Ultrasonic Wave Transmission to Monitor Self-healing Concrete
Posted: 2016-2-15
Source:
Technical University of Munich Chair of Non-destructive Testing
Self-healing concrete aims at the autonomous healing of small cracks, with widths in the order of a few hundred micrometers. This way, the service life of reinforced concrete structures can be extended and their watertightness guaranteed for longer periods, while costly and potentially complex repair works can be avoided.
As with other emerging concrete technologies, this novel repair technique poses new challenges regarding the conception of new test methods that are able to assess its performance in realistic conditions and able to continuously monitor it. Thus, this paper presents results of applying the transmission of ultrasonic shear waves for continuous monitoring of small scale cement mortar specimens cracked and healed with encapsulated precursors of flexible polymers.
Preliminary results on larger concrete specimens showed already that this technique successfully detects the continuous hardening of the precursors after rupture of the capsules and further filling of the crack, corresponding to an increase of the amplitude of shear waves transmitted through the healed crack. Additionally, the reverse was observed when failure occurred, due to rupture of the polymer’s matrix or to its detachment from the crack walls.
In this study, the transmission of ultrasonic shear waves is used to assess the limits of the elongation of the polymers bridging the cracks and their resistance to fatigue while healing a moving crack induced by cyclic loads. The polymer precursors used include moisture curing polyurethanes forming solid films or foams with closed-cell structure.
Published as:
Ultrasonic wave transmission to monitor the performance of self-healing concrete based on encapsulated polymer precursors
J. Feiteira1,E. Gruyaert1, N. De Belie1
Magnel Laboratory for Concrete Research, Ghent University, Technologiepark-Zwijnaarde 904, 9052 Ghent, Belgium
About HEALCON
Within the theme ‘Self-healing materials for prolonged lifetime’ (NMP.2012.2.1-3) of the Seventh Framework Programme, self-healing concrete is an important topic. The project HEALCON, which deals with self-healing concrete to create durable and sustainable concrete structures, is funded by EU-FP7 and started in January 2013. The coordinator of the project is Prof. Nele De Belie (UGent) and the consortium partners are UGent, Avecom, TU Delft, Acciona, TUM, TTI, VTT, COWI, DTI, CEINNMAT, Devan and Fescon.
Adequate perpetuation of the road, tunnel and bridge network, is crucial to preserving European cohesion and business operations; and around 70% of this infrastructure is made of concrete. In order to guarantee liquid tightness of concrete structures, and enhance durability of elements prone to bending cracks, smart concrete with self-healing properties will be designed.
Thanks to the existing expertise of the consortium in the field of self-healing concrete at a lab-scale, a thoughtful selection of promising techniques is possible.
- For early age cracks, a non-elastic repair material can be proposed, such as calcium carbonate precipitated by bacteria, or new cement hydrates whose formation is stimulated by the presence of hydrogels.
- For moving cracks under dynamic load, an elastic polymeric healing agent is suggested.
HEALCON aims to further develop some initial concepts that have been explored earlier by the different partners, in order to ensure practical application in concrete structures.
Different healing agents and encapsulation techniques are tested and scaled up. Self-healing efficiency is evaluated in lab-scale tests using purposefully adapted monitoring techniques, and optimized with the help of suitable computer models.
Finally the efficiency is validated in a large scale lab test and implemented in an actual concrete structure. Life-cycle cost analysis will show the impact of the self-healing technologies on economy, society and environment compared to traditional construction methods.
Image: Reprinted with Permission from Technical University of Munich Chair of Non-destructive Testing, Munich, Germany
As with other emerging concrete technologies, this novel repair technique poses new challenges regarding the conception of new test methods that are able to assess its performance in realistic conditions and able to continuously monitor it. Thus, this paper presents results of applying the transmission of ultrasonic shear waves for continuous monitoring of small scale cement mortar specimens cracked and healed with encapsulated precursors of flexible polymers.
Preliminary results on larger concrete specimens showed already that this technique successfully detects the continuous hardening of the precursors after rupture of the capsules and further filling of the crack, corresponding to an increase of the amplitude of shear waves transmitted through the healed crack. Additionally, the reverse was observed when failure occurred, due to rupture of the polymer’s matrix or to its detachment from the crack walls.
In this study, the transmission of ultrasonic shear waves is used to assess the limits of the elongation of the polymers bridging the cracks and their resistance to fatigue while healing a moving crack induced by cyclic loads. The polymer precursors used include moisture curing polyurethanes forming solid films or foams with closed-cell structure.
Published as:
Ultrasonic wave transmission to monitor the performance of self-healing concrete based on encapsulated polymer precursors
J. Feiteira1,E. Gruyaert1, N. De Belie1
Magnel Laboratory for Concrete Research, Ghent University, Technologiepark-Zwijnaarde 904, 9052 Ghent, Belgium
About HEALCON
Within the theme ‘Self-healing materials for prolonged lifetime’ (NMP.2012.2.1-3) of the Seventh Framework Programme, self-healing concrete is an important topic. The project HEALCON, which deals with self-healing concrete to create durable and sustainable concrete structures, is funded by EU-FP7 and started in January 2013. The coordinator of the project is Prof. Nele De Belie (UGent) and the consortium partners are UGent, Avecom, TU Delft, Acciona, TUM, TTI, VTT, COWI, DTI, CEINNMAT, Devan and Fescon.
Adequate perpetuation of the road, tunnel and bridge network, is crucial to preserving European cohesion and business operations; and around 70% of this infrastructure is made of concrete. In order to guarantee liquid tightness of concrete structures, and enhance durability of elements prone to bending cracks, smart concrete with self-healing properties will be designed.
Thanks to the existing expertise of the consortium in the field of self-healing concrete at a lab-scale, a thoughtful selection of promising techniques is possible.
- For early age cracks, a non-elastic repair material can be proposed, such as calcium carbonate precipitated by bacteria, or new cement hydrates whose formation is stimulated by the presence of hydrogels.
- For moving cracks under dynamic load, an elastic polymeric healing agent is suggested.
HEALCON aims to further develop some initial concepts that have been explored earlier by the different partners, in order to ensure practical application in concrete structures.
Different healing agents and encapsulation techniques are tested and scaled up. Self-healing efficiency is evaluated in lab-scale tests using purposefully adapted monitoring techniques, and optimized with the help of suitable computer models.
Finally the efficiency is validated in a large scale lab test and implemented in an actual concrete structure. Life-cycle cost analysis will show the impact of the self-healing technologies on economy, society and environment compared to traditional construction methods.
Image: Reprinted with Permission from Technical University of Munich Chair of Non-destructive Testing, Munich, Germany
