods must be developed by the supplier for ensuring that the concrete supply is controlled within these predetermined limits, and that this control is verified.

    (d) The process of verification must be so reliable and the records so appropriate, that they can be used in place of currently used product test results as the primary grounds for acceptance.

 

No.7: A new philosophy of mix design and approval should be instituted by owners, and put into practice by the concrete industry. Because of the lengthy period required to verify the durability characteristics of proposed concrete mixes, let alone aggregate properties such as alkali - aggregate - reactivity; potential concrete mixes should be pre-selected and pre-approved, together with the plant supplying each mix, (based on the verified level of control over batching - mixing - delivery processes). This prequalification of the concrete suppliers and their mixes should be carried out by the owner, before awarding the construction contract, and tenderers advised accordingly.

The owner should also verify that the approved mixes are compatible with the reinforcement details, and should incorporate appropriate process validation requirements into the construction specification, in such a way that it becomes the contractor's responsibility to supply the necessary vibration system to ensure that the cover concrete is homogenous and without entrapped air.

Each approved mix needs to be defined by the following:

1) nominal batch proportions (including total water content Wnom),

2) allowable variation, (achievable control), in total water content (W min to W max),

3) range of flow characteristics from W min to W max, (for constant superplasticiser content),

4)nature and intensity of vibration required for full compaction, without excess loss of entrained air,

5) range in durability properties of hardened concrete from W min to W max,

6) range in routine acceptance criteria, e.g. compressive strength, from W min to W max.

7) effects of various curing regimes upon development of properties defined in (5) and (6).

Selected approved mixes, (where long-term consistency of supply for constituent raw materials can be guaranteed), should be classified as Reference Mixes. These mixes should be used to produce test blocks and associated smaller samples, where the composition of this concrete is consistent and known, and which can be tested by coring and other means, to determine reproducibility in measuring properties such as electrical resistivity, diffusion coefficient, etc., as well as shrinkage coefficients.

Small quantities of constituent materials for Reference Mixes should be stockpiled, and made available for export, to facilitate international collaboration in durability research programmes.

Where Reference Mixes have been used in structures, and water content and location of each batch delivered to a part of the structure have been recorded, it will be easier for in situ measurements of chloride profiles etc., to be correlated reliably to relevant concrete properties.

 

No.8: A new joint Task Group should be formed by fib Commissions 10 and 8, (with required input from other Commissions) to initiate and/or facilitate each of the above recommendations.

 

No.9 (a) Co-operative owners should be encouraged, and provided with appropriate expert advice, to establish suitable "process-focused QA contracts," where the above recommendations are put into practice experimentally. It is envisaged that these special contracts would be targeted initially at concrete structures being built in marine environments.

        (b).Each special contract would be for the design and/or construction of selected parts of a structure or project, but these parts would be separated contractually from the main contract.

        (c).The selection of raw materials, the design  of the concrete mix, the design (or redesign) of the reinforcement, the formwork design, the specified requirements (and the complying procedures) for placing, compacting and monitoring the concreting processes, the selection of the curing regime, and the specified concrete acceptance criteria and associated sampling and testing procedures; as well as the construction auditing procedures and results, should all be documented and recorded, with a view to building up a data base for use by the industry, as indicated by R2 and R1 in Fig. 3.

       (d) When a number of such "process-focused QA contracts" have been initiated in various parts of the world, the experience should be shared, and activities and documentation coordinated, as an international project. The project management team could report to, and be advised by the fib Task Group recommended above.

       (e) The ultimate purpose of this project would be to train up and accredit expert "concrete workers", and to develop practical specifications and procedures for the benefit of all owners and the concrete industry at large.

       (f) By incorporating the special contracts within larger standard contracts, the cost of the research and development work can be minimised, and conveniently absorbed. It may even be possible to demonstrate at an early stage, that the additional costs of true quality control and assurance, are more than compensated for by other cost reductions for the contractor, and reduced claims upon the owner.

      (g) The selection of “process-focussed QA projects” should encompass the full range of “flowing” concrete, from stiff mixes requiring intense vibration to self-compacting concrete.

No.10: This final recommendation is aimed beyond politics and at the hearts of those who claim to be followers of the carpenter of Nazareth. Even those who believe in him only as a prophet or a good man would expect him to have been a competent, thoughtful, and conscientious tradesman-one who planned his work in such a way that the desired end result was assured. How much more should that be true of those who believe he still empowers their lives.[12] They should know, like the prophets of old, that the processes of deterioration attacking our concrete structures, are symptomatic of the underlying processes at work throughout all creation. The universe has a use-by date known only to God, but over and over again the prophets have spoken out his principles for service life prediction.[13] If we are made in the image of God, surely he designed us to be able to create durable structures and to be able to predict with reasonable accuracy the service life of those structures.

This final recommendation has a very practical application for "concrete workers" at every level, including senior management. If God is God then he is both creator and sustainer of the universe. But if he is also a redeemer, he loves to get alongside men and women and help them with their problems. He knows we have a problem with our structures. He also has the solutions. Why don't we ask him to guide and empower our future planning and let him lead us into a durable concrete future?

 

 

7 REFERENCES

 

[1] Curtis, S.,: Quality assurance - the gap between myth and reality. Bridges - Essential to our     Economy, (Proc. AUSTROADS Bridges Conference), Vol. 1, Paper No. 22, 42 pp., 1994

[2] Rostam, S., and Schiessl,P.,: Service life design in practice -  today and tomorrow . Concrete     Across Borders, International Conference, Odense, Denmark, pp. 1-11, 1994

[3] Curtis, S.,: A new approach to contract specifications for constructing durable marine structures     using self-compacting concrete. First International RILEM Symposium on Self Compacting     Concrete, Stockholm, Sweden, pp. 755 - 766, 1999

[4].Andrade, C., Alonso, C., Arteaga, A., and Tanner, P.,: Methodology based on the electrical     resistivity for the calculation of reinforcement life, Proc. Fifth International Conference on Durability     of Concrete, Barcelona, Spain. Supplementary Papers pp 899-915, 2000

[5] Standards Australia,:  the ISO 9001 comparison - 2000 versus 1994, 29 pp, 2000

[6] Curtis, S.,: Design for durability by bridging the gap between designers intent and construction     contract practice. Proc. Fifth International Conference on Durability of Concrete, Barcelona, Spain.     Supplementary Papers pp.823-837,2000

[7].Gimsing, N.,: Concrete Technology, publ. by The Storebaelt Publications,271pp.,1999

 

[8].Mehta, P.K., and Burrows, R.W.,: Building durable structures in the 21st century, Concrete     International,Vol.23,No.3,March,pp 57-63,2001

 

[9].CEB Bulletin 234, Quality Management,(Guidelines for the implementation of the ISO Standards of     the 9000 Series in the construction industry),1997

 

[10]RILEM TC 116 - PCD,: Concrete durability - an approach towards performance testing. Final     report,     Materials and Structures, Vol. 32, No. 217, April, pp. 163 -173, 1999

 

[11].Bentz, D.,: Modelling cement microstructure; pixels, particles, and property prediction, Materials     and Structures,Vol.32,No.217,April,pp 187-195,1999

 

[12]Jesus Christ, (according to his words as recorded in) The Gospel according to John, Chap.5,

Verses 17-21, The Open Bible, Expanded Edition, Thomas Nelson Publishers, p.1080, circa A.D.75

 

[13]Paul, Letter to the Romans, Chap.8, Verses 19 to 28, The Open Bible,p.1148,A.D.57