Miguel Ángel Rogerio-Candelera

Primary bioreceptivity of limestones used in southern European monuments

Abstract Different Mediterranean Basin limestones, like Calcário Ançã (Portugal), Calcário Lioz (Portugal), Piedra San Cristobal (Spain), Piedra Escúzar (Spain) and Pietra di Lecce (Italy), have been widely used as building materials in the European architecture. The aim of this study was focused on biodeterioration, mainly on evaluation of the primary bioreceptivity of those materials. A set of samples was inoculated with a cultured photosynthetic biofilm under laboratory conditions. Several assessment tools were applied to monitor the colonization overtime of the different lithotypes. After 3 months of incubation the colonization occurred endolithically in some lithotypes, namely Piedra San Cristobal and Piedra Escúzar. Spectrophotometric determination of chlorophyll a was a useful analytical technique to achieve the total amount of photosynthetic biomass on rock substrates, demonstrating that Piedra Escúzar and Calcário Lioz were the highest and lowest bioreceptive lithotypes, respectively. Microscopic and image analyses were essential to understand the stone colonization process and its pattern of distribution. Physical stone parameters and exposure conditions were shown to play an important role in the establishment and development of photosynthetic colonization.

Assessing the influence of surface roughness on the epilithic colonisation of limestones by non-contact techniques

La colonizacion de la piedra por microorganismos ha generado una extensa literatura sobre los mecanismos y tasas de degradacion fisicoquimica de las superficies petreas, tanto en laboratorio como en estudios de campo. La colonizacion biologica de piedra de construccion depende de parametros intrinsecos como son su composicion mineral, textura, porosidad y permeabilidad, asi como de parametros ambientales. Este estudio demuestra la relacion entre la rugosidad superficial de la piedra y la colonizacion epilitica, cuantificada en tres tipos de caliza mediante tecnicas no destructivas: medida de la rugosidad superficial usando un perfilometro optico y analisis digital de imagenes. De acuerdo con la rugosidad media aritmetica (Ra) y la amplitud media de rugosidad (Rz), determinadas para la caliza de Anca, la caliza de Lioz y la piedra de Lecce, puede concluirse que las piedras con alta rugosidad superficial son mas propensas a la colonizacion microbiana.

The deterioration of Circular Mausoleum, Roman Necropolis of Carmona, Spain

The Circular Mausoleum tomb in the Roman Necropolis of Carmona was carved on a calcarenite sequence in an ancient quarry located in the town of Carmona, Southern Spain. This rock-cut tomb, representative of Roman burial practices, currently suffers from serious deterioration. A detailed survey over several years permitted the identification of the main tombs pathologies and damaging processes, which include loss of material (scaling, flaking, granular disintegration), surface modifications (efflorescences, crusts and deposits) and extensive biological colonization. The results obtained in this study indicated that anthropogenic changes were largely responsible and enhanced the main alteration mechanisms observed in the Circular Mausoleum. Based on the deterioration diagnosis, effective corrective actions were proposed. This study shows that any conservative intervention in the interior of the tomb should be preceded by accurate in situ measurements and laboratory analyses to ascribe the source of the deterioration damages and thus designing effective treatments.

An integrated approach for assessing the bioreceptivity of glazed tiles to phototrophic microorganisms

Abstract A laboratory-based methodology was designed to assess the bioreceptivity of glazed tiles. The experimental set-up consisted of multiple steps: manufacturing of pristine and artificially aged glazed tiles, enrichment of phototrophic microorganisms, inoculation of phototrophs on glazed tiles, incubation under optimal conditions and quantification of biomass. In addition, tile intrinsic properties were assessed to determine which material properties contributed to tile bioreceptivity. Biofilm growth and biomass were appraised by digital image analysis, colorimetry and chlorophyll a analysis. SEM, micro-Raman and micro-particle induced X-ray emission analyses were carried out to investigate the biodeteriorating potential of phototrophic microorganisms on the glazed tiles. This practical and multidisciplinary approach showed that the accelerated colonization conditions allowed different types of tile bioreceptivity to be distinguished and to be related to precise characteristics of the material. Aged tiles showed higher bioreceptivity than pristine tiles due to their higher capillarity and permeability. Moreover, biophysical deterioration caused by chasmoendolithic growth was observed on colonized tile surfaces.