The weathering of sandstone, with particular reference to buildings in the West Midlands, UK
AbstractThe West Midlands contains a number of historic buildings constructed from local New Red Sandstones, which exhibit evidence of severe weathering. To identify and explain the mechanisms and weathering forms responsible for the deterioration of these buildings, and the influence of the environmental conditions in the West Midlands, selected experiments have been conducted. A microcatchment experiment highlighted that weathering mechanisms, associated with the deposition of atmospheric particles, hydrolysis of silicates and the formation of salts, operate on this sandstone. An exposure trial examined the influence of different environmental conditions upon these weathering mechanisms. No statistically significant differences were found between samples exposed in urban and rural locations. However, sheltering the samples from precipitation increased the accumulation of salts and atmospheric particles, but reduced dissolution and hydrolysis. Chemical and microscopic analysis of stone samples affected by different weathering forms, showed that differences in salt concentrations exist between weathering forms. To asses the importance of climatically induced cycles, a data logger controlled monitoring system recorded stone temperature and moisture conditions at Lichfield Cathedral. Thermal and moisture cycles, calculated for each of the four cardinal points, showed that aspect exerts a significant influence upon the occurrence and severity of these cycles. A quantitative survey of thirty sandstone buildings in the West Midlands, recorded the occurrence of different weathering forms, which were found to be influenced by environmental conditions. Weathering forms, associated with the deposition of atmospheric particles, affected up to four times more stone in urban areas than in rural areas, while weathering forms associated with autotrophic colonisation typically affected twice as much stone in rural areas than in urban areas. This pattern was largely attributed to the distribution of coal burning over the last 150 years. Aspect influenced the occurrence of weathering forms and it was shown that certain weathering forms, such as black flaking, occurred where thermal and moisture cycles were active, whilst others, such as granular disintegration, occurred under relatively stable temperature and moisture conditions. In general, weathering forms were shown to be polygenetic, with chemical and/or biological mechanisms operating initially, followed by physical mechanisms, causing the loss of stone. A model indicating the importance of different weathering mechanisms in the formation of specific weathering forms and their changing importance with time was formulated.
PublisherUniversity of Wolverhampton
TypeThesis or dissertation
DescriptionA thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy
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