Surface hardness as a proxy for weathering behaviour of limestone heritage: a case study on dated headstones on the Isle of Portland, UK

Wilhelm, Katrin; Viles, Heather; Burke, Órlaith; Mayaud, Jerome R.

doi:10.1007/s12665-016-5661-y

Cited by 37 publications

(30 citation statements)

References 80 publications

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“…Although the rock layers occupied by pHPC displayed higher porosity and exhibited a mineral‐leached structure, their elastic and plastic properties appeared improved with respect to freshly broken and microbial biofilm controls. Such findings support the recent hypothesis that lichens were responsible for higher hardness (HLDL S ) of uncleaned Portland headstones with respect to regularly cleaned ones (Wilhelm et al ., ). As biogenic calcite of several biological systems, such as seashells, was shown to display superior hardness, and model synthetic calcite crystals with contents of amino acids revealed enhanced hardness (Kim et al ., ), our results suggest the opportunity to investigate if and how hardening patterns may also accompany lichen biogeochemical processes on limestones.…”

Section: Discussionmentioning

confidence: 97%

“…The median value of the SIM series (HLDL S.med ) and the median of the maximum values of the five RIM series (HLDL R.med ) were used to calculate for each measuring area the robust hybrid dynamic hardness (HDH robust , sensu Wilhelm et al ., ) as follows:…”

Section: Methodsmentioning

confidence: 99%

“…For each measuring area (colonization type x block), a combination of two measuring procedures [single impact method (SIM) and repeated impact method (RIM)] was adopted to provide a more robust evaluation of surface hardness characteristics (Yilmaz, 2013;Wilhelm et al, 2016b). A series of 45 randomly distributed readings (SIM; for a confidence level of 95%) was carried out first to evaluate the elastic and plastic properties of the rock surfaces covered by the different colonization types.…”

Section: Equotipmentioning

confidence: 99%

See 2 more Smart Citations

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

Morando

Wilhelm

Matteucci

et al. 2017

Earth Surf Processes Landf

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Section: Discussionmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Equotipmentioning

confidence: 99%

See 1 more Smart Citation

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

Morando

Wilhelm

Matteucci

et al. 2017

Earth Surf Processes Landf

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“…Surface hardness measurements are often made as part of geomorphological studies into the degree and rate of rock weathering and stone deterioration (André et al, 2014;Wilhelm et al, 2016a) and assessments of the performance of conservation materials such as consolidants (Perez Ema and Bustamente Montoro, 2013;Zornoza-Indart and Lopez-Arce, 2016). The Equotip has recently been used in geomorphological research on topics including the erosion of coastal engineering structures (Coombes et al, 2013), shore platforms (Feal-Pérez and Blanco-Chao, 2013) and the weathering history of limestone gravestones (Wilhelm et al, 2016a). The Equotip has recently been used in geomorphological research on topics including the erosion of coastal engineering structures (Coombes et al, 2013), shore platforms (Feal-Pérez and Blanco-Chao, 2013) and the weathering history of limestone gravestones (Wilhelm et al, 2016a).…”

Section: Introductionmentioning

confidence: 99%

“…A range of probes are available with different impact energies and geometries, but the D (11.5 Nmm), DL (11.1 Nmm) and C (3 Nmm) are the most commonly used probes in research on geomorphology and stone conservation (Torok and Prikryl, 2010, Wedekind et al, 2016, Wilhelm et al, 2016a. A range of probes are available with different impact energies and geometries, but the D (11.5 Nmm), DL (11.1 Nmm) and C (3 Nmm) are the most commonly used probes in research on geomorphology and stone conservation (Torok and Prikryl, 2010, Wedekind et al, 2016, Wilhelm et al, 2016a.…”

Section: Introductionmentioning

confidence: 99%

A laboratory study of Equotip surface hardness measurements on a range of sandstones: What influences the values and what do they mean?

Désarnaud

Kiriyama

Biçer-Şimşir

et al. 2019

Earth Surf Processes Landf

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The Equotip rebound tester is a simple, non‐destructive technique to measure the surface hardness of materials. Having a low impact energy gives the Equotip advantages over the commonly used Schmidt Hammer on weathered rock and stone. In this study we have investigated the influence of different parameters (sample size, moisture content and surface roughness) on the surface hardness values obtained from freshly cut blocks of four types of sandstone. In a series of laboratory experiments both Single Impacts (SIM) and Repeat Impacts (RIM) methods have been used with C and D probes (which have different impact energies). Our results show that whilst sample size is of great importance we find that smaller samples can be reliably evaluated than previously reported. Moisture contents are also found to exert a more important influence on both SIM and RIM results than previously thought, with up to 26% lower hardness values recorded on saturated vs dry sandstone. Conversely, we find that surface roughness (over Sz values of 100 to 800 microns) does not have a significant impact on SIM measurements collected using the D probe. Both SIM and RIM data are found to be good proxies for compressive strength and open porosity, with SIM data collected with the C probe showing the best fits. Data collected using 3D microscopy helps visualize and quantify the small impact marks created by the Equotip and confirms that these are much reduced when using the C vs D probe. The results highlight the benefits of the Equotip to studies of the nature and deterioration of sandstone, the need for careful evaluation of any confounding factors which might influence the values obtained, and illustrate the different advantages of C and D probes. © 2019 John Wiley & Sons, Ltd.

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Lichen impact on sandstone hardness is species‐specific

Tonon

Bernasconi

Martire

et al. 2022

Earth Surf Processes Landf

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The balance between lichen biodeterioration and bioprotection processes on stone surfaces depends on many variables and is crucial to understanding the role of lichens in biogeomorphology and their threat to stone heritage conservation. However, stones colonized by lichens have still been mostly examined in terms of affected volumes and physico-chemical modes of interactions, overlooking the overall effects on properties related to surface durability. In this study, the impact of lichen colonization patterns on Cortemilia sandstone was examined beneath thalli of three lichen species. Rock hardness, a proxy for rock durability, was measured at different depths from the surface using an Equotip hardness tester and compared to that of freshly cut surfaces and exposed surfaces uncolonized by lichens. Mineralogical analyses were performed by X-ray powder diffraction on rock beneath lichen colonization, in comparison with unweathered rock. Equotip analyses quantified a differential, species-specific decrease in stone hardness. This variability was related to differences in hyphal penetration patterns and, possibly, calcite (re-)precipitation. In particular, in the case of the species most impacting rock hardness, X-ray diffraction patterns of calcite showed a remarkable stability of crystallographic plane (01-12), known to be enhanced in the presence of organic chelants. These results confirm that decisions on lichen removal from stone surfaces should consider species-specific behaviour. Moreover, the innovative approach of measuring stone hardness variation in association with the analysis of biomineralization processes contributes to unveil the extension of the sphere of lichen interaction within the stone substrate beyond the limit of the hyphal penetration.

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Surface hardness as a proxy for weathering behaviour of limestone heritage: a case study on dated headstones on the Isle of Portland, UK

Cited by 37 publications

References 80 publications

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

A laboratory study of Equotip surface hardness measurements on a range of sandstones: What influences the values and what do they mean?

Lichen impact on sandstone hardness is species‐specific

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