Temperature Monitoring in Mass Concrete

Hi everyone, welcome to the webinar. I’m going to start if other people join great. I hope everyone is having a great day. Today we’re just going to cover mass concrete, but more specifically the temperature and gradient monitoring within mass concrete application. So, a couple of people joining us today know me, my name is Sarah. I manage the engineering solution department here at Giatec. I’ve been with Giatec for over 4 years, almost five. I have a masters in structural engineering and I am part of the I’m a member of the ACI 207 committee for mass concrete.  

Before we start today’s presentation, I just wanted to remind everyone that if you do have any questions, please feel free to ask questions in the chat. I’ll be monitoring this because I’m by myself today, I will be attending the questions towards the end of the presentation. So don’t be shy to ask any questions that you might have. 

So, before we start about the topic, just a quick introduction about Giatec. So, for people who don’t know Giatec, we’re a company that makes technology for concrete. And our main vision is to revolutionize the concrete industry. So implement technology from every aspect of the concrete, either from the poring, to the placing, to the hardening, all the way through the long-term monitoring of the structures. 

So today in the agenda we’re going to focus on one application that is really a main focus with our SmartRock 2® sensors, SmartRock sensors sorry, and it’s mass concrete. 

So, we’re just going to cover, mostly on the temperature side of it. So what is mass concrete? Why is temperature monitoring important in mass concrete? Thermal gradients. We’re also going to touch base quickly on thermal control plans, so give you an idea of what to look for and how you can set it up, as a basic, general understanding. And then we’re going to go and see how we can actually optimize thermal gradients and thermal gradient analysis. So this is the most exciting part, and it’s the newest part of mass concrete if you want to. And I’m just going to finish with a really small case study. 

Okay, so what is mass concrete? Mass concrete. If we look at the definition here, any volume of concrete with dimensions large enough to require that measures be taken to cope with that generation of heat from hydration of the cement and attend volume changes to minimize cracking. So basically, if we look at this, mass concrete definition doesn’t have a standard. Well, if the concrete is bigger than this amount, that is thicker than this, or you know has a larger volume than this, this is considered mass concrete. This is not what mass concrete is. Mass concrete basically is telling us that if the concrete inside your element is going to reach a certain temperature, a high temperature, then this would be considered mass concrete. So basically there’s two things that affect the mass concrete. The first one is the size of the element, and the second one would be the concrete mix design.  

So, when we’re looking at the size of the element, what is important to see is that a concrete when it, so when cement and water reacts, it creates an exothermic reaction. And this means it creates heat. Concrete has a really low thermal conductivity, which means that the heat that gets trapped in this inside of your concrete, takes a really long time to exit the concrete itself. So it takes a really long time to cool off, if no additional measures are taken. Typically, so this is what we called an adiabatic condition. So this is the condition where the influence of the environment where the ambient temperature wouldn’t take effect on how the concrete is cooling down in the core of your element. Typically, adiabatic conditions is reached roughly 2 feet deep in the concrete. So if you just look at the chart here just quick, you know visuals on this. If you have a 6-inch slab, which is a typical slab, you would be looking at roughly an hour and a half for your concrete to stabilize with environment past hydration. If you go higher, like thicker, like 5 feet, you would go around seven days, you know. And even higher, 50 feet, two years, and those really big big dams like I’m thinking about the Hoover Dam for example, it’s still warm, it’s still cooling down as we speak. So it can take up to 200 years to cool down okay. So, really important, the size of the element.  

The second portion, the second portion that is really important is the mix design. So, heat of hydration. So, your concrete is going to react, your cement is going to react with the water, it’s going to create heat. You want to minimize that heat. So, the first thing to look at is the heat rise, so heat rise would be considered if you look at this graph for example, is the placement temperature and the maximum temperature here. In this specific case it would be 72 Fahrenheit, so this is your heat rise. Placement temperature, maximum temperature minus placement temperature. So, you want to minimize this because like I mentioned earlier, the temperature in the core of your concrete is going to heat up, heat up, but it’s not going to cool down. So, you want to make sure that it doesn’t reach a certain temperature, and we’re going to talk about this. There’s different things we can do to minimize heat rise, the main ones you know in terms of the concrete mix design itself, reducing cement content. Using any pozzolans or SEMs, to reduce, or F-Ash for example, or slag, to reduce the heat of hydration. Or select a type of cement that generates less heat, for example type IV.  

So, I’m going to on the next slide here, I’m going to show how you can kind of do a quick estimation of what would be your heat rise. So this equation here, Gajda proposed it. You can find this equation in multiple different documents and some of them you’ll see different factors, slightly different factors, but the idea remains the same. So, this is just a quick rule of thumb if you’re looking at understanding what’s your heat rise in your concrete if you’re using type I, type II Portland cement. So, in this specific case I’m assuming, as an example, I’m assuming a 450 cubic pounds per cubic yard of concrete, of cement sorry. And then my you know, approximate if he tries would be 72, So exactly like we had in this this graph here. But if I replace some of it with fly ash for example, 20% replacement. I’m lowering my heat rise to 65, and so forth and so on. If I’m adding more to it, let’s say for example 40%, I’m reducing to 58. So, quite considerable decrease of heat rise from their concrete itself. So, you can play around with this equation and find just a general idea of how your concrete would react, and what would be the approximative heat rise in that exhibited condition. Once again, this is in the middle of the concrete core in a mass element. There’s other ways to, you know measure the heat rise. You can use any finite element or any software, some software out there to do it, but this would be just a quick and easy rule of thumb to start. 

So, if we take those two elements to what is considered your mass concrete, we have two things right. We have the thickness of our element on the X axis in this case, and we have the equivalent cement content on the Y axis. So, if we’re looking at it from a different perspective, here a 6-inch slab, which is a typical slab, you know it’s never going to be a mass element, unless you’re using a really high cement content, which would be a because other issues as a whole. 

The opposite is also true, like after a certain thickness, let’s say for example 15 feet. Whatever you do in terms of your cement or your mix design, you’re going to be in the presence of a mass element. But there’s this kind of region in the middle here, so let’s take for example, a four feet deep element, which is typically what is kind if the border between non mass and mass concrete element. Because of that two feet from adiabatic condition, right? And so if we look at this here, same example as above, 450 cubic pounds per cubic yard. We would be in what we consider the mass element for example. But if we for example, replace with some fly ash, in this case 30%. We might actually get out of the mass element effect, just because the heat rise inside the element is not going to be as high, and therefore temperature differential is not going to be an issue. And delayed ettringite formation is not going to be an issue, which I’m going to talk about in the next slides. 

So here, just to recap, it’s not you know, the definition is not a certain thickness or not a certain cement content, it’s a combination of both that makes your mass concrete a mass concrete element. 

So, why is it important to monitor temperature in your mass concrete? There’s two main reasons. The first one is to ensure quality of your concrete, and the second one is to prevent cracking.  

So, the first thing here we want to talk about is delayed ettringite formation. So, some of you might be familiar with this term. Actually, DEF, which is what is referred to, is something that is a phenomenon that happens when the concrete reaches too high of a temperature. So typically, if you’re using just plain Portland cement concrete. Anything over 158 Fahrenheit or 70 degrees Celsius, would be considered to be at risk for DEF. If you’re actually using some SEMs, which again, I’m going to show in the next slide, you can actually push the boundary and you might be able to get away without the DEF up to 185-degree Fahrenheit, 85 Celsius. So, if your concrete gets heated up to the point that it reaches 85, the chances of you having DEF is extremely high, so this is the cap limit that it’s put on the cement hydration temperature as the maximum temperature. So, what is actually DEF? DEF is actually when your concrete hydrates at high temperature it’s not stable, so it creates some mono sulfates instead. And what happens is that when the concrete cools down, those mono sulfates actually reacts with the sulfate in the pour solution of your concrete. Which is what is forms ettringite. The thing with ettringite is that in order to form it, you need the presence of water. So, you need some moisture sources. This is why DEF is not a phenomenon that’s going to be observed one day after your concrete is poured, but this is something that’s on the long-run, when your concrete is actually in use. Your structure is actually in use, and the water starts to penetrate, or you know just general moisture around it. So, this is something that you need to take care of when you actually create, when you actually build, to make sure you don’t have later problem in your concrete. Another thing is the higher curing temperature you have in general, the weaker and more permeable the concrete would be. So, it creates more pour and more interconnection between the pours. So, this means it’s more vulnerable to deterioration or freeze and toss cycles, for example, or for sulphite attacks, and things like that. So just at lower quality of concrete in general. 

So, on this slide here, you can see on what ACI 201.2R, you know, refers as what is considered to be you know, at risk for delayed ettringite formation. We can clearly see here that 185 is the maximum temperature that should never be achieved, and that 70 degrees Celsius is, you know, we’re good, anything below 70 Celsius we’re not really concerned about this. And this is the proposition that the ACI has in terms of fly ash replacements, or slag replacements, or any combination of replacements. To allow you to go within 70 Celsius to 85 Celsius, or 158 to 185 Celsius. So, some leeway around that maximum temperature here to make sure DEF is not an issue. 

So, what can you do to actually control the heat rise? So, the first thing we talked about is making sure that your mix design is done properly. So, this is the main key, you need to have a good concrete mix design. However, this is not always, you know, it’s not going to solve all your problems, so a good thing to do is actually lower your initial temperature. So heat rise if you’re starting at a really high temperature of your pour, you’re adding that extra temperature on top of it, so if you can reduce the initial temperature, your heat rise is going to be the same because your initial temperature’s lower, then your final temperature is not going to be as high. So little tricks could be pouring at night, cooling the water, cooling the aggregates before the pour, ice, and on the more extreme side liquid nitrogen, could be all examples of things that can be used. 

After the pour there’s not that much that can be done. The only thing that can really be done is cooling pipes. This is something that needs to be taken in consideration beforehand, so you need to plan ahead on knowing that you would require cooling pipes, so they need to be integrated in the design. And this is how you would attempt to cool down your concrete by passing cold water through pipes that are going through your structure. So other than that, there’s nothing that can be really done from a external perspective, how to cool down your concrete after the fact that it’s being poured. 

The second thing that is important, so we talked about the quality of your concrete. The second thing is the thermal cracking. So why is it important to monitor temperature? You don’t want cracking. So, concrete as we know is really good on compression, very weak in tension. What happens is that if the tensile stresses inside your concrete are higher than what the concrete can withstand, it’s going to crack. What can make this crack? It’s a large and rapid temperature differential. So, if your concrete is really hot in the middle and really cold outside, what’s going to happen is that the concrete outside is going to try and contract, but the hot concrete is going to try and restrain it, which is going to cause some internal stresses, and this is where concrete starts to crack if the concrete is not strong enough. So, this is what we want to prevent, and this is why monitoring your concrete temperature is extremely important at different location. So, you maintain a certain temperature differential between your hot and your cold to make sure that you can withstand those stresses. 

So just to give you an example of a typical, not a typical, what you should not have in your mass element. So, this is a mass element here on the left, we’ve measured temperature in the core, the surface and on the side right here. This is what it looks like. So, this is the surface is in blue, and the dark green here is the maximum temperature. So, if we look at this and we start to plot the differential, which means is the maximum minus minimum of this concrete, this is what we end up with. 

Big problem, this is way too much differential, so basically there is a limit that your concrete should not achieve, and we’re going to talk about this in the next few slides. If that concrete reaches above that 35 Fahrenheit threshold which is 20 degrees Celsius, it tends to crack. This is what the thermal cracking is going to occur. So, we’re going to look at those standards right now and see what we can do to monitor and prevent this. 

Thermal gradient limits, really important, ACI 207 US standard. The main number that we see everywhere is 35 degrees Fahrenheit. Your concrete cannot exceed a differential of 35 degrees Fahrenheit. So, if you look here on this graph right, we’ve exceeded quite considerably. We’re almost at 60, which is double. 

But so if we look at it, so I’m going to, this is a picture of what the actual compressive strength of the concrete is and the allowable temperature differential. This is a graph that I’m going to show you how to build this in a couple of slides, but for now let’s look at it this way. Anything that’s below this curve is a no cracking zone, and anything that’s above this curve would be a cracking zone. So, for example, if we take that ACI 207 standard and we put it in there, what we’re saying is that whatever the concrete compressive strength is, your allowable temperature differential is always going to be the same at 35 degrees Fahrenheit. What does this mean in this example for example? Here at the early age, in the lower strength portion of the graph we would have an overestimation. So basically, here you could have potential for thermal cracking at lower differential.  And you know when your concrete starts to gain strength well you’re way conservative, like you have a lot more room to play because your concrete actually gains strength therefore gain a lot of compressive strength, but also tensile strength. So, it can withstand more stresses inside the concrete. So we’re really conservative in general with this approach. 

I just want to point out that really interestingly, Giatec is from Canada, but we work a lotwith the US. The Canadian standard is actually different from the American standard in that regards. So we notice that at 35 degrees Celsius, which is the 63 Fahrenheit, you know, elements could actually be used, then there was no cracking. So why is that? So, what the standard did is that it put a bit more freedom in the way that someone can specify the maximum allowable temperature differential.  

So basically what they did, this is just an example, but basically what they did is saying that you can specify your concrete temperature to be differential to be a certain value within a certain time frame. So in this case, the first 24 hour would be lower, and then one day to three days would be the typical 35 Fahrenheit, 20 degrees Celsius, and then after that you can go a bit beyond. 

Similarly, they’re also saying you can specify it in terms of the actual concrete strength. So, if your concrete strength reaches this value, then you’re allowed to have this amount of temperature differential. So, if we actually look at those two standards on top of each other in this example, it would look like something like this. This is the Canadian standard, or what it could look like as it would depend on your concrete and anyone can specify it as they wish, and this is what the ACI guideline the American would look like. So, we can clearly see here that it makes it a bit more conservative on the early age portion of the graph, but also allows for a lot more room in the later age and the longer strength portion of the concrete. Which means that you don’t have to be as diligent to keep that 35 degree when your concrete reach a certain strength where it is perfectly able to withstand those cracking, those stresses inside your concrete. 

So. what are the advantages of optimizing your level gradient? Cost saving on additional cooling methods is one of them. Cooling methods are expensive, especially the cooling pipes. So if you can avoid it, great. Cost saving on mix optimization. You might be able to get away with a concrete that goes a bit higher in temperature. Curing optimization. When do you want to remove the blanket? How long do you have to monitor this? This is all things that you know are taking a big toll on the GCs, on the general contractors. This is usually a big nightmare, not nightmare, but this is something people really stressed about and providing that, you know, an actual optimized gradient, a local temperature differential, is actually a big relief for the engineers on-site and for the people you know monitoring that structure as a whole. That being said, right now the ACI and the Canadian standard are different, but ACI is actually going to put in provisions to allow for something bigger than a 35 Fahrenheit. This is not implemented yet, but this is where they’re going in the future, and I’m going to talk about what they’re going to do in a couple slides. 

Thermal control plans. So, before we go and look at optimization, I just wanted to touch base on thermal control plans because this is a really important topic and we actually get calls all the time about this. Can you help us build 1? How do I do this? What do I need to take into consideration? 

I’m going to focus mostly on the temperature side of things, but this is a list of roughly 15 points of things that you want to make, you may want to consider or look into when you’re actually planning for your mass element. So, the first thing you want to ask yourself is I might actually, in the presence of a mass concrete element, right? If the answer is yes, you follow, if no, you’re good to go. The second thing is that you need to, you know, have a concrete mix design that is going to, you know, do the structural specification and the exposure class specifications, right you need to come up with a mix design. Then you need to define the maximum allowable temperature in the element based on the mixed properties. As we saw, depending on if you’re using certain supplementary material, you might be able to have a higher maximum temperature in your concrete, then if you’re not using it. That’s the first thing you need to check. 

Understand the heat rise of your mix design. You can do this through the equation that I showed earlier or through any modeling software you might have. Just to see if you understand, you know your maximum allowable temperature minus the heat rise. That would give you an idea of you know what is your temperature at place. You can do this the opposite way if you want to, but this is important because if you end up having a concrete temperature replacement that is extremely low and not feasible, you have to go back to the drawing board and change your mix design right? So this is like an iterative. It could be an iterative process. Right, if your placement temperature is too low, for example something like 35 Fahrenheit. That’s not, you know something that is feasible, so you need to lower down your heat rise one way or another. 

Do you need additional cooling methods at pouring? Right, this where you would be based on #5. Be like what can we do to do this? So, I want to say it’s kind of an iterative process, you might have to go back to the design, and so on and so on. 

Point 7 here I’m putting it out there, understand ambient conditions. If you’re pouring in the winter versus the summer, you’re going to have a different mix. The summer that the temperature outside is much higher, so your differential is usually a bit smaller, but you know your temperature at pouring might be a bit higher. Therefore, your heat rise, might, you know, exceed your maximum temperature. Kind of the opposite, in the winter.  

Another thing I want to point out about this is I came across something along those lines a couple months ago, where a mass concrete was designed and poured in September. Great, everything is good, but those are really big elements, they’re still cooling down a couple weeks or months after they’re actually being placed. So, three weeks after first cycle of temperature going below the freezing point in Canada. Now their differential is too high and they have to go and heat up the entire thing, so they ended up putting like a massive heating section on top of it, which was super expensive. 

So, point 7 is just here to as a reminder that you know temperature differential is something that you might have to monitor for a longer term if necessary, and that ambient condition might be an important factor to take in consideration. 

Okay then number 8, define gradient limits and specifications. So, if you want to keep the 35 degree Fahrenheit or 20 degree Celsius differential, that’s good it’s fine with me, but if you want to, you know optimize it, we’re going to look at that in the next couple slides. That would also help you in terms of, you know, defining your mix design. How do you maintain the gradient within limits like what are going to be the things that you have on site, that are making sure that those temperature at the surface stays what you want? So, are you going to use insulation? Are you going to use blankets? Are you going to use a heating system? Are you going to use any kind of cooling system, right? So that’s really important to have that in mind, you know as well. 

Number 10, test block. So, a mock-up. So, this is something that is done regularly on a mass concrete and basically, it’s 1 meter, by 1 meter, by 1 meter, 4 feet, 4 feet, 4 feet and base. I have a picture on the next slide, but basically you pour your concrete and everything it’s insulated, which means it recreates an adiabatic condition for you. And this is where you get the chance to test your mix and to make sure that that maximum temperature is not reached, making sure that you know your temperature differential is not reached when you removed at the top. So, you can look at all the aspect from 1 to 9 within that little test block. You can use other methods, test blocks are usually the easiest way, but if you have any finite element model or anything along those lines or programs that can do that for you, that’s another solution. 

Things that are also to be considered in your thermal control plan. Define the length of monitoring. Do you want to monitor your concrete for a week, two weeks, six months, two months? Typically, 56 days is the time, so two months, but up to you. Define monitoring location in your structure. That’s another important thing. Where are you going to measure that temperature? Always keep in mind that the hottest location is going to be in the core, but the coldest location could be at the surface, it could be on an edge, so it’s really dependent on every project is different. You might want to have some redundancy in there, so that’s something we can help you with. But just figuring out where you want to place your temperature monitoring device. 

13, what kind of tools are you going to use? So here at Giatec we do have our SmartRock sensors are meant for temperature monitoring. But there is a lot of people out there making different systems, and whatever system is the most applicable for you is something that you need to look into. 

14, define reporting. What type of reporting you want? When do you want those reports to be done? How do you want this to be communicating? You want to monitor maximum temperature and differential on a daily basis and you want the reports, so that’s going to help you also define your temperature monitoring system because different systems have different tools for that. 

And then lastly, make sure that your contractor and your ready-mix producer or aware of all that specification. So, this should be written down, everyone should be on the same page, everyone should know what the plan is in case something goes wrong, and just to make sure that it runs smoothly as a whole. So those are usually the main 15 points that people are going to look into, and kind of how this would be done. 

So, this is what a test block looks like, just a regular wooden box with insulation everywhere and temperature being monitored at different locations, surface, and core for example. 

How to optimize gradient and thermal gradient analysis? This is where it becomes a bit more, it could be a bit more of a newer subject for some people. Earlier I showed this graph here of potential cracking versus no cracking. So what I want to show you guys is how to build this graph. So this is what the ACI 207 standard, new standard that’s going to come up, I don’t have a date, is going to look into building.  

So, how can you actually come up with this? So, the first thing that you need to know is tensile strength. So, we mentioned that concrete, the reason why there’s thermal differential cracking is because the tensile stresses are too high for the concrete to withstand it. So, we need to understand what is the tensile strength in the concrete itself. Two option, flexural tests, or split tests, or anything like that. Or the option number two, which I don’t necessarily encourage all the time, is the correlation between compressive and tensile through equations. There’s different equations available, really up to you. That’s the first thing understanding when your tensile strength of your concrete. Why do you want to do that? Here in this equation, okay. This is the main equation that is used to build that graph where F prime T is your tensile strength. You can also always relate it to F prime C as well. And then different factors here. Coefficient of thermal expansion, this is something that 207 provides some guidelines. Astro does provide some guidelines on how to find this value. Modulus of elasticity, this easy lab test that can be done. Degree of restraint and creep factor, sometimes are combined together depending on which documentation you look into. And on 207 and CIRIA also provides some guidelines, so I provided the link right here to look at this. So it’s just pretty much a plug and play for numbers, as long as you’re using the right approximation and the right judgment, you can easily implement this curve for any concrete that you wish. 

So, this is great, right? You have this equation, you have this graph. How can you use it on-site right? It’s great, I know that my compressive strength or my tensile strength reaches a certain value then I’m good, my differential can be this much. But like how practical is this? How can you make this practical? So, basically the way to do this is to be able to monitor live temperature in your concrete and live strength in your concrete. How to do that? Option one is not really live, but you can always break cylinders, break flexural beams for example. A lot of manual work doesn’t really represent accurately what’s going on, and a lot of delays, but it can give you a good approximation of like where you’re standing on your concrete and what should be your temperature differential. The thing is that when you’re looking at this in the mass concrete element, you have your really warm temperature in the core, and you have your colder temperature at the surface. So basically, what you want to do is monitor that cold temperature there, which is going to be your lowest concrete strength. The best way to do this is through the maturity method, because with the maturity method you can get information about what is actually going on in the concrete in real-time, exactly where you want to monitor. Cause sometimes your Field cured are not exactly the same temperature as your element itself. Yet real-time you don’t need additional equipment, which is great because you’re already monitoring temperature. All the system nowadays, most of them allow you to do maturity right away with that temperature data. So you’re not, you don’t have to like buy new equipment or anything like that, it’s all it’s a 2 in 1. 

Also, maturity allows for both compressive and tensile strength monitoring, so you can set up your maturity concept in either the compressive or the tensile strength, but you get the live temperature, you get the live strength inside your concrete, therefore you know exactly when you can, you know change brackets according to your thermal control plan, and where you’re standing on this chart pretty much on a live frequency. 

So, for people that are not familiar with maturity. So just a quick, quick introduction. So maturity is a technique to estimate concrete strength and it’s based on the assumption that a given concrete mixture attains equal strength if the contains equivalent maturity. So if we look at it from a really easy perspective on this chart, on the left side we have a concrete, and on the right side we have the same exact concrete. The only difference is that one of them was cured on higher temperature and one of them was cured on lower temperature. The theory is that if they have the same maturity in this case, for example, the area under the temperature, temperature curve, or the summation of temperature, they have the same strength, so independently of how they got to that maturity value or how long it took, they should have the same strength. So, this is this is the theory behind maturity. It does require calibration in order to use it, but once you have your calibration done, you can easily implement it on-site with any temperature monitoring system that you have. 

In-Situ strength and temperature monitoring. How do you want to do that? So, a couple of things that you want to look into when you’re actually looking into your system that you want to use to monitor is that you can do, it’s compatible with maturity, you can collect your data either remotely or not. You can have, temperature, compressive, and tensile strength at the same time. A lot of times a really, really, really good tool has limits, so thresholds. So, a couple of system out there allow you to set thresholds or limit for example, I don’t want my concrete differential to reach 35 Fahrenheit. I can set that limit and I get an alert like automatic notification if this happens. Right, this is really good tool, especially if you’re not on the job site 24/7. How is the data shared between team members? How can you easily share that data between members? How can you send a report? What kind of report do you need? So different types of system would allow you to do that kind of analysis or sharing and overall data collection. 

Another really really important thing that you’re looking for in your system is something that allows you to do real-time gradient analysis, so real-time temperature differential, with alerts if possible. So, plotting sensors data next to each other just to make sure that you’re obtaining that temperature, you’re staying within that temperature range that you’re looking for. So, something along those lines, right. Temperature curves, gradient limits, you can set your limits a bit lower so you are notified when it might reach the you know, the 35 or something like that. So, there’s a lot to play around with this and you can depend on the system you’re using, these different things you can do. 

So, I’m just going to finish this on a really small, really, really small case study, so this was done in in Chicago. Massive foundation element as you can see in the pictures. The specified maximum differential was 35 Fahrenheit. Sorry, this is a typo right here. So, what they did is they actually use maturity and the chart that that we saw to modify and shorten the protection system, so they notice that didn’t need to protect the concrete as long as they did. It allows them to know exactly when to remove blankets, or maybe when they needed to add them back. Especially in those you know, November kind of situation where the temperature can fluctuate a lot. 

So, this is just, this is the actual project. This is the specs on how maturity was monitored, and strength was monitored. Temperature was measured in this in the foundation, and this is the actual graph that was used to maintain that. So, what they did, is they didn’t go with the 35 Fahrenheit, they just use this instead. And I just saw tremendous improvement, and it’s just more flexibility as a whole to be able to get your differential limits a bit higher than that 35-degree limits. 

This is all the time we had today. If you have any questions on our website, a lot of good information. Also, support@giatec.ca, support@scientific.com are all good places to answer to ask you questions. sales@giatec.ca is also a great place to start. I’m really looking forward to hearing back from every single one of you, and I wish you guys. I wish you every good day and stay safe, bye.