Concrete sensors are sensors embedded in concrete to record its temperature and humidity. The data collected by these sensors is retrieved either using a mobile application or Bluetooth connection. Concrete sensors monitor the real-time site temperature and the differentials of concrete to study the maturity and strength-gain properties.
Image Credits: Hilti North America, Plano, Texas; www.hilti.com
This article briefly explains the features and types of concrete sensors used in concrete construction industry.
Contents:
Working of Concrete Sensors
Concrete sensors embedded in concrete collect the temperature data and send it to a computer to conduct further analysis. Most concrete sensors are anchored or tied to the reinforcement in an array. These sensors provide data to the contractors and are further analyzed for conclusions.
Several types of concrete sensors are available to accurately monitor and report the concrete's temperature and maturity levels. In addition, they are manufactured in smaller sizes to withstand harsh environments.
Types of Concrete Sensors
The selection of concrete sensors for a particular project is dependent on the cost, the accuracy of measurement required, ease of use, and the return of investment (ROI) in the project. The most common concrete sensors commercially available in the market are enlisted below:
- Concrete thermocouples
- Wired temperature and maturity loggers
- Wired sensors with external wireless transmitter
- Fully embedded wireless sensors
1. Concrete Thermocouples
The typical arrangement of concrete thermocouples is depicted in Figure-2. It consists of two different metal wires connected and twisted to form an electric junction.Â
The thermoelectric property of the thermocouple produces a temperature-dependent voltage which is later measured using external equipment. This later estimates the concrete temperature.Â
Concrete thermocouples are inexpensive, but their measurement accuracy is low. The standard error limit is twice that mentioned by ASTM C1064 (0.5 t 10C). Hence, it is not used for accurate measurement and thermal control plans.
The arrangement of thermocouples is not designed for harsh construction environments. So the wires coming out of the concrete need to be protected throughout the entire temperature measurement.
2. Wired Temperature and Maturity Loggers
This device consists of a temperature logger with a self-contained circuit board embedded in the concrete, as shown in Figure-3. The logger collects the data and gives it to a wired handheld device. The final data is then given to the computer for analyzing and determining the results. This method is hence labor-intensive like thermocouples.
3. Wired Sensors with External Wireless Transmitter
In some commercial systems, the ends of wires used for thermocouples or loggers (wired sensors) can be connected to a wireless system or wireless transmitter. This wireless transmitter facilitates the direct transfer of data to the cloud or local hub, where the project managers or superintendents can get alerts, even if they are not onsite.
This system has limited use where cell network connectivity is absent. In addition to this, the complex system of wires, external transmitters, and local hub installation is challenging.
4. Fully Embedded Wireless Concrete Sensors
With advancements in electronics and wireless technologies, self-contained wireless concrete sensors overcoming the drawbacks of the above-mentioned sensors were developed. These wireless sensors and loggers are fully embedded in concrete. The measured temperature data is stored in the sensor and downloaded through various communication protocols like Bluetooth, LE, LoRa, Wi-Fi, etc.
How to Choose the Right Concrete Sensor?
Choosing the right concrete sensor for an important project is a very challenging task. Many companies have come up with different concrete sensors with multiple solutions. It is very difficult to rate each type and make a selection. But there are a few aspects based on which concrete sensors are purchased. They include:
- Ease of installation of concrete sensors
- The reusability of concrete sensors (whether it is one sensor per sample or multiple samples)
- The method by which the data is collected and visualized
- The method of data analysis (automatically or manually)
- The cost of sensor or cost per monitoring
FAQs
Concrete sensors are sensors embedded in concrete to record its temperature and humidity. The data collected by these sensors is retrieved either using a mobile application or Bluetooth connection.
Concrete sensors embedded in concrete collect the temperature data and send it to a computer to conduct further analysis. Most concrete sensors are anchored or tied to the reinforcement in an array. These sensors provide data to the contractors and are further analyzed for conclusions.
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