『Abstract
Historic sandstone structures carry an inheritance, or a ‘memory’,
of past stresses that the stone has undergone since its placement
in a facade（cにはセディーユが付く）. This inheritance,
which conditions present day performance, may be made up of long-term
exposure to a combination of low magnitude background environmental
factors (for example, salt weathering, temperature and moisture
cycling) and, superimposed upon these, less frequent but potentially
high magnitude events or ‘exceptional’ factors (for example, lime
rendering, severe frost events, fire). The impact of complex histories
on the decay pathways of historic sandstone is not clearly understood,
but this paper seeks to improve that understanding through the
use of a laboratory ‘process combination’ study. Blocks of quartz
sandstone (Peakmoor, from NW England) were divided into subsets
that experienced different histories (lime rendering and removal,
fire and freeze-thaw cycles in isolation and combination) that
reflected the event timeline of a real medieval sandstone monument
in NE Ireland, Bonamargy Friary (McCabe et al. 2006b). These subsets
were then subject to salt weathering cycles using a 10％ salt solution
of NaCl and MgSO4 that represents the ‘every-day’
stress environment of, for example, sandstone structures in coastal,
or polluted urban, location. Block response to salt weathering
was monitored by collecting, drying and weighing the debris that
was released as blocks were immersed in the salt solution at the
beginning of each cycle. The results illustrate the complexity
of the stone decay system, showing that seemingly small variations
in stress history can produce divergent response to salt weathering
cycles. Applied to real-world historic sandstone structures, this
concept may help to explain the spatial and temporal variability
of sandstone response to background environmental factors on a
single facade（cにはセディーユが付く）, and encourage
conservators to include the role of stress inheritance when selecting
and implementing conservation strategies.
Keywords: Sandstone; Process combinations; Complexity; Inheritance』
Introduction
Methods
‘Exceptional’ pre-treatments
Lime render pre-treatment
Heating pre-treatment
Freeze-thaw pre-treatment
Low magnitude, background stressing of stone
Salt weathering
Results and discussion
Conclusions
Acknowledgments
References