Experimental silica nanoparticles products for the consolidation of silicate stones.

Abstract

Nanosilica-based consolidants are promising nano- structured strengthening agents mainly used for consolidation of mortars and cements. Due to their specific physical-chemical characteristics and sizes, theoretically, silica nanoparticles (SNP) improve the penetration depth of the product, promote water repellency of the treated surfaces and increase the cohesion of the material. However, in some cases, their use revealed undesired drawbacks.
In order to improve the knowledge in strength and limitations of SNP products, the present work aims to develop a specific SNP compound suitable for the consolidation of silicate stones. Two phases are underlined: (i) the synthesis of the nano-compound and (ii) the application of the product synthetized for the consolidation purpose. Two sandstones and a granite were chosen for the purpose of the research, due to the chemical compatibility between stone compositions and SNP.
The characterization of stone materials and the study of their porosity allowed to choose the best SNP dimensional ranges, synthesized by sol-gel synthesis. For each material, sound and degraded specimens were treated. Periodic monitoring of weight and morphology of treated samples permitted to evaluate the quantitative of SNP absorbed, the actual evaporation of carrier, and the condensation reaction. Porosimetric measurements, capillary absorptions, microscopic observations, colorimetrical analysis, ultrasounds measurements and sponge- tests were carried out for studying the effectiveness of the consolidation treatment. The success of the consolidant applied on sound and deteriorated materials were verified and the results obtained showed promising aspects.