As someone with almost twenty years of professional experience working with cement and cementitious materials, including seven years in advanced product development for Cemex, what were your initial thoughts about Concremote when you first heard about it?
I’ve used thermal maturity techniques since 2007 and there are various packages available now based on the principle, but the fundamental challenge out here is finding something that’s sufficiently packaged for consultants and people who’ve not used this technology before, to try and understand and more importantly buy into it.
I remember using this in the reverse scenario to how we use it here, i.e. in cold conditions where the rate of hydration is much slower, your strength development is therefore much slower and consequently you’re monitoring the situation to know when you can actually apply a load onto that concrete structure. The other thing we extensively worked with was cement replacements, as an example in PT slabs, post tension floor slabs. If you rewind ten or fifteen years ago people will tell you, “You can only do it (PT slabs) with CEM1 and you need 400kgs of powder in there,” and all the rest of it because we had to hit the strengths to initial stress the tendons. We worked with a big contractor in the U.K, we introduced cement replacements, we dropped the total binder content and we’re still doing initial stressing, and final stressing earlier than what the general recommended guidance was, because you’re basing it on what the concrete is telling you, not what you think the concrete is up to.
How does that apply in this project considering the location?
This project takes exactly the same technology, same principle, but it turns it completely the other way around. We have a lot of heat, a lot of sun and that increases the rate of reaction, therefore the whole plan of attack here was not to follow the usual guidelines, but to take full advantage of the heat and the increased rate of hydration and the increased rate of strength development. At the end of the day what matters is the strength of the block so it can be lifted. If that strength has been met in order to safely lift it, I’m not bothered about whether that happens in 25 hours, 50 hours, 75 hours or whatever, but from a production point of view the sooner that block achieves that required strength, the greater you can turn that block around, the faster you can move onto the next one.
Having had the opportunity to use Concremote on site in the Middle East, most recently on the RAK Ports Saqr Port Terminal expansion, what was your experience with the device like and how did it perform?
Before we started this project we’d already cast the largest chunk, of the largest block we need to make, which incidentally is 1.8m wide, 2m high by 10m long. This confirmed that the key challenge was going to be the control of the peak temperature. If you take an ambient temperature of greater than 30 degrees Celsius plus a low cement replacement mix you will be borderline with regards to the maximum permitted peak temperature. This means when the ambient temperatures rise higher than this like during summer, the maximum permitted peak temperature is going to be exceeded and by a wide margin. If you take a high replacement mix, which is what we’ve used here, along with a low coefficient thermal expansion aggregate which we’ve also used here, it means we can let the ambient temperature rise much higher before we hit that peak temperature hydration. So we cast very early on the large blocks to ascertain exactly what this rate of rise to the peak temperature was. That clearly demonstrated, that for these larger blocks, high cement replacements were going to have to be a must. They also indicated that the control of the whole thermal process was also going to be critical and throughout the whole casting calendar. It could not be done as initial “approval” trial, which is usually the case because the ambient temperature was the largest variable.
Another part of this jigsaw puzzle are thermal differentials between the core, the outside face, the shutter and the ambient temperature and consequently, we knew before we started what we were going to have to monitor. I’m quite relaxed in doing that monitoring; I understand what I need to do, and how to do it. It comes back to the point I made earlier, which is how do I get the consultant to accept that process and that procedure, and that mechanism when he’s most likely not ever used it before, and that is fundamental reason why I looked for a package to be able to provide weight for that argument. How can I turn around and say, “It’s easy for me to present all the data,” the consultant will say, “This is all your data,” and I’ll say, “Yes, and? What’s your problem?” You need a sufficient amount of weight of support to get something past a consultant if they’ve never done it before. They may understand the principle, but because they’ve never used it, they may not want to use it. This is also very important to acknowledge because the respective impact of the different variables is different here in the Middle East, to the majority of Western Europe for example.
You’re looking to hit a certain degree of weight to twist it, and the fact that I was able to present the data we’d done in the initial trials, the work we’d done with the Concremote system, the data that’s been running live post-that, the fact that the whole lot fits together and it makes the same argument, there’s got to be something here. The other side of the coin is, we ran on a code two, for the thick end of ten weeks production until it was formally accepted that this would work. So we’d made 1227 blocks, before the consultant actually accepted that this was a principle that delivered without any problems. This comes back to knowing the technology, knowing what it’s giving you and knowing that we haven’t got any problems. It’s the detailed understanding of the whole concrete technology discipline; what reacts on what; what key parameters drive what factors, and it’s taking full advantage of those different parameters to maximise that potential. And this to me is one of the key parts: the challenge of moving forward with any form of technology like this, it’s getting people to understand how all the parameters within concrete technology fit together. Its understanding that looking at a mix design on it’s own without all the factors that come into play is potentially not going to give you the best solution and it’s also not necessarily going to give you the value-added benefits either, because continually erring on the safe side of caution then ramps up considerably the costs within the actual production process.
At Doka, we believe Concremote has a wide range of benefits that cover safety, quality, time and cost. In your experience, what was the strongest benefit Concremote brought to the RAK Terminal project?
Confidence. We had to produce to hit the program requirements and it got to the point that we had cast so many blocks without any concrete or thermal problems, that 25% of the project had been produced before the whole process was signed off. At the end of the day I’d look at it differently, and suggest it’s my opinion that counts. It had got to the point where, I’m on a code two: I’m the one carrying risk; it’s me that matters at the end of the day. I have to deliver the required production and when those blocks go down to the jetty, the contractor will inspect size wise, will check that they’ve met the strength and will inspect that the concrete was in specification. If those three parameters are met and it’s past the minimum 14 days of age, it goes in the water. That’s it.
Where the Concremote process really matters, from my point of view is when we originally planned this, was to turn the big moulds A, D, & L potentially, in 96 hour intervals. The plan was then to turn the others sizes at 60 hours. In reality we’re turning A, D and L at 60 hours, and the others at 36 hours. So it’s given us the ability to take an axe to the time that the blocks are sat in the moulds and that has also meant that we have additional mould capacity available most evenings. We’d planned to cast up to 25 but now we’re casting in a night up to 29. That to me is the other real benefit; productivity.
From the consultant’s point of view at the end of the day, he’s not bothered, he just wants product in specification. From our point of view, it means that we’re meeting contract, even thought we started late. So, it’s got us back on track and touch wood, yes we have some challenges ahead, but it’s opened up some breathing space. We know there are always going to be challenges with these types of things, but it remains because of the challenges we’ve got now, we’re probably only going to scrape within target for September. But the fact is we still have good warm weather, we’re still in position where we can turn around at a high rate of knots, so we’ve still got that production benefit. The next part of the development curve, when the weather drops off, we know we’re going to have to increase the duration the blocks are in the mould. What the technology allows us to do, is that when the ambient temperature starts to drop, we’ll rerun those tests to work out how long they need to be extended and at what temperature, so at all times we can maximise the turnaround time.
One of your duties includes overseeing the mix design of the concrete used on site. Could you tell us how Concremote helps to give a more detailed insight into hardening conditions when compared to traditional test cube strength results?
There are several factors that come into that, particularly when you’re running with high cement replacements. When you run with high cement replacements your reaction kinetics change considerably, your rate of exothermic heat driven from the mix design is greatly reduced, which is one of the reasons why we’re running with high mix replacements in the first place. Consequently understanding the kinetic mass of the concrete you’re working with becomes vitally important because if you cure cubes at a standard 20 degrees Celsius, it will have no relation to what’s actually going on within that concrete mass at whatever temperature it so happens to be at. As a consequence of the temperature your rate of reaction is different and therefore your ultimate strength development will be very different.
Put that into number terms, using the mix design we have at present you’d expect to reach lifting strength at 20 degrees Celsius at around 90 hours, whereas the actual lifting strength in the blocks themselves particularly in the biggest ones, you are going through that in around 30 hours, purely due to the differences in temperature and the differences in the reaction kinetics which they’re associated with.
Many acknowledge the construction industry has been slow to adapt new technologies over the past forty years – do you believe the sector is on the verge of a renaissance, or do you think the transition to using and integrating technologically superior products and systems will take longer?
There are two ways of looking at that. A lot of the people in the concrete industry or in the traditional areas where there’s been concrete technology, the UK being a classic example of this – the UK is now short of concrete technologists. The ICT used to be concrete technology and if I look at a lot of my former concrete colleagues, they came from a school where you sat your advanced concrete technology diploma, there was a lot of training both in labs and on site, there was very much a good school of people who understood the discipline and collectively used it to move it forward. This was in part driven by the construction boom of the Eighties in the UK. There was active participation in particular Universities, bi-Annual conferences etc. That has now moved on because a large part of that group of people has now retired. One of the challenges now, is trying to bring in a new group of people, who understand, learn and develop that level understanding. Associated with what you have, these newer technologies moving in – couple that with the fact that, generally in B.Eng. courses in civil engineering, the amount of detailed understanding students are taught in concrete is very small. One of the guys I knew in the UK does a lot of post graduate training in a lot of the big construction companies in hands-on concrete technology, how to get the benefits out of it, how to understand this material, how does it work etc. So essentially you end up with a perfect firestorm happening, where the level of understanding of the material at a time when it needs to be evolving and moving forward is actually dropping.
As a consequence you end up in a position where when new developments come about, you have a combination of resistance of, “This is the way we’ve always done it,” and the other side of the coin you’ve got is a green crop of people coming through with regards to concrete technology who don’t understand enough of the details or inter relationships to combat that, so you tend to fall then between these two stalls and then how do you actually move this technology forward?
How much time before people catch up?
It’s an interesting question; one of the guys I used to work with very heavily using this technology from early on, worked extensively in this part of the world before he went back to the U.K. There does seem to be a pattern, if I look at the guys I first started working with at RMC, a lot of the good guys left whilst I was there and came to work out here. Several of them have now gone back to the U.K and now formed the foundation of this new group of people who are now pushing technology forward. In other words this part of the World is behaving like the building boom in the UK did in the Eighties and draws talent into the industry. Unless you’ve seen or been allowed to work in a different environment you don’t realise that you can try out other ways of doing something. That doesn’t mean to say there aren’t controls out here; there are and there are some very good controls out here. ACI, are out here, and so there is in fact a pretty good situation where a lot of hands on training is being done out here, so there is a growing pool of good reason and good understanding. You’ve also got European (particularly German) concrete technologists out here as well, who again come from that mentality, which like to push new ideas and new schools of thought. This market does provide a scenario for quite a large peer group of people from many backgrounds who are at a high level, in terms of their understanding of what needs to be done and how to do it. As a consequence you get quite a good melting pot of ideas, ways to look at something, and push that technology forwards. However, particularly out here, you also have to keep in the back of your mind the capabilities of the people who are using / working on the ground. If you take the bigger picture; why are we using Doka formwork here? It’s because they’re willing to look at things differently. The system we’re using is a standard 50 system, but the way it’s being used is different. We went to them and explained what we were trying to do, I know you’ve got travelling form systems, can we use these in a different way, and Christian sat down and said “Let me think about it and I’ll come back to you,” and they went through a series of variations to make a solution. That’s what we’re looking for – people who are willing to look at our objective and to find a better way of achieving that objective.
How would you summarise Doka’s contribution been to the project?
Very positive. If you look at all the people who’ve worked on this project, they all have the same fundamental mentality. It’s a mentality that says, “let’s look outside the box.” – on several of these blocks we have to do an exposed aggregate finish to provide a surface for the capping beam to adhere to. There are various ways we can achieve that, we’ve tried three or four different ways that have given us the right result, it’s not just looked at there’s only one way of doing it. That to me is the key part, it’s finding people who can look at the objective and then bring you the right solution, rather than trying to micromanage the process. The mould solution we are using has its share of challenges, which is not surprising as it is a new concept and we have to make some modifications to it. But these problems would have been far less, and probably avoided if the skill level of the worker assembling and using the system was much higher.
The key thing to remember with the consultant, their primary objective is to ensure that what the client has requested is met. The challenge you have is, and this is a lot of the battle we faced here, if you get into a scenario here which is design and build and the client is being represented by the consultant, you often get a lot more flexibility, because ultimately all the client’s representative, i.e. the consultant, should be worrying about is making sure the objective is achieved. The problem arises when you’re using the traditional consultant led process where the consultants then tries to micro manage the method. This isn’t just out here; in my experience consultants tend to be the last people to take on any information that is new, which tends to make these types of battles even more fraught.
When we did our own harbour last year, which was essentially design-build, we employed the consultant as a designer to provide us with the expertise which we didn’t have in various aspects, but then it was left to us to achieve the objective. It’s a far easier process to work with. The flip side of that of course, if someone is not up to the job or is trying to pull a fast one, you may not have got those checks and balances there to ensure they’re picked up. If the right capability is there, it has the right bearings.
On this particular project I was able to tell him the calculations; there are three different models, Nurse Saul, another one is Arrhenius and finally Sadgrove, which is the one I’d used historically, all of them are based on same principle. There are pro’s and con’s for using any of them. We’ve done several manually, and the mock ups manually, I know what the data was, I knew where we were sitting, the key issue is not necessarily the time taken to do it, but if you were to present that excel sheet, to someone who doesn’t understand thermal maturity it’s totally meaningless. This is why I went down the road with Concremote. It’s about being able to present something to someone who’s not used it, giving them a fighting chance of understanding it, otherwise you’re fighting a brick wall.
The system I’d most used in the UK was the Engius (now FLIR Instruments) Intellirock system, which has the sensor/logger packaged in like the old 35mm film containers which is embedded in the concrete and then the data is manually downloaded to the reader for onward processing. The Concremote system has sensors embedded in the concrete which run to a box which also records the ambient temperature and it then relays all the information via GSM to a server and on to the client. The original method I’d used was using thermal couple wires embedded in the concrete and linked to a logger, from which the data is downloaded. The key here is getting that understanding across. They need to understand how the data is determined and then how you process that data. The subtle differences in the systems are not what are important.
What factors of safe do we run with? We run with a factor of safety of 100%, because I’m not just using the Concremote system as the lift controller. I’m also using it to know when the block is cooling. If we’re on a cooling cycle, i.e. peak temperature has been reached and you’re cooling down, you’re at a much lower risk of thermal shock than if the block is still generating heat and this also comes back to a vital part of mould selection, particularly for this kind of mould.
Traditional for this type of block application you’d use a steel mould. However the size of the blocks we have here and the ambient temperatures we’re running under means that a steel mould would be a major problem because we would exceed the maximum permitted peak temperature stated in the specification all the through the summer. Therefore you have to turn the scenario on its head. Steel is a poor insulator, but it’s also very good conductor, so if you leave it in the sun, it will absorb a lot of heat and then transmit that into the concrete, exacerbating the problem with thermal shock and other parameters. Therefore very early on, we made the decision to run with a timber system, because timber is an insulator. You can then take the whole thermal concept and say right, I’m going to cast that block of concrete, it’s going to evolve this amount of heat and then keep it fully wrapped. These moulds have polythene and moisture blankets over the top of the concrete after it’s been cast and then over that it has a thermal blanket which is also white to help reflect solar energy. The block will now evolve heat, which it can then only very slowly lose that heat, but the key thing in doing that, is it means the gradient between the core and the face is kept as low as possible. In fact we are almost achieving a perfect straight line, where the block is almost totally isolated from the daily temperature variations. Whereas if you have a steel mould which is heating up and cooling, it will not only conduct that energy to the concrete, it will also be constantly changing the thermal gradient, which is also a lot steeper. This is also a key part of why we’ve run with the Concremote system, so rather than having to use 5 - 6 separate thermal couples to monitor that, the system is already measuring the ambient temperature in the box. The single cable could have three, four, five different sensors on it. So you could just run one cable in, pick it up there, you’re picking it up there; you’re already monitoring that thermal gradient, and to me the strip time we know we’re exceeding lift strength, that’s a given. Strip time is now being driven when the thermal gradient is at its lowest, the thermal differential is at it’s lowest and therefore the risk of thermal shock is at its lowest.
• This project will be in service by March 2019
VALUE OF PROJECT
• Two deep-water berths
• 18 metres draft
• Designed to expand the capability of RAK Ports Saqr Port Terminal