Khác biệt giữa các bản “Vữa”

chép từ wikipedia
(chép từ wikipedia)
*Theo khối lượng thể tích: gồm vữa nặng [[khối lượng riêng]] ρ<sub>V</sub> > 1500 kg/m<sup>3</sup>; vữa nhẹ ρ<sub>V</sub> < 1500 kg/m<sup>3</sup>
*Theo công dụng: gồm vữa xây, vữa trát, vữa lát, ốp, vữa dùng để trang trí hoặc những loại đặc biệt như vữa chống thấm, vữa chịu nhiệt độ cao, vữa chịu độ mặn...
==Lịch sử==
{{đang dịch}}
The first mortars were made of mud and [[clay]]. Because of a lack of stone and an abundance of clay, [[Babylonia]]n constructions were of baked brick, using lime or [[Pitch (resin)|pitch]] for mortar. According to [[Roman Ghirshman]], the first evidence of humans using a form of mortar was at the [[ziggurat]] of [[Sialk]] in Iran, built of sun-dried bricks in 2900 BC.<ref>{{cite web|url= |title=No Operation | |date= |accessdate=2012-11-03}}</ref> The [[Chogha Zanbil]] Temple in Iran was built in about 1250 BC with kiln-fired bricks and a strong mortar of [[bitumen]].
In early [[Egyptian pyramids]] constructed about 2600–2500 BC, the limestone blocks were bound by mortar of mud and clay, or clay and sand.<ref>{{cite web|url= |title=Egypt: Egypt's Ancient, Small, Southern, Step Pyramids | |date=2011-06-21 |accessdate=2012-11-03}}</ref> In later Egyptian pyramids, the mortar was made of either [[gypsum]] or lime.<ref name="">{{cite web|url= |title=HCIA - 2004 | |date= |accessdate=2012-11-03}}</ref> Gypsum mortar was essentially a mixture of [[plaster]] and [[sand]] and was quite soft.
In the [[Indian subcontinent]], multiple cement types have been observed in the sites of the [[Indus Valley Civilization]], such as the [[Mohenjo-daro]] city-settlement that dates to earlier than 2600 BC. Gypsum cement that was "''light grey and contained sand, clay, traces of calcium carbonate, and a high percentage of lime''" was used in the construction of wells, drains and on the exteriors of "''important looking buildings''." Bitumen mortar was also used at a lower-frequency, including in the [[Great Bath, Mohenjo-daro|Great Bath]] at Mohenjo-daro.<ref name="ref12ciceh">{{Citation | title=History of science and technology in India, Volume 1 | author=O. P. Jaggi | publisher=Atma Ram, 1969 | isbn= | url= | quote=''... In some of the important-looking buildings, gypsum cement of a light gray colour was used on the outside to prevent the mud mortar from crumbling down. In a very well constructed drain of the Intermediate period, the mortar which was used contains a high percentage of lime instead of gypsum. Bitumen was found to have been used only at one place in Mohenjo-daro. This was in the construction of the great bath ...''}}</ref><ref name="ref60hozoj">{{Citation | title=History of Indian science, technology, and culture | author=Abdur Rahman | publisher=Oxford University Press, 1999 | isbn=978-0-19-564652-8 | url= | quote=''... Gypsum cement was found to have been used in the construction of a well in Mohenjo-daro. The cement was light grey and contained sand, clay, traces of calcium carbonate, and a high percentage of lime ...''}}</ref>
Historically, building with [[concrete]] and mortar next appeared in [[Greece]]. The excavation of the underground aqueduct of Megara revealed that a reservoir was coated with a [[pozzolan]]ic mortar 12&nbsp;mm thick. This aqueduct dates back to c. 500 BC.<ref>[]</ref> Pozzolanic mortar is a lime based mortar, but is made with an additive of volcanic ash that allows it to be hardened underwater; thus it is known as hydraulic cement. The Greeks obtained the volcanic ash from the Greek islands Thira and Nisiros, or from the then Greek colony of Dicaearchia ([[Pozzuoli]]) near Naples, Italy. The Romans later improved the use and methods of making what became known as pozzolanic mortar and cement.<ref name=""/> Even later, the Romans used a mortar without [[pozzolan]]a using crushed [[terra cotta]], introducing [[aluminum oxide]] and [[silicon dioxide]] into the mix. This mortar was not as strong as pozzolanic mortar, but, because it was denser, it better resisted penetration by water.<ref>{{cite web|url= |title=American Scientist Online | |date= |accessdate=2012-11-03}}</ref>
Hydraulic mortar was not available in ancient China, possibly due to a lack of volcanic ash. Around AD 500, sticky rice soup was mixed with [[slaked lime]] to make an inorganic−organic composite mortar that had more strength and water resistance than lime mortar.<ref>{{cite web | title = "Revealing the Ancient Chinese Secret of Sticky Rice Mortar"[[Science Daily]]| url= | accessdate = 23 June 2010 }}</ref><ref>[ Fuwei Yang, Bingjian Zhang, and Qinglin Ma, ‘’ Study of Sticky Rice−Lime Mortar Technology for the Restoration of Historical Masonry Construction’’, Acc. Chem. Res., 2010, 43 (6), pp 936–944]</ref>
It is not understood how the art of making hydraulic mortar and cement, which was perfected and in such widespread use by both the Greeks and Romans, was then lost for almost two millennia. During the [[Middle Ages]] when the Gothic cathedrals were being built, the only active ingredient in the mortar was lime. Since cured [[lime mortar]] can be degraded by contact with water, many structures suffered from wind blown rain over the centuries.
==Tham khảo==
{{tham khảo}}
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