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  Monitoring of self-healing concrete using embedded transducers
   
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Arnaud Deraemaeker, Grigorios Karaiskos

   
Keywords Piezoelectric transducer, ultrasonics, embedded in concrete, cracking, self-healing
   

Motivation

The damage indicator developed for crack monitoring has been used to monitor the stiffness regain of self-healing concrete developped at VUB by the team of Prof D. Aggelis and D. Van Hemelrijck. Self-healing concrete consists in embedding healing capsules during casting. When cracking occurs, the capsules are broken and release the healing agent which is responsible for a stiffness regain.
 
   
Test setup

A concrete beam with embedded healing capsules as well as two pairs of embedded transducers has been tested under a four-point bending test (Figure 1). The force-displacement curve is shown on Figure 2 for the initial test. After a time sufficient for the healing agent to act, the beam was reloaded. The force-displacement curve shows the stiffness regain but highlights the fact that the self-healed beam is weaker than the initial beam.

Figure 1: Concrete beam with embedded healing capsules and piezoelectric transducers subject to a four-point bending test

Figure 2: load-displacement curve for the initial (loading) and self-healed (reloading) concrete beam.

During the two tests, the damage indicator was measured on-line. Its evolution is shown on Figure 3 as a function of the load applied, both for the loading and the reloading cases. Two damage indicators are represented, one for the 1-2 pair, and one for the 1-3 pair (Figure 3). For the loading case, one can note that the DI for the 1-2 pair starts to increase before the DI for the 1-3 pair. This is because the crack initiates at the bottom of the beam, so that pair 1-2 catches it earlier than pair 1-3. After the loading, the DI has satured to a value of 1 for both pairs. After self-healing, these values are decreased to 0.7 and 0.6 respectively, showing that the healing of the concrete is effective. The values reach 1 again after the maximum load has been applied for the reloading.

The results clearly show the effectiveness of the damage indicator to follow the evolution of damage and self-healing in concrete.

Figure 3: Evolution of the damage indicator as a function of the load applied

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

Selected publications

[1] E. Tsangouri, G. Karaiskos, D.G. Aggelis, A. Deraemaeker, and D. Van Hemelrijck. Crack sealing and damage recovery monitoring of a concrete healing system using embedded piezoelectric transducers. Structural Health Montoring, 2015. 1475921715596219.