"සිමෙන්ති" හි සංශෝධන අතර වෙනස්කම්

the raw materials and the process used. Most cement kilns today use coal and petroleum coke as primary fuels, and to a lesser extent natural gas and fuel oil. Selected waste and by-products with recoverable calorific value can be used as fuels in a cement kiln, replacing a portion of conventional fossil fuels, like coal, if they meet strict specifications. Selected waste and by-products containing useful minerals such as calcium, silica, alumina, and iron can be used as raw materials in the kiln, replacing raw materials such as clay, [[shale]], and limestone. Because some materials have both useful mineral content and recoverable calorific value, the distinction between alternative fuels and raw materials is not always clear. For example, sewage sludge has a low but significant calorific value, and burns to give ash containing minerals useful in the clinker matrix.<ref>[http://www.wbcsd.org/DocRoot/Vjft3qGjo1v6HREH7jM6/tf2-guidelines.pdf Guidelines for the Selection and Use of Fuels and Raw Materials in the Cement Manufacturing Process], ''[[World Business Council for Sustainable Development]]'', published 2005-06-01.</ref>

 

[[Image:2004cement (hydraulic).PNG|thumb|right|Cement output in 2004]]

{{See also|List of countries by cement production }}

In 2002 the world production of hydraulic cement was 1,800 million metric tons. The top three producers were China with 704, India with 100, and the United States with 91 million metric tons for a combined total of about half the world total by the world's three most populated states.<ref>http://web.archive.org/web/20051221043539/http://www.indexmundi.com/en/commodities/minerals/cement/cement_table23.html</ref>

 

"For the past 18 years, China consistently has produced more cement than any other country in the world. [...] (However,) China's cement export peaked in 1994 with 11 million tons shipped out and has been in steady decline ever since. Only 5.18 million tons were exported out of China in 2002. Offered at $34 a ton, Chinese cement is pricing itself out of the market as Thailand is asking as little as $20 for the same quality."<ref>http://www.atimes.com/atimes/China/FA07Ad02.html ''Asia Times'' January 7, 2004</ref>

 

[[File:Cement Production.JPG|360px]]

 

{{See also|Cement in Africa }}