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Over the years, the construction industry has been gradually transitioning more and more towards real-time monitoring to test in place concrete strength. However, there is still quite a bit of uncertainty over how effective and reliable real-time monitoring is when compared to more traditional methods of concrete strength testing.
Join Matthew Denton in this exclusive on-demand webinar from Giatec. Get a more in-depth look at how real-time concrete strength and Giatec are revolutionizing the concrete industry.
Channel Manager, Giatec Scientific
Good day, good afternoon, good morning, good evening, whatever time it may be where you are today. Thank you so much for joining us today on our on-demand webinar where we’re going to be covering real time concrete monitoring utilizing the Giatec solution.
My name is Matthew Denton. I have been in the construction industry since 2002. Give are take almost 20 years now and I’m proud to bring you our presentation today. I look after our international market for Giatec, covering the Asia and EMEA region. If you need to reach out or if you have any questions after today, please feel free to take down my contact information over there. You can pop me an email, there will be an email at the end of this webinar as well.
I want to show you a quick video just to introduce our company to you so you have a bit of an idea of where we come from, who we are and what we’re about. We turned whole 10 years old in the year 2020, so we celebrated a covert birthday. As many of us have already done so and I’m proud to bring to you are short little introduction and our corporate video.
Video: “Welcome to our modern world! Vast expanses of megastructures designed and engineered to keep us safe. Give us power, expand our horizons, and bring us joy. Centuries of human innovation built on a foundation of concrete, a foundation that has been laid with aging techniques, leaving infrastructures that could last for thousands of years, crumbling after 50. At Giatec, our mission is to revolutionize the concrete industry with dedication to creativity, passion and integrity. Giatec is leveraging the latest in research tech and artificial intelligence to create leading edge construction solutions. Our suite of smart testing concrete products combined with our easy to use software give you real time data on concrete curing, hardening, humidity, and structural performance over its service life. Giatec is committed to a world class customer experience providing training, support, and access to our knowledgeable team of concrete experts. At Giatec, we will never stop innovating; bringing cutting edge solutions to century old problems. Allowing you to build concrete structures faster, safer, and more economically. Giatec. Revolutionizing the concrete industry.”
Our vision at Giatec is to revolutionize the construction industry with a strong focus on the concrete testing world and specifically using IOT solutions to provide to you real time data on the concrete in your construction project. Specifically looking at the full lifecycle all the way from our batching stage, to the pouring stage, to the curing stage, and then of course the long-time life cycle of our concrete with some of the non-destructive testing devices that we have.
As you can see, we have been able to cover the world a little bit in the 10 years that we have been busy revolutionizing the construction industry, having a broad span. Our main base of operation, operating from Ottawa over here and then, of course, in Northern America is where a strong base has been, but certainly broadening out to northern Europe, Savarkar Partners based out of Northern Europe, we have some partners out in Asia for East Asia and then of course, down in Oceana, and down here in sunny South Africa.
The agenda for today and the topics that will be covering for today is our in place concrete strength. How do we determine in place concrete strength? What are the current methods that we’re using to determine concrete strength? Then we’ll jump straight into what is maturity. How is maturity used? How is applied? There’s a couple of aspects to cover with maturity, but today we’re going to talk a little bit about what is maturity and what can it do for us. Of course, we’re going to talk about our Giatec solution and what Giatec is bringing to the table in the world of concrete maturity, and then if we have a little bit of time right at the end, we’ll talk a little bit about some artificial intelligence in concrete and how we are changing the landscape of concrete testing with our technology.
In order to talk about maturity, we have to start first with in place concrete strength. Currently, how are we determining in place concrete strength and perhaps more importantly, why are we determining in place concrete strength? So, some of the main aspects and if we talk about our field operations and what we’re doing out in our projects at the moment, we know the critical path of many of our projects is the strength of the concrete. This brings around the discussion of: When do we remove our form work? When has our concrete reached enough strength to hold itself and to maintain its own structure, and then of course, when can we remove that form work if we’re doing post tensioning? We are waiting for a critical strength in our concrete to be able to tension those cables and then of course continue on with our critical path. If we’re doing road works, open traffic on concrete pavements, how are we doing that? How are we determining when that concrete is ready for us to open up to the public? Heat curing, saw cutting; these are a number of the points that we’ve highlighted here for in place concrete strength, but of course what we’re looking for is whenever we need to know the strength of the concrete. These are some of the critical aspects and critical moments that we’re looking for that information.
If we look at our current standard concrete operation process that we’re following right now, it’s pretty easy. Pretty straight forward. We’re following from the batching plant. We go from our batching plant. We delivered that aside and of course then we have our on-site operations, our pouring of the concrete on site, and then they will take our standard samples where they were doing field samples or lab cured samples. We’re taking some sort of sample of the concrete that has been delivered, we’re distributing that back to the lab to be crushed for results. And once we have that strength result, we’re able to perform our critical operations. And this is where our in place concrete strength becomes important to us: We want to know when our concrete on site is ready for us to continue work, as we know. Where does maturity come in? Where does the Giatec solution come in? Here’s a nice little quick overlay for you. This is where we see our smart truck and the software that we are offering play a role in our current process and operations.
So, if we take a look at our three most commonly used methods right now that we’re using to determine in place concrete strength, the first one that we all are aware of and is probably more commonly used in some markets than others is field cured samples. This is when we take a sample of the concrete instead of sending that back to the nice curing boss of the lab, we would leave that sample on site to try and mimic and imitate the site conditions and the impact the site conditions would have on that concrete that we have placed on site. The second most common, and probably this is the most commonly practiced around the world, every market that you go to this is pretty much the standard. This is the lab cured samples, so whether it’s a cylinder, whether it’s a cube we’re taking that sample on site with that delivered concrete, and we’re sending that to our lab, the lab is curing that at that constant temperature anywhere between 20 to 25 degrees, depending on what country you’re in, which market you are dealing with at that moment, and of course that will be crushed at the intervals as required. So, if we’re looking for that early age strength typically, we all do a few extra samples to then, of course, allow for us to crush that early age strength to do post tension, move the form work, whatever it may be, and then our fairly standard 714, and ultimately a 28 day, and of course sometimes a 56 day test. Further to that we have maturity meters. This is, of course, what we’ll talk a little bit later, about how Giatec comes in and, of course, we have a nice picture of our SmartRock 3® there. But maturity meters is when we’re measuring the temperature of the concrete and we’re determining the strength of that concrete from the temperature.
What are some of the limitations that we have with the current practice of using cubes and cylinders? One of the first things is of course that we do not have accurate temperature conditions. So, in other words, the samples that we’re taking out from the delivered concrete they’re being sent off to a lab, or they have been cured, or even if they have been left on site there certainly not replicating. If we take a look at this example that we have here, we see the cubes here, all the samples being kept on site next to the slab. But of course, as a result of just as simple physics, the size and the mass of those elements are completely different to the actual poured concrete, so we know there’s a difference there. Delayed results, that’s the other one that has popped up there as well. Delayed results we’re waiting for those labs to compile their reports to crash those cylinders. And of course, you know if it’s over a weekend or if it’s a weird obscure time, there’s always that little bit of a delay, so we’re never going to have that real time information of the results from the samples; cubes or cylinders that we have sent away to the lab. Limited information. We’re taking a sample, we’re taking fixed samples or crushing them at certain times, and that’s giving us snapshot images of the life cycle of that concrete. So, if we have a cube or cylinder on day seven, we don’t necessarily know what’s happening to the concrete on day six, or day five, or day eight, or day nine. So, it’s very limited information to what we can have at the moment. Local variations. Again, this is a challenge that I’ve seen throughout many of our markets around the world where there are variations from one market to the other of how exactly you need to put the concrete into the samples, how you need to poke them, how you need to vibrate them high, you need to finish them off, even to the degree of what molds are used, and the impact that those molds have on the samples. These all play very, very critical roles in affecting that final string as those samples are crushed. And then of course we have low visibility. When we take all those earlier points into consideration, you, as the contractor on-site, the engineer on-site, does not get a very clear picture of what is happening with your concrete on site. And of course, this is one of the major limitations that we have with the current practice that we are experiencing in our markets and in our concrete technology and industry at the moment.
So, what is maturity, right? Well, let’s dive right into that today. Maturity. Maturity is a non-destructive method to estimate the real time strength development of concrete, typically within early age. So normally we talk about within the first 14 days of a concrete sample or the lifespan of the concrete after it is poured. What does maturity do? Maturity uses the temperature history of a particular concrete mix, and from that temperature history we can determine a correlation to the strength development, so we know that specific concrete mixers or mix designs perform in a specific way over a certain time at a certain temperature. If we keep mix A at 20 degrees for seven days, it’s going to reach a concrete strength of X. If we take concrete mix Y and we keep that at 20 degrees, it’s going to obtain a concrete strength of B, and with that basic formula that we all understand and we know, we are able to draw a correlation between the strength and the temperature of a particular concrete mix.
So, when we take a look at the ASTM standard C1074 and the definition, there is, as I’ve mentioned in as many words, it’s a technique of estimating concrete strength that is based on the assumption that the samples of the given concrete mix attain equal strengths. So, in other words, we start talking about maturity. So, if we have a look at these two graphs here, the first graph we can see here, if you look on the time axis, we see the shorter the amount of time is required when we have a higher temperature value. And of course, the inverse is true when our temperature value is lower; we have a longer amount of time required and that is the basic formula in which we will operate from using our maturity method.
As you can see here, we have a standard maturity strength relationship graph and this graph shows us that if we can determine what the maturity index of a particular concrete mix design is, we can correlate that maturity index to a strength. So, the maturity index might be a new number for you. If you have not used maturity before, it’s not something you would be familiar with, but this is the calculation of degrees over hours, so it’s essentially the accumulative value of the degrees per hour over all the hours accumulated together, and then we correlate that directly to our concrete strength. Some of the standards in North America that are followed here are the ASTM standard which I’ve mentioned a little bit earlier. We have some ACI standards, AASHTO standards as well, and of course is also now become the accepted standard for some of the DOTs around North America. CSA also accepts this when we go further afield, and we start looking at Europe. We know it’s within the Eastern standard, the BSE in standards, and of course the NEN standard as well, and we see more and more markets and countries beginning to adopt this maturity method as a standard, often following the C1074 standard.
What are the applications for our concrete maturity? So, you’ll see some of these points that we’ve mentioned already when we start talking about are in place concrete strength, formwork removal, post tensioning, opening traffic for concrete pavements, mass concrete. That’s an interesting one. We’ve seen that grow and grow as we start delving more into the market that, with our mass concrete, there’s definitely a strong push towards understanding what’s happening within those mass elements. Yes, in most times we’re doing our temperature differential, but we can take that further. Simultaneous temperature measurement as well. Of course, when we’re doing maturity, we’re getting temperature readings and continuous temperature readings. Heat curing optimization if you’re doing precast, because if you’re doing some controlled pours, you’re trying to cure that concrete as quickly as possible. Of course, we can look at how you doing there curing and how can we optimize the process that you have there. Saw cutting, mentioned that already. Precast are briefly mentioned and essentially at any time that you have a requirement to measure the concrete strength, concrete maturity can be applicable.
We’re going to jump into our maturity function next and go into a little bit more detail about and the science behind the actual function. And of course, if you again have any questions after this presentation after we’ve covered all these topics, please do reach out to us. There will be email at the end, there will be a email on the login screen where you’ve been. Support at Giatec is a great place to start, and of course you can reach out directly to me at any time as well.
There’s two functions that I wanna talk about today. One is the Nurse-Saul method, which uses the time-temperature factor. And then there’s also the Arrhenius method, which is the equivalent age. And again, both of these fall within the realm of the maturity, the standard that exist, and so whichever one you’re going to use at the end of the day, is up to you. However, there are some differences between the two methods, and one is certainly a little bit easier to apply than the other and we will go into that in a little bit more detail next.
Alright, so the Nurse-Saul and the Nurse-Saul function, or what we call easiest, is the Temperature-Time Factor, or TTF. It’s certainly the most common one used, especially in North America. It is more conservative as well, so many of our engineers, many of the QC QA guys like the idea that there is a little bit more safety built into the factor. So, while we are being more accurate, while we are being more precise about the concrete strength, there is a little bit of safety built into this, and of course this is a lot less complicated. I’m not going to spend too much time going into the actual equation itself, but if that is something that you’re interested in, I’m happy. Again, I will send this presentation to everybody, and of course, please put a question in the Q&A and I’m happy, happy, happy to share that and, of course, discuss it in a little bit more detail.
But if we had to put this into a graph, a very simple representation here would be quite easy to show with our temperature overtime. So we’ll have the line, we’ll have a graph and we’ll be able to plot that temperature overtime. Plus, we have a datum temperature which you’ll hear me talk about possibly a little bit later again. The date and temperature is the temperature below which your concrete will gain strength. So typically, we use zero for that because our datum temperature very typically is zero degrees. It is commonly accepted that if your concrete temperature is below 0, no curing is going to take place, and the chemical reaction really is put on hold, so that is one thing we know. So therefore, we have now an area in which we can work between because the other aspect that we have is time. So, we know that between the start time, so when we pull the concrete to the time that we’re looking for our strength result and we have a date and temperature, we have the temperature line curve on top. We get an area, and this might seem a little bit familiar. You might remember this from the graph a little bit earlier that I showed where when the temperature is higher, the time is shorter when the temperature is lower, the time is longer, and therefore we’re going back to that same basic concept here and with this area we are able to extract a function from that and an equation from that, and this is really as simple as the maturity method is. If we know the temperature, continuous temperature. If we know the start time and the end time, so in other words, a time period, in the number of hours. We are able to determine a maturity index from that.
All right. So, if we go into the science a little bit more, we can look into a bit more detail here. We’ve got the temperature time factor, all right, so that’s typically in degrees over hours and we’ve got the average concreting temperature during that time interval. We have a date and temperature and then we have the time interval and when we put this into a graph, we can see the following. So, we’re going to do some calculation here. Like I said, what we’re showing here is how do we get to the maturity value that we will talk about which is the maturity that’s degrees over hours that is calculated as such. All right, so we are, again, as a very easy function working at the area. If we put it simply below the line that we’re interested in and that temperature line that we’re measuring, we’re able to accumulatively add up that degrees per hour and that will give us a number. And as you can see, as we plug these points along here, we are able to plot a graph on our maturity graph on the right-hand side. If there are any questions about this, I’m happy to go into some more detail at the end of the webinar, but I don’t wanna spend too much time in the nitty gritty. I’d like to get to the application here a little bit more, and as you can see, for our example that we’ve shown here, the area that’s below zero is not counted towards our the accumulative time. And again, you do not have to worry about this because this is something that the technology that we bring into the table will automatically calculate for you, and therefore you’ll see the same graph that I showed you a little bit earlier. Then we can draw a correlation, because if we go back here in a moment and have a look, you’ll see that we’ve got these time periods in the temperature-time, and with these time periods for the calibration we are able to determine a strength value for each one of those points. With that strength value, we can correlate that back to a graph that looks like this. To say that on our X axis we have the strength, which is an MPA in this example, and we have our maturity values and then we have our maturity strength relationship. And as you can imagine, as I said a little bit earlier, this is specific to one mix design, not batch. So it’s not each time that you do a batch but per mix design. That particular method follows the AST MC107 full method and one of the important things as well, and you can see we’ve got a chair here, the minimum of five data points is required. To have an accurate maturity curve. And then of course the other thing as well is what you want to do to get this line accurate and as accurate as possible is to really use it in a controlled environment. So, this information that we want to gather here, and we’ll talk about the calibration over later, has to be gained in an accurate environment, OK? Alright.
I’m gonna jump to the maturity calibration, but before I do, I’m gonna ask everyone another question quickly. Thank you very much for answering that previous poll. I’m going to share the results here. Very interesting that 85% of us of the people that are attending today are faced with challenges when concrete testing. And of course, those challenges could vary from project to project, from market to market, to region to region. But certainly, as you can see, by far the majority of us are struggling with issues of concrete testing.
Alright, so I’d like to share another poll with you, and I want to just ask this question because I’d love to know in the crowd in the audience today who have used. Have you used maturity on any of your projects, whether it’s existing or whether it’s in the past? I just want to get a feeling because it will set the tone a little bit for what I’m going to follow on next. So please do let me know. Please do answer that. Have you used maturity on any of your projects yet? Let’s see if we can find anyone here who has has used maturity. OK, I see a couple popping in, that’s great. All right, super. And we were even ready for 30 minutes. If you need to stand up and stretch your legs and move around a little bit, that’s OK. Videos aren’t on, so that’s alright we’re OK with that. But you know, it’s good to stay healthy especially our current situation, many of us are spending many hours behind the screen, so it’s not a bad idea to just stand up and and then stretch your legs and move around a little bit as well. Alright, so OK, waiting for a few more votes on this on this poll. That’s very interesting. Very interesting. So, we do have a couple of people and I can see the results you can’t see yet, but I’ll leave that poll up for everyone to answer that as we go through here. But one of the things that we’ve seen around the world, and especially as we branch into the Asia market, is maturity is not a very commonly known method or commonly known method to use or standard to apply. We see it growing because we see the requirements you know, and as a result you know that part. First poll that we did. 85% of us are faced with challenges when it comes to concrete testing, and one of the things that we do want to do is change that, we can improve that. If we can use technology, we can use existing methodologies, existing standards to improve that process, then we should be doing that. That is certainly a goal that we at Giatec or striving hard to to reach for.
Alright, so I’d like to talk about maturity and the calibration of maturity. Again, we’re going into quite some detail here and nitty gritty, but I think it does help us get a better understanding of how can we take this maturity and put it into our project and apply it in a practical way to our requirements.
So I see the polls and I’m going to leave the poll up for a second. So, so I’d like to just show the results for polling. There’s a couple more questions because I think that is very interesting; some of the results that we’re getting there, right perfect.
Right, so I’d like to encourage us to think about the maturity method a little bit and where we are. We’re going to look at the calibration now. We’re going to take the steps of calibration. I’m going to walk you through the process here a little bit, and I don’t want to rush through too much here, but we are always a bit stuck for time in these webinars, ’cause I don’t want to take up too much of your time today. So, the calibration is done in five very, very easy steps. The first thing we’re going to do is we’re going to paste the samples. There’s some curing that takes place. We’re going to workout the strength results that we get from that. After that, we’ll be able to determine a maturity index, and then we’ll be able to put the strength results we have together with the maturity index, all right.
So, the actual getting the concrete strength and the curing and the first three steps are as simple as a normal sample test, and normal cube test, and normal set that we take from site to get the strength of the concrete. So, this isn’t something different, this isn’t something new. The only new aspect to this, which would be perhaps unfamiliar with you if you are part of the 80% that have not used maturity before, that is to use the maturity system. That is to determine the maturity index and to determine the maturity strength curve.
So, the first thing we’re going to do is we’re going to prepare a set of samples. Again, forgive the slides. They talk about cylinders, but whether it’s cylinders or samples, that certainly does not make a difference. The key here is it’s your standard strength testing pro step process that you follow. And that is taking a set of samples, whether it’s cubes or cylinders, curing them in a certain condition and then crushing them to determine those compressive results will do those compressive tests. So, what we require for the maturity calibration is we require 15 samples to be taken for strength, and as you can see, we’ve determined here that the fairly standard process to follow is a set of three samples for day one, a set of three samples for day three, day seven, day 14, and 1228. I’m willing to bet that many of you are already doing a typical 7 or 14 or 28 day sample collection for those results. So, this is really just adding another two or three points to your existing sample that you are taking. In addition to these 15 you’re going to take an additional 2 samples and these samples are going to control or contain two temperature sensors. Why? What are we trying to do with these two? These here two are going to tell us the temperature of the concrete inside these samples. So, if you can think back to our previous section that we’re on, what are we trying to do? We’re trying to find the correlation between the strength of a particular concrete mix in correlation to the temperature of that concrete mix.
Step two is the curing. This is quite an important step. All five steps are important, but I find this is often the step where there’s sometimes a bit of confusion. What is very important about Step two is that all the samples that are taken are kept in the same condition. So, whether you’re carrying them in a bath, whether your steam curing them, whether you’ve got to control temperature room, whatever it may be, whatever method or process you’re following to control the temperature of your samples that you’re taking, you need to make sure that all 15 plus the two with the SmartRock in or your temperature sensors in are kept in the same condition and this is very important. Typically, according to the ASTM standard, this is done in a bath or some sort of curing bath where the temperature is maintained or a moist room. Again, this might change from your industry or your market, but I think that the fairly common practice worldwide is certainly taking those samples, putting him in a curing bath, keeping them at that constant temperature, and that’s what we’re going to be using.
Alright, so how do we determine the strength? Which is step three. So, step three is determined by us crushing, doing compressive tests of those 15 samples that we have. So, the first three samples are taken on the first starting point. So, weather that’s day one, or it could be on 12 hours or 48 hours, whatever it may be, that could vary from your requirements, but the standard practice is 135137, fourteen and 28. So depending on which ones you’re doing, what you’re looking for is you’re looking for a strength result at a particular point in time. It’s just important that you note the hour in which their compressive test is done, because that’s going to give us pinpoint accuracy as to when that concrete that was kept at that certain temperature reached that particular strength. Alright, and of course, the standard practices you’re going to break two of those samples if there’s a variance or big variance in one of them, you will break the third one, but essentially breaking two, taking the average between those two, looking at that and, of course, recording that information.
The maturity index, and that’s the beauty of technology nowadays. Not so long ago; 10 years ago, 20 years ago, the Maturity Index was a manual calculation. All those calculations that I showed you previously of the volume, the area underneath the temperature line, all of that had to be done manually so that you could determine what your maturity index was for a set period of time. The advantage of using a system like our maturity system or the smart rock system is that when you put the temperature in, and that sensor is activated and it is working, it will automatically calculate the temperature index for that particular concrete or that situation that you’re monitoring. So again, it’s just that continuous temperature monitoring overtime, and one of the important things as well is that we want the the actual temperature point to come from the center of the sample. So, whether it’s a cube, whether it’s a cylinder, what you’re trying to do is get the measurement of temperature management from the core right in the middle of that sample there. OK fantastic.
And then we get to the magic stuff. So, this is where we start, now correlating. So, in our first line here, you’ll see that in step three we got the strength results, so we got the day one, day three day seven, day 14, and day 28 strength results. And that we can plot, of course, on the X axis. The next thing that we got is the maturity index, and that is from the sensors that we embedded into two samples, and that is going to give us some maturity information, and it’s going to give us at the same points in time. We’re going to have a maturity value and again, that’s automatically calculated by the software in the application that is applied here. But again, you can see that once we have these two very easy X and Y values, we now have got a strength maturity or maturity strength relationship, all right.
So, if we talk about the actual implementation of this and if we get a little bit of time towards the end, I’ll be happy to do a bit of a demonstration here. But we’ve got two software versions of our software, that is, we’ve got the online where you can access it through a web browser, our 360 Dashboard and we’ve got the mobile application. All you need to function is the mobile application in a smartphone and to be able to connect to the SmartRock like that. But if you want to delve in a little bit deeper, do some more project management on a larger scale, multiple projects access through like that, and also even manage your calibrations as we’re talking about now, that will be done on the Giatec 360™, which of course makes the accessibility a little bit easier. And that’s what we see here. We have got the automatic functionality to generate your maturity calibration. So, what you need to do is you’re still going to do the same process. Follow the same process of the 17 samples, two sensors in two samples and the other 15 are used for strength determination. But once you’ve got those strength points, you can automatically take the information that you got from the two SmartRocks, implement that into your dashboard, plug in those five strength points that you have at the time and the date they were crushed, and our software will automatically calculate for you the maturity calibration. For those who don’t know as well and if you have got some time, do go to our website. I’ll actually, I’ll try posting the chat a little bit later. But on our website, we’ve got a concrete tab. We’ve got some concrete tools there as well, and there’s actually a simplified maturity calibration that you can do as well. So, if you’ve got a few data points on your concrete mix, perhaps you’ve got the results for a day seven and a day 14 and a day 20 crush result, you were able to take that and plug that into the simplified maturity calculator and it will give you a simplified curve. Again, it’s not going to be a very accurate curve to with one degree, but it’s going to give you an indication certainly of what your maturity strength graph will look like. Alright.
Good, if there are any questions at this point, please do pop them into the Q&A. I remind you also in the chat. Please feel free to use the chat and put some questions in there. I see a few comments coming through. Thank you, Praveen, for your comment there. Appreciate that. And certainly, again we will be sharing the presentation via email to everybody who is attended today, so we will be doing that. Alright.
What I’d like to jump to next is actually share the polling question. So, I asked the question: “Have you used maturity on any of your projects?” And let me share those results very quickly. Interestingly enough, we do have a couple of people here in the session today that have used maturity and that’s fantastic. Great to have that, great to see that. 17% of the people use that, whereas 83% have not used maturity yet. I hope that that is something that we can change in the future for you, but great. Thank you very much for your participation there. I really do appreciate that, all right super.
OK, so we’re going to look into some real examples. One of the things that that always comes back to us when we start talking about maturity to markets that are perhaps a little bit unfamiliar with it is that, “Where’s the proof?” Where’s the how we tried and tested it? Can we do some correlations? Do we need to do some, you know, checks and double checks, and certainly that is something that you can do. But the advantage that we come to the table with today is that this is a tried and tested standard method that has been used around the world right now and and as we see, even in in the market that we’re talking to today. Alright?
So, let’s let’s jump back to our field cured versus in place strength discussion. And again Parveen, I think this is a back to your question a little bit is field cured versus in place concrete are subjected to very different temperature profiles. So, when we look at our in-place concrete, it retains a lot more heat because of the mass effect. Whereas our field cured specimens, or samples on site or even our samples that are going to lab, they do not retain as much heat because they have a large surface area in relation to the mass volume and this is important, all right. So, as we established as well is that with a greater strength value, and I’m going to scribble a little over this slide today. So, with the greater strength value, greater temperature value on our in-place concrete we know, as we said a little bit earlier, we can expect one higher maturity index value because there are more degrees per hour in that equation versus your samples that are taken here, which are a little bit lower. So, if we translate this graph that we looked at a little bit earlier into a maturity graph with the maturity in degrees over hours, we can see that our in-place concrete is going to have a greater temperature or greater number, greater value in the early age. So, if you look at here, we’re talking 24 hours 4870 to 9620. So, in those first stages, the first five, six, seven days, we’re expecting a much higher maturity value from the same concrete, and I think it’s important to emphasize this. This is it taken from, and this is real results, taken from exactly the same concrete mix that was batched on site. They batched the concrete on site, sensors were put into the concrete that was placed into the slab. SmartRock and a sensor was put into the lab cured and the field cured samples so we could accurately determine the maturity values for each of those concrete scenarios. And here you can see this is a very different profile formed around the maturity value.
If we have a look at the next slide, I think this is where it gets really interesting. This is what we’re looking at and this is what we’re talking about. If we talk about accuracy versus the lab cured and field cured. When we look at our in-place strength curve, this is the strength curve that we’re looking at, and this is based on the maturity values that we got from having embedded sensors in the concrete that we placed. So, as you can see, this particular mix it was designed for a 40 MPA mix, but they wanted to get some early strength so they could post tension and move the job quickly. They wanted to get the form work out, they want to tension the slab, etc etc. So, what we see from the maturity values that we got is that 30 MPA on the in-place concrete was already reached after 24 hours whereas when we look at the lab sample, and this is the salt that was sent to the lab and cured, we only reach that 30 MPA one day later, a full 24 hours later. And the last sample, if you had to think about it; where do you think the field cured sample would be? If you thought it would be in between you are correct, so of course the field code sample is a little bit closer to being accurate to your actual in place concrete, but as you can see, it’s still almost 12 hours, half a day, behind the strength gain of your actual in place concrete. So again, to answer the question, how much more accurate is the maturity method versus your lab and you’re cured samples? There you can see.
Alright, we’re getting accurate strength results from our in placed concrete, and if you can imagine; what are the ramifications of this if we take this one step further? We can go to a building, and again this is a building that we actually had, was 50 floors of 50 stories. Each building had three pours and even if we looked at the 12-hour savings, so let’s go back to the previous graph here. There you can see that if we’re looking at this as a strength result on 24 hours versus the field cured sample that we were keeping on site to try and determine a more accurate strength result from our samples, you can see that we can save 12 hours per pour. So, if you are quick at maths and you’ve done the math, you can imagine a project of that size. We’re talking about 1800 hours of time savings, just on our concrete strength gain, so that’s outside all the other domino effect that this could have. But in reality, what we’re able to do is make more accurate decisions on our concrete strength based on the real time data that we’re getting. And with that, we can of course make more informed decisions and increase our efficiency on site. Right, fantastic.
OK, so if we talk about implementation and, I’m going to push through this section a little bit, we want to get to some of the things and we’ve got about another 6 minutes left. I’m going to take a little bit longer than I anticipated today, so I completely understand if you need to jump off the cool on the hour, that’s understandable. But if you give me about another 15 minutes, we will be complete in the webinar and I’ll be able to cover everything. And then I will remain online for a few extra questions and conversations afterwards. I’ll be happy to do that.
So, let’s talk about the implementation. How do we implement this method? So whatever Matthew said, OK, great Matthew, we got the maturity method. We know that it works. It’s a tried and tested method. It’s a fixed method. How do we take that and put it onto our projects? So, it’s very simple. Actually, it’s quite straightforward. The ultimate goal of replacing our field cured cylinders and trying to replace those early age cylinders is that we want to do away with unnecessary testing. There’s a couple of advantages to that, of course, less concrete wasted, less delays, less hassles, less cost. There are other bigger things. But when we talk about how much is required, how many sensors do we need? If we’ve got a project next week while on another project right now, how many sensors do I need for my project? How many sensors do I need to implement maturity? And here is a good guideline, this is our recommendation. We’re saying that anything between or bigger than 75 to 100 cubes, a pour size were saying you want two sensors. When you go over that, so anything for every 75 to 100 cubic meters after the first hundred just add an additional one. So typically, the minimum you’re going to have is one, unless you’ve got a very small pour, then you can get away with two. Sorry, then you get away with one if you have a very small poor, but anything bigger than 75 to 100 cubic meters, you’re going to want to have two measurements to measure there, and then for every 100 cubic meters after that, you’re going to have one sensor.
The next question that we often get asked is where do we measure the maturity? And according to the ASTMC 1074, the important thing is critical locations, alright. So now the next question is what is a critical location? So, some of the main criteria is where would the coldest or the hottest, and you can add that in there, but the most exposed areas be in the structural element. The coldest, and the reason why we start with the coldest is because that is where the concrete will cure and set at the slowest rate. So that’s certainly one point that you want to monitor, so perhaps you’ve got an area of your slab or your project that’s in shade, or that’s covered by another building in some way perhaps. Wherever you’re going to have the coldest concrete temperatures, that’s going to be one of the critical aspects to measure. The other thing as well is to think about where is your start and your end time. If you’re pouring 1000 square meters of deck and you start over here at. 4:00 o’clock in the morning, and you finish on the other side at 4:00 o’clock in the afternoon. Then we know that the part that’s going to reach strength last or the latest would be the last place that we placed concrete, so that’s another way to think about that. And then, of course, what are the critical locations on your structural elements? So, from a structural perspective, you know, have you got perhaps some big bulkheads, big columns that you’re worried about that are taking a lot of load? Perhaps you’ve got big spans between your columns. So, you need to know where above those columns is my concrete getting the strength that I’m looking for. That is the information that you want to use there, and that is certainly some of the information that you want to address that would be a critical location there.
OK, ladies and gentlemen, I have gotten to the end of the presentation. I would like to flash the screen on site. That’s some contact information there. Alright, great again. I’d like to thank everyone for being here today that is the end of our webinar today. So officially, that we will stop there.
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