Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation

Abstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generat...

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Autores principales:	Kerstin Elert, Encarnación Ruiz-Agudo, Fadwa Jroundi, Maria Teresa Gonzalez-Muñoz, Barbara W. Fash, William L. Fash, Nieves Valentin, Alberto de Tagle, Carlos Rodriguez-Navarro
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Materials of engineering and construction. Mechanics of materials TA401-492
Acceso en línea:	https://doaj.org/article/74184a82527b4348a812d08a40b94d83
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spelling	oai:doaj.org-article:74184a82527b4348a812d08a40b94d832021-12-02T15:10:45ZDegradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation10.1038/s41529-021-00191-42397-2106https://doaj.org/article/74184a82527b4348a812d08a40b94d832021-08-01T00:00:00Zhttps://doi.org/10.1038/s41529-021-00191-4https://doaj.org/toc/2397-2106Abstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generated by humidity-related clay swelling resulting in spalling and material loss, a damaging process that appears to be facilitated by the microbial bioweathering of the tuff stone minerals (particularly feldspars). Such a weathering process is not prevented by traditional polymer- and alkoxysilane-based consolidants applied in the past. As an alternative to such unsuccessful conservation treatments, we prove the effectiveness of a bioconservation treatment based on the application of a sterile nutritional solution that selectively activates the stone´s indigenous bacteria able to produce CaCO3 biocement. The treatment generates a bond with the original matrix to significantly strengthen areas of loss, while unexpectedly, bacterial exopolymeric substances (EPS) impart hydrophobicity and reduce clay swelling. This environmentally-friendly bioconservation treatment is able to effectively and safely preserve fragile stones in tropical conditions, opening the possibility for its widespread application in the Maya area, and elsewhere.Kerstin ElertEncarnación Ruiz-AgudoFadwa JroundiMaria Teresa Gonzalez-MuñozBarbara W. FashWilliam L. FashNieves ValentinAlberto de TagleCarlos Rodriguez-NavarroNature PortfolioarticleMaterials of engineering and construction. Mechanics of materialsTA401-492ENnpj Materials Degradation, Vol 5, Iss 1, Pp 1-12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Materials of engineering and construction. Mechanics of materials TA401-492
spellingShingle	Materials of engineering and construction. Mechanics of materials TA401-492 Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
description	Abstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generated by humidity-related clay swelling resulting in spalling and material loss, a damaging process that appears to be facilitated by the microbial bioweathering of the tuff stone minerals (particularly feldspars). Such a weathering process is not prevented by traditional polymer- and alkoxysilane-based consolidants applied in the past. As an alternative to such unsuccessful conservation treatments, we prove the effectiveness of a bioconservation treatment based on the application of a sterile nutritional solution that selectively activates the stone´s indigenous bacteria able to produce CaCO3 biocement. The treatment generates a bond with the original matrix to significantly strengthen areas of loss, while unexpectedly, bacterial exopolymeric substances (EPS) impart hydrophobicity and reduce clay swelling. This environmentally-friendly bioconservation treatment is able to effectively and safely preserve fragile stones in tropical conditions, opening the possibility for its widespread application in the Maya area, and elsewhere.
format	article
author	Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro
author_facet	Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro
author_sort	Kerstin Elert
title	Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
title_short	Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
title_full	Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
title_fullStr	Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
title_full_unstemmed	Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
title_sort	degradation of ancient maya carved tuff stone at copan and its bacterial bioconservation
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/74184a82527b4348a812d08a40b94d83
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Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation

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