Nanolime- and nanosilica-based consolidants applied on heated granite and limestone: Effectiveness and durability

This paper shows a study on the consolidation effectiveness of nano-silica and nano-lime-based consolidants (i.e. Nano Estel (R) and Nanorestore (R), respectively), both available on the market, on two stones with different mineralogy and texture (i.e. two micas granite and Lioz limestone) previously subjected to 500 degrees C during 24 h with a rapid cooling by water jet simulating the real practice in a fire. The consolidation effectiveness was determined through the evaluation of hydro-physical properties (i.e. open porosity, apparent density, water absorption by capillarity and water absorption at atmospheric pressure), the determination of P-wave velocity (compressional wave velocity) and the study of their side-effects by using stereomicroscopy, colour spectrophotometry, Fourier transform infrared spectroscopy and scanning electron microscopy. Durability of the consolidants was determined by measuring their resistance to salt crystallization cycles and the subsequent surfaces were evaluated by open porosity measurements, stereomicroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. Results showed, as expected, that both granite and limestone samples increased their porosity after the heating process. In the case of granite stone, both products yielded similar reduction of the porosity and similar resistance to salt crystallization cycles. In case of limestone, nanolime samples yielded lower effectiveness in terms of dry matter, porosity, and water absorption by capillary coefficient, which is attributed to the low penetration of Nanorestore (R) particles in the fine pore structure of this stone. Ethyl silicate treated samples presented higher levels of decay after crystallization cycles in the limestone samples, which could be attributed to the difficulty to bond silicate materials to fine porous calcite-based substrates. (C) 2019 Elsevier Ltd. All rights reserved.