[1,2,3,4]

Weathering is the process by which natural elements of nature (such as wind, water, CO2) act upon a rock or mineral composition. [a] The reaction, based on a mechanical or chemical process, causes the rocks or minerals to disintegrate to a sand or soil. [b] Weathering on a building depends on the exposed material of the building and bonding agents used to hold the material together. [c]

Various forms of weathering include:

Physical Weathering – Physical forces, such as ocean waves or high speed winds, are exerted onto the building and breakaway the stone compounds [figure 1, 3]. The process of this weathering can be slow and steady. In the event of a shift in temperature, a condition such as Freeze Thaw can occur. Water in the stone can freeze resulting in the alternation of the physical condition of the stone. [c]

Chemical Weathering – Chemicals found in rainfall interact with the buildings stone at the molecular level causing the material to dissolve or change its substance composition. Acidic rainfall is based off the acid in rainfall and it’s interaction with calcium based minerals such as limestone. In cities with dense pollution, rainfall is acidic enough to dissolve some of the minerals. Salt Weathering results from the travel (through rain or wind) of salt into the holes of the building’s stone [figure 2]. Crystallization with the salt and stone begins making the structure weak [figure 4] [c]

Although considered to be a failure mechanism, weathering can be used as a design choice with the use of weathering steel. Rust is allowed to develop acting as a protective shield on the steel. Weathering steel is popularly used in sculptures.

Sources

[a] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

[b] The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

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