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The durability of Tasmanian building sandstones

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Sharples, C (1990) The durability of Tasmanian building sandstones. Research Master thesis, University of Tasmania.

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Abstract

Tasmanian building sandstones have been almost entlrely quarried from fluvial sandstones
of the Early Triassic Quartz Sandstone Sequence and the Permian Lower Freshwater
Sequence. These continue to be the only horizons considered prospective for new sources of
high quality building sandstone.
Technical data on all significant Tasmanian building sandstone sources is presented.
There are three methods of assessing and predicting sandstone quality and durability in the
built environment:
1 ) Inferring predicted stone behaviour from measurement of sandstone properties.
2 ) Accelerated decay tests.
3 ) Observed performance in existing buildings.
Each method is subject to limitations. Optimum assessments are made by interpreting a
combination of data from all three approaches, in the light of an understanding of the nature
of sandstone properties and of the processes of sandstone decay.
Investigation of the geological processes controlling the genesis of sandstone properties has
led to the development of models to facilitate exploration for high quality building
sandstones:
Most jointing in Parmeener Supergroup sandstone is related to Mid-Mesozoic and Early
Tertiary faulting. The areas most prospective for widely-jointed sandstones are predicted
on the basis of known regional variations in fault densities.
The bulk colour of sandstone is related to the content of iron-rich minerals in the sandstone,
particularly vermiculite, smectite and chlorite, which oxidise to yield brown ferruginous
colouring. Liesegang rings form in proximity to iron-rich basic igneous rocks, probably
through weathering-related groundwater processes.
For most building purposes, thick and massively-bedded sandstone is the ideal. There is no
way of predicting the occurrence of such beds on a regional or local scale, except insofar as
they are more prevalent in the stratigraphlcally lower parts of the Triassic Quartz
Sandstone Sequence as a whole.
Sandstone strength and porosity are functions of mineralogy and intergranular texture. The
geological controls on these properties are discussed. The occurrence of superficial
pachydermal fractures on natural outcrops is considered to be an indicator of sandstones
having weak intergranular textures resulting in a high degree of dimensional instability.
Smectite swelling clay is detrimental to sandstone durability. The proportion of smectite in
sandstone varies markedly within individual outcrop areas, but on a larger scale there
appear to be regional and possibly stratigraphic patterns in smectite occurrence. The
smectite (together with vermiculite) is considered to have formed by alteration of volcanic
dust deposited from ash clouds produced by contemporaneous volcanic sources to the
southeast of the Tasmania Basin.
Weathering of natural outcrops alters important sandstone properties, most importantly
through near-surface kaolinisation. An exploration program for high quality building
sandstones is proposed which takes account of this limitation, and of the exploration models
developed in this work.
The major contribution of this thesis is that an understanding has been achieved of the
avenues of research which are necessary to further the development of models explaining
the genesis of important quality and durability-related sandstone properties. These are
listed.

Item Type: Thesis (Research Master)
Keywords: Sandstone, Sandstone
Copyright Holders: The Author
Copyright Information:

Copyright 1990 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Sc.)--University of Tasmania, 1990. Includes bibliographical references (p. 237-247)

Date Deposited: 03 Feb 2015 03:21
Last Modified: 19 Jul 2016 23:38
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