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A concrete mixer (also commonly called a cement mixer) is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components. For smaller volume works portable concrete mixers are often used so that the concrete can be made at the construction site, giving the workers ample time to use the concrete before it hardens. An alternative to a machine is mixing concrete by hand. This is usually done in a wheelbarrow; however, several companies have recently begun to sell modified tarps for this purpose. The concrete mixer was invented by Columbus industrialist Gebhardt Jaeger. ==Industrial mixers== Today's market increasingly requires consistent homogeneity and short mixing times for the industrial production of ready-mix concrete, and more so for precast/prestressed concrete. This has resulted in refinement of mixing technologies for concrete production. Different styles of stationary mixers have been developed, each with its own inherent strengths targeting different parts of the concrete production market. The most common mixers used today fall into 3 categories: *Twin-shaft mixers, known for their high intensity mixing, and short mixing times. These mixers are typically used for high strength concrete, RCC and SCC, typically in batches of . *Vertical axis mixers, most commonly used for precast and prestressed concrete. This style of mixer cleans well between batches, and is favoured for coloured concrete, smaller batches (typically ), and multiple discharge points. Within this category, the Pan mixers are losing popularity to the more efficient Planetary (or counter-current) mixers as the additional mixing action helps in production of more critical concrete mixes (colour consistency, SCC, etc.). *Drum mixers (reversing drum mixer and tilting drum mixers), used where large volumes (batch sizes of ) are being produced. This type of mixer dominates the ready-mixed market as it is capable of high production speeds, ideal for slump concrete, and where overall cost of production is important. Drum mixers have the lowest maintenance and operating cost of the three styles of mixers. All the mixer styles have their own inherent strengths and weaknesses, and all three styles of mixers are used throughout the world to varying degrees of popularity. 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「concrete mixer」の詳細全文を読む スポンサード リンク
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