Adverse effects arising from conservation treatments on archaeological sites: theory, practice and review

Conservation and restoration of archaeological sites developed significantly in the second half of the twentieth century, with greater emphasis in recent decades, which has led to a considerable number of interventions. Methodology of intervention has changed significantly since more interventionist measures are performed against the current criteria of minimum intervention, although what actually occurs today is a difficult balance between innovation (experimental application of new techniques and products) and minimum intervention. The debate, in the case of archaeological sites, has focused on the actions traditionally more aggressive: cleaning, consolidation or reintegration, as this is where most notable has been the restorative action throughout history. The restoration, like everything else, has been subject of trends, in relation to the appearance of new products and technologies, and today remains a discipline that widely develops experimental practice. It certainly brings great benefits and constant renewal of criteria and methodologies, but also risks by introducing new compounds that may interact negatively with original substrate, although their effects cannot be checked in the short or medium term. The lack of knowledge of the causes of decay arising from previous interventions has generated a series of continuous protection and consolidation treatments at different periods. Restorers currently must deal with decayed areas where the products, methodology or techniques used, have caused a negative effect on the original material. This paper attempts to explore the general study of effects and alterations arising from restoration treatments, as well as reviewing of scientific publications related to this issue.series of continuous protection and consolidation treatments at different periods. Restorers currently must deal with decayed areas where the products, methodology or techniques used, have caused a negative effect on the original material. This paper attempts to explore the general study of effects and alterations arising from restoration treatments, as well as reviewing of scientific publications related to this issue.This research was supported by the PICATA fellowship program from Campus of International Excellence of Moncloa. Our acknowledgements to GEOMATERIALES programme (S2009-MAT1629/GEOMATERIALES) within Instituto de Geociencias (CSIC, UCM), to AIPA programme (ETSAM, Polytechnic University of Madrid) and to the Research Group financed by the Complutense University of Madrid "Alteration and Conservation of heritage stone materials” (ref. 921349).Peer reviewe

Características generales de las subcuencas del margen peninsular meditarráneo ("Rift" del Surco de Valencia)

This paper describes the general characteristics, namely the geometry and the sedimentary infill, of several troughs of Tertiary age present in the off-shore eastem Mediterranean margin of Spain. Al1 of them are included within the Valencia Trough, a rift basin developed during Paleogene and early Miocene times between the Balearic archipelago and mainland Spain. Although some authors (Soler et al., 1983; Fontboté et al., 1990; Roca and Desegaulx, 1992; Watts and Torné, 1992; Martínez del Olmo, 1994) have recently described the Valencia Trough as a foredeep basin of the Betics, we think that the referred foredeep does not extend as far as to the westernmost area of the Mediterranean. This is based on the evidence provided by the interpretation of numerous seismic surveys and nearly two hundred wells drilled without finding a single repetition or a clear evidence of compression in the area of this study. This rift is tbe southemmost branch of the European rift, which crosses most of western Europe from the Rhine graben through the westem Alps southwards into Morocco along the eastem coast of Spain (Sanz de Galdeano, 1990; Fontboté et al., 1990). The substratum of the basin is basically formed by Mesozoic (mainly carbonates) and pre-Mesozoic sediments (mainly clastics and metamorphics), folded and deformed during the Pyrenean orogeny and later fractured as horsts and grabens during the rift stage. The carbonates were severely fractured and intensively karsted during subaerial exposure following the deformation of the region. These processes have enhanced tbeir reservoir cbaracteristics (porosity and permeability) thus allowing the accumulation of hydrocarbons. Aborted during middle Miocene times, this rift started its development in the north during Paleogene times (Rosas and Barcelona troughs) and the sediments of this age constitute the bulk of the infill. On the contrary, in the southern sub-basins (Tarragona and Castellón troughs) the formation of the rift was younger, dunng early middle Miocene times, and the bulk of sediments infilling the troughs are of this age. This change in the age of the sedimentary infill, younger towards the south paralells the southwards development of the main rift. The sediments were filling the rift troughs, and by middle Miocene times al1 reliefs (horsts and grahens) had been leveled off. During early Miocene times the sedimentation in the troughs (mainly starved basins) took place under restricted marine conditions that favored the accumulation and preservation of the organic matter and the subsequent development of hydrocarhon source beds in some of them (Demaison and Bourgeois, 1984). The high thermal gradient, typical of rift hasins, favored the early maturation of the organic matter. The migration of the newly generated hydrocarbons into the neighbour paleoreliefs, mostly formed by karsted carbonates (Martínez del Olmo and Esteban, 1983), brought about severa1 oil fields that have been actively explored and exploited. So far only in the Tarragona trough commercial accumulations have been found (Amposta, Casablanca, Dorada and Tarraco) but other troughs (namely Rosas and Barcelona) have had good shows and the geocheniical analysis have also demonstrated the existence of good source rocks. Frorn the middle Miocene on, the sedimentation changed dramatically to a prograding continental shelf of passive margin type. Two megasequences are distinguished: the first one during the rniddle-late Miocene and the second one during Plio-Quatemary times, separated by the Messinian unconformity that locally produced important erosional canyons in the underlying sediments

Effects of Conservation Interventions on the Archaeological Roman Site of Merida (Spain). Advance of Research

Efectos derivados de tratamientos de conservación y restauración sobre material inorgánico en yacimientos arqueológicos. Caso de estudio: Mérida

Effects of conservation interventions on the archaeological Roman site of Merida (Spain). Advance of research

Research on the assessment of the effects of conservation/restoration treatments on stone material has been significant in recent years, with focus on the early observation of decay caused by the application of these treatments. However, in the case of archaeological sites, research is still scarce and few studies on the subject have been published. Restoration, as everything else, has changed according to trends, mainly guided by the release of new products and technologies, an experimental field where scientific assessment of suitability, efficacy and durability pre-evaluations of treatments are not always conducted. Some efforts have been made to solve this problem in the architectural field, where functional needs and technical requirements force to set clear standards. Unfortunately, archaeological sites, unlike historic buildings, have specific features that preclude the extrapolation of these results. A critical review of the methodologies, products and restoration materials is necessary, coupled with deeper research on degradation mechanisms caused by these treatments in the mid- and long-term. The aim of this paper is to introduce the research on the above issues using Merida as a case study.Peer Reviewe

Piedras artificiales: morteros y hormigones. El cemento como máximo representante de estos materiales de construcción

12 págs, 7 fig.-- Publicado en el libro "Ciencia, Tecnología y Sociedad" dentro del programa Maternas financiado por la Comunidad de Madrid, en colaboración con la Asociación Restauradores sin Fronteras (RSF).[EN] From the dawn of architecture to the present day, artificial stones have been the most in-demand building material. Natural stones, because of their beauty, fine quality, etc., are now favoured over artificial stones, but the use of the latter has always been indispensable. The most representative group of artificial stones is that of mortars and concrete. These mortars are obtained from the mixture of natural dry materials with a binding material and water. The binding materials may be common (lime, plaster, clay, etc) or hydraulic (hydraulic lime and cements). Over the last two centuries, 19th and 20th, the prominence of hydraulic mortars and concrete has been enormous and has given cement the starring role in modern construction.[ES] Desde los albores de la arquitectura y hasta el día de hoy, piedras artificiales han sido las más demandadas dentro de los materiales de construcción. Las piedras naturales, debido a su belleza, gran calidad, etc, han sido mejor valoradas que las piedras artificiales, pero el uso de estas últimas siempre ha sido indispensable. El grupo más representativo de piedras artificiales es el de los morteros y hormignones. Estos morteros se obtienen a partir de la mezcla de un árido natural seco con un aglomerante y agua. Los aglomerantes pueden ser de materiales comunes (cal, yeso, arcilla, etc) o hidráulicos (cal hidráulica y cementos). En los últimos dos siglos, XIX y XX, la utilización de morteros hidráulicos y hormigones ha ido en aumento, lo que implica que el cemento juega un papel importante en la construcción moderna.Proyecto Maternas financiado por la Comunidad de Madrid (Referencia S-0505/MAT-0094)

Evaluación de tecnicas de limpieza y desalinización en la catedral de Segovia, España

Los materiales pétreos (naturales o artificiales) utilizados en la construcción del patrimonio cultural se ven afectados por procesos de cristalización de sales que conducen a una pérdida de compacidad y cohesión del material. Cuando se observan sales en la superficie de un muro pétreo el problema es que existan también en el interior, bajo la superficie, por lo cual lo realmente importante es saber la extensión de estos procesos en el interior de los muros. En este trabajo se presenta una metodología basada en análisis mediante cromatografía iónica de muy pequeñas cantidades de muestras a diferentes alturas de un muro y a diferentes profundidades. Por otro lado, son numerosos y muy variados los métodos de limpieza que se utilizan hoy en día en el patrimonio construido. Se presenta a este respecto una metodología para la evaluación de la eficacia de cualquier sistema de limpieza mediante la combinación de varias técnicas, dos de ellas no destructivas – medida del color mediante espectrofotómetro, y de la rugosidad mediante rugosímetro superficial 3D, junto con el uso de la microscopía electrónica de barrido (MEB/SEM) y el microanálisis por dispersión de energías de rayos X (EDX)

The measurement of surface roughness to determine the suitability of different methods for stone cleaning

Trabajo presentado a la EGU General Assembly 2011.In order to select the best bead blasting based method to clean the stone masonry of specific areas of the Cathedral of Segovia (Segovia, Spain), measurements of the roughness of the stone surface were performed, before and after cleaning processes.Peer reviewe

Non-destructive testing for the assessment of granite decay in heritage structures compared to quarry stone

Several types of granite found in two architectural heritage monuments were assessed with two non-destructive, portable techniques: Schmidt hammer rebound and ultrasound velocity (Vp). Similar assessments were conducted on the rock from which the granite was originally quarried for comparison. The results obtained, which revealed the existence of a direct correlation, constitute a useful indication of decay, particularly if the approximate dates of construction are known. And conversely, if they are not, such stone assessments may provide a rough estimate of when the structure was built. Both of these convenient, portable and non-destructive techniques may be used as reliable indicators of the degree of stone decay

Control térmico de la meteorización de superficies endurecidas en rocas graníticas (La Pedriza de Manzanares, España)

[ES] La Pedriza de Manzanares es parte del Parque Nacional del Guadarrama en el Sistema Central Español. Se caracteriza por formar un paisaje laberíntico constituido por una alternancia de bloques y grandes paredes de granito. Gran parte de las superficies de estas rocas están recubiertas por costras endurecidas de espesores milimétricos, que controlan la alteración superficial y favorecen el desarrollo y distribución de micro-relieves sobre las paredes. Para explicar el proceso de alteración que favorece la formación de irregularidades sobre la superficie del granito, en este trabajo se analizan algunas variables tales como la temperatura, índice de esclerometría y morfología de los micro-relieves. Por otra parte, el artículo establece relaciones entre la primera fase de formación de las superficies endurecidas en condiciones subedáficas, asociada al frente de alteración, con los espesores de las costras endurecidas y la erosión del regolito. Las relaciones definidas y resultados obtenidos son de aplicación en otras regiones graníticas del mundo de características similares.[EN] Pedriza de Manzanares is part of the Guadarrama National Park in the Spanish Central System. It is characterized by a labyrinthine landscape composed of alternating blocks and large walls of granite. Case-hardened crusts of millimetric thickness covering most of these rock surfaces control the surface alteration and favor the development and distribution of micro-reliefs on the walls. Some variables such as temperature, sclerometric index and micro-relief morphology are analyzed in this paper in order to explain the destructive process of alteration that favors the formation of irregularities on the granite surface. On the other hand, the paper establishes the relation between the first stage of case-hardening in sub-edaphic conditions, which is associated with the alteration front, and the thickness of such crusts and regolith erosion. These results can be applied to other granitic regions with similar characteristics all over the world.Peer reviewe