Biomimetic superhydrophobic surface of concrete: Topographic and chemical modification assembly by direct spray

Concrete is an inherently multi-scale hydrophilic composite. Superhydrophobic surfaces have not been created solely by using chemical modification to reduce surface energy. A superhydrophobic concrete surface was fabricated by direct spraying nano-silica gel functionalized by low surface-energy surfactants to simultaneously modify the inherent multi-scale microstructure and surface chemical properties. The newly modified microstructures were characterized by scanning electron microscopy (SEM) and digital holographic microscopy (DHM) to facilitate an understanding of the effects of micro- and nanoscale topological features on the super-wetting properties. The superhydrophobic and self-breathing properties of the modified surface were confirmed by its large contact angle (CA = 162 degrees +/- 3 degrees), small slide angle (SA = 5 degrees +/- 1 degrees) and carbonation depth measurements. The chemical bonding between hydrophobic functional group grafted with nano-silica and cement hydration products, as well as the interface hydration of nano-silica in an alkaline environment, are estimated by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). (C) 2018 Published by Elsevier Ltd.