Use of TEOS for fired-clay bricks consolidation

Ethyl silicate (tetraethylorthosilicate, TEOS) is one of the most used consolidants for natural stones in the restoration of architectural and cultural heritage and the literature concerning its performance in this application is quite abundant. In this paper, the need, and sometimes urgency, of preserving ancient fired-clay elements (bricks and terracotta decorations) is highlighted as well, and the effects of ethyl silicate consolidation (75 wt% TEOS in white spirit) are investigated from a microstructural, physical–mechanical and aesthetic point of view. Fired-clay brick samples (open porosity 45 %; compressive strength 14 N/mm2) were treated and then characterized by mercury intrusion porosimetry, scanning electron microscopy, water absorption, compressive strength test and spectrophotometry, to assess the effects of the treatment. The TEOS treatment gave encouraging results: a good penetration depth (about 10 mm), a limited reduction in porosity, a large decrease in water absorption, a significant improvement in compressive strength and a positive aesthetic outcome. The results obtained pointed out TEOS treatment as a promising solution for fired-clay bricks consolidation.