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

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. Highlights (3-5, 85 Characters Each) Structures can be observed within the variance of permeability using geostatistics. Observed variogram structures indicate the block is sampling sedimentary features. Alteration of permeability through weathering overwrites sedimentary structures. Co-Kriging is used to model conduits for moisture movement through a weathered block.

Insight into a Bentonite-Based Hydrogel for the Conservation of Sandstone-Based Cultural Heritage: In Situ Formation, Reinforcement Mechanism, and High-Durability Evaluation

“…Major ancient sandstone artifacts are generally outdoors and subject to environmental factors. , In particular, acid rain can be lethal. , We evaluated the acid resistance of B-H–sandstone (Figure a). Compared with the complete degradation unprotected sandstone can undergo, the acid resistance of B-H–sandstone was greatly improved (88.83% residual mass).…”

“…Sandstone-based cultural relics are an important component of historical and cultural heritage. They are widely distributed around the worldin ancient buildings, architectural decoration, carved statues, and historical monuments. − Unfortunately, long-term environmental factors (temperature, humidity, ultraviolet light, acid rain, wind erosion, corrosion due to salt crystals) lead to unstoppable deterioration. − To conserve these relics, we must protect or delay the erosion and destruction due to these factors. ,,, …”