The potentials of our concrete

Has it really been 30 years in UHPC??????

 

As Tommy did last week I will give a brief (if possible) overview of my own experience with UHPC so you know at least part of my background for posting on this blog – but please bear in mind that I have at least 10 years more to cover than Tommy did!

I am not exactly sure when I became a UHPC nerd, but I have been working on this subject for longer than I am sometimes comfortable admitting. As my story is very closely linked with the story of CRC, I will also describe the development of CRC as seen from my personal angle (and you are welcome to skip the parts you have heard before).

As Tommy did, I also graduated from Aalborg University – just a few years earlier than Tommy. I did my Master’s thesis in 1987 – a joint project with Claes Ellegaard – where we decided to focus on the newly developed material CRC – a fibre reinforced UHPC, although at the time we just called it High Strength Concrete (HSC). With the inventor of CRC, Hans Henrik Bache, as our supervisor from Aalborg Portland we produced a thesis called “Fracture Mechanics Applied to CRC Concrete” – a theoretical study combined with uniaxial tensile testing and fatigue testing. We were very enthusiastic and put a lot of effort into the project – but I must admit that it is probably no great loss that no copies can be located now 30 years later.

This first brush with UHPC hadn’t completely scared me away – and even though the lab at Aalborg Portland had gotten to know who I was they were still willing to hire me, so in 1988 I started working with CRC – and other exotic (at least for that time) types of concrete.

My main job at Aalborg Portland was to manage the international – and internal – research projects we were doing to document CRC, but I also had a lot of time to play around with the materials. This was very much encouraged by Bache, who sometimes liked to spend a lot of time building the theoretical basis for something before he started developing, but at other times would experiment and just try things on a hunch (often with very good results).

This meant that I could spend time on projects just to learn something new without considering the commercial aspects. One such project was trying to develop as strong a concrete as possible based on the CRC formulation – something I got to do together with Claus Bo Jensen, who was a lab technician (Claus is now production manager here at Hi-Con, where he is the only one left from the very start of Hi-Con). The maximum compressive strength we reached was 514 MPa – a combination of bauxite aggregate, 12% fibres and heat curing, so definitely not a type of concrete suitable for building applications. Another project – initiated by Bache – was called LCD (Low Cement Densit (the company selling DSP products) – or Bache would sometimes substitute “Lousy” for “Low”). Not really a project suitable for a cement producer as we ended up achieving 40 MPa with a cement content of 6 kg per m3 – and Aalborg Portland decided that this was probably not the direction they wanted to go in. Yet another project – again initiated by Bache – was magnetic concrete. Bache had developed a concrete motor by using magnetic concrete, and the job for Claus and I was to develop the composition further and find other applications.

What I could see from our research projects – and from participating in conferences and workshops – was that Aalborg Portland were really ahead of everyone else at the time – at least in the relatively narrow field of fibre reinforced HSC – with regard to research and Densit (a daughter company of Aalborg Portland at the time) was ahead with regard to applications.  Peter Buitelaar – who worked at Densit in the early years – has written several papers about this. At my first conference – the 2^nd International Symposium on Utilization of High Strength Concrete held in Berkeley in 1990 – the presentations were about 100 MPa concrete and only a few of the formulations incorporated fibres. The symposium was part of a series of conferences on High Strength Concrete started in Stavanger in 1987 and Berkeley was followed by a conference in Lillehammer in 1993. Norway was one of the leading countries in this field, as a lot of the work in this area related to the gravity structures used in offshore oil and gas projects – but as fibres were typically not used this was again quite different from what we were working on. The projects that were looking at fibre reinforced concrete would typically not look at high strength concrete at the same time – even work like what Namaan was doing with SIFCON and SIMCON. This was one of the reasons we were spending a lot of time and effort on documenting every aspect of CRC – if we wanted to use CRC in structural applications we would need to have answers for all the questions engineers and building authorities would come up with.

Around 1993 we started to focus more on applications in our research efforts. The properties we were documenting were becoming more and more exotic as we were looking at tri-axial compression and material compositions including very high fibre contents, heat-curing and autoclaving. Instead of trying to think up new tests and new properties to document we wanted to start looking at applications – and we were well aware that this would raise a lot of new questions. Our first attempts were aimed at offshore structures, tunnel linings, bridges and columns in high-rise buildings, but either the world was not ready for our concrete – or as researchers we were not really very good at selling (yes – it is difficult to imagine). This didn’t mean that we were finished with the international research projects – they just became more application-oriented.

 

The Steering Group for the MINISTRUCT project – a reasonably young author is the third from the left.

 

In 1993 Aalborg Portland initiated a 3 year project (MINISTRUCT) together with Carl Bro (later Sweco) from Denmark, Instituto Eduardo Torroja from Spain and Bouygues from France. The project – with me as project manager – was part of the Brite/EuRam programme sponsored by the EU and was aimed at preparing CRC for large-scale applications. We learned a lot from the project, but it was quite apparent that Bouygues wanted something a little different than what we could do with CRC – especially with regard to workability and emphasis on passive reinforcement vs prestressing. The project manager for Bouygues was Marcel Cheyrezy – and the person responsible at Bouygues was Pierre Richard – and as MINISTRUCT was in its last year Cheyrezy told us that Bouygues was developing a UHPC of their own – RPC (Reactive Powder Concrete) – or BPR in French. We weren’t too happy about that as we had hoped that after the MINISTRUCT project Bouygues – as the largest contractor in Europe at the time – would start using CRC on some of their projects. As they were developing a UHPC of their own it was clear that this was not going to happen. However, as the two types of UHPC had some differences, we did look at options for combining the two types of concrete in a project – and one example was the pedestrian bridge at Sherbrooke that was completed in 1998. In the first designs Bouygues were investigating CRC for the bridge deck and RPC for the rest of the bridge. In the end, the bridge was designed in RPC – and it took a very long time before the first bridge in CRC was produced.

 

CRC Bridge in Leiden – not the first CRC bridge, but perhaps the most elegant.

 

RPC was presented in several papers in 1996 – and especially at the Fourth International Symposium on Utilization on High-Strength/High-Performance Concrete, which was held in Paris in 1996. RPC took up a full session at the symposium, so where CRC had flown a bit under the radar, the story was quite different with RPC – and very soon this led to a lot of different versions of UHPC being developed in France. Lafarge became responsible for the further development of RPC around 1998 and changed the name to Ductal. Although Ductal and CRC could perhaps be viewed as competitors, we very rarely competed for the same projects, so we maintained relatively close relations as both types of UHPC were being developed. An example of this was the project HITECO – another Brite/EuRam project carried out from 1996 to 1999 – that looked at HPC and UHPC under fire loads or high temperatures. A total of nine partners participated in the project where Mouloud Behloul of Bouygues was project manager. Projects like this – and participation in the fib TG 8.6 work on guidelines for UHPC – has given me a chance to stay well informed about other types of UHPC than CRC – the challenges that the different types of UHPC present and their advantages. As I have covered in other posts (Montpellier, Guidelines) there is a lot of new UHPC’s being developed – but I still see a place in the world for our special brand of UHPC – CRC i2.

Aalborg Portland had initiated the first applications of CRC in 1995, where CRC was used for 42,000 drain covers in the Great Belt-Link in Denmark and 700 M3 of CRC was used for joints in new buildings for Aalborg University in 1995 and 1997. Applications for balconies and staircases started in 1997, but for a cement company like Aalborg Portland – who would sell the special CRC binder – the volumes involved were pretty small.

 

  
One of the first balcony applications in CRC.

 

As Aalborg Portland started emphasizing applications I had changed positions from manager of our Materials Research Department at Aalborg Portland to manager of the newly developed CRC department. One young engineer I had hired for the department – Jan Karlsen – very quickly concluded that if we wanted applications of CRC to really develop, we would need to start a pre-cast production of our own rather than trying to fit UHPC production into existing pre-cast plants. The CRC would invariably be produced at the end of the shift – because of the steel fibres – and while the sales force would include CRC in their portfolio, their main focus was conventional concrete. Jan wanted a pre-cast producer that only produced CRC. This conflicted with the main business of Aalborg Portland, as they would be competing with their own customers, so this limited the effectiveness of what we did.

In 2000 Aalborg Portland decided that they wanted to focus on becoming the worlds leading white cement supplier (the effort that Tommy became part of) and part of that focus included terminating their efforts with regard to UHPC. The small CRC department, however, decided that we still saw a future in UHPC – also for the three of us. Jan Karlsen and Claus Bo Jensen started Hi-Con in 2001 and at the same time I started CRC Technology. CRC Technology would supply the special CRC binder to precast producers (who would add sand and fibres) and CRC JointCast (a dry-mix for use on-site) to contractors along with the necessary advice and documentation. CRC Technology supplied the CRC binder to three producers in Denmark – and after a few years Hi-Con became the biggest customer, which meant I maintained the very close relations. By 2008 Hi-Con wanted to take more control of its supply chain and I agreed to the sale of CRC Technology (that is now a daughter company to Hi-Con). At the same time I started as R&D manager at Hi-Con – a position I am still happily occupying.

I have been lucky enough to learn a lot – and have a lot of fun – at each of my employments. At Aalborg Portland I was able to experience the start of UHPC – and I had the free reins to try a lot of different things in my 13 years there. For 7 years at CRC Technology I was lucky enough that the company was profitable from the start, which gave me the freedom to develop my network further as well as installed a modicum of business sense in me. For my last 10 years at Hi-Con I have been a part of a very exciting journey into new markets and new applications as well as further material developments, so even though it can be hard to believe there is no getting around the fact that it has been 30 years working with UHPC.

I have known people that claim to have 20 years of experience, but really they have 2 years of experience that is 18 years out-dated. They learned something for the first 2 years, and then they applied that for the next 18 years without learning anything new. I hope this is not the case for me. I have been known to refer back to things that we have tried in the past, but I still enjoy learning new things (and I may even remember some of them) and I anticipate some very interesting developments in the near future.

 

 

By education I am a structural engineer, but today most of my efforts are spent in other areas – including material development. In my contributions to this blog I will often include a bit of historical perspective even as I try to challenge the readers a little bit – or as I tease some of colleagues in the field of UHPC. This has perhaps been more of a story about the efforts developing CRC – but I have been along for every step of the way.

I did notice that Tommy included a number of pictures of him working in his own presentation, but it has been impossible to locate any pictures like that in my case :).

And as always – if you have any questions or comments feel free to post them below and I will get back to you.