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    Hydrophobic and hydrophilic SiO2-based hybrids in the protection of sandstone for anti-salt damage

    Year: 2019

    Journal: J. Cult. Herit., Volume 40, NOV-DEC, page 80–91

    Authors: Jia, Mengjun; Liang, Junyan; He, Ling; Zhao, Xiang; Simon, Stefan

    Keywords: SiO2-based hybrid; Anti-salt damage behaviour; Salt-loaded hygrothermal aging cycle; Sandstone; Protection

    The anti-salt damage of sandstone protected by hydrophobic and hydrophilic SiO2-based hybrids is evaluated in NaCl, Na2SO4 and NaCl-Na2SO4 salt-loaded hydrothermal aging (SLHA) cycles. Although both hydrophobic and hydrophilic SiO2-based hybrids could prevent the sandstone from salt damage through improving the matrix strength, the hydrophobic hybrid performs much better protection than hydrophilic one. The sandstone protected by hydrophobic SiO2-based hybrid shows nearly no salt-damage, which is attributed to its excellent water repellence, high adhesive strength and good compatibility with sandstone matrix. However, the hydrophilic SiO2-based hybrid tends to induce an exterior-to-interior salt-damage behaviour due to the frequent circulation movement of water with salt to result in the formation of surface efflorescence and interior sub-efflorescence in the protected sandstone. Furthermore, the hydrophobicprotective effect is also confirmed by another alternative hydrophobic POSS-based hybrid to offer stronger protection in anti-salt damage than that protected by hydrophilic hybrid. Nevertheless, there lies the difference, the hydrophobic SiO2-based hybrid penetrates into the inner pores of the sandstone and develops a strong cohesion with sand-grain through the formation of Si-O bonds, but the hydrophobic POSS-based hybrid protects the sandstone with a weaker physical interaction between hybrid and sand-grains resulting in a fractured damage. Therefore, SiO2-based hybrid is superior to POSS-based hybrid in promoting the anti-salt ability of sandstone. It is believed that these results could contribute much to the future protection of stone monuments by different hybrids. (C) 2019 Elsevier Masson SAS. All rights reserved.
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