Performance evaluation of commercial nanolime as a consolidant for friable lime-based plaster

Abstract

This thesis focuses on the performance evaluation of commercial nanolime as a consolidant for friable historic lime based plaster such as found at Mission San Jose de Tumacácori, a Spanish Colonial mission site near Tucson, Arizona. The church's façade was originally finished with a polychromatic painted on fired brick and adobe. Though generally stable over time, the exterior plaster at Tumacácori became friable and detached after repeated weathering cycles of high diurnal temperature swings and precipitation concentration during monsoon season in the summer. As friable stucco is vulnerable to loss, consolidation should be considered a first priority in the conservation plan for the Tumacácori's façade.Derived from an older limewater method, nanolime is a relatively recent material created by synthesizing nanoscale calcium hydroxide particles and obtaining stability through using alcohol solvents. CaLoSiL®, produced by IBZ-Salzchemie GmbH&Co. KG, was selected for performance testing as a consolidant for friable plaster studying its effect on enhancing grain cohesion, durability to weathering, and impact on aesthetic character. ASTM and RILEM testing methods were employed including splitting tensile strength, porosity by liquid nitrogen immersion, water vapor permeability, color change, frost resistance, and optical and scanning electron microscopy. Ultimately, the analytical findings of this thesis will be used as a recommendation for future conservation of the Tumacácori façade.

Basic Protocol for On-Site Testing Consolidant Nanoparticles on Stone Cultural Heritage

“…Only small macroscopic aggregates could be observed on the lowest pore stone surfaces at high magnifications without generating the homogenous white haze discussed by other authors [31,53]. Any remarkable modification of the stone surface was observed in SEM images.…”

“…Nevertheless, they have not designed a basic protocol to support decision making on the best consolidant for on-site restoration with experimental results. Some guidelines or recommendations can be deduced of the methodologies and results of different papers, especially about application methodologies [28], testing methods [29,30] and consolidant evaluations [31] or aging tests to assess the durability of the consolidants [32]. Nevertheless, it was De Rosario et al [33] who made a substantial difference between laboratory and on-site evaluation.…”

Synthetic calcium carbonate improves the effectiveness of treatments with nanolime to contrast decay in highly porous limestone

“…similar thermal expansion, elastic modulus, assure similar permeability), long-term stability and performance (avoiding self-deterioration, colour changes, by-product formation) 4,5 . It is therefore not surprising that most of the consolidation agents available on the market show drawbacks and the design of new products is a very active field of research 6–9 .…”

Does intra-disciplinary historic preservation scholarship address the exigent issues of practice? Exploring the character and impact of preservation knowledge production in relation to critical heritage studies, equity, and social justice

“…The cleaning of materials, which involves scientific testing and treatment with a goal of minimizing harm, focuses mostly on marble and terra cotta (Hall & Matero, 2011;Matero, 1984;Matero et al, 2016;Matero & Freese, 1978;Matero & Tagle, 1994;Matero & Teutonico, 1996). Literature on consolidation, in which the loss of existing, friable, disaggregated, and/or delaminated building fabric is mitigated through the application of a variety of "compatible" contemporary and traditional organic and inorganic materials, is well represented (Correia & Matero, 2008;Ferron & Matero, 2011a, 2011bJang & Matero, 2018;Tudor et al, 1990); the use of various adhesives to reattached delaminated material, which is related to consolidation, addresses plaster materials (Hinchman et al, 2006;Matero & Bass, 1995). The conservation of limestone is also represented in TAPE literature (Matero & Siravo, 2004) along with mortar analyses and replication (Matero, 2001a(Matero, , 2001b.…”