CONCRETE IN HOT ENVIRONMENTS - CHAPTER 3

Mineral Admixtures and Blended Cements - Phụ gia, theo định nghĩa, một loại vật liệu khác so với nước, cốt liệu, xi măng thủy lực và tăng cường chất xơ được sử dụng như một thành phần của bê tông hoặc vữa và được thêm vào hàng loạt ngay lập tức trước hoặc trong quá trình trộn (ASTM C125). Định nghĩa một đáp ứng một loạt các vật liệu, nhưng một cuộc thảo luận toàn diện về tất cả các loại tham gia không phải là cố gắng ở đây. Theo đó, các bài trình bày sau đây được. | Chapter 3 Mineral Admixtures and Blended Cements . MINERAL ADMIXTURES Admixtures are by definition a material other than water aggregates hydraulic cement and fibre reinforcement used as an ingredient of concrete or mortar and added to the batch immediately before or during mixing ASTM C125 . Such a definition satisfies a wide range of materials but a comprehensive discussion of all types involved is not attempted here. Accordingly the following presentation is limited to the so-called mineral admixtures whereas another group of admixtures known as chemical admixtures is discussed in section . The preceding reference to mineral admixtures is not always accepted and the term additions rather than admixtures has been suggested . Moreover this term of mineral additions was defined to include materials which are blended or interground with Portland cement in quantities exceeding 5 by weight of the cement and not only those which are added directly to the concrete before or during mixing. On the other hand the term addition was defined as a material that is interground or blended in limited amounts into hydraulic cement as a processing addition to aid manufacturing and handling of the cement or as a functional addition to modify the use properties of the finished product ASTM C219 . That is the latter is quite a different definition which covers a different type of materials. Hence in order to avoid possible misunderstanding the term mineral admixtures as defined by ASTM C12588 is used hereafter. Copyright 1993 E FN Spon Generally mineral admixtures are finely divided solids which are added to the concrete mix in comparatively large amounts . exceeding 15 by weight of the cement mainly in order to improve the workability of the fresh concrete and its durability and sometimes also its strength in the hardened state. It will be seen later section that these materials are also used as partial replacement of Portland cement in the production of blended .

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