Geoscience Reference
In-Depth Information
CONSERVATION
To aid the process of locating aggregate sources, lists
of suppliers and test data for some currently available
building aggregates suitable for use in restoration have
been published. These include the English Heritage
Directory of Building Sands and Aggregates (2000) that
lists approximately 60% of the sources in England.
Information regarding Scottish aggregate sources can be
found in Scottish Aggregates for Building Conservation
(Leslie & Gibbons, 1999). Addresses of other potential
sources in the United Kingdom can be found in the
Directory of Mines and Quarries (British Geological
Survey, 2002) or the Directory of Quarries and Quarry
Equipment (Quarry Management, 2007/2008).
When conserving and restoring historic buildings it is
often necessary to find a match for aggregate used
originally in historic mortars, plasters, and renders. Data
from petrographic examination can be used to pinpoint
the original source by comparing the petrographic data
with geological and historical information. The original
source may no longer be operational and it may be
impossible/inappropriate to commence new extractive
works due to planning restrictions. In these circumstances
a good match may be found by comparison with that of
commercially available material. This is a visual process,
supplemented by petrographic examination findings, with
the main aggregate characteristics considered being
colour (often controlled by mineralogy), grading, and
particle shape.
