You could think of him as Mr Sprayed Concrete. Tom Melbye did not invent sprayed concrete; but he has improved it, and made it easier, safer and much more pleasant to apply. Also – over the course of 40 years – he has transformed a once small Finnish equipment company called Normet into a global concern supplying equipment, expertise, concreting chemicals and additives worldwide.
Melbye is officially retired now and living in Switzerland, but that has not stopped him from setting up and running his own company, Tamcon, specialising in sprayed concrete, grouting and underground rock support – as well as advising Normet as an active board member – and he keeps himself generally useful, preventing himself from becoming bored. In particular, he supports other businesses as an advisor and board member to develop and promote sustainable solutions.
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TBMs are perhaps the glamorous part of tunnelling: gigantic machines visibly excavating rock and carrying it away. Almost every tunnel however needs some sort of lining once it has been dug, and this is where Melbye has carved out his life’s work. How did it happen?
It was of course an accident. “When you are young and you really don’t know what to do, you do what your friends do,” he says, “and there were a couple of guys who were friends of mine and had started studying at engineering school and I thought maybe I should also try that.” But then he struck out independently: “This was the 1970s, and a little before we finished all my classmates were saying ‘Consulting is a very pleasant way to spend your life because you are in a nice warm comfortable office and you can get to play with these wonderful big new computers that are coming in just now, so you get the excitement of that as well.’”
“They may have been right, but that has never attracted me. I always like to be hands on, to be curious about things and to be looking at things and doing things myself. So, I got a job on a big hydropower project for the Oslo Electricity Board as a control engineer. Out of thirty classmates, I think I was one of only two who went into construction. I was on the mountain, I was working shifts, I was out with the hard hat on and all of that – but that was my decision, and that was my way.
“I spent a year, more or less, a season, on the hydro project. I found myself in charge of others; but just telling other people what to do was not my style either. So, I joined Thor Furuholmen, which at the time was the country’s largest tunnel contractor.
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By GlobalData“That is a time that I will never regret: I learned a lot, and at a very young age I was given huge project responsibility. And as well as that, it all had to do with rock support. It was working with sprayed concrete, and injection, and things that became very important for what I was later to do in life.
“This was around 1977. In Norway, they started to use wet-mix sprayed concrete in the early 1970s and it was still what you might call a pretty Stone Age solution. I was on this huge hydropower project on the west coast of Norway and spraying concrete was a very dirty job: it is dusty and hard work, and there was nobody that really wanted to do it. So of course, on any project the youngest engineer always gets given the dirtiest, nastiest job; and the youngest engineer was me.
“But I took an interest in it because I thought ‘this could be improved very much.’ And I started to do – and I was allowed to do – some testing, and of course, some failing in the tests; but we started around then to spray concrete with silica fume and with steel fibre mixed in, and we modified the equipment from hand-held to first robotic wet-mix spraying equipment.
“Some things that are in standard use today we had begun doing already by the end of the 70s; and with those changes we were able to improve the whole process.”
It was not one single change that made the difference, but all kinds of factors were involved: “We were improving the working environment: there was much less dust. We replaced mesh with use of steel fibre in the mix. The material was being applied more evenly and with much enhanced safety, with better adhesion, so there was also less rebound and waste, and so importantly we could increase production, reduce the cycle time, and of course that brings money into the contract. Time is money in any contract so that was our start on this and a good incentive for it to be taken up.
“And Thor Furuholmen, the owner and technical director of the company, became interested in what this young engineer was doing on this big project of his, and they supported me, and encouraged me to do more testing and more development. In hindsight, I think that is probably why you can say that this was how – with a couple of other guys – we really developed the whole thing of what today is modern sprayed concrete.
“In the course of that, I have been responsible for two patents in the industry – a concrete improver admixture for sprayed and normal concrete that replaces external curing agents, and an admixture system that gives total consistency control in sprayed concrete and grouts.
“At that time, there was a real benefit to be working on sprayed concrete in Norway. This was also the time when we were starting to build oil platforms; the engineers working on those were making a push in concrete technology in using superplasticisers and other types of admixture. And I followed that and added the same products into sprayed concrete, and of course, that further improved the quality of the mix.
“You could lower the water/cement ratio, you could limit the amount of cement, and in that way you could move from something that was very temporary, to techniques and products that had quality and durability about them; and of course, in the last 20 years that has been developed even further.
“So, I think what really happened overall was that we looked not only at the single things – mix, design or the type of additive – but at the whole process. We had quite modern, self-propelling robots; we brought in special mono-pumps that could deliver the mix without pulsation and so could spray more evenly; and today, those still, more or less, form the basis for spraying equipment.
“Because in my philosophy it is important that if you want to get to a new solution or innovation you have to understand the whole process of what is going on. It is not only one individual part that needs to be changed: to improve a process you need to understand the entire chain of it; you need to think holistically. I spend a lot of my time now as a trouble-shooter. I have been advising around the world on problems with sprayed concrete and tunnel linings, and if you do not understand the whole process you cannot come up with even a prototype for a solution.
“You can find many factors involved in a problem. If you talk about sprayed concrete it can be the mix design; perhaps you have the wrong sand or gravel; you may have a cement that is not really working with the accelerator that you have chosen, so perhaps you have to choose another cement and other accelerators. It can be that you have too much water which is affecting the quality. You normally start by doing a screening with the material you use: you try it in the lab with a formula that you think will work, then you take it to the next step with a test spray outside the tunnel, or wherever you are working and see if it works well there.
“You have also to understand the requirement – what is it the client actually wants? Because in the early days, I have seen some projects where they have not really had a modern specification: what do they mean when they say this or that? That is one of the reasons that I became heavily involved in EFNARC, the European Federation for Specialist Construction Chemicals and Concrete Systems. Among other things, it sets guidelines and specifications for sprayed concrete, for suppliers and contractors, but also best-practice training and certification for sprayed-concrete nozzlemen.
“A similar problem is that there are no specifications for a method that is new. It takes several years for the legislation to catch up. Of course, to try anything experimental or new in a project as large and expensive as a tunnel is not easy. A lot depends on the client. Some clients are risk averse; some like to test new methods; some are very rigid.
“So the client role is vital; and that is also true now that we must take climate change into account when building our tunnels. Of course, tunnels take a lot of concrete, and we must tackle their CO2 emissions. But it is already possible: we can reduce carbon emissions and reduce them to meet the international goal of net zero. The Portland cement component is the big emitter; you can replace that with slag or with fly ash. You can actually reduce the cement in concrete down to zero if you use new binders such as geopolymers and other additives. You can use activators to make it set at low temperatures. All of that is possible, and it is possible today.
“But much more than simply adjusting the concrete mix is necessary. You have to consider the entire process of building the tunnel, its entire life, and maintenance after it has been built. It needs everybody to be involved. The designer has to design it so that it uses fewer materials; the contractor has to use electric-powered construction vehicles and sprayers; the supplier has to produce zero emissions in making the components and chemicals and in transporting them to the site. We now have solutions to all of those; within a relatively short time, we can reduce emissions from sprayed concrete by more than 50%; and then we can bring it down to net zero.
“And none of that can happen unless the client is part of the process as well, and unless there are real incentives for it to happen. The entire tendering process is central. For example, there are currently several big tunnel projects tendering in Norway. Up to thirty percent of the tender price is discounted if the tenderer scores highly on sustainability and the CO2 footprint. Thirty percent is a substantial amount, therefore people will be inspired to be innovative and imaginative, and to work on sustainable, CO2-reducing solutions. CO2 reduction makes good economic sense, in both the short- and long-term, and the smart solution brings far less damage. But to do all that you need incentive. The politicians made the Paris Agreement back in 2015; but we must walk the walk, not just talk the talk.
So, what’s next for Melbye? “I retired from Normet in 2016 and I am proud that during my time we built it up from a small Finnish company to a global player. We are present in 30 countries, on all five continents, and we are now a company that supplies not only the equipment and the expertise for sprayed concrete, but makes the admixture chemicals you need for it as well. Every company has more or less the same technology and the same equipment. It is the people who make the difference.
“And the fun of tunnelling lies mostly with the people. Underground engineering is a big family. There are maybe ten thousand or twenty thousand people: you meet them on a project in Hong Kong, then you meet than again on a project in the UK. They tend to be honest, hardworking people who are direct and speak frankly.
“The big difference I have seen over the course of my career is the change from dry- to wet-sprayed concrete. The dry spraying made an appalling amount of dust; now, with wet-sprayed concrete, modern admixture technology and alkali-free accelerators, we have less dust, low rebound, good quality and increased performance. Traffic down a tunnel is always an issue and delivering wet-spray to schedule in the window before it set was crucial; now, we have additives that can put the mixture to sleep for 72 hours, which adds flexibility to the logistics. Using robotic spraying equipment means that it can be applied cleanly, safely and accurately, much faster than before, and to a predetermined thickness with the aid of modern scanning technology.
“Modern sprayed concrete is altogether a better, more efficient and quality product – far different from the unpleasant, dusty stuff that all the poor young engineers were sent to work with. I have been involved in much of that transformation, and that is something I am proud of.
Tom Melbye will be giving a presentation at WTC2022 Copenhagen (2-8 September 2022) on his work and the history of sprayed concrete over the past 40 years.
