1.3 Research on Sandstone Decay in Scotland

369 Pages·2012·22.42 MB·English

Duthie, Laura Jane (2012) The impact of climate change on blond sandstone
decay in Glasgow. PhD thesis.

http://theses.gla.ac.uk/3300/

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The Impact of Climate Change on Blond
Sandstone decay in Glasgow

Laura Jane Duthie
BSc. (Hons) University of Glasgow

Submitted in fulfilment of the requirements for the
Degree of Doctor of Philosophy

School of Geographical and Earth Science
College of Science and Engineering
University of Glasgow

June 2011
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Abstract

Glasgow contains many buildings made from local ‘blond’ sandstones that are showing
the legacy of 150 years of urban weathering and this decay may accelerate as climate
changes in the future. Most of the blond sandstones are Carboniferous in age and
comprise of micaceous quartz arenites with varying amounts of diagenetic minerals
including ankerite and kaolinite. Chemical decay can be visually identified in the
carbonate minerals, but the combination of quantitative X-ray microanalysis (chemistry of
mineral) and Raman spectroscopy (structure of mineral) also allows chemical decay to be
observed in both kaolinite and muscovite. The Raman spectroscopy shows a variation in
the muscovite minerals between the outermost surface and internal region (20 mm
depth), demonstrating that structural decay is occurring within the micas and reduces
them to an “ionic slurry state” in a relatively short time frame. The impact of microbial
colonisation on the stones was also investigated. Using osmium stained polished blocks,
complimented by scanning electron microscope imaging, microorganisms were found to
be living cryptoendolithically in a few samples but at very shallow depths (<2 mm). Light
penetration results revealed that a thin weathered crust (<1 mm) on the surface of
sandstone will restrict the transmission of light into the rock, thereby preventing the
colonisation of photosynthetic microbes. As a result, most microbial communities are
restricted to the stone surface but only where they will not be subjected to photo-
oxidative damage, which frequently occurs during summer months. Consequently, the
most extensive microbial colonisation is restricted to the sandstone’s surface and during
the winter. Using novel internal microclimate monitoring technologies it was found that
stone temperature and humidity is decoupled from ambient conditions. During the
summer the stone interior is considerably hotter than air temperature, whilst relative
humidity is generally comparable to external conditions, whereas in the winter interior
temperatures are closely related to ambient conditions and relative humidity is generally
much higher. To understand how sandstone buildings will react to a change in climate,
current conditions were extrapolated to 2080 using predictive models for the Glasgow
region and the impact of these conditions was investigated by accelerated weathering
experiments in a climate chamber. Results reveal rapid granular disintegration, the rates
of which are independent of grain size. Overall, this study concludes that rates of
chemical decay will increase as the climate warms and becomes wetter overall, primarily
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through dissolution, decay and loss of diagenetic minerals, and the extent of microbial
activity will change, but these effects will be strongly dependent on local
microenvironment. Implications of these findings are that more work on conservation
and preservation techniques will be very important to protect the stone-built heritage of
Scotland.
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Table of contents

Abstract…………………………………………………………………………………………………………………………...ii
List of Figures…………………………………………………………………………………………………………………..xi
List of Tables…………………………………………………………………………………………………………………..xiii
List of Equations……………………………………………………………………………………………………………. xiv
Acknowledgements…………………………………………………………………………………………………………xv
Declarations………………………………………………………………………………………………………………….xvii
Abbreviations………………………………………………………………………………………………………………..xvii
1 Introduction ........................................................................................................ 22
1.1 Definition of Weathering ..................................................................................... 22
1.2 Literature Review of Weathering on Sedimentary Rock ..................................... 23
1.2.1 Weathering due to Pollution ............................................................................ 24
1.2.2 Summary of Pollution Weathering .................................................................. 26
1.2.3 Weathering due to Salts ................................................................................... 27
1.2.3.1 Summary of Salt Weathering ................................................................... 31
1.2.4 Weathering due to Freeze-thaw ...................................................................... 32
1.2.4.1 Summary of Freeze-thaw ......................................................................... 33
1.2.5 Weathering due to Chemical Decay ................................................................. 33
1.2.5.1 Summary of Chemical Decay.................................................................... 35
1.2.6 Weathering due to Clays .................................................................................. 35
1.2.6.1 Summary of Clay Weathering .................................................................. 38
1.2.7 Weathering due to Thermal Heating ............................................................... 38
1.2.7.1 Summary of Thermal Weathering ............................................................ 40
1.2.8 Weathering due to Biological Activity .............................................................. 41
1.2.8.1 Review of Biological Activity .................................................................... 47
1.3 Research on Sandstone Decay in Scotland .......................................................... 47
1.3.1 Decay of Sandstone within Scotland ................................................................ 48
1.3.1.1 Microbial Decay on Sandstones within Scotland ..................................... 49
1.4 Geology of the Glasgow Region ........................................................................... 50
1.4.1 Mineralogy of Glasgow Sandstones ................................................................. 53
1.4.1.1 Blond Sandstone Descriptions ................................................................. 54
1.5 Glasgow’s Past Climate ........................................................................................ 56
1.5.1 Temperature .................................................................................................... 57
1.5.2 Rainfall .............................................................................................................. 59
1.5.3 Sunshine ........................................................................................................... 61
1.5.4 Discussion ......................................................................................................... 63
1.6 Detailed Aims of the Present Study ..................................................................... 64
2 Methods and Materials ....................................................................................... 67
2.1 Methods ............................................................................................................... 67
2.1.1 SEM Techniques ............................................................................................... 67
2.1.1.1 SEM Imaging ............................................................................................. 69
2.1.1.2 Point Counting and Grain Size .................................................................. 71
2.1.1.3 EDS Maps .................................................................................................. 72
2.1.1.4 Cathodoluminescence Imaging ................................................................ 74
2.1.1.5 X-ray Microanalysis Under High and Low Vacuum .................................. 74
2.1.1.6 Quantitative EDX ...................................................................................... 75
2.1.2 Permeability ..................................................................................................... 77
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2.1.3 Raman Spectroscopy ........................................................................................ 78
2.1.4 Protein and Chlorophyll-a assay ...................................................................... 80
2.1.5 Osmium Stained Polished Blocks ..................................................................... 82
2.1.6 Optical Light Transmission ............................................................................... 83
2.1.7 Chamber Experiment ....................................................................................... 84
2.1.7.1 Prediction of Future Climate Conditions .................................................. 90
2.1.8 Observatory Wall Microclimates ..................................................................... 92
2.1.9 Thermal Imaging .............................................................................................. 94
2.1.10 Calibration of Decagon Dataloggers ............................................................ 95
2.1.11 Internal Moisture Experiments .................................................................... 97
2.1.12 Mitigation Experiments ................................................................................ 98
2.2 Background to all Sandstone Samples ................................................................. 99
2.2.1 Dalry Samples .................................................................................................100
2.2.2 RGU Samples ..................................................................................................103
2.2.3 University Samples .........................................................................................105
2.2.4 St Vincent Street Samples (SVS) .....................................................................106
2.2.5 Replacement Samples ....................................................................................108
2.2.5.1 Bearl .......................................................................................................108
2.2.5.2 Blaxter ....................................................................................................108
2.2.5.3 Clashach .................................................................................................109
2.2.5.4 Cullalo .....................................................................................................110
2.2.5.5 Dunhouse Buff ........................................................................................111
2.2.5.6 Scotch Buff .............................................................................................111
3 Description of External Crust and the Structure of Weathering Layers ................ 113
3.1 Dalry School ........................................................................................................114
3.1.1 Light Microscope Observations......................................................................114
3.1.2 SEM Imaging of Outer Surface .......................................................................116
3.2 RGU Samples ......................................................................................................119
3.2.1 Light Microscope Observations......................................................................119
3.3 University Samples .............................................................................................121
3.3.1 Light Microscope Observation .......................................................................121
3.3.2 SEM Imaging of the Outer Surface .................................................................123
3.3.3 Summary ........................................................................................................127
3.4 St Vincent Street Samples ..................................................................................127
3.4.1 Light Microscope Observations......................................................................127
3.4.2 SEM Imaging of the Outer Stone Surface ......................................................128
3.4.3 Summary ........................................................................................................130
3.4.4 Discussion .......................................................................................................130
4 Mineralogical and Chemical Results ................................................................... 134
4.1 Dalry School ........................................................................................................135
4.1.1 Sandstone Mineralogy, Porosity and Grain Size ............................................135
4.1.2 Mineralogical Impact of Decay on the Minerals ............................................136
4.1.3 Physical Weathering Evidence .......................................................................138
4.1.4 X-ray Mapping ................................................................................................140
4.1.5 Summary ........................................................................................................142
4.2 RGU Samples ......................................................................................................147
4.2.1 Sandstone Mineralogy, Porosity and Grain Size ............................................147
4.2.2 Mineralogical Impact of Weathering on the Minerals...................................148
4.2.3 Physical Weathering Evidence .......................................................................150
4.2.4 Summary ........................................................................................................151
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4.3 University Samples .............................................................................................155
4.3.1 Sandstone Mineralogy, Porosity and Grain Size ............................................155
4.3.2 Mineralogical Impact of Weathering on the Minerals...................................158
4.3.3 Physical Weathering Evidence .......................................................................159
4.3.4 X-ray Mapping ................................................................................................160
4.3.5 Summary ........................................................................................................161
4.4 St Vincent Street Samples ..................................................................................166
4.4.1 Sandstone Mineralogy, Porosity and Grain Size ............................................166
4.4.2 Mineralogical Impact of Decay on the Minerals ............................................168
4.4.3 Physical Weathering Evidence .......................................................................170
4.4.4 Summary ........................................................................................................172
4.4.5 Discussion of Overall Decay Patterns .............................................................175
4.5 Permeability .......................................................................................................179
4.6 Chemical and Structural Damage to Individual Minerals ..................................180
4.6.1 Kaolinite .........................................................................................................181
4.6.1.1 EDX Microanalysis of Kaolinite ...............................................................181
4.6.1.2 Raman Spectroscopy of Kaolinite ..........................................................185
4.6.1.3 Summary ................................................................................................187
4.6.2 Mica ................................................................................................................187
4.6.2.1 EDX Microanalysis of Muscovite ............................................................188
4.6.2.2 Raman Spectroscopy of Muscovite ........................................................190
4.6.2.3 Depth Profile Using Muscovite ..............................................................193
4.6.2.4 Summary ................................................................................................195
4.6.3 Carbonate cement..........................................................................................196
4.6.3.1 EDX Microanalysis of Carbonate ............................................................196
4.6.3.2 Raman Spectroscopy of Carbonate ........................................................198
4.6.3.3 Summary ................................................................................................200
4.6.4 Oxides .............................................................................................................200
4.6.4.1 Raman Spectroscopy of Oxides ..............................................................200
4.6.4.2 Raman and EDX results discussion .........................................................201
4.6.5 Chemical Weathering Discussion ...................................................................202
5 Microbial Results ............................................................................................... 205
5.1 Dalry School ........................................................................................................205
5.1.1 Protein and Chlorophyll-a Assays ..................................................................206
5.1.2 SEM Imaging of the Outer Surface of the Stones ..........................................208
5.1.3 Osmium Stained Cross-Sections.....................................................................211
5.1.4 Dalry Summary ...............................................................................................213
5.2 RGU Samples ......................................................................................................214
5.2.1 Protein and Chlorophyll-a Assays ..................................................................214
5.2.2 SEM Imaging of the Outer Surfaces of the Stones .........................................215
5.2.3 Osmium Stained Cross-Sections.....................................................................216
5.2.4 Summary ........................................................................................................218
5.3 University Samples .............................................................................................219
5.3.1 Chlorophyll-a Assay ........................................................................................219
5.3.2 SEM Imaging of the Outer Surface of the Stones ..........................................220
5.3.3 Osmium Stained Cross-Sections.....................................................................221
5.3.4 University Summary .......................................................................................222
5.4 St Vincent St Church Samples ............................................................................222
5.4.1 Chlorophyll-a Assay ........................................................................................223
5.4.2 SEM Imaging of the Outer Surface of the Stones ..........................................224
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5.4.3 Osmium Stained Cross-Sections.....................................................................225
5.4.4 Summary of SVS Samples ...............................................................................225
5.5 Discussion ...........................................................................................................226
5.6 Light Penetration into Sandstone ......................................................................230
5.6.1 Discussion of OLT Experiments ......................................................................240
5.7 Discussion and Conclusions of Microbial Results ..............................................244
6 Internal Monitoring and Accelerated Weathering Results .................................. 248
6.1 Climate Change ..................................................................................................249
6.2 Quantifying the Impact of Future Climate on Stone Surfaces ...........................252
6.2.1 Bearl ...............................................................................................................254
6.2.2 Blaxter ............................................................................................................258
6.2.3 Clashach .........................................................................................................261
6.2.4 Cullalo .............................................................................................................265
6.2.5 Dunhouse Buff ................................................................................................269
6.2.6 Scotch Buff .....................................................................................................273
6.2.7 Discussion .......................................................................................................278
6.2.8 Further Chamber Block Experiments .............................................................281
6.3 Internal Monitoring Results: Part 1 ....................................................................282
6.3.1 IButton Observations “micro”: Winter Day (20th Jan 2010) ..........................284
6.3.1.1 Temperature ..........................................................................................284
6.3.1.2 Relative Humidity ...................................................................................285
6.3.2 IButton Observations “micro”: Summer Day (6th July 2009) .........................286
6.3.2.1 Temperature ..........................................................................................286
6.3.2.2 Relative Humidity ...................................................................................287
6.3.3 IButton Observations “macro”: Winter Cycle (January 2010) .......................288
6.3.3.1 Temperature ..........................................................................................288
6.3.3.2 Relative Humidity ...................................................................................292
6.3.4 IButton Observations “macro”: Summer Cycle (July 09) ...............................294
6.3.4.1 Temperature ..........................................................................................294
6.3.4.2 Relative Humidity ...................................................................................298
6.3.5 Discussion .......................................................................................................302
6.3.5.1 Temperature Summary ..........................................................................302
6.3.5.2 Relative Humidity Summary...................................................................305
6.4 Internal Monitoring Results: Part 2 ....................................................................307
6.4.1 Leaf Wetness Sensor Results .........................................................................308
6.4.2 Evaporation ....................................................................................................313
6.4.3 Absorption ......................................................................................................315
6.4.4 Summary ........................................................................................................317
6.5 Internal Monitoring and Accelerated Weathering Summary ............................318
7 Thesis Discussion ............................................................................................... 322
7.1 What weathering processes have occurred historically and are at work presently
on the blond sandstones of Glasgow? ...........................................................................322
7.1.1 Pollution .........................................................................................................322
7.1.2 Salt ..................................................................................................................324
7.1.3 Freeze-thaw ...................................................................................................325
7.1.4 Chemical .........................................................................................................326
7.1.5 Clays ...............................................................................................................327
7.1.6 Biology ............................................................................................................328
7.1.7 Thermal heating .............................................................................................331
7.1.8 Summary ........................................................................................................331
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7.2 How will current decay cycles alter with climate change? ................................333
7.2.1 Pollution .........................................................................................................333
7.2.2 Salt ..................................................................................................................334
7.2.3 Freeze-thaw ...................................................................................................335
7.2.4 Chemical .........................................................................................................336
7.2.5 Clay .................................................................................................................341
7.2.6 Thermal heating .............................................................................................342
7.2.7 Biological ........................................................................................................342
7.2.8 Other effects ..................................................................................................344
7.3 Which buildings are most at risk? In addition, how can we mitigate against these
degradation processes? .................................................................................................346
8 Further Work .................................................................................................... 350
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List of Figures:
Figure 1-1: Schematic diagram illustrating possible decay pathways of sandstone. .......... 31
Figure 1-2: Schematic diagrams of intracrystalline and osmotic swelling. .......................... 37
Figure 1-3: Diagram detailing the various layers formed by microbial communities and the
step like weathering process. .............................................................................................. 42
Figure 1-4: Model of the changing effectiveness of biological weathering. ....................... 43
Figure 1-5: Algal weathering on siderite. ............................................................................. 45
Figure 1-6: Bluck and Porter (1991A) model of fluid flow through a blond sandstone. ..... 48
Figure 1-7: Bluck and Porter (1991A) model of fluid flow through a red sandstone. ......... 49
Figure 1-8: Image of historic quarries within the Glasgow region. ..................................... 51
Figure 1-9: Map of the geology underlying the Glasgow region. ........................................ 52
Figure 1-10: Stratigraphic column. ....................................................................................... 53
Figure 1-11: Images showing the typical appearance for each blond sandstone group. .... 56
Figure 1-12: Location map of weather stations. .................................................................. 57
Figure 1-13: Left) Absolute winter temperature values from 1868 – 1994 with linear trend
line, Right) Offset in temperatures from the absolute mean. ............................................. 58
Figure 1-14: Left) Absolute summer month temperature values from 1868 – 1994 with
linear trend line, Right) Offset in temperatures from the absolute means. ....................... 59
Figure 1-15: Left) Absolute winter month rainfall values from 1866 – 1990 with linear
trend line, Right) Offset in rainfall from the absolute mean. .............................................. 60
Figure 1-16: Left) Absolute summer month rainfall values from 1866 – 1990 with linear
trend line, Right) Offset in rainfall from the absolute mean. .............................................. 61
Figure 1-17: Sketch diagram of the MK2 sunshine recorders.............................................. 62
Figure 1-18: Total number of sunshine hours in each month. ............................................ 63
Figure 2-1: Schematic diagram of where signals are generated within a sample, when
viewed under SEM conditions. ............................................................................................ 70
Figure 2-2: Position of detectors within the FEG-SEM. ....................................................... 70
Figure 2-3: Schematic diagram illustrating point counting procedure. ............................... 72
Figure 2-4: Comparison of optimum acquisition conditions for EDS maps on the FEG-SEM.
.............................................................................................................................................. 73
Figure 2-5: Low and high vacuum comparison within FEG-SEM. ........................................ 75
Figure 2-6: Quantitative EDX comparison of kaolinites. ...................................................... 76
Figure 2-7: Quantitative EDX comparison of muscovites. ................................................... 77
Figure 2-8: Quantitative EDX results from carbonates. ....................................................... 77
Figure 2-9: Diagram of laser pathway through the Raman microscope. ............................. 79
Figure 2-10: Protein calibration graph. ................................................................................ 81
Figure 2-11: Image and sketch of optical light transmission experimental design. ............ 84
Figure 2-12: Plan view of environmental chamber set up. .................................................. 86
Figure 2-13: Internal view of the environmental chamber. ................................................ 86
Figure 2-14: Comparison images of microbes seen and its morphological consistent image
of suggested microbe. .......................................................................................................... 87
Figure 2-15: Sketch graph of cycles experienced by chamber blocks. ................................ 90
Figure 2-16: Data from environmental chamber showing the programmed conditions
against data recorded by the IButton. ................................................................................. 90
Figure 2-17: A replica of the UK maps used in the UKCIP02 report. ................................... 91
Figure 2-18: Test blocks situated at Garscube campus (University of Glasgow). ................ 93
Figure 2-19: IButton dimensions. ......................................................................................... 94
Figure 2-20: Image of leaf wetness sensor with dimensions (actual size)........................... 95