Integrated design of a robust superhydrophobic cement mortar layer via sizing sand grains

Abstract

This work reported a facile route for fabricating super-hydrophobic cement mortar layer via sizing sand grains. It was found that mixing the sands with a size ranging from 150-180 µm into cement enabled the formation of a lotus-like surface with a papillary structure at micro-scale. SEM showed that the size of bumper was about 3 μm. When spraying a fluorocarbon solution onto this surface, the porous nature of the cement matrix showed the advantage of taking the fluorocarbon into the internal structure of the cement mortar layer via capillary force. As a result, the sub surface up to a depth of ~1.5 mm was transformed into a thick superhydrophobic layer directly. The contact angle (CA) of water droplets could reach 157o on this surface, and which could remain more than 150° after abrasion 100 cycles under a weight of 300 g at 360 grit sandpaper. This thick hydrophobic layer significantly reduced the corrosion rate of the steel at the Cl- environment by 620 times. The measurement of British pendulum number and compression strength revealed that this superhydrophobic layer was beneficial for maintaining the friction coefficient of the surface in wet condition without altering the mechanical integrity of the cement mortar layer.