How to Set up Concrete Maturity with HardTrack

How to Set up Concrete Maturity with HardTrack


Introduction

The HardTrack Concrete Maturity Monitoring software is designed to provide accurate and useful information on the maturity and strength of concrete. Every effort has been made to make this product as easy to use as possible, while still retaining enough flexibility for advanced users. 

HardTrack records and displays large amounts of data, but requires minimal setup and user intervention.  HardTrack is designed to be robust. 

HardTrack is designed to work with two kinds of projects: typical duration and expedited. HardTrack will allow you to switch your project back and forth between the two, although this would be atypical.

A typical project is as described by ASTM C 1074. Cylinders are expected to be broken after 1, 3, 7, 14 and 28 days. The maturity-strength graph summarizes the first 28 days of the concrete’s strength, calculated on a daily basis.

An expedited project is one where the strength gain during the first few days is what is important. In this case, the cylinders are broken earlier and more frequently. It is likely that many more cylinders would be broken. The maturity-strength graph summarizes the first 60 hours of the concrete’s strength, calculated on an hourly basis.

Building the Maturity Curve

A “Maturity Curve” is simply a graphical representation of the relationship between concrete strength and maturity. 

The goal of this step is to batch and test concrete that will be as close as possible to the concrete used during construction.  This includes batch size, mixing equipment, mix proportions, material sources, and manufacturers.  Any deviations in concrete preparation will reduce the quality of strength estimates from concrete maturity.


 

ASTM Standard 1074 reference Test Method C39 states test days of 1, 3, 7, 14, and 28 days as the five test ages.  With five test days, breaking 3 cylinders/beams per day of the test will require a minimum of 15 cylinders/beams.  A suggestion is to make 19, three extra to have as spares if one cylinder/beam tests way out of line on a test day.  Also, one cylinder/beam will contain the maturity sensor; this sensor will be connected to the HardTrack Cloud Sensor which will have the logging turned on to gather the temperature, time and dates to create the TTF factor for the Nurse-Saul maturity method.  

Where should the Sensors be Placed?

Industry Guidelines

In general, sensors should be placed between 2 and 6 inches from any exposed surface, or at the mid-depth of the section, whichever is less.

Your engineers should be able to tell you where they want the sensors placed. Your project owner typically specifies the sensor location as part of the Thermal Control Plan (TCP) supplied to you as part of the project specifications, usually, this will be in locations where:

• An estimation of the strength is desired.
• Strength is critical, because of structural considerations or exposure conditions considerations.
• The concrete is of a different thickness.
• Critical temperatures are likely to be generated.

Setting up HardTrack for Maturity


Please refer to instructions on how to set up a project for temperature monitoring.  We will pick up with instructions here after you have your project set up for temperature monitoring.


To set up a concrete temperature monitoring project for a HardTrack Cloud Sensor or HardTrack Cloud Sensor II, Click on one of the images below:
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Telling a Sensor About the Concrete

HardTrack needs to know a few things about the concrete before it is able to determine how mature it is. 


Some of these things won’t be known until later, and some of them may change. This is not a problem. As long as the sensor is in the concrete and the HardTrack Cloud Sensor device is logging temperatures, all of these things can be modified.

Here is a summary of the steps we will follow:

• Set the pour date & time and location of this sensor
• Define a concrete type specific to this project/pour and the concrete being used
• Add some notes to the sensor, that may be helpful

Setting the Pour Date & Time and Location

The most efficient way to set the pour date & time for all of the sensors in a project is to click on Options, Project Duration.  Fill in the Pour Date & Time and click on the green button to update all of the sensors in this project.





Then click OK.  Your project will now be saved with all of the sensors set to the same pour date & time.

It is also possible to set the pour date & time on an individual sensor basis by clicking on each sensor and setting the pour date & time on the ConcreteInfo tab for that sensor.


If you have not already done so, please update each of the sensors with an appropriate location name and save these on each of the sensors. 

If you have already defined concrete types, you can assign the correct concrete type to your sensors.  When you assign a concrete type to one of your sensors, HardTrack will ask you if you would like to assign this same concrete type to all of the sensors, excluding the ambient sensors.

If you have not defined any concrete types when setting up your temperature monitoring project, there is no point in trying to set a concrete type on your sensors at this point. You can assign the concrete type to your sensors after defining them in the next step.

Defining a Concrete Type for Maturity

First set your Display Options so that HardTrack knows your preference for temperature reading type,  pressure,  and Time Duration by clicking on Options, Display





Pressure is almost always set to MPa outside of the United States.  Within the United States, Pressure is almost always set to psi, which is derived from MPa.

Do not overlook the Time Duration setting.  This will affect how you report your concrete sample's strength.

Next, set the concrete maturity method that you plan to use and fill in the settings for your concrete method.

Click on Options, Maturity Method



Nurse Saul (TTF) is very typical in the United States, while Arrhenius (Equivalent Age) is more popular internationally.

When using TTF, the Datum Temperature will default to -10 degrees C.  Currently, it is more typical to set the Datum to 0 degrees C. In some cases, it is set to -10 degrees C.  Please check with your concrete engineer for assistance with selecting the proper setting for the Datum Temperature.

Now let’s add a concrete type that we can assign to our sensors.  In this case, we are going to use the standard 25 MPa/3,626 psi concrete, without actually doing any cylinder compression tests. So the data that we have is such that the concrete attains 25 MPa/3,626 psi after 28 days at 20 degrees C/68 degrees F. We also know that it attains 80% of its strength (20 MPa/2,900 psi) after 7 days.

For your TTF settings, you do not have to calculate these by hand.  Use HardTrack, by setting up a project with no concrete type and monitor the temperature of your curing samples.  Export the Maturity Report from this project in HardTrack and it will include the TTF settings that can be entered into the concrete type for your mass pours.

To export the Maturity Report, after opening the project that is monitoring your curing samples, click on:
Project, Export Data,  Project Maturity Reports

Select Project, Concrete Type



The Concrete Types window pops up. initially, it will look like this, with all of the fields blank. This example assumes that you are using the TTF maturity method with MPa and that your project duration is set to typical.  If you have your Concrete Maturity Options set to EA, then your form will look different, and you will be required to enter the results from your tests specifying the maturity of your concrete in Equivalent Age.



Double-tap on the first row of the Test Results list. An editor pops up. The TTF for the 7-day strength will be 5040 (7 days x 24 hours X 30 Degrees Celsius). The strength will be 20 MPa. Tap on OK.



Double-tap on the second row of the Test Results list. Once again, the editor pops up. The TTF for the 28-day strength will be 20160 (28 days X 24 hours X 30 Degrees Celsius). The strength will be 25 MPa. Tap on OK.



Now the Fit Curve button will be enabled. Tap on it, and HardTrack fits a curve to the test data and then fills in the Strength Table.



Tap on the Save Type As button and save your strength table data to a file. In this case, the concrete type has been called Type25.

If you want to see a graph of your predicted strength, tap on the Graph button.



These values can also be exported along with other concrete data once this concrete type is used by a sensor.