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Article

The Effect of Exposure on the Autogenous Self-Healing of Ordinary Portland Cement Mortars

1
Building Materials, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, 97187 Luleå, Sweden
2
Skanska, Warfvinges väg 25, 112 74 Stockholm, Sweden
*
Author to whom correspondence should be addressed.
Materials 2019, 12(23), 3926; https://doi.org/10.3390/ma12233926
Received: 18 October 2019 / Revised: 18 November 2019 / Accepted: 24 November 2019 / Published: 27 November 2019
(This article belongs to the Section Construction and Building Materials)
Exposure conditions are critical for the autogenous self-healing process of Portland cement based binder matrixes. However, there is still a significant lack of fundamental knowledge related to this factor. The aim of this paper was to investigate and understand the effects of various potentially applicable curing solutions on the efficiency of the crack closure occurring both superficially and internally. Four groups of exposures were tested, including exposure with different water immersion regimes, variable temperatures, application of chemical admixtures, and use of solutions containing micro particles. The self-healing process was evaluated externally, at the surface of the crack, and internally, at different crack depths with the use of optical and scanning electron microscopes (SEM). The phase identification was done with an energy dispersive spectrometer combined with the SEM. The results showed very limited self-healing in all pure water-based exposures, despite the application of different cycles, temperatures, and water volumes. The addition of a phosphate-based retarding admixture demonstrated the highest crack closure, both internally and externally. The highest strength recovery and a very good crack closure ratio was achieved in water exposure containing micro silica particles. The main phase observed on the surface was calcium carbonate, and internally, calcium silicate hydrate, calcium carbonate, and calcium phosphate compounds. Phosphate ions were found to contribute to the filling of the crack, most likely by preventing the formation of a dense shell composed of hydration phases on the exposed areas by crack unhydrated cement grains as well as by the additional precipitation of calcium and phosphate-based compounds. The micro sized silica particles presumably served as nucleation sites for the self-healing products growth. Changes in the chemical composition of the self-healing material were observed with a distance from the surface of the specimen. View Full-Text
Keywords: autogenous self-healing; cementitious materials; cracking; exposure; microstructure; calcium phosphate autogenous self-healing; cementitious materials; cracking; exposure; microstructure; calcium phosphate
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MDPI and ACS Style

Rajczakowska, M.; Habermehl-Cwirzen, K.; Hedlund, H.; Cwirzen, A. The Effect of Exposure on the Autogenous Self-Healing of Ordinary Portland Cement Mortars. Materials 2019, 12, 3926. https://doi.org/10.3390/ma12233926

AMA Style

Rajczakowska M, Habermehl-Cwirzen K, Hedlund H, Cwirzen A. The Effect of Exposure on the Autogenous Self-Healing of Ordinary Portland Cement Mortars. Materials. 2019; 12(23):3926. https://doi.org/10.3390/ma12233926

Chicago/Turabian Style

Rajczakowska, Magdalena, Karin Habermehl-Cwirzen, Hans Hedlund, and Andrzej Cwirzen. 2019. "The Effect of Exposure on the Autogenous Self-Healing of Ordinary Portland Cement Mortars" Materials 12, no. 23: 3926. https://doi.org/10.3390/ma12233926

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