Inhibition of swelling clays and consolidation of Itararé Sandstone using diaminoalkanes (DAA) and ethyl silicate (TEOS)

Abstract

The conservation of stones containing swelling clay minerals such as montmorillonites is a challenging task. In this context, swelling inhibitors (DAA) were tested and a treatment based on consolidation with TEOS (ethyl silicate) was carried out on a sandstone containing swelling clay minerals: the Itararé Sandstone (commercial name). In this laboratory experiment, the inhibition of swelling, pore size and distribution, capillarity, colorimetric alteration, durability of treatments against the action of water, effectiveness of consolidation, and penetration depth were evaluated. Swelling inhibitors were effective in inhibiting the clay minerals from swelling. The consolidant, despite its effectiveness, altered the pore size and distribution and water absorption significantly, forming a very cracked gel, darkening the stone, reducing resistance to the action of water and presenting small penetration depth. When swelling inhibitors were applied before the consolidant, swelling inhibition also occurred, the porosity was less altered, the consolidant was less cracked, there was less chromatic modification and the sample became more resistant to the action of water. Therefore, this treatment proved to be more effective with fewer changes to the physical characteristics of the stone than the sole application of the consolidant.

KEYWORDS:
ethyl silicate; swelling clays; diaminoalkanes; sandstone; consolidation; stone conservation