Cement kinds

In the European standards, above all inEN 197-1, another principle was adopted, dividing cement on kinds according to the quantity and kind of mineral additions. However, the division on class is common, independently of cement kind. These rules of division facilitate the classification of cements for concrete production, designated for constractions exploiting in different expositions. 

In the past the division of cements on the basis of phase composition was applied, as follows alite, alite-celite (Tdmebohm called brownmillerite celite), alite-aluminate and others (Fig. 1.5) [31]. Such division, although fully justified, gives few information to the user— properties of several classes are very approximate, it has no application to cements with additions and for these reasons has no practical use. However, the chemists use it frequently enough for cement kind definition, especially in the case of special cements, which are discussed in Chap. 9. 

Properties Control test Cement kind Strength class Required value... 

Cement kind Class Strength niin./max in MPa after days Addition, %... 

The usual practical situation is that in which two solids are bonded by means of some kind of glue or cement. A relatively complex joint is illustrated in Fig. XII-14. The strength of a joint may be measured in various ways. A common standard method is the peel test in which the normal force to separate the joint... 

Estrlch, m. plaster floor layer of mortar, -gips, m. estrich gypsum, flooring plaster (a form of anhydrous calcium sulfate similar to Keene s cement), -stein, m, a kind of paving brick. 

Marmor-kalk, m. lime from marble, -kiesel, m. a kind of hornstone. -lack, m. marble varnish. -mehl, fi. marble dust, -papier, n. marbled paper, -weiss, n. whiting (as a pigment). -zement, m. marble cement specif., Keene s cement. 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

The PMMA bone cement is formed from a mixture of prepolymer PMMA powder, which contains a free-radical initiator, and liquid MMA monomer. In the operating theatre the powder and liquid are mixed, causing the initiator to dissolve and bring about polymerisation in the monomer component. The powder pre-polymer does not dissolve in the monomer but remains in the newly polymerised materials as a kind of reinforcing filler. 

Tops made from solid epoxy compounds are resistant to just about any kind of chemical abuse but are very expensive. They are often sold with an integral backsplash and curved junction, which makes cleaning easy. They are much easier on glassware than either stone or cement composition. 

Ion binding by reduction of repulsive forces also causes the attractive forces between polyions to increase, and the cement paste thickens. This interaction between polyions may be regarded as a kind of bridge formed by multivalent ions located between the polyions. At this stage the cement paste has the characteristic of a lyophilic sol - high viscosity. 

Poetschke (1925) patented a dental silicate powder prepared by fusing zinc silicate with calcium fluoride. This is a kind of silicophosphate cement (Section 6.6). Thomsen (1931) attempted to formulate a water-setting dental cement. Heynemann (1931) included lithium salts in the flux and Brill (1935) included them in the liquid. 

Fig. 11.10 SEM photographs of the surfaces of the cements modified with MPS and various kinds of calcium salts after soaking in SBF for 7days.

A.Macias. A. Kindness, F.P. Glasser, Impact of carbon Dioxide on the immobilization potential of cemented wastes Chromium,Cem.Concr.Res.27 (2), 215-225, 1997. 

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