Comparative investigation of the spatial distribution of past weathering impacts on sandstone masonry

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Abstract

Inspection of the deterioration of both natural outcrops and historical built stone facades reveals that patterns of disruption are not uniform, indicating the influence of material and environmental properties. Sandstones have a spatial variability in weathering response. For this reason, geostatistical techniques have been applied to studies of sandstone properties, mineralogical and structural, that influence susceptibility to decay. For this study, a comparative analysis of permeability data acquired from a ‘quarry fresh’ stone and a weathered sample is undertaken.

The depositional processes that resulted in the formation of sandstone also create structures of spatial variation such as laminations or larger bedding planes within the material. Using geostatistical techniques, the permeability variance observed within ‘quarry fresh’ blocks of sandstone indicates the subsampling of larger geological structures when cut from the quarry face. Once blocks have been emplaced within a building they will be subjected to the increased stress of the urban environment. These conditions result in exacerbated weathering through processes such as salt and chemical weathering. Weathering can alter material properties such as permeability with the creation of a secondary permeability produced by the opening pores and alteration of pore connectivity. Through the application of geostatistics in the analysis of permeability data observed from the weathered block, variography reveals the presence of smaller scale structures. This suggests that alteration of the sandstone’s permeability has led to the creation of new weathering structures within the stone, overwriting the initial sedimentary structures.
These weathering related structures will affect both the magnitude and spatial distribution of permeability within the weathered block. The interconnected pathways of permeability, created by past weathering, facilitate the migration of moisture and salts in solution through the substrate. This work has demonstrated that through a geostatistical approach with the application of co-kriging, these potential moisture pathways can be identified and visualised.
Original languageEnglish
Pages (from-to)25-35
Number of pages11
JournalGeomorphology
Volume324
Early online date28 Sep 2018
DOIs
Publication statusPublished - 01 Jan 2019

Keywords

  • Sandstone
  • Variograms
  • Geostatistics
  • Weathering Legacies

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