Editing Clay (section)

=== Construction ===
[[File:WMEE-exp2019-(113).jpg|thumb|left|A clay building in [[South Estonia]]]]
Clay as the defining ingredient of [[loam]] is one of the oldest [[building material]]s on [[Earth]], among other ancient, naturally occurring geologic materials such as stone and organic materials like wood.{{sfn|Grim|2016}} {{cn span|date=December 2020|Between one-half and two-thirds of the world's population, in both traditional societies as well as developed countries, still live or work in buildings made with clay, often baked into brick, as an essential part of their load-bearing structure.}} Also a primary ingredient in many [[natural building]] techniques, clay is used to create [[adobe]], [[cob (material)|cob]], [[cordwood]], and structures and building elements such as [[wattle and daub]], clay plaster, clay render case, clay floors and clay [[paints]] and [[ceramic building material]]. Clay was used as a [[mortar (masonry)|mortar]] in brick [[chimneys]] and stone walls where protected from water.

Clay, relatively [[permeability (fluid)|impermeable]] to water, is also used where [[Puddling (civil engineering)|natural seals]] are needed, such as in pond linings, the cores of [[dam]]s, or as a barrier in [[landfill]]s against toxic seepage (lining the landfill, preferably in combination with [[geotextile]]s).{{sfn|Koçkar|Akgün|Aktürk|2005}} Studies in the early 21st century have investigated clay's [[sorption|absorption]] capacities in various applications, such as the removal of [[heavy metals]] from waste water and air purification.{{sfn|García-Sanchez|Alvarez-Ayuso|Rodriguez-Martin|2002}}{{sfn|Churchman|Gates|Theng|Yuan|2006}}