Stone Deterioration

Apresenta-se uma breve resenha sobre as principais pedras tradicionalmente usadas nos monumentos de Coimbra focando, em especial, as formas e taxas de degradação e abordam-se, de forma sumária, alguns aspectos relativos aos problemas de conservação que se levantam com estes materiais.

Samples of sandstone from the interior of the Art Gallery and Museum at Kelvingrove in Glasgow were characterised.  The samples investigated comprised those cleaned using an EDTA/natural rubber latex poultice method during the 2004-6 refurbishment of the Gallery and uncleaned samples with an intact black soiling patina. This study was undertaken in order to provide a petrographic explanation of the stone coloration and the efficacy of the cleaning methodology. The stone is a medium grained, well sorted quartz arenite, containing mono-crystalline quartz, extensively dissolved microcline feldspars, muscovite micas, opaque oxide minerals and rare accessories such as zircon, tourmaline, apatite and rutile. Sub-angular to sub-rounded framework grains exhibit pressure solution contacts and occasional overgrowths. Secondary minerals are ankerite cements, kaolinite clays and iron oxyhydroxides. The stone exhibits a warm honey colour or a more grey tone, related to secondary iron oxide mineral content. Relationships between iron oxyhydroxide, ankerite and kaolinite suggest a complex diagenetic history for the stone, in addition to an overprint of mineral growth related to post quarrying exposure. We tentatively propose two morphologies for ankerite. In euhedral masses, a compositional zoning is evident as a late Fe and Mn enrichment and Mg depletion. The honey-coloured surface patina common on many of the cleaned blocks in the Gallery is generally present in a zone up to 5 mm from the exterior surface. Interstitial masses of iron oxyhydroxide can be seen increasing in occurrence towards the exterior of the stone in the honey-coloured samples. There is evidence for the progressive replacement of ankerite with the iron oxyhydroxide phases. In some, the brown iron oxyhydroxide coloration is present throughout the thickness of the sample, but these samples exhibit a greyish surface colour, with a depleted Fe zone on the exterior, and do not contain any carbonate cement. Samples with a honey-coloured surface contain abundant ankerite cement but less interstitial iron oxyhydroxide, except near the surface where replacement of carbonate becomes common. Uncleaned samples have a thin black, opaque surface layer up to 100 µm thick, whose elemental composition includes Si, Al, S and Fe.  In one sample,  Ba is also present in small barite grains. Gypsum is present in the soiling layer, but full characterisation of the blackened surface has not been undertaken.

The first step in the restoration
of a medieval stained glass window is the evaluation of
its degree of degradation. This implies the study of the
chemical composition of the stained glass as well as the
new mineral phases developed on its surface (patinas).
Patinas are clearly related to glass composition, time,
environmental conditions, microenvironments developed
in local zones, bioactivity, physical and chemical factors,
etc. This study was carried out on patinas developed in
selected Na-rich stained glass of the Santa Maria de
Pedralbes Monastery (Barcelona, Spain). The location of
this monument in the city (about 5 km from the shoreline
and close to the Collserola hill flank) helped to determine
the environmental conditions in which patinas developed.
The aim of our study was to characterize the patinas formed
on the surface of the selected glass of this monastery in
order to understand the role of the chemical composition of
the original glass (Na-rich) as well as the environmental
conditions in which they developed.

Salt crystallization is accepted to represent one of the major causes for the degradation of building and ornamental stone. As such, it has attracted the attention of researchers, who over the years have progressively unraveled most mechanisms involved in salt damage. Despite this, many questions subsist about how to quantitatively predict damage or its progression, and in particular how to relate performance on site to that in laboratory tests. In this context, a new RILEM TC has been started with the objective of defining laboratory tests that deliver more reliable predictions of field behavior. One deliverable of this TC, is to provide a theoretical insight into this question based on recent progress on the understanding of salt damage. This paper presents a summary of this work, highlighting key aspects relating to crystallization pressure, chemo-mechanics and transport. Implications are more specifically discussed in relation to existing accelerated tests in an attempt to bette...

May, A. (1998c): Verwitterung und Verwitterungsbeständigkeit von Naturbausteinen aus Kalkstein am Beispiel des Osnabrücker Wellenkalks (Trias). - Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 208: 637-651, 6 figs.; Stuttgart.

Abstract: New results about the weathering decay and weathering resistance of limestone building stones are presented by the example of the Osnabrücker WeIlenkalk (Lower Muschelkalk), an important building stone in the vicinity of Osnabrück (Northern Germany). Weathering decay and weathering resistance of its varieties are investigated at stones from two building walls in Osnabrück. The limestones are mainly damaged by fissures essentially based on frost phenomena. The dimensions of the building stone influence its weathering decay. Remarkable differences of the weathering resistance are visible between the six distinguished varieties (microfacies types A-F). The mircofacies types A and B are best resistant against weathering, because they are not laminated, and the quantities of the cold water absorption, the Schurecht ratio (ratio cold/boiling water absorption), and the residue insoluble by hydrochloric acid are relatively low.

Zusammenfassung: Neue Forschungsergebnisse zur Verwitterung und Verwitterungsbeständigkeit von Mauersteinen aus Kalkstein werden am Beispiel des Osnabrücker Wellenkalks (Unterer Muschelkalk), einem wichtigen Naturbaustein, dargestellt. Die Verwitterung und Verwitterungsbeständigkeit seiner Varietäten werden an Mauersteinen aus zwei Gebäuden in Osnabrück untersucht. Die Mauersteine werden hauptsächlich durch (lang aushaltende) Risse geschädigt, die im wesentlichen auf Frost- Tau- Wechsel-Prozessen und Frostsprengung beruhen. Es lassen sich deutliche Unterschiede in der Verwitterungsbeständigkeit der sechs im Osnabrücker Wellenkalk unterschiedenen Gesteinsvarietäten (Mikrofaziestypen A-F) erkennen. Am verwitterungsbeständigsten sind die Mikrofaziestypen A und B, die geringmächtige Lagen bilden. Die Mik.rofaziestypen A und B sind so verwitterungsbeständig, da sie nicht feingeschichtet sind und freiwillige Wasseraufnahme, Schurecht-Ratio (= freiwillige Wasseraufnahme geteilt durch effektive Porosität) sowie der Gehalt an salzsäureunlöslichem Rückstand relativ gering sind.

May, A. (1997a): Verwitterungsbeständigkeit und Verwitterung von Naturbausteinen aus Kalkstein. - Geologie und Paläontologie in Westfalen, vol. 48: p. 3-185, 94 figs., 2 tabs., pl. 1-11; Münster.

Abstract: Weathering durability and weathering process of natural building stones from the Lower Muschelkalk, the Upper Muschelkalk, and the Devonian have been investigated. Various properties of each building stone and its limestone material are measured (microscopy, SEM, porosity, ultrasonic velocity, geochemical methods). Defined microfacies types show clear differences in their weathering durability. The quantities of the cold water absorption, the Schurecht ratio (= ratio cold/boiling water absorption), and the residue insoluble by hydrocloric acid strongly affect the weathering durability. Together with the investigation of thin-sections, these properties enable prognoses about the weathering durability. A diagram of correlation between coldwater absorption and Schurecht ratio is developed, which is able to discriminate more durable and less durable limestones by a boundary line (Fig. 59-60).The limestones are mainly damaged by fissures which harm the unity of the stone. Probably these fissures are mainly based on frost phenomena. Connections between the sedimentary environment and the weathering durability are recognizable: generally limestones of the agitated (shallow) marine are more durable than other limestones.

Kurzfassung: Es wurden die Unterschiede in der Verwitterungsbeständigkeit zwischen verschiedenen Varietäten jeweils eines Kalksteins untersucht. Beprobt wurden Kalksteine des Muschelkalks im Raum Osnabrück-Bielefeld und des Devons im Sauerland in Bauwerken und Aufschlüssen. Eine neue Klassifikation des Verwitterungszustandes von Kalkstein-Mauersteinen wurde entwickelt. Die Oberflächenschäden auf der Außenseite sind nur ± gering und stellen bloß ein "kosmetisches" Problem dar. Die Stärke der Schädigung des inneren Zusammenhaltes des Mauersteins durch Risse ist viel wichtiger, da sie die Sicherheit und Stabilität des Bauwerks gefährdet. Die Untersuchung von Dünnschliffen ermöglichte es, insgesamt 17 Mikrofaziestypen zu definieren und erstmalig Unterschiede in der Verwitterungsbeständigkeit zwischen den verschiedenen Mikrofaziestypen eines Kalksteins zu erkennen. Kalksteine, die in ± turbulentem (und damit ± flachem) Meereswasser abgelagert wurden, sind tendenziell verwitterungsbeständiger als solche aus anderen Ablagerungsräumen. Mit der Auftriebsmethode wurden wichtige Porositätsparameter festgestellt. Freiwillige Wasseraufnahme und Schurecht-Ratio (= Quotient freiwillige Wasseraufnahme / effektive Porosität) beeinflussen die Verwitterungsbeständigkeit sehr stark, wenn ihre Größe zunimmt, nimmt die Verwitterungsbeständigkeit ab. Die Ultraschall-Untersuchungen zeigten, daß in Kalksteinen Spannungen viel weiter geleitet werden als in Sandsteinen und deshalb zu (lang aushaltenden) Rissen führen. Die rasterelektronenmikroskopische Untersuchung erlaubte Aussagen über einzelne Aspekte des Verwitterungsprozesses. Die im salzsäurelöslichen Gesteinsanteil gemessenen Element-Konzentrationen spielen keine Rolle für die Verwitterungsbeständigkeit der Kalksteine.  Die Verwitterungsbeständigkeit der bearbeiteten Kalksteine wird am stärksten von freiwilliger Wasseraufnahme und Schurecht-Ratio beeinflußt. Der Einfluß des Gehaltes an salzsäureunlöslichem Rückstand ist erheblich geringer. Darüber hinaus spielen auch die Merkmale Feinschichtung und Kristallgröße (Mikritl Sparit) eine gewisse Rolle. Die Entwicklung von Stylolithen hat nur nachrangige Bedeutung. Einen sehr großen praktischen Nutzen für Prognosen über die Verwitterungsbeständigkeit verspricht die erstmalig ermittelte Grenzlinie Schurecht-Ratio/freiwillige Wasseraufnahme, die unabhängig vom Probenkollektiv überdurchschnittlich und unterdurchschnittlich verwitterungsbeständige Kalkstein-Mauersteine mit ziemlich großer Schärfe voneinander trennt. Darauf aufbauend wurden leicht durchzuführende Verfahren zur Auswahl besonders verwitterungsbeständiger Kalksteine entwickelt. Im Gegensatz zur vorherrschenden Literaturmeinung werden Kalksteine im wesentlichen durch Risse geschädigt, die wahrscheinlich aufgrund von Frosterscheinungen (bzw. Frost-Tau-Wechsel-Prozessen) entstehen und hauptsächlich durch Frostsprengung vergrößert werden. Da die Schädigung der Gesteinsoberfläche ± gering ist, kann die chemische Verwitterung für Kalksteine nicht wichtig sein. Hierdurch unterscheiden sich Kalksteine in ihrem Verwitterungsverhalten sehr stark von Kalksandsteinen.

English summary of important results of the research project on weathering durability and weathering of limestone as natural building-stones. This project was performed by Andreas May 1991-1997.

Concerning the project see also https://www.researchgate.net/project/Weathering-durability-of-limestone

Stone monuments are important symbols of cultural heritage of countries. However, many environmental factors negatively affect these monuments. The increasing damage on the stone monuments and the danger of irreversible loss of cultural heritage have resulted in growing efforts for the preservation of the monuments. Eflatunpınar Hittite Water Monument in Beyşehir, Konya, Turkey, is a unique Hittite cultural monument that has survived for nearly 3200 years even though it has been exposed to many environmental effects. In this study, non-destructive testing (NDT) was used to detect the degradation on the building stones of the Eflatunpınar Hittite Water Monument and change-deterioration maps were prepared subsequently. It was also investigated whether the chemistry of the Eflatunpınar spring water may cause deterioration. Additionally, the petrographic, chemical, and physico-mechanical properties of the rocks taken from the ancient stone quarry were determined in order to compare with the properties of the monument's building stones. Based on the physico-chemical characteristics of the Eflatunpınar spring water and XRD results of crusts in building stone surface of the monument, it was identified that water can be effective on the formation of calcite and gypsum crusts especially in the lower parts of the monument. However, applied NDT methods and change-deterioration maps indicated that the deterioration as well as neglect and abandonment in the monument are mostly associated with the capillary effect of the flowing water through the structure and the deterioration effect is more apparent in contact points between the building stone and the flowing water. Additionally, in the building stones above the capillary front, the conservation condition is significantly better.

May, A. (1998a): Die Verwitterung von karbonatischen Naturbausteinen in Mitteleuropa. - Geoökodynamik, 19 (1/2): 71-88, 4 figs.; Bensheim.

SUMMARY: Calcareous sandstones are severely damaged by acid rain and dry depostion of acid-producing pollutants both at and just below the stone surface. This appears to be normal for a carbonatic rock, which, however, is largely due to quite different properties unrelated to their carbonate content, such as pore space, the dynamic modulus of elasticity and the percentage of quartz and clay minerals contained in the rock. Their effect is further increased by other weathering processes also unrelated to air pollution. The situation is totally different for limestone weathering. Limestone building stones are primarily damaged by frost-fissuring, whereas the role of solution processes at the surface, which in the opinion of most authors do most of the damage, is in fact only low. This can also be explained by specific stone properties, especially the dynamic modulus of elasticity. The fact, that the disastrous damage done to limestone by frost-fissuring has been overlooked by almost all authors so far can only be explained by the fact that studies largely concentrated on superficial damage to limestones and that experiments measuring the damage concentrated on air pollutants (cf. MAY 1997: 132-134). These mistakes could have been avoided by not only concentrating on the function of the objects, but the types of damage as weil that particularly affect it.  The weathering process in carbonatic building stones are very complex and must thus be studied separately for each group of stones, for which some geological knowledge is mandatory. Calcareous sandstones are especially sensitive to anthropogenic air pollution. Consequently the reduction of air pollution achieved so far, above all by S02, has recognizably slowed down the rate of stone decay. It had only a minor effect on limestones, as for them frost is the major problem. The effect global warming by air pollution is likely to have on building stone decay in central Europe is difficult to assess, for example, the frequency of freeze and thaw cycles is more important than frost intensity.

ZUSAMMENFASSUNG: Werksteine aus Kalksandstein werden durch den "Sauren Regen", bzw. die trockene Ablagerung säurebildender Bestandteile der Luft an und nahe der Gesteinsoberfläche stark geschädigt. Kalksandsteine verhalten sich dabei so, wie es für Karbonatgesteine allgemein erwartet wird. Dies liegt allerdings nicht nur an ihrem Karbonatgehalt, sondern zu einem wichtigen Teil an ganz anderen Gesteinseigenschaften (z. B. dem Porenraum, dem dynamischen Elastizitäts-Modul und den Quarz- und Tonmineral-Anteilen), die davon unabhängig sind. Außerdem verstärken andere Verwitterungsprozesse, die nicht von der Luftverschmutzung abhängig sind, deren Wirkung. Ganz anders verhält sich die Kalkstein-Verwitterung: Diese Bausteine werden hauptsächlich durch frostbedingte Risse zerstört, während die Lösungserosion der Gesteinsoberfläche, die von den meisten Bearbeitern als hauptsächliche Schädigungsursache angesehen wird, beim Kalkstein nur gering ist. Auch dieses Verhalten erklärt sich aus den Gesteinseigenschaften (insbesondere dem dynamischen Elastizitäts-Modul). Daß die viel verheerendere Schädigung des Kalksteins durch Risse von fast allen Autoren bisher ignoriert wurde, läßt sich nur dadurch erklären, daß vorwiegend Oberflächenschäden an Kalksteinen untersucht und Experimente zur Messung der Schädigung von Kalksteinen vorzugsweise auf Luftschadstoffe bezogen wurden (vgl.: MAY 1997: 132-134). Diese Fehlentwicklung hätte vermieden werden können, wenn bei den Untersuchungen auch die Funktion des Objekts und die Art der Schäden, die diese besonders stark beeinträchtigen, nachgefragt worden wäre. Die Verwitterung der in Bauwerken verwandten karbonatischen Natursteine ist zudem sehr komplex und muß für jede Gesteinsgruppe getrennt beantwortet werden. Dazu sind geologische Kenntnisse unbedingt notwendig. Während Kalksandsteine sehr empfindlich auf die anthropogen verursachte Luftverschmutzung reagieren, ist diese bei Kalksteinen kein großes Problem. Die Bekämpfung der Luftverschmutzung bzw. die dabei schon erzielten Erfolge (insbesondere durch Reduzierung des S02) schlagen sich deshalb nur bei Kalksandsteinen in einer erkennbaren Verlangsamung des Steinzerfalls nieder (GRIMM 1992:255-256, Abb. 8), auf die Verwitterung der Kalksteine haben sie nur geringen Einfluß, denn dort ist die Frosteinwirkung das größte Problem, Welche Folgen die mit der Luftverschmutzung verknüpfte globale Erwärmung auf die Gesteinsverwitterung in Mitteleuropa hat und haben wird, läßt sich nicht abschätzen, denn z. B. für die Intensität der Frostschädigung ist die Häufigkeit des Frost-Tau-Wechsels wichtiger als die Intensität des Frostes.

A simulation model of the solar energy impinging on stone blocks is made to ascertain the impact of solar radiation on the walls of the Pyramids of Giza, Egypt. The model considers the solar radiation hitting the upper surface, and the vertical sides of stone blocks on the four walls. The calculation concerns: the solar height and azimuth; the daily total amount of solar radiation; the instantaneous values of the flux of solar radiation. The results are reported and discussed, pointing out the main features of the daily and seasonal cycles, as well as the impact on the various exposures.

The performance of structures such as bridges, machine foundations and base isolated buildings are very much affected by the condition of their elastic bearing supports, which eventually deteriorate due to wear and tear or which can be damaged during the service life of the structure. In this study, the dynamic parameters, namely natural frequencies and mode shapes are used to detect the deterioration of the elastic bearing supports of a simply supported bridge girder. For this purpose, force vibration testing was conducted on a reinforced concrete bridge girder supported at the ends by rubber bearings to simulate the actual conditions in a bridge deck. Three different levels of deteriorations were investigated namely that of no deterioration, partial deterioration, and full deterioration, whereby rubber with different stiffness was used to simulate the different deterioration levels. Vibration data were obtained for two cases i.e. an undamaged girder and a damaged girder after being subjected to a load exceeding its service limit for flexure. A direct relationship was observed between the dynamic parameters and the elastic bearing stiffness. Based on the results obtained in this study, the natural frequency of mode 3 is a good indicator of the deterioration in elastic bearing support conditions while mode 1 is the most sensitive to changes in support conditions. The Modal Assurance Criteria (MAC) index can be a useful indicator to identify different causes of deterioration in the structural system. In order to confirm and verify the observations, further tests were conducted on a different beam with more deterioration levels in the elastic bearing stiffness. The results support the deductions made regarding MAC and bending frequencies. © 2011 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0950061811007203

The susceptibility of sandstones to deteriorative factors when used for construction requires detailed experimental evaluation. This study investigated the (bio)weathering behaviour of Lower-Silesian Cretaceous sandstones (quartz arenites) to quantify the deteriorative effect of bacterium Acidithiobacillus thiooxidans. For controls, ultrapure water (in undersaturated conditions) and sterile acidic medium (in abiotic acidic conditions pH 2.5) were used. Sandstone exposure to A. thiooxidans mimicked the extremely acidic conditions (pH up to 0.9) that may develop under long-term weathering, which promote microbial activity and acidic metabolite production. Element release was assessed using triple quadrupole inductively coupled plasma mass spectrometry (QQQ-ICP-MS) and identifying potential element donor minerals through scanning electron microscopy, coupled with energy dispersive spectrometer (SEM-EDS). The results demonstrated that sandstones were relatively susceptible to weathering...

Stone monuments are the most visible and essential structures of our cultural heritage; however, many of the historical structures around the world are now suffering from stone deterioration. Diyarbakır City Walls, which were acknowledged the status of World Heritage Site by UNESCO, are among the most extensive surviving structures from ancient times. The City Walls have also some deterioration related problems. Basalts having such different textural properties as massive and vesicular were employed as the principal material in the construction of the Diyarbakır City Walls. Weathering is strongly related to the climatic and environmental conditions of the site. In order to evaluate the physical deterioration, environmental conditions were artificially simulated in accelerated weathering tests such as wetting-drying, freezing-thawing, and salt crystallization. For this purpose, 180 massive and vesicular basalt samples were prepared. The effects of these tests were evaluated by visual examination, weight loss, effective porosity, dry and saturated unit weights, water absorptions under atmospheric and vacuum pressure, sonic velocity and uniaxial compressive strength. It is found that the salt crystallization is the most effective accelerated weathering test deteriorating the basalt samples most aggressively.

The study of the physical state of historic monuments – the main content of the first and decisive stage in the process of their conservation, is a frequently treated topic in two distinct areas: scientific research and university courses. Can the two be combined to their mutual benefit?
This paper examines a specific part of this question: whether students’ output on completion of their courses can be used by scientists and conservationists in material deterioration study and research on historic monuments. An approach applicable to non-conservational curricula is outlined in brief, with a view to narrowing the existing gap between educational tradition and the needs of contemporary conservation.