Beton Monitoring/ Concrete Monitoring mit Christian Steffes von Infrasolute

Concrete Monitoring – rebar corrosion detection

with Christian Steffes, COO of Infrasolute

Beton Monitoring/ Concrete Monitoring mit Christian Steffes von Infrasolute

Summary

In this episode, Christian Steffes, COO of Infrasolute, elucidates the application, functionality, examples, and benefits of concrete monitoring for engineers and builders. The discussion covers how data is captured, transmitted, and visualized, as well as who is responsible for processing and interpreting the data.

Introduction in Concrete Monitoring

Concrete monitoring is a specialized field within construction material monitoring and Structural Health Monitoring (SHM). While SHM usually focuses on the overall structural integrity of structures, concrete monitoring delves into the details, analyzing the behavior and integrity of concrete at the sensor location. It acts as a bridge between SHM and Non-Destructive Testing (NDT), providing continuous and in-depth insights into damage processes and material behavior. Many providers in the market offer concrete sensors for electrical resistance measurement or corrosion measurement. They mainly differ technically in terms of measurement parameters (sacrificial system, potential measurement between sensor anode and existing steel reinforcement, or pH and chloride content measurement), installation methods (replicating realistic conditions and preventing weaknesses), the number of necessary cables (none to fully wired), and their durability.

Four Sensor Examples:

Duramon Sensor Aufbau: https://www.duramon.ch/

Duramon Sensor

The most scientifically advanced concrete sensor on the market measures parameters such as chloride content, pH value, concrete moisture (electrical resistance), potential, and temperature at various depths. Parameters such as corrosion current (density) or corrosion risk are calculated. The sensors are embedded in pre-extracted concrete cores. The reinstallation process is specialized to replicate realistic conditions as closely as possible.
More
Concrete Monitoring Corrodec System https://infrasolute.com/en/infrared-humidity-sensor-for-buildings/

Infrasolute Sensor

(CorroDec 2)
The CorroDec system from Infrasolute consists of a sensor for corrosion (red) and another (black) for moisture measurement. Both are embedded in the concrete without the need for cables, functioning similarly to contactless payment with a credit card. Corrosion is measured using a sacrificial anode in the form of a thin wire at two depths. When the wire corrodes, it sends a binary signal. The data can be collected through manual measurement or a data logger.
More
TFB Betonsensor https://www.tfb-diagnostic.ch/ds-en/Products/Monitoring-System-1/Sensors/Sensors.html#

TFB Sensor

(CS-302 und CS-322)
The TFB sensor (CS-302 and CS-322) measures concrete moisture (electrical resistance) between the three cylinders of the probe. The corrosion current is measured from the reference rebar (anode) to the existing rebar. The reference rebar is visible through the two small circles in the sensor.
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Sensortec Multiring Elektrode http://sensortec.de/sensoren-sensors/multiring-elektrode-multiring-electrode.html

Sensortec Sensor

(Multiringelektrode)
The Multiring Electrode measures moisture (electrical resistance) in the concrete between two rings at different depths. This provides a detailed depth profile for determining concrete drying or water absorption.
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Components of a Concrete Monitoring System:

  1. Sensors: Embedded in the concrete. Emit signals and measure frequencies.
  2. Data Transmission Unit: Data logger and/or gateway that transmits the data – the brain of the measurements.
  3. Visualization: Software that displays and analyzes the data.

Concrete Monitoring Using the Corrodec System as an Example

Operation of the Sensors

The sensors are entirely passive, requiring no batteries and boasting a lifespan of over 80 years. They utilize RFID technology to induce energy from outside and transmit data wirelessly. During retrofitting, sensors are inserted into drilled holes and sealed with special embedding mortar (at least 1.5 cm). A strong connection to the existing concrete is critical to replicate real conditions and provide reliable early warning of issues. The wireless system allows the Corrodec System to deliver corrosion indication long-term without additional effort (e.g., battery replacement) and can be installed during new construction.

Data Transmission and Processing

The captured data can be collected manually or automatically via a gateway and transmitted to the cloud. There, it is processed and visualized in the software. Data transmission occurs via the NarrowBand standard, known for long waves and deep penetration into structures.

Integration into Existing Systems

If the sacrificial anode corrodes and breaks, this can be measured binary through externally introduced signals. Infrasolute enables direct transmission of measurements to their cloud via a gateway. They visualize the data for their clients but also provide an API interface, allowing information to be visualized in existing asset management systems. Thresholds must be input separately by external engineers involved in the project.

A central aspect is the precise planning and placement of sensors in the structure. To ensure monitoring efficiency and accuracy, 2D plans are often created, indicating the exact positioning of sensors in concrete. In the future, more 3D plans and BIM models will be utilized for this purpose.

Retrofit Sensor Application:

  • Corrodec System:

Example Projects

South bridge near Koblenz 

An outstanding example of the application of the Corrodec system is the Südbrücke in Koblenz. As part of concrete repair work, both corrosion and moisture sensors were installed. The sensors detected a corrosive condition early on, attributed to improper sealing. Thanks to the sensor data, the faulty area was identified and rectified. Watch video below for more information.

aus Wikipedia: https://de.wikipedia.org/wiki/S%C3%BCdbr%C3%BCcke_(Koblenz)

Gotthard Street Tunnel

Extending the service life of the suspended tunnel ceiling in co,binational with monitoring and concrete protection. Find out more here.

Car Park Sass-Fee

Monitoring the car park concrete floor plates for chloride contamination. Find out more here.

More Applications

Application of Concrete Monitoring

The retrospective integration of sensors into existing structures is a critical task, especially with older buildings. They enable the measurement of parameters not detectable through visual inspection (chloride-induced corrosion, moisture spots after rain events, hard-to-reach areas, etc.). Additionally, they offer the following crucial advantages:

  • Establishment of a maintenance/monitoring plan after concrete repairs
  • Extension of the lifespan of a structure in critical cases

It is advisable to connect concrete moisture sensors with corrosion sensors and weather data to understand the sources of critical influences and to obtain comprehensive early indications.

The Future of Concrete Monitoring

The future of concrete monitoring looks promising, especially considering aging infrastructure. Digitalization and integration of sensor data into BIM models, along with the use of AI for data analysis, will play a significant role. Many robust concrete sensors already exist in the market. The next challenge lies in data management, such as how data from various sensors can be combined at a portfolio level to improve asset management. Here, political leadership at the infrastructure company level is crucial.

Concrete monitoring is crucial to ensure the safety and longevity of structures and to address the significant challenges posed by our aging infrastructure.

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