Admixtures classification

Although the variety of admixtures that are commercially available are marketed under a multitude of benefit-orientated classifications, namely waterproofers, densifiers, workability aids, etc., it is possible to categorize the basic chemicals used as shown in Table 1.1. 

Air-entraining admixtures Air content (%) Relative classification of freeze-thaw resistance ... 

Few comprehensive classification schemes for CCP exist. The American Society for Testing and Materials (ASTM 1994) classifies two catgories of fly ash (Class F and Class C) based upon chemical and physical properties of the fly ash (the total amount of Si + A1 + Fe, sulphate, loss on ignition). This classification system was developed for the use of fly ash as an admixture in concrete. More recently, new classification schemes have been developed that place emphasis on textural descriptions, the form of carbon (or char ), and the surface properties of fly ash (Hower Mastalerz 2001). These new classification schemes for fly ash may be the result of growing concern over mercury emissions from coal-fired boilers. Studies have shown that mercury adsorption onto the surface of fly ash particles is a function of both the total carbon content and the gas temperature at the point of fly ash collection (Hower et al. 2000). 

A common method to enhance the humoral response to weak immunogens is the admixture of the immunogens with so-called adjuvants. These adjuvants are immunopotentiators which activate one or more sectors of the immune system resulting in an enhanced immune response. A rigid classification of adjuvants or a unifying concept of the mechanism of their action is, therefore, impossible (Dresser,... 

The scope to alter both the efficiency and safety of application through control of the fate of applied material has been explored in a classification of application equipment by hazard (Parkin et al., 1994). Application techniques as well as equipment are required to be taken into account for such a classification, which covers all four possible distinct styles of application i.e. direct, liquid, solid and space. The direct style of application, which is typified by the need to bring treated items into intimate contact with pesticide, is exemplified by admixture processes, e.g. seed treatments. Direct applications take place under highly controllable conditions and often within relatively confined environments, which can potentially mitigate the exposure risks from applied material (presented either in... 

Figure 5.13 Functional classification of solid and liquid admixtures (after Hewlett and Young, 1983).

The proposed classification does not cover all kinds of composite materials because only three variables are used. Therefore, several kinds of materials obtained with various types of admixtures and by using different technologies may be imagined only in a multi-dimensional space. 

As already stated, the CaO-bearing component is usually a limestone. Limestones which already contain some natural admixture of clay are to be preferred, as already noted above. The following approximate classification is applicable ... 

The values of the mixing coefficients or the amount of an admixture of metal character to the lowest states cannot be calculated as yet, but it is possible to develop a classification based on experimental results, allowing us to signify the importance of this admixture with respect to a series of physical properties. This can be achieved by a comparison with the uncoordinated bpy, on the one hand, and with [Ru(bpy)3] and [Os(bpy)3], on the other. Such results are summarized in Table 12, where the compounds are arranged according to increasing importance of metal character for the lowest excited and emitting states. 

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