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Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation

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Abstract
Insulated concrete elements used in building facades, e.g.,sandwich panels, are frequently exposed to sun radiation, which causes high temperatures on the outside. Although the inner and outer cladding are supposed to be independent, a high temperature difference between the outside and the inside of the elements causes thermal bending, which can lead to cracking. These cracks may have an impact on the durability of the outer cladding and are not wanted from an esthetic point of view. A possible solution for this problem is the embedment of encapsulated polyurethane in the concrete matrix in order to repair cracks autonomously. However, healing agents with suitable properties are needed to heal cracks at these conditions. In this research, newly developed polyurethane resins with relatively high viscosity were tested for their healing efficiency at high temperatures. The mechanical properties of the polyurethanes such as bond strength and elasticity were determined. Second, the healing agents were encapsulated and evaluated for their efficiency to heal cracks by capillary absorption tests, strength regain evaluation, and X-ray computed tomography. The new polyurethanes were much more elastic than the commercially available ones and thus more able to withstand opening and closing of cracks due to temperature changes. The water ingress in specimens with healed cracks was found to decrease with increasing viscosity of the polyurethanes. At a temperature of 50 degrees C, the polyurethanes were able to heal cracks so that the water absorption of cracked mortar was reduced to a value that was comparable to the water absorption of uncracked mortar. Also, a strength regain of 100% or more was obtained. Therefore, using self-healing concrete in building facades may have a positive effect on the durability and service life of the construction elements. (c) 2018 American Society of Civil Engineers.
Keywords
CONCRETE, COMPOSITE, CRACKS

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Chicago
Van Belleghem, Bjorn, E. Gruyaert, Kim Van Tittelboom, Wim Moerman, B. Dekeyser, Jeroen Van Stappen, Veerle Cnudde, and Nele De Belie. 2018. “Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation.” Journal of Materials in Civil Engineering 30 (7).
APA
Van Belleghem, B., Gruyaert, E., Van Tittelboom, K., Moerman, W., Dekeyser, B., Van Stappen, J., Cnudde, V., et al. (2018). Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation. JOURNAL OF MATERIALS IN CIVIL ENGINEERING, 30(7).
Vancouver
1.
Van Belleghem B, Gruyaert E, Van Tittelboom K, Moerman W, Dekeyser B, Van Stappen J, et al. Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation. JOURNAL OF MATERIALS IN CIVIL ENGINEERING. Reston: Asce - amer Soc Civil Engineers; 2018;30(7).
MLA
Van Belleghem, Bjorn, E. Gruyaert, Kim Van Tittelboom, et al. “Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation.” JOURNAL OF MATERIALS IN CIVIL ENGINEERING 30.7 (2018): n. pag. Print.
@article{8565957,
  abstract     = {Insulated concrete elements used in building facades, e.g.,sandwich panels, are frequently exposed to sun radiation, which causes high temperatures on the outside. Although the inner and outer cladding are supposed to be independent, a high temperature difference between the outside and the inside of the elements causes thermal bending, which can lead to cracking. These cracks may have an impact on the durability of the outer cladding and are not wanted from an esthetic point of view. A possible solution for this problem is the embedment of encapsulated polyurethane in the concrete matrix in order to repair cracks autonomously. However, healing agents with suitable properties are needed to heal cracks at these conditions. In this research, newly developed polyurethane resins with relatively high viscosity were tested for their healing efficiency at high temperatures. The mechanical properties of the polyurethanes such as bond strength and elasticity were determined. Second, the healing agents were encapsulated and evaluated for their efficiency to heal cracks by capillary absorption tests, strength regain evaluation, and X-ray computed tomography. The new polyurethanes were much more elastic than the commercially available ones and thus more able to withstand opening and closing of cracks due to temperature changes. The water ingress in specimens with healed cracks was found to decrease with increasing viscosity of the polyurethanes. At a temperature of 50 degrees C, the polyurethanes were able to heal cracks so that the water absorption of cracked mortar was reduced to a value that was comparable to the water absorption of uncracked mortar. Also, a strength regain of 100\% or more was obtained. Therefore, using self-healing concrete in building facades may have a positive effect on the durability and service life of the construction elements. (c) 2018 American Society of Civil Engineers.},
  articleno    = {04018145},
  author       = {Van Belleghem, Bjorn and Gruyaert, E. and Van Tittelboom, Kim and Moerman, Wim and Dekeyser, B. and Van Stappen, Jeroen and Cnudde, Veerle and De Belie, Nele},
  issn         = {0899-1561},
  journal      = {JOURNAL OF MATERIALS IN CIVIL ENGINEERING},
  language     = {eng},
  number       = {7},
  pages        = {12},
  publisher    = {Asce - amer Soc Civil Engineers},
  title        = {Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation},
  url          = {http://dx.doi.org/10.1061/(ASCE)MT.1943-5533.0002360},
  volume       = {30},
  year         = {2018},
}

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