Cement classification

Presenting the rules of Portland cements classification and derived from them others kind of hydraulic binders, it must be underlined that the basis of this classification are their useful properties. In relation to this that cement is an intermediate product—the raw material for concrete production, these properties will concern the corrverrtiorral rrricro-concrete or the mortar, sometimes paste, and now and again cemerrt itself for example phase composition. Some experts reckon the mortar to some kirrd of concrete, however, it is a subject of controversy. 

The presented important principles of cements classification can be divided into three groups form the point of view of paste influence on concrete properties. They ate the following ... 

Because of the many types of advanced castables on the market today and due to the specialized development of many of these materials for specific uses, it is harder to characterize their strength development. The refractory manufacturer has less leeway in development of most dense conventional castables since they are viewed more or less as a commodity product (every manufacturer makes similar products) in the marketplace, and price dictates formulation constraints. This is sometimes true for low end (superduty, 50% alumina) advanced castable types in the low- and ultralow-cement classifications. However, application and performance criteria can and do call for the development and use of premium castables where the use of expensive formulations and exotic modifiers can modify physical properties and characteristics such as strength in specific temperature ranges that correspond to the anticipated service condition. 

Carbides Cemented Carbide Producers Association 712 Lakewood Center North Cleveland, Ohio 44107 Standards Developed bj Cemented Carbide Producers Association ie, standard shapes, sizes, grades, and designations and defect classification. 

There are at least four different classification systems for cemented carbides (7,12). The U.S. system is based on relative performance the U.K. system is based on properties, and the former USSR system on composition the fourth system, widely used in Europe and supported by the ISO, is based on apphcation and chip form. In this article, the U.S. system and the ISO system are briefly reviewed. 

Table 8. ISO Classification of Cemented Carbide Tools According to Use ...

The original objective of the ISO classification was to issue detailed standards for cemented carbides in terms of microstmcture, composition, and properties for quaUty control and performance rehabiUty. This objective, however, is yet to be realized. Increased emphasis on worldwide implementation of ISO 9000 standards and globalization of manufacturing, may lead the industry-at-large to adopt the ISO classification. 

Other countries have similar types, some classifications, as in Germany, are based on age-strength levels by standard tests (70). A product made in Italy and Prance known as Perrari cement is similar to Type V and is sulfate-resistant. Such cements have high iron oxide and low alumina contents, and harden more slowly. 

Table 1. Classification and Composition of Aqueous Dental Cements...

Certain treatment systems fall in the category of cement-pozzolanic processes and have been in use for some time outside the U.S. In these systems, both cement and lime-siliceous materials are used in combination to give the best and most economical containment for the specific waste being treated In general, the bulk of the comments (under both classifications above) hold for techniques using a combination of treatment materials. 

Before proceeding further it is well to consider the term cement, for its definition can be the source of some confusion. Both the Oxford English Dictionary and Webster give two alternative definitions. One defines a cement as a paste, prepared by mixing a powder with water, that sets to a hard mass. In the other a cement is described as a bonding agent. These two definitions are quite different. The first leads to a classification of cements in terms of the setting process, while the second lays emphasis on a property. In this book the term cement follows the sense of the first of these definitions. 

The classification of Lewis acids and bases relevant to AB cements is shown below. 

According to Yatsimirskii, group (2) and (3) species are equivalent to Pearson s hard acids and bases, and group (4), (5) and (6) species correspond to Pearson s soft acids and bases. This classification is of more value than HSAB theory to our subject. It can be seen that all cementforming anions come from group (3) and cations from groups (3), (4) and (5). Thus, the bonding in cement matrices formed from cation-anion combinations is not purely a but contains some n character. 

Another feature of the metal ions that are typically involved in cementitious bonding in AB cements is that most of them fall into the category of hard in Pearson s Hard and Soft Acids and Bases scheme (Pearson, 1963). The underlying principle of this classification is that bases may be divided into two categories, namely those that are polarizable or soft, and those that are non-polarizable or hard. Lewis acids too may be essentially divided into hard and soft, depending on polarizability. From these classifications emerges the useful generalization that hard acids prefer to associate with hayd bases and soft acids prefer to associate with soft bases (see Section 2.3.7). 

The API has nine classes of well cements [63]. The classification is similar to ASTM C 150, Type I [80]. The well cement classes are summarized in Table 10-4. 

See also Iron entries hydration, 5 477-478 in Portland cement, 5 467 in Portland cement clinker, 5 473t classification of, 11 55-58 crystal chemistry of, 11 59-71 defined, 11 55 energy losses in, 11 64-66 physical properties of, 11 59-71 processing of, 11 71-75 properties of spinel and M-type,... 

Medical devices may be assisted in their function by pharmacological, immunological or metabolic means, but as soon as these means are not any more ancillary with respect to the principal purpose of a product, the product becomes a medicinal product. The claims made for a product, in accordance with its method of action may, in this context, represent an important factor for its classification as MD or medicinal product. Examples of MDs incorporating a medicinal substance with ancillary action include catheters coated with heparin or an antibiotic, bone cements containing antibiotic and blood bags containing anticoagulant. ... 

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