TEOS–colloidal silica–PDMS‐OH hybrid formulation used for stone consolidation

Abstract

The consolidation of materials concept, which consists of introducing a chemical substance (consolidant) into degraded stone, has been applied to architectural conservation. Silicon compounds such as tetraethoxysilane (TEOS) are frequently used as a base for commercial consolidant formulations due to their ability to form a siloxane polymer such as SiO 2 . However, the silica xerogels deposited into the stone show poor performance and the gels obtained are non-porous and tend to crack during the drying stage. In order to avoid the fractures and to improve gel properties, we propose the synthesis of a hybrid consolidant based on TEOS and fillers such as colloidal silica (200 nm in diameter) and hydroxy-terminated polydimethylsiloxane (PDMS-OH). Both additives enhance gel properties such as porosity and elasticity, leading to the formation of non-fractured and permeable gels. Characterization of the hybrid xerogel was carried out by nitrogen adsorption and 29 Si MAS-NMR. The properties of the hybrid xerogels were compared with those prepared from a formulation based on TEOS (T-ME) with a composition similar to a commercial product. In order to evaluate the effectiveness of the hybrid consolidant, it was applied to tuff-stone of historical monuments in the city of Guanajuato, Mexico. The tuff-stone was also treated with the formulation T-ME. Both treatments were studied by determining the percentage of consolidant deposited, evaluating changes in porosity and hardness of the treated stone. The applicability of the hybrid consolidant for the decayed tuff-stone is under study.

New Consolidant-Hydrophobic Treatment by Combining SiO2 Composite and Fluorinated Alkoxysilane: Application on Decayed Biocalcareous Stone from an 18th Century Cathedral

“…This confirms the role played by the nanoparticles in increasing the consolidant effect of the product, as previously reported by other authors [6,[26][27][28][29]. Table S1 show water droplet static and dynamic contact angle (CA) values.…”

Performances and Coating Morphology of a Siloxane-Based Hydrophobic Product Applied in Different Concentrations on a Highly Porous Stone

“…In fact, products which polymerise by a sol-gel route, such as silanes and siloxanes [5,40], frequently exhibit cracks. These cracks are ascribed to shrinkage phenomena taking place throughout the drying phase [41][42][43]. In the sol-gel process, shrinking is initiated by evaporation of both solvents and by-products of the condensation step [44].…”

An Approach to the Use of Glycol Alkoxysilane–Polysaccharide Hybrids in the Conservation of Historical Building Stones

“…The interest of our research group in the use of alkoxysilanes in the conservation of historical building stone has led to investigations on many topics, such as chemical, physical, geological, and mineralogical characterization of historical building stones; considering decay and biodecay evaluation; and the synthesis and application of consolidant and hydrophobic formulations based on alkoxysilanes in siliceous stones, with the aim of solving reported problems in the performance of some of the commercial formulations through the development of hybrid systems based on TEOS/SiO 2 St/PDMS-OH. Most of our work in the field has focused on siliceous stones [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ].…”