Other cements

The hydration of the ferrite phase (C AF) is of greatest interest in mixtures containing lime and other cement compounds because of the strong tendency to form soHd solutions. When the sulfate in solution is very low, soHd solutions are formed between the cubic C AH and analogous iron hydrate C FHg. In the presence of water and siUca, soHd solutions such as C3 ASH4-C3FSH4 may be formed (33). Table 7 Hsts some of the important phases formed in the hydration of mixtures of pure compounds. 

The tobomorite gei bonds the hydrated iime (CH) to the pozzoiana particies. These two equations are aii you need to know about the chemistry of pozzoiana cement. Those for other cements are oniy siightiy more compiicated. 

The glass polyalkenoate cement uniquely combines translucency with the ability to bond to untreated tooth material and bone. Indeed, the only other cement to possess translucency is the dental silicate cement, while the zinc polycarboxylate cement is the only other adhesive cement. It is also an agent for the sustained release of fluoride. For these reasons the glass polyalkenoate cement has many applications in dentistry as well as being a candidate bone cement. Its translucency makes it a favoured material both for the restoration of front teeth and to cement translucent porcelain teeth and veneers. Its adhesive quality reduces and sometimes eliminates the need for the use of the dental drill. The release of fluoride from this cement protects neighbouring tooth material from the ravages of dental decay. New clinical techniques have been devised to exploit the unique characteristics of the material (McLean Wilson, 1977a,b,c Wilson McLean, 1988 Mount, 1990). 

Beaudoin, J. J. Ramachandran, V. S. (1975). Strength development in magnesium oxychloride and other cements. Cement and Concrete, 5 (6), 617-30. 

These cements have unusual rheological properties (Wilson, 1975b). They can be mixed to higher powder/liquid ratios (6 1 by mass, or more) than any other dental cements and are very fluid. Whereas pastes of other cements behave as plastic bodies, the EBA cement has the characteristics of a very viscous Newtonian liquid and flows under its own weight, even when mixed very thickly (Wilson Batchelor, 1971). High powder/liquid ratios are required for optimum properties 3-5 g cm for luting and 5 to 6 g cm for linings and bases. 

Concretes are cements containing a large proportion of gravel. Hydraulic cements are cements that set (harden) in wet environments, as required when building structures submerged in water. Like all other cements used in ancient times, hydraulic cements were also composite materials in which one particular component, such as pozzolana in ancient Rome (see text below), endowed the cement with the property of setting in wet environments (Gani 1997 Akroyd 1962). 

Abnormal retardation of superplasticized mixes The factors responsible for extended retardation of superplasticized mixes are closely related to the Blaine surface area and to the chemical composition (mainly the C3A content) of the cement used to produce it it is also dependent upon the SP dosage, the prevailing ambient and concrete temperature. Low-C3A cements like Type V are susceptible to extension of their set even at dosages that are considered normal for other cements with higher C3A. contents [125, 137, 139]. 

Fly ash addition was obviously (Table 8) increasing the demand for the water for the standard consistence and prolonging the setting time, but has no influence on the other cement characteristics. All characteristics were in the compliance with the Yugoslav standard JUS B.C1.011. 

Calcium Aluminate. Expansive and Other Cements 323 10.1.5 Thermodynamic calculations... 

The X-ray diffraction output of this ceramic and its microstructure is shown in Figs. 9.7 and 9.8, respectively. The X-ray diffraction pattern does not contain any peaks other than those of MKP and unreacted MgO. Similarly, the scanning electron microphotographs show only crystals of MKP. Thus, unlike other cements such as those formed by ammonium phosphates in which reaction products contain more than one phase, this product is comparatively phase pure. 

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