Synthesis of TEOS/PDMS-OH/CTAB composite coating material as a new stone consolidant formulation

A new stone consolidant formulation based on tetraethoxysilane (TEOS) and additives such as hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and cetyl trimethyl ammonium bromide (CTAB) has been developed denoted as TEOS/PDMS-OH/CTAB composite coating material. The hydrophobic property, surface morphology, and abilities to resist acid corrosion and salt crystallization weathering have been measured to evaluate the stone protection performance of as-prepared TEOS/PDMS-OH/CTAB composite coating materials. The results demonstrate that the addition of PDMS-OH contributes to improve the hydrophobic properties of sandstones. The addition of CTAB to the siloxane composition results in the formation of superficial protrusions with a micro- and nanoscopic structure and overall alteration of surface morphology and roughness, thus preventing the cracking during the drying process. In addition, after treatment by TEOS/PDMS-OH/CTAB composite coating materials, the sandstone has improved the abilities to resist acid and salt crystallization weathering significantly. These advantages make TEOS/PDMS-OH/CTAB composite coating materials exhibit good comprehensive performance in terms of stone heritage protection.