Microbiologically Induced Carbonate Precipitation in the Restoration and Conservation of Cultural Heritage Materials

Abstract

Microbiologically induced carbonate precipitation (MICP) is a well-known biogeochemical process that allows the formation of calcium carbonate deposits in the extracellular environment. The high concentration of carbonate and calcium ions on the bacterial surface, which serves as nucleation sites, promotes the calcium carbonate precipitation filling and binding deteriorated materials. Historic buildings and artwork, especially those present in open sites, are susceptible to enhanced weathering resulting from environmental agents, interaction with physical-chemical pollutants, and living organisms, among others. In this work, some published variations of a novel and ecological surface treatment of heritage structures based on MICP are presented and compared. This method has shown to be successful as a restoration, consolidation, and conservation tool for improvement of mechanical properties and prevention of unwanted gas and fluid migration from historical materials. The treatment has revealed best results on porous media matrixes; nevertheless, it can also be applied on soil, marble, concrete, clay, rocks, and limestone. MICP is proposed as a potentially safe and powerful procedure for efficient conservation of worldwide heritage structures.

Bioconservation of Historic Stone Buildings—An Updated Review

“…Microbially influenced precipitation occurs due to the interactions of extracellular biopolymers and the geochemical environment. This is seen, for example, in the production of moonmilk speleothems, natural calcium carbonate deposits in caves, which has been associated with filamentous actinomycete activity through metabolic profiling of biomineralization pathways [81]. This, indeed, could be an interesting option for further research into bioconsolidation.…”

“…Conditions will certainly vary depending on the type of stone to be consolidated. Pore structure affects penetration depth and treatment performance [81]. The polymorphs produced by biocalcification are mainly calcite (rhombohedral), aragonite (needles) and vaterite (hexagonal), the final form depending on environmental conditions and bacterial strains.…”

Self-Healing Construction Materials: The Geomimetic Approach

“…Technology has been developed for producing wall materials with autoclave hardening through the use of clay rocks at an imperfect phase of mineral development with the possibility of reducing the time and pressure of autoclaving to 2-4 atm [40]. These rocks make it possible to control the structure formation processes of new generation autoclave materials [41]. At the same time, new growths of various compositions and morphology have been synthesized, forming cementing compounds of optimal composition, which ensures the high properties (physical and mechanical) of the products.…”

Morpho-Mineralogical and Bio-Geochemical Description of Cave Manganese Stromatolite-Like Patinas (Grotta del Cervo, Central Italy) and Hints on Their Paleohydrological-Driven Genesis

“…Moreover, our results show microbial imprints, some identified as putative predivisional cells (this fact has already been reported from other Mn deposits of Grotta del Cervo, see Vaccarelli et al, 2021), associated only with vernadite, suggesting a microbial origin for this highly disordered compound. In addition, bacteria of the genera Bacillus, Flavobacterium, Pseudomonas, Lysinibacillus, etc., appeared to be involved in calcium carbonate precipitation (Meier et al, 2017;Farrugia et al, 2019;Ortega-Villamagua et al, 2020). Most of these bacteria are ureolytic strains (Mitchell et al, 2019;Reeksting et al, 2020), although nonureolytic precipitation was reported (Lee et al, 2017).…”