Investigation of polysiloxane coatings with two-components for synergistic improved corrosion resistance of cementitious materials

The application of polysiloxane coatings represents an effective means of improving the durability of cementitious materials. However, conventional polysiloxane coatings with a single component are unable to provide adequate surface protection for cementitious materials due to the disordered nature of their molecular structure. In this paper, four functional monomers are employed to regulate the molecular structure of octyl polysiloxane, and polysiloxane composite emulsions with two-components were prepared in an innovative manner. The results demonstrated that the two-component polysiloxanes induced the formation of a plentiful of silicate crystals with low Ca/Si ratios on the surface of the hydration products, which reduced the proportion of polyhazardous pores to 4.56 %. The composite polysiloxane coating enhances the crystallinity of the cementitious material by repairing crystal defects and improving the surface mechanical characteristics of the cement substrates. The static capillary water absorption of the TOS coating modified by TEOS was reduced by 30.55 %, and the chloride and sulphate corrosion were reduced by 31.96 % and 27.56 %, respectively, and the carbonization depth was reduced by 46.7 %, in comparison to the conventional silane coating. The TOS coating enabled the concrete to achieve a relative dynamic modulus of 88.1 % after 100 freeze-thaw cycles. Moreover, the composite polysiloxane coating effectively resists acid-alkali corrosion and ultraviolet aging on the microstructure of the cementitious materials, thereby maintaining the superior impermeability of the cement substrates. •Four functional monomers were used to regulate the molecular structure of octyl polysiloxanes.•The two-component polysiloxane networks have a greater degree of crosslinking and branching.•The two-component polysiloxane reduced the proportion of polyhazardous pores within the cementitious material to 4.56 %.•The two-component polysiloxane coatings offer superior resistance to ionic attack, carbonation and freeze-thaw deterioration.•The two-component polysiloxane coatings provide stable surface protection against acid - alkali corrosion and UV aging.