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Recent Advances and New Discussions on Superhydrophobic Coatings and Admixtures Applied to Cementitious Materials



Laísa do Rosário Souza Carneiro1, Manuel Houmard2, Péter Ludvig1, *
1 PPGEC, Department of Civil Engineering, Prédio 18, Centro Federal de Educação Tecnológica de Minas Gerais, Av. Amazonas, 7675, 30510-000, Belo Horizonte, Minas Gerais, Brazil
2 Department of Chemical Engineering, Escola de Engenharia, Universidade Federal de Minas Gerais, Av. Presidente Antônio Carlos, 6627, 31270-901, Belo Horizonte, Minas Gerais, Brazil


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Creative Commons License
© 2020 Carneiro et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at PPGEC, Department of Civil Engineering, Prédio 18, Centro Federal de Educação Tecnológica de Minas Gerais, Av. Amazonas, 7675, 30510-000, Belo Horizonte, Minas Gerais, Brazil; Tel: +5531983500943; E-mails: carneirola@hotmail.com; peter@cefetmg.br


Abstract

Increasing the durability of buildings is one of the biggest challenges of the construction industry of the 21st century. The problems concerning durability are usually related to the presence of humidity or to water infiltration in the porous cementitious materials used in buildings. Advances in biomimetics have allowed the development of superhydrophobic surfaces and materials, with contact angles greater than 150°, which are able to repel water and aqueous products. In this context, this work summarizes the recent advances on superhydrophobic coatings and admixtures applied to cementitious materials. Recommendations for the future improvement of such products are made. The synthesis of superhydrophobic coatings generally includes the deposition of a low surface energy material (LSEM), especially fluoroalkylsilanes, on a microroughened surface, which, in cementitious materials, is usually achieved with the help of nanoparticles or micrometric molds. In this sense, variables as the spraying time duration, and the nanoparticles concentration, surface area and average particle size were identified as directly influencing the surface superhydrophobicity. Functionalized nanoparticles can also be introduced in cement matrix during the paste mixing in order to obtain a longer lasting waterproofing effect. In this case, hybrid nanosilica may react with Ca(OH)2 through pozzolanic reaction. The C-S-H formed may incorporate the organic group of hybrid nanosilica, and might present superhydrophobicity as well, modifying the composite’s microstructure. Besides, the cost of fabricating hydrophobic materials is decisive for their market entry. Hence, the partial or total replacement of fluoroalkylsilanes with less expensive LSEMs seems promising and needs to be further explored.

Key words: Superhydrophobic coatings, superhydrophobic admixtures, Concrete durability, Superhydrophobic concrete, Waterproof concrete, Water repellent concrete.