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   Crack monitoring in concrete using embedded ultrasonic piezoelectric transducers
   
Contact

Arnaud Deraemaeker, Cédric Dumoulin, Grigorios Karaiskos

   

Past Collaborations

Dr J.Y. Sener (MS3, Belgium)
   
Keywords Piezoelectric transducer, ultrasonic, embedded in concrete, Structural Health Monitoring (SHM), damage/crack monitoring
   

Motivation

Concrete cracking can occur at early age, or later in its lifetime. The causes can be restrained shrinkage, surface drying, loss of pre-stress, water infiltrations and corrosion of the rebars, or chemical degradations.

Ultrasonic testing is efficient to detect very small changes of the microstructure of concrete and is therefore an excellent technique for crack detection. Here again, we take advantage of the embedded transducers technology to perform on-line real-time monitoring of cracking in concrete elements

     

1st application

Crack monitoring in a  concrete beam subjected to a three-point bending test

The test consists in a three point bending test of a concrete beam in which an emitter-receiver pair has been embedded , as shown in Figure 1. Based on the signal measured at the receiver, a damage indicator which is sensitive to both the change of velocity and amplitude of the wave is defined [1]. This damage indicator is recorded in real-time in order to follow the evolution of the cracking. Thanks to the development of a low-voltage fast interrogation unit, several measurements are taken each second which allows to follow in details the crack formation and propagation.

Figure 1 : Concrete beam with a pair of embedded emitter-receiver for crack monitoring

 

The load displacement curve at the center of the beam is shown in Figure 2 together with pictures of the central zone, showing that cracking is visible after 28 mins in the test.

 

Figure 2: load displacement curve and pictures of the central zone showing the appearance of the crack after 28 minutes

Figure 3 shows the evolution of the damage index, computed from the ultrasonic measurements, as a function of the time. The damage index is 0 at the beginning of the test and starts to increase after 22 minutes, before the crack is visible in the central zone. This shows the very high sensitivity of this indicator which is able to detect micro-cracking, before the actual crack opening. After 28 minutes, when the crack opens, the damage indicator reaches a value close to 1.

Figure 3: Evolution of the damage index as a function of the time

   
More applications

We have applied the crack monitoring using the damage indicator on a reinforced concrete beam under three-point bending, a concrete cylinder under compression, and during a pull-out test [1]. Similar results have been obtained showing the wide applicability of the technique

     
Support

2011-2013: FNRS-MIS: Automated damage localization systems for civil engineering structures : application to cracking in prestressed concrete

2012-2016 : FNRS-GRANT : C. Dumoulin : In situ monitoring of concrete behaviour based on embedded piezoelectric transducers

   

Selected publications

[1] C. Dumoulin, G. Karaiskos, J.Y. Sener, and A. Deraemaeker. On-line monitoring of cracking in concrete structures using embedded piezoelectric transducers. Smart Materials and Structures, 23(11), 2014. 115016.

[2] C. Dumoulin, G. Karaiskos, and A. Deraemaeker. Monitoring of Crack Propagation in Reinforced Concrete Beams using Embedded Piezoelectric Transducers. Acoustic emission and related nondestructive evaluation techniques in the fracture mechanics of concrete: fundamentals and applications. Woodhead, 2015. ISBN: 978-1-78242-327-0.

[3] C. Dumoulin and A. Deraemaeker. Real-time fast ultrasonic monitoring of cracking in a concrete cylinder subject to compression. In Proc Eurodyn 2014, Porto, Portugal, June 2014.