Neutron Radiography Study of Laboratory Ageing and Treatment Applications with Stone Consolidants

Abstract

A nano-silica consolidant and nano-titania modified tetraethyl-orthosilicate were applied on two building stones, a carbonate and a silicate, by brush, poultice or capillary absorption. Neutron radiography was used to monitor capillary water absorption, and to analyse changes in physical properties caused by heat treatment of specimens for the purposes of artificially ageing and different treatment applications with stone consolidants. Moreover, ultrasonic pulse velocity and gravimetrically determined water absorption were analysed to cross-validate neutron radiography. The results reveal that reactive systems like tetraethyl-orthosilicates need an unknown period for polymerisation, which makes nano-silica consolidants more favourable for construction follow-up work. While polymerisation is incomplete, hydrophobic behaviour, water trapping and pore clogging are evident. Within the tetraethyl-orthosilicate treatment, poultice and brushing are strongly influenced by the applicant, which results in wide ranging amounts of water absorbed and anomalous water distributions and kinetics. The carbonate lithotype displays polymerisation initiated in the core of the specimen, while the lateral surfaces are still mostly hydrophobic. Reaction time differences can be attributed to the different amounts of consolidants applied, which is a result of the chosen application settings. Artificial ageing of stone specimens is a prerequisite when mechanical strength gain is studied, as demonstrated by sound speed propagation.

Cohesion Gain Induced by Nanosilica Consolidants for Monumental Stone Restoration

“…Various nanomineral- and polymer-based consolidants have been demonstrated to partially restore the lost cohesion within the weathered stone surface layers. These most often include water or organic solvent-dispersed inert nanosized inorganic particles, which provide cohesion upon their aggregation (such as colloidal silica, calcium hydroxide, calcite, or metal oxides − ) or synthetic organic polymers and reactive alkoxysilanes, which consolidate grains via self-polymerization reactions. ,, Although grouting materials such as cement or organic adhesives may act as suitable cohesives and sealants in geotechnics, they are often inappropriate for cultural heritage applications as they may fail to preserve the initial surface appearance, lack chemical or microstructural compatibility with stone material, or induce undesirably drastic changes in the mechanical properties of the reconsolidated surface layers.…”

Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials

“…Conversely, this behaviour was not observed in the limestone samples, where NL showed a higher weight increase than NC and DAP. As recently observed by Ban et al [40], other phenomena related to the compositional and microstructural features of the stone fabric may influence the deposition process of consolidants, resulting in a weaker correlation between the absorbed and the precipitated consolidant. However, the specific characteristics (such as alkalinity, polarity of the Ca(OH) 2 nanoparticles, particle size distribution, etc.)…”

“…This study aimed to evaluate the effectiveness and compatibility of the combinations of an aqueous solution of DAP and two Ca-based nanomaterials, namely an ethanol-based nanosuspension of Ca(OH) 2 and a novel aqueous nanosuspension of calcite. The advantages brought by the use of these products are manifold: (i) the low environmental impact of nanosuspensions and phosphate solutions with respect to other common formulations based on solvents harmful to the health and environment ([16] and references therein]); (ii) calcium-based nanomaterials are aimed at boosting HAP formation and allow DAP application to calcium-poor substrates, as it had been previously tested using limewater poultice as additional calcium source [37]; (iii) the reduced particle size should promote penetration and inter-molecular interaction with the substrate [40]; and (iv) the high concentration allows for reducing the number of necessary applications, and therefore introducing a lessened amount of water into the stone, unlike limewater treatment.…”

Weathering Mechanisms of Porous Marl Stones in Coastal Environments and Evaluation of Conservation Treatments as Potential Adaptation Action for Facing Climate Change Impact

“…All treatments were carried out by capillary absorption, as a time-controlled [48] and easily reproducible laboratory-scale procedure [49] (Figure 2). All stone specimens were previously washed with deionized water, left to dry until constant weight at 40 ± 5 • C, and then kept under laboratory conditions for 2 h. Each side of the cubic stone specimens was placed in direct contact with the material for 30 min, in order to ensure penetration by capillary forces [48]. Upon completion of the above procedure, all specimens were stored in a ventilated box under controlled laboratory conditions (T = 22 • C ± 2 • C, RH = 65-70%).…”