Graphene oxide regulated by polydopamine towards improved cooperative protection of polysiloxane coatings for cementitious materials

Polysiloxane hydrophobic coatings modified by graphene oxide (GO) play a significant role in improving the corrosion resistance of cementitious materials. However, the issue of poor spatial dispersion and few surface reaction sites seriously restricts the chemical regulation of polysiloxanes by GO. To optimize the molecular structure of polysiloxane components effectively, nano-modified octylpolysiloxane protective coatings were synthesized using functionalized GO in this paper. The interfacial grafting between GO sheets and polysiloxane molecules was increased to 94.7 % by surface modification with polydopamine. The modified polysiloxane reduced the proportion of polyhazardous pores in the cementitious material to 4.05% by inducing the formation of abundant silicate crystals on the surface of the hydration product. The surface contact angle of the polysiloxane coating is approximately 140 degrees, which effectively blocks the transport of water molecules, corrosive ions, and CO2 within the cementitious material, and inhibits the formation of Friedel's salt, CaCO3, gypsum, and ettringite. The concrete treated with modified polysiloxane coatings maintain a relative dynamic modulus of above 84.5 % after 100 freeze-thaw cycles. Furthermore, the functionalized GO enhances the acid and alkali corrosion and UV aging resistance of the polysiloxane coating, and maintains the blocking effect on the transport of aggressive medium.