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Magnesium oxide, more commonly called magnesia, is a versatile mineral that when used as part of a cement mixture and cast into thin cement panels under proper curing procedures and practices can be used in residential and commercial building construction. Some versions are suitable for a wide range of general building uses and for applications that require fire resistance, mold and mildew control, as well as sound control applications and many other benefits. As an environmentally friendly building material, magnesia board has strength and resistance due to very strong bonds between magnesium and oxygen atoms that form the magnesium oxide molecules (chemical symbol MgO). Magnesia boards are used in place of traditional gypsum drywall as wall and ceiling covering material and sheathing. It is also used in a number of other construction applications such as fascias, soffit, shaft-liner and area separation, wall sheathing, and as tile backing (backer board) or as substrates for coatings and insulated systems such as finish systems, EIFS, and some types of stucco. Magnesia cement board for building construction is available is various sizes and thickness. It is not a paperfaced material. It generally comes in a light gray, white or beige color. Numerous versions and value of grades exist including smooth face, rough texture, utility, versatile grades as well as different densities and strengths for different applications and uses. Presently various magnesia cement boards are widely used in Asia as a primary construction material. Some versions have been designated as the ‘official’ construction specified material of the 2008 Summer Olympic Games and some versions are used extensively on the inside and outside of all the walls, fireproofing beams, and as the sub-floor sheathing in one of the world’s tallest buildings, Taipei 101, located in Taipei, Taiwan. Magnesia cement is manufactured in a number of areas around the world, primarily near areas where magnesia based ore (periclase) deposits are mined. Major deposits are found in China, Europe, and Canada.〔(Periclase at Mindat )〕 Magnesia ore deposits in the US are negligible. Estimates put the use of magnesia board products at around 8 million SQF in Asia alone. It is gaining popularity in the US, particularly near coastal regions. ==History== *Magnesia cement uses in masonry construction is ancient. It was used primarily as a mortar component and stabilizer for soil bricks. Magnesia has also been identified in the Great Wall of China and other ancient landmarks. Roman cement is reported to have contained high levels of magnesia. *In the West, Portland cement replaced magnesia for masonry uses in the 20th century when energy was cheap (see energy efficiency) and mold infection was poorly understood. *However, some projects continued to use magnesia. New York City’s Brooklyn Bridge base is made from locally mined cement, a mixture of calcium oxide and magnesia cement commonly called Rosendale Natural Cement, the only natural non-fired cement made in the US. *Magnesia cement boards were approved for construction use in the US around 2003. *Due to its fire resistance and safety ratings, New York and New Jersey were early adopters of magnesia cement board. Florida has adopted magnesia boards for mold/mildew resistance. It is hurricane and impact tested and approved in Miami-Dade County. *Located in Taipei, Taiwan, magnesia board can be found on all 101 stories of Taipei 101, currently the second tallest building in the world. Magnesia sheeting was used on the inside and outside of all the walls, fireproofing beams and as the sub-floor sheathing. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Magnesium oxide wallboard」の詳細全文を読む スポンサード リンク
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