An experimental study conducted to determine the effectiveness and durability of preservation treatments on volcanic tuff stones

Abstract

In this study, two treatments were performed on deteriorated volcanic tuff stone samples taken from a 16th-century historical structure: (i)solventless mixtures of ethyl silicates (TEOS) tetraethoxysilane consolidation product followed by application of two different silane-siloxane-based water-repellent commercial products (TEOS+WR1 and TEOS+WR2), (ii) two different silane-siloxane based water repellent commercial products (one emulsion (WR2) and the other solution (WR1) based). This study aims to determine the effectiveness, compatibility, durability and service life of the studied conservation treatments on tuff stones. Therefore, colorimetric measurements, chemical and petrographic analyses (XRF, XRD, SEM-EDS) and physical and mechanical characterization tests were performed on the treated and untreated samples.Additionally, accelerated weathering tests were performed in the laboratory on all treated stones to determine the long-term performance of the chemical treatments.After these weathering tests,physical (water absorption under atmospheric pressure, water capillarity coefficient, water vapour permeability) and mechanical (ultrasonic pulse velocity, flexural and compressive strength) property tests were performed again and according to the results, the performance change in the efficiency indexes (TEI,%) was calculated. All results were compared and discussed. The results showed the best performance of TEOS+WR1 treatment in improving the consolidating and water-repellency abilities of tuff stone samples.However, the least colour change in the colour measurements after the treatments was in the treatments using emulsion-type water-repellent products.