We’ve answered the questions about COMMAND Center and concrete temperature and maturity monitoring we hear most often.
How often do the concrete sensors take readings?
COMMAND Center Sensors can be set to take readings anywhere between 1 to 255 minutes. Over 2,000 readings can be stored continuously, meaning that a five-minute measurement interval will store a total of seven days of readings, and a 20-minute interval will store 28 days of readings. The data from the sensors can be downloaded multiple times to achieve virtually any measurement frequency and monitoring period.
Do the concrete sensors have to be initialized during construction?
No. COMMAND Center was designed to minimize interruption with construction activities. Therefore, the sensors are already fully functional when they arrive. You only need to note the time when concrete covers the maturity sensor, although it is possible to extract this time from the concrete temperature record.
How do I read the concrete sensors?
You can read the sensors in three ways:
- Connect the sensors to the Sensor Reader Module to transmit the data wirelessly to your iOS device or store on the Sensor Reader Module for later transfer.
- Connect the sensors to the rugged Trimble Nomad reader.
- Use a serial or USB download cable to connect the sensors to a Windows PC, laptop, or tablet.
Once sensor data is downloaded, you can view and analyze it using free COMMAND Center software. Data can be transferred seamlessly between devices.
What is the accuracy of the concrete sensors?
COMMAND Center uses iButtons® with an accuracy of ±1 °C (1.8 °F), meeting the criteria of ASTM C1074.
Do the concrete sensors have to be connected to anything during curing?
No, COMMAND Center Sensors are self-powered and self-contained—they’ll automatically begin collecting and storing your concrete’s temperature and maturity data as soon as they are covered by the concrete. Whenever you want to read the sensor data, just use your COMMAND Center compatible device to access the data.
If you are using COMMAND Center Wireless, you have the option of leaving the SRM connected to the sensor so data can be retrieved wirelessly and repeatedly from a distance.
Do I need a separate system to track concrete temperatures?
Which graphical method does COMMAND Center use when making concrete maturity curves?
COMMAND Center allows the user to choose between a semi-log fit specified by the Iowa and Texas DOTs or a sigmoidal relationship used by the FHWA HIPERPAV program.
Which concrete maturity method does COMMAND Center use?
COMMAND Center uses the Nurse-Saul and Arrhenius methods.
Isn't it more expensive to monitor maturity and temperature?
Maturity and temperature monitoring does require an upfront cost. However, contractors, owners, and engineers who use maturity frequently save money on their projects, because maturity can speed project schedules, reduce the risk of reconstruction caused by inferior concrete, and decrease the need for costly concrete repairs over the lifetime of a project.
Read about how The Beck Group used COMMAND Center to lower a project budget by $3 million in Dallas, Texas.
Maturity’s advantages can far outweigh the costs associated with it. Adding maturity to traditional testing can increase safety, expedite construction schedules, and improve construction methods.
How are maturity sensors used in concrete strength testing?
The maturity method doesn’t take the place of laboratory testing requirements for strength. Instead, construction teams monitor concrete maturity in addition to breaking cylinders or beams according to standard test procedures, although in many cases the amount of breaks can be reduced over the course of a project by implementing maturity.
Maturity monitoring is implemented to verify standard testing and to estimate in-place concrete strength in real-time strength at the job-site. The advantage: calculate strength at the job site instead of waiting for standard testing intervals, and increase quality control and assurance with strength verification.
Once standard strength tests have been completed, the maturity method uses that test data to calculate a strength-maturity relationship and a maturity curve for the specific concrete mix. This mathematical relationship allows you to use maturity as an indicator of your in-place concrete’s strength. Simply track your concrete’s maturity by placing sensors in your concrete at the job site—then read the sensor at any time to receive an estimate of your concrete’s strength based on the established strength-maturity relationship for that mix.
Even when the maturity method is being implemented on a project, concrete samples are also tested throughout construction in order to validate the maturity curve.
Learn more about the specific tests that will be conducted during construction on a project using COMMAND Center maturity monitoring.
What laboratory testing do I need to conduct when implementing the maturity method?
You’ll conduct two rounds of strength tests (compression or flexural) on concrete specimens in a lab. In the first round, you’ll use the data to develop your concrete mix’s maturity curve. In the second round, you’ll use the data to verify your concrete mix’s maturity curve while your in-place concrete is curing on the job site.
Your first strength tests allow you to develop a calibrated maturity curve that graphs the relationship between temperature, time, and strength for your project’s concrete mix design. If you will use multiple mix designs on a project, you will conduct tests and develop a maturity curve for each mix. Each maturity curve is specific to each mix’s unique combination of materials and proportions.
Testing should follow standard methods such as ASTM International C 1074: Standard Practice for Estimating Concrete Strength by the Maturity Method. In summary, ASTM C 1074 works like this:
- A trial batch of the desired concrete mix design that will be used in the structure, pavement, or slab is prepared.
- The mix is poured into a series of test specimens (cylinders or beams).
- Temperature-monitoring sensors are inserted into two of these specimens.
- The specimens are all cured in the same manner, typically in a water bath or moist room.
- While curing, the temperature sensors are read and maturity data is calculated by software.
- Specimens that do not contain the sensors are periodically broken and tested for strength at ages of interest.
- A relationship between maturity and strength is established, and together this data is used to estimate the strength of the field concrete.
These laboratory tests are conducted prior to construction. You’ll develop your concrete mix’s calibrated strength-maturity curve in the lab, and then you’ll use that relationship to evaluate your in-place concrete at the job site.
Subsequent strength tests take place during construction and allow you to verify your concrete mix’s maturity curve. This testing is part of regular concrete construction: specifications for quality control and acceptance on any concrete project require you to cast concrete specimens and conduct compression strength tests at regular intervals during construction. When using maturity, you’ll add one extra step to this standard procedure: embed a sensor into one of the specimens to monitor its temperature over time. Evaluate your maturity curve by comparing the specimen’s maturity data with strength data from your strength tests. If a specimen breaks within a 10% deviation of the strength predicted by the maturity data, the curve has been verified.
Using the maturity method is not a replacement for traditional testing methods, but it can reduce the number of extra cylinders cast for traditional tests. Most specifications require construction teams to cast specimens in the field, cure them in ideal conditions, and then conduct compression strength tests at specific time intervals. Construction teams will commonly cast extra specimens for these tests because often several specimens must be discarded due to unexpectedly low strengths. Maturity decreases the chance of these discards—if a temperature sensor is embedded in the specimen, construction teams can determine its strength by reading the sensor data and determining strength from the maturity curve instead. This prevents construction teams from conducting a strength test on a specimen before enough strength is gained. By preventing discarded specimens, they can reduce the number of extra specimens needed for testing.
What do I need to buy to use COMMAND Center?
COMMAND Center Sensors are required to read your data on any device. COMMAND Center software is completely free and you have several options for what device to use it with. You can purchase a durable handheld Trimble Nomad, which comes loaded with COMMAND Center software and includes all cables and accessories. Upgrade to the COMMAND Center Wired Kit to include 50 sensors in your order. You can also use an iPhone, iPod, or iPad along with a reusable Sensor Reader Module (SRM) to transmit sensor data wirelessly. To use your own Windows PC, laptop, tablet, or handheld PC, you’ll need our USB or serial download cable. Software files are compatible across readers, so you can use any combination.
Still not sure what you need? Contact us online or by phone to discuss your project needs: +1 (888) 451 6233
How do I buy COMMAND Center?
If you’re interested in purchasing COMMAND Center, you can buy any of our products online or call us at +1 (888) 451 6233.
Is COMMAND Center data secure?
Yes, COMMAND Center data files are encrypted and all PDF reports generated in COMMAND Center for Windows software are secure.
Do you have a question we haven’t answered here?
Call us at +1 (888) 451 6233 or send us a message.