In one of our earlier posts “Do we really need another UHPC Guideline?” I mention that Hi-Con has applied for an ETA and we are now ready to add a CE-marking to our balcony elements. It took a little longer than expected, but in the following we will explain a little more about what this means, why we decided to do this – and how the process has been.
Before you get started, however, we will note that this blog entry doesn’t really contain a lot of information specifically on UHPC – it is a description of how we have decided to move forward with documentation of our products and what was required (and as we discovered a description that contains an inordinate amount of acronyms!). we expect that this blog entry will mainly be of interest to those who consider doing something similar – or those who are just wondering how this actually works. So if you read on consider yourself duly warned :)
Why did we decide to CE-mark our balconies?
As described in the Construction Products Regulation (CPR) for EU it has long been mandatory for manufacturers of building products to produce a Declaration of Performance (DoP) and apply CE marking to any of their products. This is true if they follow a harmonised standard, as they are then automatically complying with EU directives for safety and health. In this case the CE-marking indicates a “fitness for intended use”. In our case we are producing elements in UHPC and if we want to design according to this, we have no harmonised standard that we can follow.
That just means that we have to document our solution in each case – and we are not allowed to put a CE-marking on our products. In some cases this has given us more freedom in how we choose to do things and after the first few projects were carried out in Denmark, the lack of CE-marking – or standards that we could follow – has not really been much of an issue – in Denmark. The first balcony and staircase projects were carried out in 1997 and since then I can’t really think of any projects where we have been disqualified because we didn’t have the proper documentation.
One of the first CRC balcony projects – from 1998.
The same has been true for projects in Sweden and Norway, where our documentation has been accepted as equivalent to a standard. Holland was a bit different, as we had to go through a very thorough process on the first few projects – including full scale testing and a “second opinion”. In this case it was a thorough evaluation of the project by Professor Walraaven from Delft. After this there has been no further special requirements in Holland and approval by authorities is very similar to Denmark.
In some countries, however, it is very evident that CE-marking would probably be quite helpful in selling our projects. While we provide our own documentation for a project, the engineer has to make an assessment and decide whether this level of documentation is sufficient – in the case where the product has a CE-marking, the engineer, the owner or the building authorities don’t really have to consider whether our balconies are suitable for installation, as this has already been done by somebody else. This way of thinking has especially been evident in Finland and in England. In London we actually had a project, where our solution was approved by everyone we had thought of – the owner, the engineer, the architect and the building authorities – but the insurance company then decided that they would not insure the building if the balconies were not CE-marked! We have explained our design methods and our material properties quite often – but rarely to an insurance agent. In this case, the interest in understanding our explanation and making a decision in favor of our product was not really there.
At the moment we are looking at a few projects in Germany, and that is another market where we hope that the CE-marking will be helpful – even though we expect that some additional testing may be necessary in the form of a special approval.
In the past we have often been asked why we don’t get national approvals – for instance from the British Board of Agreement – but we have been reluctant to do this, as any approval would typically be limited to a specific product and specific dimensions. The CE-marking is different as it covers a larger market and is wider in scope. With the hope that a stamp of this type would make acceptance easier in our new markets, we decided to start the process. We initiated things in the spring of 2014 – and had not really expected that the process would take close to 5 years.
What is required for a CE-marking?
If you comply with a harmonized standard the steps to CE-marking should be relatively straight-forward, but as no relevant standard is available for us, we had to take another approach. It is also possible to CE-mark a product based on an ETA (European Technical Assessment) if the product is not fully covered by a harmonized standard. So we spoke to ETA Denmark about getting one of these – and soon discovered that the ETA required another document – an EAD (European Assessment Document).
The EAD describes the methods and criteria for assessing the performance of a construction product and an EAD is adopted in cooperation with the manufacturer, the European Commission and the TABs. TAB is short for Technical Assessment Bodies and there are currently 35 of these institutions that are in charge of the technical assessment of pre-cast concrete products – in an organisation called EOTA. That these TABs – that are involved in both the EAD and the ETA – include VTT from Finland, DIBt from Germany and BRE and BBA from the UK was especially interesting for us, as they represent markets that have specifically requested some kind of certification. Rather than going country by country for our certification, we had a chance to be assessed by representatives of all of our targeted markets - and adress any comments they may have – at the same time. A full list of the TAB’s is shown here: https://www.eota.eu/en-GB/content/how-to-find-a-tab/55/
We had hoped to obtain an ETA for our special type of UHPC, but we soon discovered that the ETA – and EAD - had to be based on a specific product – it could not just be pre-cast elements produced in CRC. We chose CRC balconies as a starting point – and then started to put together an EAD in cooperation with ETA Denmark.
EAD and ETA – what should they include?
As we were the ones putting the EAD together – in cooperation with ETA Denmark – we really had a lot of options with regard to what should be included – and apparently we have opted for the complicated route :) The EAD lists documentation methods and acceptance criteria for a construction product and should cover the essential characteristics. What the “essential characteristics” are, is open for interpretation, and we could perhaps have settled for a few parameters such as compressive strength, tensile strength and water permeability. Our concern, however, is that even if you have a UHPC product that can comply with these requirements – you could still have a lousy product. We wanted to provide a description, where if the producer complies with all of these requirements, he should have a product well suited for the application. So in our case, the EAD includes an extensive list of essential characteristics, that we consider important in relation to UHPC performance (examples are compressive strength, shape of stress-strain curve in compression after maximum load is achieved, stiffness, ductility, tensile strength, creep and shrinkage, freeze/thaw, carbonation, fiber distribution, chloride ingress and fire resistance). Also, design calculations are to be verified by full-scale tests.
After the EAD had been accepted by the European Commission (in May 2016), the next step was to prepare an ETA, that would then be assessed based on the EAD. While we had a lot of the test results already, it was still necessary to do a lot of additional testing to document the balconies. For example we have performed extensive testing on behavior at high temperatures over the years, but these tests have typically been done at universities, and when we needed a classification report, it turned out that we needed to do another test at a laboratory accredited for fire testing of load-bearing structures. A short mention of the test is found here. The additional tests – and compiling all the documentation – took another year, but in May 2017 our ETA was accepted. The ETA is only 13 pages, but hundreds of pages have been sent to ETA Denmark as annexes for the documentation. After this we “only” needed the certification by Dancert to be able to CE mark our balconies.
The certification process
Getting the EAD and ETA ready had taken longer than expected – and the same turned out to be true for the certification. We had chosen Dancert as our certifying body, and the first step for them was to receive a certification themselves – so that they would be able to certify based on the EAD we had prepared in cooperation with EOTA and the European Commission. Once this was in order, we had our first visit by Dancert to go through our production and our Factory Production Control (FPC) based on the EAD and ETA.
We had thought that our quality control was quite good, but it turned out that there were a number of things we had really not considered carefully enough. Things like whether all our suppliers had CE marking – and had the right information on every delivery – and tractability in general was one of the issues that took us a while to get fully sorted. One result of this – as I have mentioned in an earlier post – was the need to install two large fiber dispensers, so every mix report would show the exact amount of fibers used. The mix reports were also changed a bit, so they would indicate a number of key parameters for our mixes (w/p-ratio, cement/silica ratio, fiber index). If these key parameters are not within certain limits, this will now trigger an alarm for the mix.
Pictures of automated fiber dosing
Certifying a UHPC material – and based on a rather complicated EAD – was new to Dancert, which also led to a bit of explanation and discussion back and forth about what was important to the certification. This could be a discussion of why ASR is not much of a problem, when you have a large puzzolanic content in your binder, what the minimum tensile strength of a steel fiber should be depending on fiber length or the reasoning (and documentation) behind the limits we have placed on the key parameters of our mix. But after a lot of documents – and a lot of discussions – we have finally received our certification and have been able to CE mark our balconies since March 18th, 2019. It has been a long process, but we have learned a lot along the way and it has left us with a better product – and certainly a better quality – than when we started in 2014. We have to provide a Declaration of Product (DoP) with the balconies and a copy of our DoP can be found here.
Compared to other concrete producers the DoP is a bit complicated and many more parameters are listed. We have been asked, why we don’t limit it to just a few parameters to make it easier for ourselves (which would certainly have reduced the time it took from the start of the EAD to the final certification), but we have actually done this on purpose. We think UHPC is complicated and a lot of very different properties combine to make a good product. We have already seen examples, where other producers – not familiar with UHPC - have copied some of our slender designs. They have copied our dimensions and produced elements based on a 100 MPa concrete. This is not difficult to do, but if you fail to provide the proper ductility by including steel fibers – or you don’t consider the risk of explosive spalling in fire exposure, there is definitely a risk involved in structural applications. We don’t mind competition (well – there is not much we can do about it), but we want them to do it the right way, by realizing that compressive strength is not the only property you need to consider for a reliable design in UHPC for projects like the one below.
Polaris Buildings on Islands Brygge in Copenhagen with Hi-Con balconies in CRC i2®.
Our CE marking is very new, so we are looking forward to seeing how it is received in the market – or if it has any effect at all. If the CE marking facilitates the approval of our balconies, we will certainly consider doing something similar for other products such as staircases and facades. Hopefully it will be a shorter process next time as our EAD, ETA and CE marking mostly deals with approval of the material – very little is really product related.
It turned out to a very long blog entry (again!) and if you made it to the end, I hope I answered any questions you had.
Thank you for reading the post, feel free to leave a comment and questions below.