Fast fabrication of superhydrophobic surfaces on hardened cement paste using sodium laurate aqueous solution

Abstract In the present work, a novel and fast fabrication method was proposed to modify the surface of hardened cement paste (HCP) imparting superhydrophobic properties. Sodium laurate was selected as the modifier among the 6 kinds of sodium carboxylates because of its good water solubility and remarkable hydrophobic modification effect. After immersing in the aqueous solution of sodium laurate at room temperature for only 5 s, the ordinary Portland cement-based HCP surface exhibits superhydrophobicity, with a water contact angle (CA) of 154.3° and a sliding angle of 8.7°. Colored superhydrophobic HCP can be prepared by using pigments or dyes to give the HCP surface a decorative effect. The aqueous solution of sodium laurate also imparts the superhydrophobic modification to the HCPs of aluminous cement and sulfoaluminous cement. Additionally, using the method of “cement coating + surface treatment”, the non-cement-based substrates can also be modified into a superhydrophobic surface with sodium laurate, thereby expanding the application range of this method. Furthermore, due to the extremely fast preparation speed, when the surface of HCP is damaged, its superhydrophobicity can be quickly repaired. After superhydrophobic modification, the capillary water absorption coefficient and water absorption rate of the HCPs decreased by 63.81% and 97.77% respectively in comparison with the pristine HCPs. Such easy fabrication, low cost, environmentally friendly, and easy repairable superhydrophobic surfaces have potential applications in the field of building materials such as rendering mortars with self-cleaning functions and colorful decorative effects.