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Influence of the curing period of encapsulated polyurethane precursor on the capillary water absorption of cracked mortar with selfhealing properties

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Abstract
Cracks serve as preferential pathways for aggressive substances (H2O, O2, Cl-, CO2, etc.) that reduce the durability and service life of steel reinforced cementitious materials. The implementation of an autonomous crack healing mechanism counts as a solution to this problem. A very promising way to achieve that goal consists of incorporating capsules filled with polyurethane (PU) precursor in the mortar/concrete. Upon crack occurrence the capsules break, the PU precursor flows into the crack, reacts with surrounding moisture and seals the crack again once hardened. Now, depending on the specific exposure conditions of the structure (very humid versus dry), the reaction kinetics of the PU can vary. In this research it has been investigated by means of neutron radiography whether the crack healing efficiency is the same regardless of the curing period, i.e., when having direct exposure to water upon release of the healing agent (after 15 min to 3 h) versus when the PU is first given enough time (at least 24 hours) to harden completely. Preferably, the healing agent works under all circumstances. However, it was found that the first scenario resulted in the highest resistance to capillary water absorption for singular cracks, 300 μm in width. Neutron radiography images and water profiles extracted from those images during a two-hour water uptake experiment clearly show that this was the case for both a high viscosity PU precursor that was developed in-house and a commercially available low viscosity PU-based healing agent.
Keywords
Neutron radiography, capillary water absorption, cracked mortar, autonomous healing

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MLA
Van den Heede, Philip, et al. “Influence of the Curing Period of Encapsulated Polyurethane Precursor on the Capillary Water Absorption of Cracked Mortar with Selfhealing Properties.” XIV DBMC 2017 Conference, edited by Geert De Schutter et al., vol. 107, RILEM, 2017, pp. 1–10.
APA
Van den Heede, P., Van Belleghem, B., Alderete, N. M., Van Tittelboom, K., & De Belie, N. (2017). Influence of the curing period of encapsulated polyurethane precursor on the capillary water absorption of cracked mortar with selfhealing properties. In G. De Schutter, N. De Belie, A. Janssens, & N. Van Den Bossche (Eds.), XIV DBMC 2017 Conference (Vol. 107, pp. 1–10). Paris (France): RILEM.
Chicago author-date
Van den Heede, Philip, Bjorn Van Belleghem, Natalia Mariel Alderete, Kim Van Tittelboom, and Nele De Belie. 2017. “Influence of the Curing Period of Encapsulated Polyurethane Precursor on the Capillary Water Absorption of Cracked Mortar with Selfhealing Properties.” In XIV DBMC 2017 Conference, edited by Geert De Schutter, Nele De Belie, Arnold Janssens, and Nathan Van Den Bossche, 107:1–10. Paris (France): RILEM.
Chicago author-date (all authors)
Van den Heede, Philip, Bjorn Van Belleghem, Natalia Mariel Alderete, Kim Van Tittelboom, and Nele De Belie. 2017. “Influence of the Curing Period of Encapsulated Polyurethane Precursor on the Capillary Water Absorption of Cracked Mortar with Selfhealing Properties.” In XIV DBMC 2017 Conference, ed by. Geert De Schutter, Nele De Belie, Arnold Janssens, and Nathan Van Den Bossche, 107:1–10. Paris (France): RILEM.
Vancouver
1.
Van den Heede P, Van Belleghem B, Alderete NM, Van Tittelboom K, De Belie N. Influence of the curing period of encapsulated polyurethane precursor on the capillary water absorption of cracked mortar with selfhealing properties. In: De Schutter G, De Belie N, Janssens A, Van Den Bossche N, editors. XIV DBMC 2017 Conference. Paris (France): RILEM; 2017. p. 1–10.
IEEE
[1]
P. Van den Heede, B. Van Belleghem, N. M. Alderete, K. Van Tittelboom, and N. De Belie, “Influence of the curing period of encapsulated polyurethane precursor on the capillary water absorption of cracked mortar with selfhealing properties,” in XIV DBMC 2017 Conference, 14th Int. Conference on Durability of Building Materials and Components (XIV DBMC), 2017, vol. 107, pp. 1–10.
@inproceedings{8530119,
  abstract     = {{Cracks serve as preferential pathways for aggressive substances (H2O, O2, Cl-, CO2, etc.)
that reduce the durability and service life of steel reinforced cementitious materials. The
implementation of an autonomous crack healing mechanism counts as a solution to this problem. A
very promising way to achieve that goal consists of incorporating capsules filled with polyurethane
(PU) precursor in the mortar/concrete. Upon crack occurrence the capsules break, the PU precursor
flows into the crack, reacts with surrounding moisture and seals the crack again once hardened.
Now, depending on the specific exposure conditions of the structure (very humid versus dry), the
reaction kinetics of the PU can vary. In this research it has been investigated by means of neutron
radiography whether the crack healing efficiency is the same regardless of the curing period, i.e.,
when having direct exposure to water upon release of the healing agent (after 15 min to 3 h) versus
when the PU is first given enough time (at least 24 hours) to harden completely. Preferably, the
healing agent works under all circumstances. However, it was found that the first scenario resulted
in the highest resistance to capillary water absorption for singular cracks, 300 μm in width. Neutron
radiography images and water profiles extracted from those images during a two-hour water uptake
experiment clearly show that this was the case for both a high viscosity PU precursor that was
developed in-house and a commercially available low viscosity PU-based healing agent.}},
  author       = {{Van den Heede, Philip and Van Belleghem, Bjorn and Alderete, Natalia Mariel and Van Tittelboom, Kim and De Belie, Nele}},
  booktitle    = {{XIV DBMC 2017 Conference}},
  editor       = {{De Schutter, Geert and De Belie, Nele and Janssens, Arnold and Van Den Bossche, Nathan}},
  isbn         = {{978-2-35158-159-9}},
  keywords     = {{Neutron radiography,capillary water absorption,cracked mortar,autonomous healing}},
  language     = {{eng}},
  location     = {{14th Int. Conference on Durability of Building Materials and Components (XIV DBMC)}},
  pages        = {{1--10}},
  publisher    = {{RILEM}},
  title        = {{Influence of the curing period of encapsulated polyurethane precursor on the capillary water absorption of cracked mortar with selfhealing properties}},
  volume       = {{107}},
  year         = {{2017}},
}